Year 2012

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Govoni, Leonardo, Dellaca, Raffaele L., Penuelas, Oscar, Bellani, Giacomo, Artigas, Antonio, Ferrer, Miquel, Navajas, Daniel, Pedotti, Antonio, Farre, Ramon, (2012). Actual performance of mechanical ventilators in ICU: a multicentric quality control study Medical Devices: Evidence and Research 5, 111-119

Even if the performance of a given ventilator has been evaluated in the laboratory under very well controlled conditions, inappropriate maintenance and lack of long-term stability and accuracy of the ventilator sensors may lead to ventilation errors in actual clinical practice. The aim of this study was to evaluate the actual performances of ventilators during clinical routines. A resistance (7.69 cmH(2)O/L/s) - elastance (100 mL/cmH(2)O) test lung equipped with pressure, flow, and oxygen concentration sensors was connected to the Y-piece of all the mechanical ventilators available for patients in four intensive care units (ICUs; n = 66). Ventilators were set to volume-controlled ventilation with tidal volume = 600 mL, respiratory rate = 20 breaths/minute, positive end-expiratory pressure (PEEP) = 8 cmH(2)O, and oxygen fraction = 0.5. The signals from the sensors were recorded to compute the ventilation parameters. The average standard deviation and range (min-max) of the ventilatory parameters were the following: inspired tidal volume = 607 36 (530-723) mL, expired tidal volume = 608 36 (530-728) mL, peak pressure = 20.8 2.3 (17.2-25.9) cmH(2)O, respiratory rate = 20.09 0.35 (19.5-21.6) breaths/minute, PEEP = 8.43 0.57 (7.26-10.8) cmH(2)O, oxygen fraction = 0.49 0.014 (0.41-0.53). The more error-prone parameters were the ones related to the measure of flow. In several cases, the actual delivered mechanical ventilation was considerably different from the set one, suggesting the need for improving quality control procedures for these machines.

Keywords: Equipment and supplies, Medical devices, Intravenous, Quality assurance, Health care quality assessment, Ventilator accuracy, Ventilation error

Gorostiza, Pau, (2012). Control celular mediante luz Investigación y Ciencia 433, 11-12

Diéguez, Lorena, Caballero, David, Calderer, Josep, Moreno, Mauricio, Martínez, Elena, Samitier, Josep, (2012). Optical gratings coated with thin Si3N4 layer for efficient immunosensing by optical waveguide lightmode spectroscopy Biosensors 2, (2), 114-126

New silicon nitride coated optical gratings were tested by means of Optical Waveguide Lightmode Spectroscopy (OWLS). A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering. The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy. As a proof of concept, the sensors were successfully tested with OWLS by monitoring the concentration dependence on the detection of an antibody-protein pair. The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

Keywords: Silicon nitride, Optical gratings, Waveguide, Biosensor

Almendros, Isaac, Carreras, Alba, Montserrat, Josep M., Gozal, David, Navajas, Daniel, Farre, Ramon, (2012). Potential role of adult stem cells in obstructive sleep apnea Frontiers in Neurology 3, 1-6

Adult stem cells are undifferentiated cells that can be mobilized from the bone marrow or other organs, home into injured tissues and differentiate into different cell phenotypes to serve in a repairing capacity. Furthermore, these cells can respond to inflammation and oxidative stress by exhibiting immunomodulatory properties. The protective and reparative roles of mesenchymal stem cells (MSCs), very small embryonic-like stem cells (VSELs) and endothelial progenitor cells (EPCs) have primarily been examined and characterized in auto-immune and cardiovascular diseases. Obstructive sleep apnea (OSA) is a very prevalent disease (4-5% of adult population and 2-3% of children) characterized by an abnormal increase in upper airway collapsibility. Recurrent airway obstructions elicit arterial oxygen desaturations, increased inspiratory efforts and sleep fragmentation, which have been associated with important long-term neurocognitive, metabolic, and cardiovascular consequences. Since inflammation, oxidative stress and endothelial dysfunction are key factors in the development of the morbid consequences of OSA, bone marrow-derived stem cells could be important modulators of the morbid phenotype by affording a protective role. This mini-review is focused on the recent data available on EPCs, VSELs and MSCs in both animal models and patients with OSA.

Keywords: Mesenchymal Stem Cells, Sleep Apnea, Endothelial progenitor cells, Very Small-like Embryonic Stem Cells, Adult bone-marrow derived stem cells

Shin, Song-Hee, Purevdorj, Odnoo, Castano, Oscar, Planell, Josep A., Kim, Hae-Won, (2012). A short review: Recent advances in electrospinning for bone tissue regeneration Journal of Tissue Engineering 3, (1), 2041731412443530

Nanofibrous structures developed by electrospinning technology provide attractive extracellular matrix conditions for the anchorage, migration, and differentiation of tissue cells, including those responsible for the regeneration of hard tissues. Together with the ease of set up and cost-effectiveness, the possibility to produce nanofibers with a wide range of compositions and morphologies is the merit of electrospinning. Significant efforts have exploited the development of bone regenerative nanofibers, which includes tailoring of composite/hybrid compositions that are bone mimicking and the surface functionalization such as mineralization. Moreover, by utilizing bioactive molecules such as adhesive proteins, growth factors, and chemical drugs, in concert with the nanofibrous matrices, it is possible to provide artificial materials with improved cellular responses and therapeutic efficacy. These studies have mainly focused on the regulation of stem cell behaviors for use in regenerative medicine and tissue engineering. While there are some challenges in achieving controllable delivery of bioactive molecules and complex-shaped three-dimensional scaffolds for tissue engineering, the electrospun nanofibrous matrices can still have a beneficial impact in the area of hard-tissue regeneration.

Fiz, J. A., Jané, R., (2012). Snoring Analysis. A Complex Question Journal of Sleep Disorders: Treatment & Care 1, (1), 1-3

The snore is a breathing sound that originates during sleep, either nocturnal or diurnal. Many procedures have been used for its analysis, from simple interrogation, going through acoustic methods that have been developed thanks to the advance of biomedical techniques in recent years. So far a procedure homologated by different laboratories for its study doesn’t exist. The present editorial describes the current state of the art in the snoring analysis procedures.

Keywords: Snoring, Sleep apnea, OSAS

Fumagalli, Laura, Esteban-Ferrer, Daniel, Cuervo, Ana, Carrascosa, Jose L., Gomila, Gabriel, (2012). Label-free identification of single dielectric nanoparticles and viruses with ultraweak polarization forces Nature Materials Nature Publishing Group 11, (9), 743-826

Label-free detection of the material composition of nanoparticles could be enabled by the quantification of the nanoparticles’ inherent dielectric response to an applied electric field. However, the sensitivity of dielectric nanoscale objects to geometric and non-local effects makes the dielectric response extremely weak. Here we show that electrostatic force microscopy with sub-piconewton resolution can resolve the dielectric constants of single dielectric nanoparticles without the need for any reference material, as well as distinguish nanoparticles that have an identical surface but different inner composition. We unambiguously identified unlabelled ~10unm nanoparticles of similar morphology but different low-polarizable materials, and discriminated empty from DNA-containing virus capsids. Our approach should make the in situ characterization of nanoscale dielectrics and biological macromolecules possible.

Keywords: Biological materials, Nanoscale materials, Characterisation and analytical techniques, Computation, modelling and theory

Shan, X., Díez-Pérez, I., Wang, L., Wiktor, P., Gu, Y., Zhang, L., Wang, W., Lu, J., Wang, S., Gong, Q., Li, J., Tao, N., (2012). Imaging the electrocatalytic activity of single nanoparticles Nature Nanotechnology 7, (10), 668-672

The electrocatalytic properties of nanoparticles depend on their size, shape and composition. These properties are typically probed by measuring the total electrocatalytic reaction current of a large number of nanoparticles, but this approach is time-consuming and can only measure the average catalytic activity of the nanoparticles under study. However, the identification of new catalysts requires the ability to rapidly measure the properties of nanoparticles synthesized under various conditions and, ideally, to measure the electrocatalytic activity of individual nanoparticles. Here, we show that a plasmonic-based electrochemical current-imaging technique can simultaneously image and quantify the electrocatalytic reactions of an array of 1.6 × 10 5 platinum nanoparticles printed on an electrode surface, which could facilitate high-throughput screening of the catalytic activities of nanoparticles. We also show that the approach can be used to image the electrocatalytic reaction current and measure the cyclic voltammograms of single nanoparticles.

Serra-Picamal, Xavier, Conte, Vito, Vincent, Romaric, Anon, Ester, Tambe, Dhananjay T., Bazellieres, Elsa, Butler, James P., Fredberg, Jeffrey J., Trepat, Xavier, (2012). Mechanical waves during tissue expansion Nature Physics Nature Publishing Group 8, (8), 628-634

The processes by which an organism develops its shape and heals wounds involve expansion of a monolayer sheet of cells. The mechanism underpinning this epithelial expansion remains obscure, despite the fact that its failure is known to contribute to several diseases, including carcinomas, which account for about 90% of all human cancers. Here, using the micropatterned epithelial monolayer as a model system, we report the discovery of a mechanical wave that propagates slowly to span the monolayer, traverses intercellular junctions in a cooperative manner and builds up differentials of mechanical stress. Essential features of this wave generation and propagation are captured by a minimal model based on sequential fronts of cytoskeletal reinforcement and fluidization. These findings establish a mechanism of long-range cell guidance, symmetry breaking and pattern formation during monolayer expansion.

Keywords: Biological physics

Artés, Juan M., Díez-Pérez, Ismael, Gorostiza, Pau, (2012). Transistor-like behavior of single metalloprotein junctions Nano Letters 12, (6), 2679-2684

Single protein junctions consisting of azurin bridged between a gold substrate and the probe of an electrochemical tunneling microscope (ECSTM) have been obtained by two independent methods that allowed statistical analysis over a large number of measured junctions. Conductance measurements yield (7.3 ± 1.5) ? 10–6G0 in agreement with reported estimates using other techniques. Redox gating of the protein with an on/off ratio of 20 was demonstrated and constitutes a proof-of-principle of a single redox protein field-effect transistor.

Ginebra, M. P., Canal, C., Espanol, M., Pastorino, D., Montufar, E. B., (2012). Calcium phosphate cements as drug delivery materials Advanced Drug Delivery Reviews 64, (12), 1090-1110

Calcium phosphate cements are used as synthetic bone grafts, with several advantages, such as their osteoconductivity and injectability. Moreover, their low-temperature setting reaction and intrinsic porosity allow for the incorporation of drugs and active principles in the material. It is the aim of the present work to: a) provide an overview of the different approaches taken in the application of calcium phosphate cements for drug delivery in the skeletal system, and b) identify the most significant achievements. The drugs or active principles associated to calcium phosphate cements are classified in three groups, i) low molecular weight drugs; ii) high molecular weight biomolecules; and iii) ions.

Keywords: Antibiotic, Bioceramic, Biomaterial, Bone regeneration, Calcium phosphate cement, Ceramic matrix, Growth factor, Hydroxyapatite, Ions, Protein

Díez-Pérez, I., Li, Z., Guo, S., Madden, C., Huang, H., Che, Y., Yang, X., Zang, L., Tao, N., (2012). Ambipolar transport in an electrochemically gated single-molecule field-effect transistor ACS Nano 6, (8), 7044-7052

Charge transport is studied in single-molecule junctions formed with a 1,7-pyrrolidine-substituted 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) molecular block using an electrochemical gate. Compared to an unsubstituted-PTCDI block, spectroscopic and electrochemical measurements indicate a reduction in the highest occupied (HOMO)-lowest unoccupied (LUMO) molecular orbital energy gap associated with the electron donor character of the substituents. The small HOMO-LUMO energy gap allows for switching between electron- and hole-dominated charge transports as a function of gate voltage, thus demonstrating a single-molecule ambipolar field-effect transistor. Both the unsubstituted and substituted molecules display similar n-type behaviors, indicating that they share the same n-type conduction mechanism. However, the substituted-PTCDI block shows a peak in the source-drain current vs gate voltage characteristics for the p-type transport, which is attributed to a two-step incoherent transport via the HOMO of the molecule.

Artés, Juan M., López-Martínez, Montserrat, Giraudet, Arnaud, Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2012). Current–Voltage characteristics and transition voltage spectroscopy of individual redox proteins Journal of the American Chemical Society 134, (50), 20218-20221

Understanding how molecular conductance depends on voltage is essential for characterizing molecular electronics devices. We reproducibly measured current?voltage characteristics of individual redox-active proteins by scanning tunneling microscopy under potentiostatic control in both tunneling and wired configurations. From these results, transition voltage spectroscopy (TVS) data for individual redox molecules can be calculated and analyzed statistically, adding a new dimension to conductance measurements. The transition voltage (TV) is discussed in terms of the two-step electron transfer (ET) mechanism. Azurin displays the lowest TV measured to date (0.4 V), consistent with the previously reported distance decay factor. This low TV may be advantageous for fabricating and operating molecular electronic devices for different applications. Our measurements show that TVS is a helpful tool for single-molecule ET measurements and suggest a mechanism for gating of ET between partner redox proteins. Understanding how molecular conductance depends on voltage is essential for characterizing molecular electronics devices. We reproducibly measured current?voltage characteristics of individual redox-active proteins by scanning tunneling microscopy under potentiostatic control in both tunneling and wired configurations. From these results, transition voltage spectroscopy (TVS) data for individual redox molecules can be calculated and analyzed statistically, adding a new dimension to conductance measurements. The transition voltage (TV) is discussed in terms of the two-step electron transfer (ET) mechanism. Azurin displays the lowest TV measured to date (0.4 V), consistent with the previously reported distance decay factor. This low TV may be advantageous for fabricating and operating molecular electronic devices for different applications. Our measurements show that TVS is a helpful tool for single-molecule ET measurements and suggest a mechanism for gating of ET between partner redox proteins.

Anon, Ester, Serra-Picamal, Xavier, Hersen, Pascal, Gauthier, Nils C., Sheetz, Michael P., Trepat, Xavier, Ladoux, Benoît, (2012). Cell crawling mediates collective cell migration to close undamaged epithelial gaps Proceedings of the National Academy of Sciences of the United States of America 109, (27), 10891-10896

Fundamental biological processes such as morphogenesis and wound healing involve the closure of epithelial gaps. Epithelial gap closure is commonly attributed either to the purse-string contraction of an intercellular actomyosin cable or to active cell migration, but the relative contribution of these two mechanisms remains unknown. Here we present a model experiment to systematically study epithelial closure in the absence of cell injury. We developed a pillar stencil approach to create well-defined gaps in terms of size and shape within an epithelial cell monolayer. Upon pillar removal, cells actively respond to the newly accessible free space by extending lamellipodia and migrating into the gap. The decrease of gap area over time is strikingly linear and shows two different regimes depending on the size of the gap. In large gaps, closure is dominated by lamellipodium-mediated cell migration. By contrast, closure of gaps smaller than 20 μm was affected by cell density and progressed independently of Rac, myosin light chain kinase, and Rho kinase, suggesting a passive physical mechanism. By changing the shape of the gap, we observed that low-curvature areas favored the appearance of lamellipodia, promoting faster closure. Altogether, our results reveal that the closure of epithelial gaps in the absence of cell injury is governed by the collective migration of cells through the activation of lamellipodium protrusion.

Ghassemi, S., Meacci, G., Liu, S., Gondarenko, A. A., Mathur, A., Roca-Cusachs, P., Sheetz, M. P., Hone, J., (2012). Cells test substrate rigidity by local contractions on submicrometer pillars Proceedings of the National Academy of Sciences of the United States of America 109, (14), 5328-5333

Cell growth and differentiation are critically dependent upon matrix rigidity, yet many aspects of the cellular rigidity-sensing mechanism are not understood. Here, we analyze matrix forces after initial cell-matrix contact, when early rigidity-sensing events occur, using a series of elastomeric pillar arrays with dimensions extending to the submicron scale (2, 1, and 0.5 μm in diameter covering a range of stiffnesses). We observe that the cellular response is fundamentally different on micron-scale and submicron pillars. On 2-μm diameter pillars, adhesions form at the pillar periphery, forces are directed toward the center of the cell, and a constant maximum force is applied independent of stiffness. On 0.5-μm diameter pillars, adhesions form on the pillar tops, and local contractions between neighboring pillars are observed with a maximum displacement of ∼60 nm, independent of stiffness. Because mutants in rigidity sensing show no detectable displacement on 0.5-μm diameter pillars, there is a correlation between local contractions to 60 nm and rigidity sensing. Localization of myosin between submicron pillars demonstrates that submicron scale myosin filaments can cause these local contractions. Finally, submicron pillars can capture many details of cellular force generation that are missed on larger pillars and more closely mimic continuous surfaces.

Keywords: Cell mechanics, Mechanotransduction, Nanofabrication

Bakker, G. J., Eich, C., Torreno-Pina, J. A., Diez-Ahedo, R., Perez-Samper, G., Van Zanten, T. S., Figdor, C. G., Cambi, A., Garcia-Parajo, M. F., (2012). Lateral mobility of individual integrin nanoclusters orchestrates the onset for leukocyte adhesion Proceedings of the National Academy of Sciences of the United States of America 109, (13), 4869-4874

Integrins are cell membrane adhesion receptors involved in morphogenesis, immunity, tissue healing, and metastasis. A central, yet unresolved question regarding the function of integrins is how these receptors regulate both their conformation and dynamic nanoscale organization on the membrane to generate adhesion-competent microclusters upon ligand binding. Here we exploit the high spatial (nanometer) accuracy and temporal resolution of single-dye tracking to dissect the relationship between conformational state, lateral mobility, and microclustering of the integrin receptor lymphocyte function-associated antigen 1 (LFA-1) expressed on immune cells. We recently showed that in quiescent monocytes, LFA-1 preorganizes in nanoclusters proximal to nanoscale raft components. We now show that these nanoclusters are primarily mobile on the cell surface with a small (ca. 5%) subset of conformational- active LFA-1 nanoclusters preanchored to the cytoskeleton. Lateral mobility resulted crucial for the formation of microclusters upon ligand binding and for stable adhesion under shear flow. Activation of high-affinity LFA-1 by extracellular Ca 2+ resulted in an eightfold increase on the percentage of immobile nanoclusters and cytoskeleton anchorage. Although having the ability to bind to their ligands, these active nanoclusters failed to support firm adhesion in static and low shear-flow conditions because mobility and clustering capacity were highly compromised. Altogether, our work demonstrates an intricate coupling between conformation and lateral diffusion of LFA-1 and further underscores the crucial role of mobility for the onset of LFA-1 mediated leukocyte adhesion.

Keywords: Cumulative probability distribution, Integrin lymphocyte function-associated antigen 1, Intercellular adhesion molecule, Single molecule detection

Gil, V., Del Río, J. A., (2012). Analysis of axonal growth and cell migration in 3D hydrogel cultures of embryonic mouse CNS tissue Nature Protocols 7, (2), 268-280

This protocol uses rat tail-derived type I collagen hydrogels to analyze key processes in developmental neurobiology, such as chemorepulsion and chemoattraction. The method is based on culturing small pieces of brain tissue from embryonic or early perinatal mice inside a 3D hydrogel formed by rat tail-derived type I collagen or, alternatively, by commercial Matrigel. The neural tissue is placed in the hydrogel with other brain tissue pieces or cell aggregates genetically modified to secrete a particular molecule that can generate a gradient inside the hydrogel. The present method is uncomplicated and generally reproducible, and only a few specific details need to be considered during its preparation. Moreover, the degree and behavior of axonal growth or neural migration can be observed directly using phase-contrast, fluorescence microscopy or immunocytochemical methods. This protocol can be carried out in 4 weeks.

Keywords: Cell biology, Cell culture, Developmental biology, Imaging, Model organisms, Neuroscience, Tissue culture

Oberhansl, Sabine, Hirtz, Michael, Lagunas, Anna, Eritja, Ramon, Martinez, Elena, Fuchs, Harald, Samitier, Josep, (2012). Facile modification of silica substrates provides a platform for direct-writing surface click chemistry Small 8, (4), 541-545

Sánchez-Danés, A., Richaud-Patin, Y., Carballo-Carbajal, I., Jiménez-Delgado, S., Caig, C., Mora, S., Di Guglielmo, C., Ezquerra, M., Patel, B., Giralt, A., Canals, J. M., Memo, M., Alberch, J., López-Barneo, J., Vila, M., Cuervo, A. M., Tolosa, E., Consiglio, A., Raya, A., (2012). Disease-specific phenotypes in dopamine neurons from human iPS-based models of genetic and sporadic Parkinson's disease EMBO Molecular Medicine 4, (5), 380-395

Induced pluripotent stem cells (iPSC) offer an unprecedented opportunity to model human disease in relevant cell types, but it is unclear whether they could successfully model age-related diseases such as Parkinson's disease (PD). Here, we generated iPSC lines from seven patients with idiopathic PD (ID-PD), four patients with familial PD associated to the G2019S mutation in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene (LRRK2-PD) and four age- and sex-matched healthy individuals (Ctrl). Over long-time culture, dopaminergic neurons (DAn) differentiated from either ID-PD- or LRRK2-PD-iPSC showed morphological alterations, including reduced numbers of neurites and neurite arborization, as well as accumulation of autophagic vacuoles, which were not evident in DAn differentiated from Ctrl-iPSC. Further induction of autophagy and/or inhibition of lysosomal proteolysis greatly exacerbated the DAn morphological alterations, indicating autophagic compromise in DAn from ID-PD- and LRRK2-PD-iPSC, which we demonstrate occurs at the level of autophagosome clearance. Our study provides an iPSC-based in vitro model that captures the patients' genetic complexity and allows investigation of the pathogenesis of both sporadic and familial PD cases in a disease-relevant cell type.

Keywords: Autophagy, Disease modeling, LRRK2 mutation, Neurodegeneration, Pluripotent stem cells

Mattotti, Marta, Alvarez, Zaida, Ortega, Juan A., Planell, Josep A., Engel, Elisabeth, Alcántara, Soledad, (2012). Inducing functional radial glia-like progenitors from cortical astrocyte cultures using micropatterned PMMA Biomaterials 33, (6), 1759-1770

Radial glia cells (RGC) are multipotent progenitors that generate neurons and glia during CNS development, and which also served as substrate for neuronal migration. After a lesion, reactive glia are the main contributor to CNS regenerative blockage, although some reactive astrocytes are also able to de-differentiate in situ into radial glia-like cells (RGLC), providing beneficial effects in terms of CNS recovery. Thus, the identification of substrate properties that potentiate the ability of astrocytes to transform into RGLC in response to a lesion might help in the development of implantable devices that improve endogenous CNS regeneration. Here we demonstrate that functional RGLC can be induced from in vitro matured astrocytes by using a precisely-sized micropatterned PMMA grooved scaffold, without added soluble or substrate adsorbed biochemical factors. RGLC were extremely organized and aligned on 2

Keywords: Polymethylmethacrylate, Micropatterning, Surface topography, Astrocyte, Nerve guide, Co-culture

Lagunas, Anna , Comelles, Jordi, Martínez, Elena, Prats-Alfonso, Elisabet , Acosta, Gerardo A., Albericio, Fernando , Samitier, Josep , (2012). Cell adhesion and focal contact formation on linear RGD molecular gradients: study of non-linear concentration dependence effects Nanomedicine: Nanotechnology, Biology and Medicine 8, (4), 432-439

Cell adhesion onto bioengineered surfaces is affected by a number of variables, including the former substrate derivatization process. In this investigation, we studied the correlation between cell adhesion and cell–adhesive ligand surface concentration and organization due to substrate modification. For this purpose, Arg-Gly-Asp (RGD) gradient surfaces were created on poly(methyl methacrylate) substrates by continuous hydrolysis and were then grafted with biotin-PEG-RGD molecules. Cell culture showed that adhesion behavior changes in a nonlinear way in the narrow range of RGD surface densities assayed (2.8 to 4.4 pmol/cm2), with a threshold value of 4.0 pmol/cm2 for successful cell attachment and spreading. This nonlinear dependence may be explained by nonhomogeneous RGD surface distribution at the nanometre scale, conditioned by the stochastic nature of the hydrolysis process. Atomic force microscopy analysis of the gradient surface showed an evolution of surface morphology compatible with this hypothesis.

Keywords: RGD gradient, Cell adhesion, Poly(methyl methacrylate), Hydrolysis, Biotin-streptavidin

Mir, Mònica , Tahirbegi, Islam Bogachan , Valle-Delgado, Juan José , Fernàndez-Busquets, X., Samitier, Josep , (2012). In vitro study of magnetite-amyloid Nanomedicine: Nanotechnology, Biology and Medicine 8, (6), 974-980

Biogenic magnetite (Fe3O4) has been identified in human brain tissue. However, abnormal concentration of magnetite nanoparticles in the brain has been observed in different neurodegenerative pathologies. In the case of Alzheimer's disease (AD), these magnetic nanoparticles have been identified attached to the characteristic brain plaques, which are mainly formed by fibrils of amyloid

Keywords: Alzheimer's disease, Biogenic magnetite, Amyloid β peptide (Aβ), Superconducting quantum interference, Scanning electron microscope, Surface plasmon resonance, Magnetic force microscopy

Almendros, I., Montserrat, J. M., Ramírez, J., Torres, M., Duran-Cantolla, J., Navajas, D., Farré, R., (2012). Intermittent hypoxia enhances cancer progression in a mouse model of sleep apnoea European Respiratory Journal 39, (1), 215-217

Chimenti, L., Luque, T., Bonsignore, M. R., Ramirez, J., Navajas, D., Farre, R., (2012). Pre-treatment with mesenchymal stem cells reduces ventilator-induced lung injury European Respiratory Journal 40, (4), 939-948

Bone marrow-derived mesenchymal stem cells (MSCs) reduce acute lung injury in animals challenged by bleomycin or bacterial lipopolysaccaride. It is not known, however, whether MSCs protect from ventilator-induced lung injury (VILI). This study investigated whether MSCs have a potential role in preventing or modulating VILI in healthy rats subjected to high-volume ventilation. 24 Sprague-Dawley rats (250-300 g) were subjected to high-volume mechanical ventilation (25 MSCs (5 x 10(6)) were intravenously or intratracheally administered (n=8 each) 30 min before starting over-ventilation and eight rats were MSC-untreated. Spontaneously breathing anesthetised rats (n=8) served as controls. After 3 h of over-ventilation or control the animals were sacrificed and lung tissue and bronchoalveolar lavage fluid (BALF) were sampled for further analysis. When compared with controls, MSC-untreated over-ventilated rats exhibited typical VILI features. Lung oedema, histological lung injury index, concentrations of total protein, interleukin-1 beta, macrophage inflammatory protein-2 and number of neutrophils in BALF and vascular cell adhesion protein-1 in lung tissue significantly increased in over-ventilated rats. All these indices of VILI moved significantly towards normalisation in the rats treated with MSCs, whether intravenously or intratracheally. Both local and systemic pre-treatment with MSCs reduced VILI in a rat model.

Keywords: Acute lung injury, Cell therapy, Injurious ventilation, Lung inflammation, Lung oedema, Mechanical ventilation

Roca-Cusachs, P., Iskratsch, T., Sheetz, M. P., (2012). Finding the weakest link: exploring integrin-mediated mechanical molecular pathways Journal of Cell Science 125, (13), 3025-3038

From the extracellular matrix to the cytoskeleton, a network of molecular links connects cells to their environment. Molecules in this network transmit and detect mechanical forces, which subsequently determine cell behavior and fate. Here, we reconstruct the mechanical pathway followed by these forces. From matrix proteins to actin through integrins and adaptor proteins, we review how forces affect the lifetime of bonds and stretch or alter the conformation of proteins, and how these mechanical changes are converted into biochemical signals in mechanotransduction events. We evaluate which of the proteins in the network can participate in mechanotransduction and which are simply responsible for transmitting forces in a dynamic network. Besides their individual properties, we also analyze how the mechanical responses of a protein are determined by their serial connections from the matrix to actin, their parallel connections in integrin clusters and by the rate at which force is applied to them. All these define mechanical molecular pathways in cells, which are emerging as key regulators of cell function alongside better studied biochemical pathways.

Keywords: Cell adhesion, Cytoskeleton, Mechanotransduction

Esquivel, Juan Pablo , Castellarnau, Marc , Senn, Tobias , Löchel, Bernd , Samitier, Josep , Sabaté, Neus , (2012). Fuel cell-powered microfluidic platform for lab-on-a-chip applications Lab on a Chip 12, (1), 74-79

The achievement of a higher degree of integration of components – especially micropumps and power sources – is a challenge currently being pursued to obtain portable and totally autonomous microfluidic devices. This paper presents the integration of a micro direct methanol fuel cell (mDMFC) in a microfluidic platform as a smart solution to provide both electrical and pumping power to a Lab-on-a-Chip system. In this system the electric power produced by the fuel cell is available to enable most of the functionalites required by the microfluidic chip, while the generated CO2 from the electrochemical reaction produces a pressure capable of pumping a liquid volume through a microchannel. The control of the fuel cell operating conditions allows regulation of the flow rate of a liquid sample through a microfluidic network. The relation between sample flow rate and the current generated by the fuel cell is practically linear, achieving values in the range of 4–18 mL min 1 while having an available power between 1–4 mW. This permits adjusting the desired flow rate for a given application by controlling the fuel cell output conditions and foresees a fully autonomous analytical Lab-on-a-Chip in which the same device would provide the electrical power to a detection module and at the same time use the CO2 pumping action to flow the required analytes through a particular microfluidic design.

Keywords: micro direct methanol fuel cell (mDMFC), Lab-on-a-chip (LOC), Microfluidic device

Esquivel, J. P., Colomer-Farrarons, J., Castellarnau, M., Salleras, M., del Campo, F. J., Samitier, J., Miribel-Catala, P., Sabate, N., (2012). Fuel cell-powered microfluidic platform for lab-on-a-chip applications: Integration into an autonomous amperometric sensing device Lab on a Chip 12, (21), 4232-4235

The present paper reports for the first time the integration of a microfluidic system, electronics modules, amperometric sensor and display, all powered by a single micro direct methanol fuel cell. In addition to activating the electronic circuitry, the integrated power source also acts as a tuneable micropump. The electronics fulfil several functions. First, they regulate the micro fuel cell output power, which off-gas controls the flow rate of different solutions toward an electrochemical sensor through microfluidic channels. Secondly, as the fuel cell powers a three-electrode electrochemical cell, the electronics compare the working electrode output signal with a set reference value. Thirdly, if the concentration measured by the sensor exceeds this threshold value, the electronics switch on an integrated organic display. This integrated approach pushes forward the development of truly autonomous point-of-care devices relying on electrochemical detection.

Parra-Cabrera, C., Sporer, C., Rodriguez-Villareal, I., Rodriguez-Trujillo, R., Homs-Corbera, A., Samitier, J., (2012). Selective in situ functionalization of biosensors on LOC devices using laminar co-flow Lab on a Chip 12, (20), 4143-4150

Many applications involving lab-on-a-chip (LOC) devices are prevented from entering the market because of difficulties to achieve mass production and impart suitable properties allowing long-term storage. To integrate biosensors on these microfluidic chips, one of the main restrictions is the fabrication and stability of the molecular modifications that must be performed on the surfaces of the sensors for a given application. The complexity of the problem increases exponentially when the LOC integrates several of these sensors. Here we present a system based on laminar co-flow to perform an on-chip selective surface bio-functionalization of LOC-integrated sensors. This method has the advantage that the surface modification protocols are performed in situ before analyte detection. This approach reduces the burdens during LOC fabrication, keeping the required reagents stored outside of the detection structure in suitable wet conditions. The proof of concept is demonstrated through an optical characterization followed by electronic detection based on a novel differential impedance measurement setup. The system can be easily scaled to incorporate several sensors with distinct biosensing targets in a single chip.

Dries, Koen, Helden, Suzanne, Riet, Joostte, Diez-Ahedo, Ruth, Manzo, Carlo, Oud, Machteld, Leeuwen, Frank, Brock, Roland, Garcia-Parajo, Maria, Cambi, Alessandra, Figdor, CarlG, (2012). Geometry sensing by dendritic cells dictates spatial organization and PGE2-induced dissolution of podosomes Cellular and Molecular Life Sciences 69, (11), 1889-1901

Assembly and disassembly of adhesion structures such as focal adhesions (FAs) and podosomes regulate cell adhesion and differentiation. On antigen-presenting dendritic cells (DCs), acquisition of a migratory and immunostimulatory phenotype depends on podosome dissolution by prostaglandin E2 (PGE2). Whereas the effects of physico-chemical and topographical cues have been extensively studied on FAs, little is known about how podosomes respond to these signals. Here, we show that, unlike for FAs, podosome formation is not controlled by substrate physico-chemical properties. We demonstrate that cell adhesion is the only prerequisite for podosome formation and that substrate availability dictates podosome density. Interestingly, we show that DCs sense 3-dimensional (3-D) geometry by aligning podosomes along the edges of 3-D micropatterned surfaces. Finally, whereas on a 2-dimensional (2-D) surface PGE2 causes a rapid increase in activated RhoA levels leading to fast podosome dissolution, 3-D geometric cues prevent PGE2-mediated RhoA activation resulting in impaired podosome dissolution even after prolonged stimulation. Our findings indicate that 2-D and 3-D geometric cues control the spatial organization of podosomes. More importantly, our studies demonstrate the importance of substrate dimensionality in regulating podosome dissolution and suggest that substrate dimensionality plays an important role in controlling DC activation, a key process in initiating immune responses.

Keywords: Mechanosensitivity, Podosomes, Dendritic cell, Adhesion

Nocentini, S., Reginensi, D., Garcia, S., Carulla, P., Moreno-Flores, Wandosell, F., Trepat, X., Bribian, A., Del Rí, (2012). Myelin-associated proteins block the migration of olfactory ensheathing cells: an in vitro study using single-cell tracking and traction force microscopy Cellular and Molecular Life Sciences 69, (10), 1689-1703

Newly generated olfactory receptor axons grow from the peripheral to the central nervous system aided by olfactory ensheathing cells (OECs). Thus, OEC transplantation has emerged as a promising therapy for spinal cord injuries and for other neural diseases. However, these cells do not present a uniform population, but instead a functionally heterogeneous population that exhibits a variety of responses including adhesion, repulsion, and crossover during cell–cell and cell–matrix interactions. Some studies report that the migratory properties of OECs are compromised by inhibitory molecules and potentiated by chemical gradients. Here, we demonstrated that rodent OECs express all the components of the Nogo receptor complex and that their migration is blocked by myelin. Next, we used cell tracking and traction force microscopy to analyze OEC migration and its mechanical properties over myelin. Our data relate the decrease of traction force of OEC with lower migratory capacity over myelin, which correlates with changes in the F-actin cytoskeleton and focal adhesion distribution. Lastly, OEC traction force and migratory capacity is enhanced after cell incubation with the Nogo receptor inhibitor NEP1-40.

Keywords: Ensheathing glia, Traction force, microscopy, Migration, Myelin-associated inhibitors

Yang, Cheng, Lates, Vasilica, Prieto-Simón, Beatriz, Marty, Jean-Louis, Yang, Xiurong, (2012). Aptamer-DNAzyme hairpins for biosensing of Ochratoxin A Biosensors and Bioelectronics 32, (1), 208-212

We report an aptasensor for biosensing of Ochratoxin A (OTA) using aptamer-DNAzyme hairpin as biorecognition element. The structure of this engineered nucleic acid includes the horseradish peroxidase (HRP)-mimicking DNAzyme and the OTA specific aptamer sequences. A blocking tail captures a part of these sequences in the stem region of the hairpin. In the presence of OTA, the hairpin is opened due to the formation of the aptamer–analyte complex. As a result, self-assembly of the active HRP-mimicking DNAzyme occurs. The activity of this DNAzyme is linearly correlated with OTA concentration up to 10 nM, showing a limit of detection of 2.5 nM.

Keywords: Ochratoxin A, Aptamer, G-quadruplex, DNAzyme, Hairpin

Pairó, Erola, Maynou, Joan, Marco, Santiago, Perera, Alexandre, (2012). A subspace method for the detection of transcription factor binding sites Bioinformatics 28, (10), 1328-1335

Motivation: The identification of the sites at which transcription factors (TF) bind to DNA is an important problem in molecular biology. Many computational methods have been developed for motif finding, most of them based on position-specific scoring matrices (PSSM) which assume the independence of positions within a binding site. However, some experimental and computational studies demonstrate that interdependences within the positions exist.Results: In this paper, we introduce a novel motif finding method which constructs a subspace based on the covariance of numerical DNA sequences. When a candidate sequence is projected into the modelled subspace, a threshold in the Q-residuals confidence allows us to predict whether this sequence is a binding site. Using the TRANSFAC and JASPAR databases, we compared our Q-residuals detector with existing PSSM methods. In most of the studied transcription factor binding sites, the Q-residuals detector performs significantly better and faster than MATCH and MAST. As compared to Motifscan, a method which takes into account inter-dependences, the performance of the Q-residuals detector is better when the number of available sequences is small.Availability: epairo@ibecbarcelona.euSupplementary information: Supplementary data (1,2,3,4) are available at Bioinformatics On-line.

Gustavsson, J., Ginebra, M. P., Planell, J., Engel, E., (2012). Electrochemical microelectrodes for improved spatial and temporal characterization of aqueous environments around calcium phosphate cements Acta Biomaterialia 8, (1), 386-393

Calcium phosphate compounds can potentially influence cellular fate through ionic substitutions. However, to be able to turn such solution-mediated processes into successful directors of cellular response, a perfect understanding of the material-induced chemical reactions in situ is required. We therefore report on the application of home-made electrochemical microelectrodes, tested as pH and chloride sensors, for precise spatial and temporal characterization of different aqueous environments around calcium phosphate-based biomaterials prepared from α-tricalcium phosphate using clinically relevant liquid to powder ratios. The small size of the electrodes allowed for online measurements in traditionally inaccessible in vitro environments, such as the immediate material-liquid interface and the interior of curing bone cement. The kinetic data obtained has been compared to theoretical sorption models, confirming that the proposed setup can provide key information for improved understanding of the biochemical environment imposed by chemically reactive biomaterials.

Keywords: Calcium phosphate, Hydroxyapatite, Ion sorption, Iridium oxide, Sensors, Animals, Biocompatible Materials, Bone Cements, Calcium Phosphates, Cells, Cultured, Chlorides, Electrochemical Techniques, Gold, Hydrogen-Ion Concentration, Hydroxyapatites, Iridium, Materials Testing, Microelectrodes, Powders, Silver, Silver Compounds, Water

Tejeda-Montes, E., Smith, K. H., Poch, M., López-Bosque, M. J., Martín, L., Alonso, M., Engel, E., Mata, Alvaro., (2012). Engineering membrane scaffolds with both physical and biomolecular signaling Acta Biomaterialia 8, (3), 998-1009

We report on the combination of a top-down and bottom-up approach to develop thin bioactive membrane scaffolds based on functional elastin-like polymers (ELPs). Our strategy combines ELP cross-linking and assembly, and a variety of standard and novel micro/nanofabrication techniques to create self-supporting membranes down to ∼500 nm thick that incorporate both physical and biomolecular signals, which can be easily tailored for a specific application. In this study we used an ELP that included the cell-binding motif arginine-glycine-aspartic acid-serine (RGDS). Furthermore, fabrication processes were developed to create membranes that exhibited topographical patterns with features down to 200 nm in lateral dimensions and up to 10 μm in height on either one or both sides, uniform and well-defined pores, or multiple ELP layers. A variety of processing parameters were tested in order to optimize membrane fabrication, including ELP and cross-linker concentration, temperature, reaction time and ambient humidity. Membrane micro/nanopatterning, swelling and stiffness were characterized by atomic force microscopy, nanoindentation tests and scanning electron microscopy. Upon immersion in phosphate-buffered saline and an increase in temperature from 25 to 40°C, membranes exhibited a significant increase in surface stiffness, with the reduced Young's modulus increasing with temperature. Finally, rat mesenchymal stem cells were cultured on thin RGDS-containing membranes, which allowed cell adhesion, qualitatively enhanced spreading compared to membranes without RGDS epitopes and permitted proliferation. Furthermore, cell morphology was drastically affected by topographical patterns on the surface of the membranes.

Keywords: Elastin-like polymers, Membranes, Nanotechnology, Scaffolds, Tissue engineering

Caballero-Briones, F., Palacios-Padrós, A., Calzadilla, O., Moreira, I. D. P. R., Sanz, F., (2012). Disruption of the chemical environment and electronic structure in p-type Cu2O films by alkaline doping Journal of Physical Chemistry C 116, (25), 13524-13535

In this work we present an experimental and theoretical study of Cu 2O films doped with alkaline ions (Li +, Na +, K +, and Cs +) prepared by Cu anodization. By X-ray photoelectron spectroscopy we determined dopant incorporation as high as 1% for Na +. Three oxygen species were found: O 2- ions in the bulk cuprite structure, adsorbed OH - and oxygen in hydroxylated dopant sites. The main effects of the alkaline doping on the optical properties were a reduction in the direct band gap and an approach of the acceptor level edge to the maximum of the valence band. Electrochemical tunneling microscopy experiments confirmed that the valence band maximum energy position is almost invariant. Additional electrochemical impedance, photoelectrochemical activity, and current sensing atomic force microscopy measurements showed an increase of the carrier density and electrical conductivity and a reduction in the photocurrent response with the dopant ion size. Urbach tail parameter analysis suggested additional interaction between copper vacancy derived states and dopant states. From first-principles calculations with the B3LYP hybrid functional on models for the alkaline-doped Cu 2O systems we determined that the main effect of the alkaline substitution of copper atoms consists of polarizing the O states, which causes a reduction in the insulating gap and splitting of the density of states just below the Fermi level. The nature of the oxygen-dopant interaction was also calculated: there is a net attractive interaction for Li-O, a slightly repulsive interaction for Na-O, and a net repulsive interaction for K-O and Cs-O. The repulsive interactions between K + or Cs + and O cause an accumulation of the dopant at the surface of the crystallites, whereas for Na + and Li + the doping ions are more uniformly distributed in the film bulk. It was found that the surface accumulation of K + and Cs + hinders vacancy diffusion and therefore blocks film growth, leading to a reduction of roughness and thickness as the ion size increases.

Darwish, Nadim., Díez-Pérez, I., Guo, S., Tao, N., Gooding, J. J., Paddon-Row, M. N., (2012). Single molecular switches: Electrochemical gating of a single anthraquinone-based norbornylogous bridge molecule Journal of Physical Chemistry C 116, (39), 21093-21097

Herein we report the electrochemical gating of a single anthraquinone-based molecule bridged between two gold electrodes using the STM break-junction technique. Once a molecule is trapped between the STM gold tip and the gold substrate, the potential is swept in order to alternate between the oxidized anthraquinone (AQ) and the reduced hydroanthraquinone (H 2AQ) forms. It is shown that the conductance increases about an order of magnitude with a net conversion from the oxidized AQ form to the reduced H 2AQ form. The results obtained from sweeping the potential (dynamic approach) on a single molecule are compared to those obtained from measuring the conductance at several fixed potentials (static approach). By comparing the static and dynamic approach, qualitative information about the kinetics of the redox conversion was achieved. The threshold potential of the conductance enhancement was found to shift to more negative potentials when the potential is swept at a single molecule. This shift is attributed to a slow redox conversion between the AQ and the H 2AQ forms. The hypothesis, of slow redox kinetics being responsible for the observed differences in the single-molecule conductance studies, was supported by electron transfer kinetics studies of bulk self-assembled monolayers using both cyclic voltammetry at different sweeping rates and electrochemical impedance spectroscopy.

McLenachan, S., Menchon, C., Raya, A., Consiglio, A., Edel, M. J., (2012). Cyclin A(1) is essential for setting the pluripotent state and reducing tumorigenicity of induced pluripotent stem cells Stem Cells and Development 21, (15), 2891-2899

The proper differentiation and threat of cancer rising from the application of induced pluripotent stem (iPS) cells are major bottlenecks in the field and are thought to be inherently linked to the pluripotent nature of iPS cells. To address this question, we have compared iPS cells to embryonic stem cells (ESCs), the gold standard of ground state pluripotency, in search for proteins that may improve pluripotency of iPS cells. We have found that when reprogramming somatic cells toward pluripotency, 1%-5% of proteins of 5 important cell functions are not set to the correct expression levels compared to ESCs, including mainly cell cycle proteins. We have shown that resetting cyclin A1 protein expression of early- passage iPS cells closer to the ground state pluripotent state of mouse ESCs improves the pluripotency and reduces the threat of cancer of iPS cells. This work is a proof of principle that reveals that setting expression of certain proteins correctly during reprogramming is essential for achieving ESC- state pluripotency. This finding would be of immediate help to those researchers in different fields of iPS cell work that specializes in cell cycle, apoptosis, cell adhesion, cell signaling, and cytoskeleton.

Keywords: Self-renewal, IPS cells, Ground-state, C-MYC, Generation, Pathway, Disease, Mice, Link, P53

Penon, O., Novo, S., Duran, S., Ibanez, E., Nogues, C., Samitier, J., Duch, M., Plaza, J. A., Perez-Garcia, L., (2012). Efficient biofunctionalization of polysilicon barcodes for adhesion to the zona pellucida of mouse embryos Bioconjugate Chemistry 23, (12), 2392-2402

Cell tracking is an emergent area in nano-biotechnology, promising the study of individual cells or the identification of populations of cultured cells. In our approach, microtools designed for extracellular tagging are prepared, because using biofunctionalized polysilicon barcodes to tag cell membranes externally avoids the inconveniences of cell internalization. The crucial covalent biofunctionalization process determining the ultimate functionality was studied in order to find the optimum conditions to link a biomolecule to a polysilicon barcode surface using a self-assembled monolayer (SAM) as the connector. Specifically, a lectin (wheat germ agglutinin, WGA) was used because of its capacity to recognize some specific carbohydrates present on the surface of most mammalian cells. Self-assembled monolayers were prepared on polysilicon surfaces including aldehyde groups as terminal functions to study the suitability of their covalent chemical bonding to WGA. Some parameters, such as the polysilicon surface roughness or the concentration of WGA, proved to be crucial for successful biofunctionalization and bioactivity. The SAMs were characterized by contact angle measurements, time-of-flight secondary ion mass spectrometry (TOF-SIMS), laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS), and atomic force microscopy (AFM). The biofunctionalization step was also characterized by fluorescence microscopy and, in the case of barcodes, by adhesion experiments to the zona pellucida of mouse embryos. These experiments showed high barcode retention rates after 96 h of culture as well as high embryo viability to the blastocyst stage, indicating the robustness of the biofunctionalization and, therefore, the potential of these new microtools to be used for cell tagging.

Keywords: Self-assembled monolayers, Wheat-germ-agglutinin, Protein immobilization strategies, Mass-spectrometry, Cell-surface, Petide, Binding, Identifications, Nanoparticles, Recognition

Tort, N., Salvador, J. P., Avino, A., Eritja, R., Comelles, J., Martinez, E., Samitier, J., Marco, M. P., (2012). Synthesis of steroid-oligonucleotide conjugates for a DNA site-encoded SPR immunosensor Bioconjugate Chemistry 23, (11), 2183-2191

The excellent self-assembling properties of DNA and the excellent specificity of the antibodies to detect analytes of small molecular weight under competitive conditions have been combined in this study. Three oligonucleotide sequences (N(1)up, N(2)up, and N(3)up) have been covalently attached to three steroidal haptens (8, hG, and 13) of three anabolic-androgenic steroids (AAS), stanozolol (ST), tetrahydrogestrinone (THG), and boldenone (B), respectively. The synthesis of steroid oligonucleotide conjugates has been performed by the reaction of oligonucleotides carrying amino groups with carboxyl acid derivatives of steroidal haptens. Due to the chemical nature of the steroid derivatives, two methods for coupling the haptens and the ssDNA have been studied: a solid-phase coupling strategy and a solution-phase coupling strategy. Specific antibodies against ST, THG, and B have been used in this study to asses the possibility of using the self-assembling properties of the DNA to prepare biofunctional SPR gold chips based on the immobilization of haptens, by hybridization with the complementary oligonucleotide strands possessing SH groups previously immobilized. The capture of the steroid oligonucleotide conjugates and subsequent binding of the specific antibodies can be monitored on the sensogram due to variations produced on the refractive index on top of the gold chip. The resulting steroid oligonucleotide conjugates retain the hybridization and specific binding properties of oligonucleotides and haptens as demonstrated by thermal denaturation experiments and surface plasmon resonance (SPR).

Keywords: Directed protein immobilization, Plasmon resonance biosensor, Self-assembled monolayers, Label-free, Serum samples, Assay, Immunoassays, Antibodies, Progress, Binding

Arimon, M., Sanz, F., Giralt, E., Carulla, N., (2012). Template-assisted lateral growth of amyloid- Bioconjugate Chemistry 23, (1), 27-32

Aguirre, A., Gonzalez, A., Navarro, M., Castano, O., Planell, J. A., Engel, E., (2012). Control of microenvironmental cues with a smart biomaterial composite promotes endothelial progenitor cell angiogenesis European Cells & Materials 24, 90-106

Smart biomaterials play a key role when aiming at successful tissue repair by means of regenerative medicine approaches, and are expected to contain chemical as well as mechanical cues that will guide the regenerative process. Recent advances in the understanding of stem cell biology and mechanosensing have shed new light onto the importance of the local microenvironment in determining cell fate. Herein we report the biological properties of a bioactive, biodegradable calcium phosphate glass/polylactic acid composite biomaterial that promotes bone marrow-derived endothelial progenitor cell (EPC) mobilisation, differentiation and angiogenesis through the creation of a controlled bone healing-like microenvironment. The angiogenic response is triggered by biochemical and mechanical cues provided by the composite, which activate two synergistic cell signalling pathways: a biochemical one mediated by the calcium-sensing receptor and a mechanosensitive one regulated by non-muscle myosin II contraction. Together, these signals promote a synergistic response by activating EPCs-mediated VEGF and VEGFR-2 synthesis, which in turn promote progenitor cell homing, differentiation and tubulogenesis. These findings highlight the importance of controlling microenvironmental cues for stem/progenitor cell tissue engineering and offer exciting new therapeutical opportunities for biomaterialbased vascularisation approaches and clinical applications.

Keywords: Calcium phosphate glass composite, Smart biomaterial, Endothelial progenitor cell, Angiogenesis, Mechanosensing, Calcium-sensing receptor

Caballero, D., Martinez, E., Bausells, J., Errachid, A., Samitier, J., (2012). Impedimetric immunosensor for human serum albumin detection on a direct aldehyde-functionalized silicon nitride surface Analytica Chimica Acta 720, 43-48

In this work we report the fabrication and characterization of a label-free impedimetric immunosensor based on a silicon nitride (Si 3N 4) surface for the specific detection of human serum albumin (HSA) proteins. Silicon nitride provides several advantages compared with other materials commonly used, such as gold, and in particular in solid-state physics for electronic-based biosensors. However, few Si 3N 4-based biosensors have been developed; the lack of an efficient and direct protocol for the integration of biological elements with silicon-based substrates is still one of its the main drawbacks. Here, we use a direct functionalization method for the direct covalent binding of monoclonal anti-HSA antibodies on an aldehyde-functionalized Si-p/SiO 2/Si 3N 4 structure. This methodology, in contrast with most of the protocols reported in literature, requires less chemical reagents, it is less time-consuming and it does not need any chemical activation. The detection capability of the immunosensor was tested by performing non-faradaic electrochemical impedance spectroscopy (EIS) measurements for the specific detection of HSA proteins. Protein concentrations within the linear range of 10 -13-10 -7M were detected, showing a sensitivity of 0.128ΩμM -1 and a limit of detection of 10 -14M. The specificity of the sensor was also addressed by studying the interferences with a similar protein, bovine serum albumin. The results obtained show that the antibodies were efficiently immobilized and the proteins detected specifically, thus, establishing the basis and the potential applicability of the developed silicon nitride-based immunosensor for the detection of proteins in real and more complex samples.

Keywords: Aldehyde, Electrochemical impedance spectroscopy, Human serum albumin, Immunosensor, Silicon nitride, Bovine serum albumins, Chemical reagents, Complex samples, Covalent binding, Detection capability, Electrochemical impedance, Electrochemical impedance spectroscopy measurements, Functionalizations, Human serum albumins, Impedimetric immunosensors, Label free, Limit of detection, Linear range, Protein concentrations, Silicon-based, Specific detection, Aldehydes

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2012). AFM-based force-clamp monitors lipid bilayer failure kinetics Langmuir 28, (15), 6403-6410

The lipid bilayer rupture phenomenon is here explored by means of atomic force microscopy (AFM)-based force clamp, for the first time to our knowledge, to evaluate how lipid membranes respond when compressed under an external constant force, in the range of nanonewtons. Using this method, we were able to directly quantify the kinetics of the membrane rupture event and the associated energy barriers, for both single supported bilayers and multibilayers, in contradistinction to the classic studies performed at constant velocity. Moreover, the affected area of the membrane during the rupture process was calculated using an elastic deformation model. The elucidated information not only contributes to a better understanding of such relevant process, but also proves the suitability of AFM-based force clamp to study model structures as lipid bilayers. These findings on the kinetics of lipid bilayers rupture could be extended and applied to the study of other molecular thin films. Furthermore, systems of higher complexity such as models mimicking cell membranes could be studied by means of AFM-based force-clamp technique.

Keywords: Chain-Length, Spectroscopy, Nanomechanics, Microscopy, Elasticity, Stability, Membranes, Reveals, Fusion, Ions

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2012). Influence of cholesterol on the phase transition of lipid bilayers: A temperature-controlled force spectroscopy study Langmuir 28, (35), 12851-12860

Cholesterol (Chol) plays the essential function of regulating the physical properties of the cell membrane by controlling the lipid organization and phase behavior and, thus, managing the membrane fluidity and its mechanical strength. Here, we explore the model system DPPC:Chol by means of temperature-controlled atomic force microscopy (AFM) imaging and AFM-based force spectroscopy (AFM-FS) to assess the influence of Chol on the membrane ordering and stability. We analyze the system in a representative range of compositions up to 50 mol % Chol studying the phase evolution upon temperature increase (from room temperature to temperatures high above the T m of the DPPC bilayer) and the corresponding (nano)mechanical stability. By this means, we correlate the mechanical behavior and composition with the lateral order of each phase present in the bilayers. We prove that low Chol contents lead to a phase-segregated system, whereas high contents of Chol can give a homogeneous bilayer. In both cases, Chol enhances the mechanical stability of the membrane, and an extraordinarily stable system is observed for equimolar fractions (50 mol % Chol). In addition, even when no thermal transition is detected by the traditional bulk analysis techniques for liposomes with high Chol content (40 and 50 mol %), we demonstrate that temperature-controlled AFM-FS is capable of identifying a thermal transition for the supported lipid bilayers. Finally, our results validate the AFM-FS technique as an ideal platform to differentiate phase coexistence and transitions in lipid bilayers and bridge the gap between the results obtained by traditional methods for bulk analysis, the theoretical predictions, and the behavior of these systems at the nanoscale.

Comelles, J., Hortigüela, V., Samitier, J., Martinez, E., (2012). Versatile gradients of covalently bound proteins on microstructured substrates Langmuir 28, (38), 13688-13697

In this work, we propose an easy method to produce highly tunable gradients of covalently bound proteins on topographically modified poly(methyl methacrylate). We used a rnicrofluidic approach to obtain linear gradients with high slope (0.5, relevant at the single-cell level. These protein gradients were characterized using fluorescence microscopy and surface plasmon resonance. Both experimental results and theoretical modeling on the protein gradients generated have proved them to be highly reproducible, stable up to 7 days, and easily tunable. This method enables formation of versatile cell culture platforms combining both complex biochemical and physical cues in an attempt to approach in vitro cell culture methods to in vivo cellular microenvironments.

Keywords: Cell-migration, Microfluidic channel, Surface, Streptavidin, Molecules, Topography, Mechanisms, Generation, Responses, Guidance

Olivares, O. , Lacroix, D., (2012). Simulation of cell seeding within a three-dimensional porous scaffold: A fluid-particle analysis Tissue Engineering Part C: Methods 18, (8), 624-631

Cell seeding is a critical step in tissue engineering. A high number of cells evenly distributed in scaffolds after seeding are associated with a more functional tissue culture. Furthermore, high cell densities have shown the possibility to reduce culture time or increase the formation of tissue. Experimentally, it is difficult to predict the cell-seeding process. In this study, a new methodology to simulate the cell-seeding process under perfusion conditions is proposed. The cells are treated as spherical particles dragged by the fluid media, where the physical parameters are computed through a Lagrangian formulation. The methodology proposed enables to define the kinetics of cell seeding continuously over time. An exponential relationship was found to optimize the seeding time and the number of cells seeded in the scaffold. The cell distribution and cell efficiency predicted using this methodology were similar to the experimental results of Melchels et al. One of the main advantages of this method is to be able to determine the three-dimensional position of all the seeded cells and to, therefore, better know the initial conditions for further cell proliferation and differentiation studies. This study opens up the field of numerical predictions related to the interactions between biomaterials, cells, and dynamics media.

Sánchez-Danés, A., Consiglio, A., Richaud, Y., Rodríguez-Pizà , I., Dehay, B., Edel, M., Bové, J., Memo, M., Vila, M., Raya, A., Izpisua Belmonte, J. C., (2012). Efficient generation of A9 midbrain dopaminergic neurons by lentiviral delivery of LMX1A in human embryonic stem cells and induced pluripotent stem cells Human Gene Therapy 23, (1), 56-69

Human embryonic stem cells (hESC) and induced pluripotent stem cells (iPSC) offer great hope for in vitro modeling of Parkinson’s disease (PD), as well as for designing cell-replacement therapies. To realize these opportunities, there is an urgent need to develop efficient protocols for the directed differentiation of hESC/iPSC into dopamine (DA) neurons with the specific characteristics of the cell population lost to PD, i.e., A9-subtype ventral midbrain DA neurons. Here we use lentiviral vectors to drive the expression of LMX1A, which encodes a transcription factor critical for ventral midbrain identity, specifically in neural progenitor cells. We show that clonal lines of hESC engineered to contain one or two copies of this lentiviral vector retain long-term selfrenewing ability and pluripotent differentiation capacity. Greater than 60% of all neurons generated from LMX1A-engineered hESC were ventral midbrain DA neurons of the A9 subtype, compared with *10% in green fluorescent protein–engineered controls, as judged by specific marker expression and functional analyses. Moreover, DA neuron precursors differentiated from LMX1A-engineered hESC were able to survive and differentiate when grafted into the brain of adult mice. Finally, we provide evidence that LMX1A overexpression similarly increases the yield of DA neuron differentiation from human iPSC. Taken together, our data show that stable genetic engineering of hESC/iPSC with lentiviral vectors driving controlled expression of LMX1A is an efficient way to generate enriched populations of human A9-subtype ventral midbrain DA neurons, which should prove useful for modeling PD and may be helpful for designing future cell-replacement strategies.

Campas, Monica, Garibo, Diana, Prieto-Simon, Beatriz, (2012). Novel nanobiotechnological concepts in electrochemical biosensors for the analysis of toxins Analyst 137, (5), 1055-1067

This article gives an overview of the biosensors for the analysis of mycotoxins, marine toxins and cyanobacterial toxins, describing in depth the electrochemical biosensors that incorporate nanobiotechnological concepts. Firstly, it presents tailor-designed biomolecules, such as recombinant enzymes, recombinant antibody fragments and aptamers as novel biorecognition elements in biosensors. It also reviews the use of metallic nanoparticles (NPs) and carbon nanotubes (CNTs) aiming at improving the electrochemical transduction strategies. Finally, the exploitation of magnetic particles (MPs) as immobilisation carriers in flow-systems and the development of arrays are also described. The incorporation of these nanobiotechnological concepts provides with electrochemical biosensors with superior analytical performance in terms of specificity, sensitivity, stability and analysis time.

Cantini, M., Rico, P., Moratal, D., Salmerón-Sánchez, M., (2012). Controlled wettability, same chemistry: Biological activity of plasma-polymerized coatings Soft Matter 8, (20), 5575-5584

Plasma polymerization was used to produce novel nanometric coatings able to direct fibronectin adsorption and cell response. Using ethyl acrylate as a monomer, we obtain coatings whose chemical composition maintains some of the characteristic functionalities of the photo-initiated polymer, while the water contact angle increases monotonically with the duration of the plasma discharge. Enhanced surface mobility of the polymer chains due to a decrease of the thickness of the coating justifies this increase in wettability at lower treatment times. The coatings with higher surface mobility are shown to promote a more active conformation of the adsorbed protein, as proved by binding of the monoclonal antibodies HFN7.1 and mAb1937. Culture of MC3T3-E1 osteoblast-like cells onto the fibronectin-coated substrates further proves that the more mobile surfaces support better initial cell adhesion, even at low fibronectin surface density, as well as stronger cell-mediated fibronectin reorganization.

Calò, A., Sanmartí-Espinal, M., Iavicoli, P., Persuy, M. A., Pajot-Augy, E., Gomila, G., Samitier, J., (2012). Diffusion-controlled deposition of natural nanovesicles containing G-protein coupled receptors for biosensing platforms Soft Matter 8, (46), 11632-11643

Natural vesicles produced from genetically engineered cells with tailored membrane receptor composition are promising building blocks for sensing biodevices. This is particularly true for the case of G-protein coupled receptors (GPCRs) present in many sensing processes in cells, whose functionality crucially depends on their lipid environment. However, the controlled production of natural vesicles containing GPCRs and their reproducible deposition on biosensor surfaces are among the outstanding challenges in the road map to realize practical biomolecular devices based on GPCRs. In this work we present the production and characterization of membrane nanovesicles from Saccharomyces cerevisiae containing heterologously expressed olfactory receptors - a member of the family of GPCRs - and study their deposition onto substrates used as biosensor supports. We show by direct observation with Atomic Force Microscopy that nanovesicles deposit and flatten without rupturing on glass substrates following approximately a diffusive law. We show that surface coverages larger than 20-25% of the substrate can be reproducibly achieved under practical nanovesicle concentrations and reasonable time scales, while keeping to the minimum the presence of background residuals coming from the nanovesicles production process. Surface chemistry modification of gold substrates indicates a higher affinity of natural nanovesicles for acid modified surfaces as compared to amino or alcohol modified surfaces. Present results constitute an important step in the practical realization of biosensor devices based on natural nanovesicles integrating G-protein coupled membrane receptors.

Valle-Delgado, J. J., Liepina, I., Lapidus, D., Sabaté, R., Ventura, S., Samitier, J., Fernàndez-Busquets, X., (2012). Self-assembly of human amylin-derived peptides studied by atomic force microscopy and single molecule force spectroscopy Soft Matter 8, (4), 1234-1242

The self-assembly of peptides and proteins into amyloid fibrils of nanometric thickness and up to several micrometres in length, a phenomenon widely observed in biological systems, has recently aroused a growing interest in nanotechnology and nanomedicine. Here we have applied atomic force microscopy and single molecule force spectroscopy to study the amyloidogenesis of a peptide derived from human amylin and of its reverse sequence. The spontaneous formation of protofibrils and their orientation along well-defined directions on graphite and DMSO-coated graphite substrates make the studied peptides interesting candidates for nanotechnological applications. The measured binding forces between peptides correlate with the number of hydrogen bonds between individual peptides inside the fibril structure according to molecular dynamics simulations.

Keywords: Amyloid fibril, Amyloidogenesis, Binding forces, Fibril structure, Graphite substrate, Molecular dynamics simulations, Nanometrics, Protofibrils, Single molecule force spectroscopy, Spontaneous formation, Atomic force microscopy, Atomic spectroscopy, Graphite, Hydrogen bonds, Medical nanotechnology, Molecular dynamics, Molecular physics, Self assembly, Thickness measurement, Peptides

Villar-Pique, A., De Groot, N. S., Sabaté, R., Acebrón, S. P., Celaya, G., Fernàndez-Busquets, X., Muga, A., Ventura, S., (2012). The effect of amyloidogenic peptides on bacterial aging correlates with their intrinsic aggregation propensity Journal of Molecular Biology 421, (2-3), 270-281

The formation of aggregates by misfolded proteins is thought to be inherently toxic, affecting cell fitness. This observation has led to the suggestion that selection against protein aggregation might be a major constraint on protein evolution. The precise fitness cost associated with protein aggregation has been traditionally difficult to evaluate. Moreover, it is not known if the detrimental effect of aggregates on cell physiology is generic or depends on the specific structural features of the protein deposit. In bacteria, the accumulation of intracellular protein aggregates reduces cell reproductive ability, promoting cellular aging. Here, we exploit the cell division defects promoted by the intracellular aggregation of Alzheimer's-disease-related amyloid β peptide in bacteria to demonstrate that the fitness cost associated with protein misfolding and aggregation is connected to the protein sequence, which controls both the in vivo aggregation rates and the conformational properties of the aggregates. We also show that the deleterious impact of protein aggregation on bacterial division can be buffered by molecular chaperones, likely broadening the sequential space on which natural selection can act. Overall, the results in the present work have potential implications for the evolution of proteins and provide a robust system to experimentally model and quantify the impact of protein aggregation on cell fitness.

Keywords: Amyloid fibrils, Chaperones, Escherichia coli, Inclusion bodies, Protein aggregation

Urban, P., Valle-Delgado, J. J., Moles, E., Marques, J., Diez, C., Fernàndez-Busquets, X., (2012). Nanotools for the delivery of antimicrobial peptides Current Drug Targets 13, (9), 1158-1172

Antimicrobial peptide drugs are increasingly attractive therapeutic agents as their roles in physiopathological processes are being unraveled and because the development of recombinant DNA technology has made them economically affordable in large amounts and high purity. However, due to lack of specificity regarding the target cells, difficulty in attaining them, or reduced half-lives, most current administration methods require high doses. On the other hand, reduced specificity of toxic drugs demands low concentrations to minimize undesirable side-effects, thus incurring the risk of having sublethal amounts which favour the appearance of resistant microbial strains. In this scenario, targeted delivery can fulfill the objective of achieving the intake of total quantities sufficiently low to be innocuous for the patient but that locally are high enough to be lethal for the infectious agent. One of the major advances in recent years has been the size reduction of drug carriers that have dimensions in the nanometer scale and thus are much smaller than -and capable of being internalized by- many types of cells. Among the different types of potential antimicrobial peptide-encapsulating structures reviewed here are liposomes, dendritic polymers, solid core nanoparticles, carbon nanotubes, and DNA cages. These nanoparticulate systems can be functionalized with a plethora of biomolecules providing specificity of binding to particular cell types or locations; as examples of these targeting elements we will present antibodies, DNA aptamers, cell-penetrating peptides, and carbohydrates. Multifunctional Trojan horse-like nanovessels can be engineered by choosing the adequate peptide content, encapsulating structure, and targeting moiety for each particular application.

Keywords: Antibodies, Aptamers, Dendrimers, Liposomes, Nanomedicine, Nanoparticles, Nanovectors, Targeting

Gramse, G., Gomila, G., Fumagalli, L., (2012). Quantifying the dielectric constant of thick insulators by electrostatic force microscopy: effects of the microscopic parts of the probe Nanotechnology 23, (20), 205703

We present a systematic analysis of the effects that the microscopic parts of electrostatic force microscopy probes (the cone and cantilever) have on the electrostatic interaction between the tip apex and thick insulating substrates (thickness>100mum). We discuss how these effects can influence the measurement and quantification of the local dielectric constant of the substrates. We propose and experimentally validate a general methodology that takes into account the influence of the cone and the cantilever, thus enabling us to obtain very accurate values of the dielectric constants of thick insulators.

Keywords: Polarization, Samples

Armendáriz, Beatriz G., Bribian, Ana, Pérez-Martínez, Esther, Martínez, Albert, de Castro, Fernando, Soriano, Eduardo, Burgaya, Ferran, (2012). Expression of Semaphorin 4F in neurons and brain oligodendrocytes and the regulation of oligodendrocyte precursor migration in the optic nerve Molecular and Cellular Neuroscience 49, (1), 54-67

Semaphorins are secreted or membrane-anchored proteins that play critical roles in neural development and adult brain plasticity. Sema4F is a transmembrane semaphorin found on glutamatergic synapses, in which it is attached to the PSD-95-scaffolding protein. Here we further examined the expression of Sema4F by raising specific antibodies. We show that Sema4F protein is widely expressed by neurons during neural development and in the adult brain. We also demonstrate a preferential localization of this protein in postsynaptic dendrites. Moreover, Sema4F is expressed not only by neurons but also by oligodendrocyte precursors in the optic nerve and along the migratory pathways of oligodendroglial cells, and also by subsets of postnatal oligodendroglial cells in the brain. Finally, in vitro experiments demonstrate that endogenous Sema4F expressed by brain cells of oligodendroglial lineage regulates the outgrowth migration of oligodendrocyte precursors and promotes their differentiation. The present data extend our knowledge about the expression of Sema4F and uncover a novel function in the control of oligodendrocyte precursor migration in the developing brain.

Keywords: Semaphorin, Oligodendrocyte, Guidance, Optic nerve, Brain

Gramse, G., Edwards, M. A., Fumagalli, L., Gomila, G., (2012). Dynamic electrostatic force microscopy in liquid media Applied Physics Letters 101, (21), 213108

We present the implementation of dynamic electrostatic force microscopy in liquid media. This implementation enables the quantitative imaging of local dielectric properties of materials in electrolyte solutions with nanoscale spatial resolution. Local imaging capabilities are obtained by probing the frequency-dependent and ionic concentration-dependent electrostatic forces at high frequency (>1 MHz), while quantification of the interaction forces is obtained with finite-element numerical calculations. The results presented open a wide range of possibilities in a number of fields where the dielectric properties of materials need to be probed at the nanoscale and in a liquid environment.

Baccar, Z.M., Caballero, D., Eritja, R., Errachid, A., (2012). Development of an impedimetric DNA-biosensor based on layered double hydroxide for the detection of long ssDNA sequences Electrochimica Acta 74, 123-129

DNA testing requires the development of sensitive and fast devices to measure the presence of nucleic acid sequences by DNA hybridization. In this paper, a simple and label-free DNA-biosensor has been investigated based on the detection of DNA hybridization on layered double hydroxide (LDH) nanomaterials with special emphasis on targeting long single stranded DNA sequences. First, the immobilization of a 20 bases long DNA probe on a thin layer of Mg2AlCO3 and Mg3AlCO3 LDH was studied. Then, DNA hybridization reaction was detected by means of Electrochemical Impedance Spectroscopy. The resulting biosensor showed a high sensitivity for the detection of 80 bases long DNA complementary sequences. The dynamic range was 18–270 ng/ml with a detection limit lower than 1.8 ng/ml.

Keywords: DNA-biosensor, Nanomaterials, Layered double hydroxide, Self-assembly

Levato, Riccardo, Mateos-Timoneda, Miguel A., Planell, Josep A., (2012). Preparation of biodegradable polylactide microparticles via a biocompatible procedure Macromolecular Bioscience 12, (4), 557-566

PLA MPs are prepared via a novel and toxic-chemical-free fabrication route using ethyl lactate, a green solvent and FDA-approved aroma. MPs are obtained by a solution jet break-up and solvent displacement method. Adjusting flow parameters allows the tuning of MPs size between 60 and 180 µm, with reduced polydispersity. Morphological analysis shows microporous particles with Janus-like surface. A fluorophore is successfully loaded into the MPs during their formation step. This versatile green solvent-based procedure is proven to be suitable for drug encapsulation and delivery applications. The method may be extended to different droplet generation techniques.

Keywords: Biocompatibility, Biodegradable, Green solvents, Microparticles, Poly(lactic acid)

Cendra, M. d M., Juárez, A., Torrents, E., (2012). Biofilm modifies expression of ribonucleotide reductase genes in Escherichia coli PLoS ONE 7, (9), e46350

Ribonucleotide reductase (RNR) is an essential enzyme for all living organisms since is the responsible for the last step in the synthesis of the four deoxyribonucleotides (dNTPs) necessary for DNA replication and repair. In this work, we have investigated the expression of the three-RNR classes (Ia, Ib and III) during Escherichia coli biofilm formation. We show the temporal and spatial importance of class Ib and III RNRs during this process in two different E. coli wild-type strains, the commensal MG1655 and the enteropathogenic and virulent E2348/69, the prototype for the enteropathogenic E. coli (EPEC). We have established that class Ib RNR, so far considered cryptic, play and important role during biofilm formation. The implication of this RNR class under the specific growth conditions of biofilm formation is discussed.

Conte, Vito, Ulrich, Florian, Baum, Buzz, Muñoz, Jose, Veldhuis, Jim, Brodland, Wayne, Miodownik, Mark, (2012). A biomechanical analysis of ventral furrow formation in the Drosophila Melanogaster Embryo PLoS ONE Public Library of Science 7, (4), e34473

The article provides a biomechanical analysis of ventral furrow formation in the Drosophila melanogaster embryo. Ventral furrow formation is the first large-scale morphogenetic movement in the fly embryo. It involves deformation of a uniform cellular monolayer formed following cellularisation, and has therefore long been used as a simple system in which to explore the role of mechanics in force generation. Here we use a quantitative framework to carry out a systematic perturbation analysis to determine the role of each of the active forces observed. The analysis confirms that ventral furrow invagination arises from a combination of apical constriction and apical–basal shortening forces in the mesoderm, together with a combination of ectodermal forces. We show that the mesodermal forces are crucial for invagination: the loss of apical constriction leads to a loss of the furrow, while the mesodermal radial shortening forces are the primary cause of the internalisation of the future mesoderm as the furrow rises. Ectodermal forces play a minor but significant role in furrow formation: without ectodermal forces the furrow is slower to form, does not close properly and has an aberrant morphology. Nevertheless, despite changes in the active mesodermal and ectodermal forces lead to changes in the timing and extent of furrow, invagination is eventually achieved in most cases, implying that the system is robust to perturbation and therefore over-determined.

Acerbi, I., Luque, T., Giménez, A., Puig, M., Reguart, N., Farré, R., Navajas, D., Alcaraz, J., (2012). Integrin-specific mechanoresponses to compression and extension probed by cylindrical flat-ended afm tips in lung cells PLoS ONE 7, (2), e32261

Cells from lung and other tissues are subjected to forces of opposing directions that are largely transmitted through integrin-mediated adhesions. How cells respond to force bidirectionality remains ill defined. To address this question, we nanofabricated flat-ended cylindrical Atomic Force Microscopy (AFM) tips with ~1 μm 2 cross-section area. Tips were uncoated or coated with either integrin-specific (RGD) or non-specific (RGE/BSA) molecules, brought into contact with lung epithelial cells or fibroblasts for 30 s to form focal adhesion precursors, and used to probe cell resistance to deformation in compression and extension. We found that cell resistance to compression was globally higher than to extension regardless of the tip coating. In contrast, both tip-cell adhesion strength and resistance to compression and extension were the highest when probed at integrin-specific adhesions. These integrin-specific mechanoresponses required an intact actin cytoskeleton, and were dependent on tyrosine phosphatases and Ca 2+ signaling. Cell asymmetric mechanoresponse to compression and extension remained after 5 minutes of tip-cell adhesion, revealing that asymmetric resistance to force directionality is an intrinsic property of lung cells, as in most soft tissues. Our findings provide new insights on how lung cells probe the mechanochemical properties of the microenvironment, an important process for migration, repair and tissue homeostasis.

Keywords: Arginylglycylaspartic acid, Arginylglycylglutamic acid, Bovine serum albumin, Calcium ion, Integrin, Protein tyrosine phosphatase, Unclassified drug

Fonollosa, Jordi, Gutierrez-Galvez, Agustin, Marco, Santiago, (2012). Quality coding by neural populations in the early olfactory pathway: Analysis using information theory and lessons for artificial olfactory systems PLoS ONE 7, (6), e37809

In this article, we analyze the ability of the early olfactory system to detect and discriminate different odors by means of information theory measurements applied to olfactory bulb activity images. We have studied the role that the diversity and number of receptor neuron types play in encoding chemical information. Our results show that the olfactory receptors of the biological system are low correlated and present good coverage of the input space. The coding capacity of ensembles of olfactory receptors with the same receptive range is maximized when the receptors cover half of the odor input space - a configuration that corresponds to receptors that are not particularly selective. However, the ensemble’s performance slightly increases when mixing uncorrelated receptors of different receptive ranges. Our results confirm that the low correlation between sensors could be more significant than the sensor selectivity for general purpose chemo-sensory systems, whether these are biological or biomimetic.

Bribián, Ana, Fontana, Xavier, Llorens, Franc, Gavín, Rosalina, Reina, Manuel, García-Verdugo, José Manuel, Torres, Juan María, de Castro, Fernando, Del Río, J.A., (2012). Role of the cellular prion protein in oligodendrocyte precursor cell proliferation and differentiation in the developing and adult mouse CNS PLoS ONE 7, (4), e33872

There are numerous studies describing the signaling mechanisms that mediate oligodendrocyte precursor cell (OPC) proliferation and differentiation, although the contribution of the cellular prion protein (PrPc) to this process remains unclear. PrPc is a glycosyl-phosphatidylinositol (GPI)-anchored glycoprotein involved in diverse cellular processes during the development and maturation of the mammalian central nervous system (CNS). Here we describe how PrPc influences oligodendrocyte proliferation in the developing and adult CNS. OPCs that lack PrPc proliferate more vigorously at the expense of a delay in differentiation, which correlates with changes in the expression of oligodendrocyte lineage markers. In addition, numerous NG2-positive cells were observed in cortical regions of adult PrPc knockout mice, although no significant changes in myelination can be seen, probably due to the death of surplus cells.

Redondo-Morata, Lorena, Oncins, Gerard, Sanz, Fausto, (2012). Force spectroscopy reveals the effect of different ions in the nanomechanical behavior of phospholipid model membranes: The case of potassium cation Biophysical Journal 102, (1), 66-74

How do metal cations affect the stability and structure of phospholipid bilayers? What role does ion binding play in the insertion of proteins and the overall mechanical stability of biological membranes? Investigators have used different theoretical and microscopic approaches to study the mechanical properties of lipid bilayers. Although they are crucial for such studies, molecular-dynamics simulations cannot yet span the complexity of biological membranes. In addition, there are still some experimental difficulties when it comes to testing the ion binding to lipid bilayers in an accurate way. Hence, there is a need to establish a new approach from the perspective of the nanometric scale, where most of the specific molecular phenomena take place. Atomic force microscopy has become an essential tool for examining the structure and behavior of lipid bilayers. In this work, we used force spectroscopy to quantitatively characterize nanomechanical resistance as a function of the electrolyte composition by means of a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve. By systematically probing a set of bilayers of different composition immersed in electrolytes composed of a variety of monovalent and divalent metal cations, we were able to obtain a wealth of information showing that each ion makes an independent and important contribution to the gross mechanical resistance and its plastic properties. This work addresses the need to assess the effects of different ions on the structure of phospholipid membranes, and opens new avenues for characterizing the (nano)mechanical stability of membranes.

Keywords: Molecular-dynamics simulation, Liquid expanded monolayers, Lipid-bilayers, Hofmeister series, Monovalent salt, Phosphatidylcholine, Microscopy, Binding, Surfaces, NaCl

Navarro, M., Pu, F., Hunt, J. A., (2012). The significance of the host inflammatory response on the therapeutic efficacy of cell therapies utilising human adult stem cells Experimental Cell Research 318, (4), 361-370

Controlling the fate of implanted hMSCs is one of the major drawbacks to be overcome to realize tissue engineering strategies. In particular, the effect of the inflammatory environment on hMSCs behaviour is poorly understood. Studying and mimicking the inflammatory process in vitro is a very complex and challenging task that involves multiple variables. This research addressed the questions using in vitro co-cultures of primary derived hMSCs together with human peripheral blood mononucleated cells (PBMCs); the latter are key agents in the inflammatory process. This work explored the in vitro phenotypic changes of hMSCs in co-culture direct contact with monocytes and lymphocytes isolated from blood using both basal and osteogenic medium. Our findings indicated that hMSCs maintained their undifferentiated phenotype and pluripotency despite the contact with PBMCs. Moreover, hMSCs demonstrated increased proliferation and were able to differentiate specifically down the osteogenic lineage pathway. Providing significant crucial evidence to support the hypothesis that inflammation and host defence mechanisms could be utilised rather than avoided and combated to provide for the successful therapeutic application of stem cell therapies.

Keywords: Co-culture, Inflammation, Mesenchymal stem cells, Monocytes, Osteoblasts

Udina, S., Carmona, M., Pardo, A., Calaza, C., Santander, J., Fonseca, L., Marco, S., (2012). A micromachined thermoelectric sensor for natural gas analysis: Multivariate calibration results Sensors and Actuators B: Chemical 166-167, 338-348

The potential use of a micromachined thermopile based sensor device for analyzing natural gas is explored. The sensor consists of a thermally isolated hotplate which is heated by the application of a sequence of programmed voltages to an integrated heater. Once the hotplate reaches a stationary temperature, the thermopile provides a signal proportional to the hotplate temperature. These signals are processed in order to determine different natural gas properties. Sensor response is mainly dependent on the thermal conductivity of the surrounding gas at different temperatures. Seven predicted properties (normal density, Superior Heating Value, Wobbe index and the concentrations of methane, ethane, carbon dioxide and nitrogen) are calibrated against sensor signals by using multivariate regression, in particular Partial Least Squares. Experimental data have been used for calibration and validation. Results show property prediction capability with reasonable accuracy except for prediction of carbon dioxide concentration. A detailed uncertainty analysis is provided to better understand the metrological limits of the system. These results imply for the first time the possibility of designing unprecedented low-cost natural gas analyzers. The concept may be extended to other constrained gas mixtures (e.g. of a known number of components) to enable low-cost multicomponent gas analyzers.

Keywords: Gas sensor, Natural gas, MEMS, Superior Heating Value, density, PLS

Kuphal, M., Mills, C.A., Korri-Youssoufi, H., Samitier, J., (2012). Polymer-based technology platform for robust electrochemical sensing using gold microelectrodes Sensors and Actuators B: Chemical 161, (1), 279-284

Rapid and inexpensive development of electrochemical sensors with good exploitation potential may be produced using a polymer as a substrate material. However, fabrication of polymer-based sensors is challenging. Using photolithography and etching of gold-coated poly(ethylene-2,6-naphthalate) (PEN), we have succeeded in fabricating disk-shaped and interdigitated microelectrodes (uEs). The electrodes have an excellent adhesion to the polymer and are encapsulated using a novel room-temperature process, applicable for low-cost, high-throughput fabrication. The PEN surface has been characterized in respect of wettability, surface energy and surface roughness. Finally, the electrodes give stable and reproducible electrochemical impedance spectroscopy and cyclic voltammetry responses, using the redox couple ferrocyanide and ruthenium hexamine. The results demonstrate the robustness and functionality of the polymer-based sensor platform with minimum feature sizes of 6 um.

Keywords: Poly(ethylene naphthalate), Photolithography, Microelectrodes, Interdigitated electrodes, Electrochemical characterization, Electrochemical sensor

Karpas, Zeev, Guamán, Ana V., Calvo, Daniel, Pardo, Antonio, Marco, Santiago, (2012). The potential of ion mobility spectrometry (IMS) for detection of 2,4,6-trichloroanisole (2,4,6-TCA) in wine Talanta 93, 200-205

The off-flavor of “tainted wine” is attributed mainly to the presence of 2,4,6-trichloroanisole (2,4,6-TCA) in the wine. In the present study the atmospheric pressure gas-phase ion chemistry, pertaining to ion mobility spectrometry, of 2,4,6-trichloroanisole was investigated. In positive ion mode the dominant species is a monomer ion with a lower intensity dimer species with reduced mobility values (K0) of 1.58 and 1.20 cm2 V−1 s−1, respectively. In negative mode the ion with K0 = 1.64 cm2 V−1 s−1 is ascribed to a trichlorophenoxide species while the ions with K0 = 1.48 and 1.13 cm2 V−1 s−1 are attributed to chloride attachment adducts of a TCA monomer and dimer, respectively. The limit of detection of the system for 2,4,6-TCA dissolved in dichloromethane deposited on a filter paper was 2.1 ug and 1.7 ppm in the gas phase. In ethanol and in wine the limit of detection is higher implying that pre-concentration and pre-separation are required before IMS can be used to monitor the level of TCA in wine.

Keywords: 2,4,6-Trichloroanisole, Gas phase ion chemistry, Ion mobility spectrometry, "Tainted wine"

Almendros, I., Montserrat, J. M., Torres, M., Bonsignore, M. R., Chimenti, L., Navajas, D., Farre, R., (2012). Obesity and intermittent hypoxia increase tumor growth in a mouse model of sleep apnea Sleep Medicine 13, (10), 1254-1260

Background: Intermittent hypoxia and obesity which are two pathological conditions commonly found in patients with obstructive sleep apnea (OSA), potentially enhance cancer progression. Objective: To investigate whether obesity and/or intermittent hypoxia (IH) mimicking OSA affect tumor growth. Methods: A subcutaneous melanoma was induced in 40 mice [22 obese (40-45 g) and 18 lean (20-25 g)] by injecting 10(6) B16F10 cells in the flank. Nineteen mice (10 obese/9 lean) were subjected to IH (6 h/day for 17 days). A group of 21 mice (12 obese/9 lean) were kept under normoxia. At day 17, tumors were excised, weighed and processed to quantify necrosis and endothelial expression of vascular endothelial growth factor (VEGF) and CD-31. VEGF in plasma was also assessed. Results: In lean animals, IH enhanced tumor growth from 0.81 +/- 0.17 to 1.95 +/- 0.32 g. In obese animals, a similar increase in tumor growth (1.94 +/- 0.18 g) was observed under normoxia, while adding IH had no further effect (1.69 +/- 0.23 g). IH only promoted an increase in tumoral necrosis in lean animals. However, obesity under normoxic conditions increased necrosis, VEGF and CD-31 expression in tumoral tissue. Plasma VEGF strongly correlated with tumor weight (rho = 0.76, p < 0.001) in the whole sample; it increased in lean IH-treated animals from 66.40 +/- 3.47 to 108.37 +/- 9.48 pg/mL, p < 0.001), while the high baseline value in obese mice (106.90 +/- 4.32 pg/mL) was unaffected by IH. Conclusions: Obesity and IH increased tumor growth, but did not appear to exert any synergistic effects. Circulating VEGF appeared as a crucial mediator of tumor growth in both situations.

Keywords: Intermittent hypoxia, Obesity, Cancer, Sleep apnea, Animal model

Rosa Hernández, M., Urbán, P., Casals, E., Estelrich, J., Escolar, G., Galán, A. M., (2012). Liposomes bearing fibrinogen could potentially interfere with platelet interaction and procoagulant activity International Journal of Nanomedicine 7, 2339-2347

Background: The contribution of fibrinogen (FBN) to hemostasis acting on platelet aggregation and clot formation is well established. It has been suggested that FBN-coated liposomes could be useful in restoring hemostasis. In the present study, we evaluated the modifications induced by multilamellar raw liposomes (MLV) or fibrinogen-coated liposomes (MLV-FBN) on hemostatic parameters. Materials and methods: Different experimental settings using whole blood or thrombocytopenic blood were used. Thromboelastometry, aggregation studies, platelet function analyzer (PFA-100®) tests and studies under flow conditions were applied to detect the effect of MLVFBN on hemostatic parameters. Results: The presence of MLV-FBN in whole blood modified its viscoelastic properties, prolonging clot formation time (CFT) (226.5 ± 26.1 mm versus 124.1 ± 9.4 mm; P, 0.01) but reducing clot firmness (45.4 ± 1.8 mm versus 35.5 ± 2.3 mm; P, 0.05). Under thrombocytopenic conditions, FIBTEM analysis revealed that MLV-FBN shortened clotting time (CT) compared to MLV (153.3 ± 2.8 s versus 128.0 ± 4.6 s; P, 0.05). Addition of either liposome decreased fibrin formation on the subendothelium (MLV 8.1% ± 4.7% and MLV-FBN 0.8% ± 0.5% versus control 36.4% ± 6.7%; P, 0.01), whereas only MLV-FBN significantly reduced fibrin deposition in thrombocytopenic blood (14.4% ± 6.3% versus control 34.5% ± 5.2%; P, 0.05). MLV-FBN inhibited aggregation induced by arachidonic acid (52.1% ± 8.1% versus 88.0% ± 2.1% in control; P, 0.01) and ristocetin (40.3% ± 8.8% versus 94.3% ± 1.1%; P, 0.005), but it did not modify closure times in PFA-100® studies. In perfusion experiments using whole blood, MLV and MLV-FBN decreased the covered surface (13.25% ± 2.4% and 9.85% ± 2.41%, respectively, versus control 22.0% ± 2.0%; P, 0.01) and the percentage of large aggregates (8.4% ± 2.3% and 3.3% ± 1.01%, respectively, versus control 14.6% ± 1.8%; P, 0.01). Conclusion: Our results reveal that, in addition to the main contribution of fibrinogen to hemostasis, MLV-FBN inhibits platelet-mediated hemostasis and coagulation mechanisms.

Keywords: Fibrin, Fibrinogen, Hemostasis, Liposomes, Procoagulant activity, Thrombocytopenia

Falasconi, Matteo, Gutierrez-Galvez, Agustin, Leon, Michael, Johnson, Brett A., Marco, Santiago, (2012). Cluster analysis of rat olfactory bulb responses to diverse odorants Chemical Senses 37, (7), 639-653

In an effort to deepen our understanding of mammalian olfactory coding, we have used an objective method to analyze a large set of odorant-evoked activity maps collected systematically across the rat olfactory bulb to determine whether such an approach could identify specific glomerular regions that are activated by related odorants. To that end, we combined fuzzy c-means clustering methods with a novel validity approach based on cluster stability to evaluate the significance of the fuzzy partitions on a data set of glomerular layer responses to a large diverse group of odorants. Our results confirm the existence of glomerular response clusters to similar odorants. They further indicate a partial hierarchical chemotopic organization wherein larger glomerular regions can be subdivided into smaller areas that are rather specific in their responses to particular functional groups of odorants. These clusters bear many similarities to, as well as some differences from, response domains previously proposed for the glomerular layer of the bulb. These data also provide additional support for the concept of an identity code in the mammalian olfactory system.

Juanola-Feliu, E., Colomer-Farrarons, J., Miribel-Català , P., Samitier, J., Valls-Pasola, J., (2012). Market challenges facing academic research in commercializing nano-enabled implantable devices for in-vivo biomedical analysis Technovation 32, (3-4), 193-204

This article reports on the research and development of a cutting-edge biomedical device for continuous in-vivo glucose monitoring. This entirely public-funded process of technological innovation has been conducted at the University of Barcelona within a context of converging technologies involving the fields of medicine, physics, chemistry, biology, telecommunications, electronics and energy. The authors examine the value chain and the market challenges faced by in-vivo implantable biomedical devices based on nanotechnologies. In so doing, they trace the process from the point of applied research to the final integration and commercialization of the product, when the social rate of return from academic research can be estimated. Using a case-study approach, the paper also examines the high-tech activities involved in the development of this nano-enabled device and describes the technology and innovation management process within the value chain conducted in a University-Hospital-Industry-Administration-Citizens framework. Here, nanotechnology is seen to represent a new industrial revolution, boosting the biomedical devices market. Nanosensors may well provide the tools required for investigating biological processes at the cellular level in vivo when embedded into medical devices of small dimensions, using biocompatible materials, and requiring reliable and targeted biosensors, high speed data transfer, safely stored data, and even energy autonomy.

Keywords: Biomedical device, Diabetes, Innovation management, Nanobiosensor, Nanotechnology, Research commercialization, Technology transfer, Academic research, Applied research, Barcelona, Biocompatible materials, Biological process, Biomedical analysis, Biomedical devices, Cellular levels, Converging technologies, Glucose monitoring, High-speed data transfer, Implantable biomedical devices, Implantable devices, In-vivo, Industrial revolutions, Innovation management, Medical Devices, Nanobiosensor, Rate of return, Research and development, Technological innovation, Value chains, Biological materials, Biomedical engineering, Biosensors, Commerce, Data transfer, Earnings, Engineering education, Glucose, Implants (surgical), Industrial research, Innovation, Medical problems, Nanosensors, Nanotechnology, Technology transfer, Equipment

Hoyo, J., Torrent-Burgués, J., Guaus, E., (2012). Biomimetic monolayer films of monogalactosyldiacylglycerol incorporating ubiquinone Journal of Colloid and Interface Science 384, (1), 189-197

Ubiquinone and plastoquinone are two of the main electron and proton shuttle molecules in biological systems, and monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in the thylakoid membrane of chloroplasts. Saturated MGDG, ubiquinone-10 (UQ) and MGDG:UQ mixed monolayers at the air/water interface have been studied using surface pressure-area isotherms and Brewster Angle Microscopy. Moreover, the transferred Langmuir-Blodgett films have been observed by Atomic Force Microscopy. The results show that MGDG:UQ mixtures present more fluid phase than pure MGDG, indicating a higher order degree for the later. It is also observed an important influence of UQ on the MGDG matrix before UQ collapse pressure and a low influence after this event, due to UQ expulsion from the MGDG matrix. This expulsion leads to a similar remaining UQ content for all the tested mixtures, indicating a limiting content of this molecule in the MGDG matrix at high surface pressures. The thermodynamic studies confirm the stability of the MGDG:UQ mixtures at low surface pressures, although presenting a non-ideal behaviour. Results point to consider UQ as a good candidate for studies of artificial photosynthesis.

Keywords: AFM, BAM, Biomimetic films, Langmuir-Blodgett film, Monogalactosyldiacylglycerol, Ubiquinone

Guamán, Ana V., Carreras, Alba, Calvo, Daniel, Agudo, Idoya, Navajas, Daniel, Pardo, Antonio, Marco, Santiago, Farré, Ramon, (2012). Rapid detection of sepsis in rats through volatile organic compounds in breath Journal of Chromatography B 881-882, 76-82

Background: Sepsis is one of the main causes of death in adult intensive care units. The major drawbacks of the different methods used for its diagnosis and monitoring are their inability to provide fast responses and unsuitability for bedside use. In this study, performed using a rat sepsis model, we evaluate breath analysis with Ion Mobility Spectrometry (IMS) as a fast, portable and non-invasive strategy. Methods: This study was carried out on 20 Sprague-Dawley rats. Ten rats were injected with lipopolysaccharide from Escherichia coli and ten rats were IP injected with regular saline. After a 24-h period, the rats were anaesthetized and their exhaled breaths were collected and measured with IMS and SPME-gas chromatography/mass spectrometry (SPME-GC/MS) and the data were analyzed with multivariate data processing techniques. Results: The SPME-GC/MS dataset processing showed 92% accuracy in the discrimination between the two groups, with a confidence interval of between 90.9% and 92.9%. Percentages for sensitivity and specificity were 98% (97.5–98.5%) and 85% (84.6–87.6%), respectively. The IMS database processing generated an accuracy of 99.8% (99.7–99.9%), a specificity of 99.6% (99.5–99.7%) and a sensitivity of 99.9% (99.8–100%). Conclusions: IMS involving fast analysis times, minimum sample handling and portable instrumentation can be an alternative for continuous bedside monitoring. IMS spectra require data processing with proper statistical models for the technique to be used as an alternative to other methods. These animal model results suggest that exhaled breath can be used as a point-of-care tool for the diagnosis and monitoring of sepsis.

Keywords: Sepsis, Volatile organic compounds, Ion mobility spectrometer, Rat model, Bedside patient systems, Non-invasive detection

Gustavsson, J., Ginebra, M. P., Planell, J., Engel, E., (2012). Osteoblast-like cellular response to dynamic changes in the ionic extracellular environment produced by calcium-deficient hydroxyapatite Journal of Materials Science-Materials in Medicine 23, (10), 2509-2520

Solution-mediated reactions due to ionic substitutions are increasingly explored as a strategy to improve the biological performance of calcium phosphate-based materials. Yet, cellular response to well-defined dynamic changes of the ionic extracellular environment has so far not been carefully studied in a biomaterials context. In this work, we present kinetic data on how osteoblast-like SAOS-2 cellular activity and calcium-deficient hydroxyapatite (CDHA) influenced extracellular pH as well as extracellular concentrations of calcium and phosphate in standard in vitro conditions. Since cells were grown on membranes permeable to ions and proteins, they could share the same aqueous environment with CDHA, but still be physically separated from the material. In such culture conditions, it was observed that gradual material-induced adsorption of calcium and phosphate from the medium had only minor influence on cellular proliferation and alkaline phosphatase activity, but that competition for calcium and phosphate between cells and the biomaterial delayed and reduced significantly the cellular capacity to deposit calcium in the extracellular matrix. The presented work thus gives insights into how and to what extent solution-mediated reactions can influence cellular response, and this will be necessary to take into account when interpreting CDHA performance both in vitro and in vivo.

Keywords: Alkaline-phosphatase activity, Saos-2 cells, In-vitro, bone mineralization, Biological basis, Differentiation, Culture, Matrix, Proliferation, Topography

Pomareda, Víctor, Guamán, Ana V., Mohammadnejad, Masoumeh, Calvo, Daniel, Pardo, Antonio, Marco, Santiago, (2012). Multivariate curve resolution of nonlinear ion mobility spectra followed by multivariate nonlinear calibration for quantitative prediction Chemometrics and Intelligent Laboratory Systems 118, 219-229

In this work, a new methodology to analyze spectra time-series obtained from ion mobility spectrometry (IMS) has been investigated. The proposed method combines the advantages of multivariate curve resolution-alternating least squares (MCR-ALS) for an optimal physical and chemical interpretation of the system (qualitative information) and a multivariate calibration technique such as polynomial partial least squares (poly-PLS) for an improved quantification (quantitative information) of new samples. Ten different concentrations of 2-butanone and ethanol were generated using a volatile generator based on permeation tubes. The different concentrations were measured with IMS. These data present a non-linear behaviour as substance concentration increases. Although MCR-ALS is based on a bilinear decomposition, non-linear behaviour can be modelled adding new components to the model. After spectral pre-processing, MCR-ALS was applied aiming to get information about the ionic species that appear in the drift tube and their evolution with the analyte concentration. By resolving the IMS data matrix, concentration profiles and pure spectra of the different ionic species have been obtained for both analytes. Finally, poly-PLS was used in order to build a calibration model using concentration profiles obtained from MCR-ALS for ethanol and 2-butanone. The results, with more than 99% of explained variance for both substances, show the feasibility of using MCR-ALS to resolve IMS datasets. Furthermore, similar or better prediction accuracy is achieved when concentration profiles from MCR-ALS are used to build a calibration model (using poly-PLS) compared to other standard univariate and multivariate calibration methodologies.

Keywords: Ion Mobility Spectrometry, Multivariate Curve Resolution, Gas phase ion chemistry, Multivariate calibration

Malandrino, A., Fritsch, A., Lahayne, O., Kropik, K., Redl, H., Noailly, J., Lacroix, D., Hellmich, C., (2012). Anisotropic tissue elasticity in human lumbar vertebra, by means of a coupled ultrasound-micromechanics approach Materials Letters 78, 154-158

The extremely fine structure of vertebral cortex challenges reliable determination of the tissue's anisotropic elasticity, which is important for the spine's load carrying patterns often causing pain in patients. As a potential remedy, we here propose a combined experimental (ultrasonic) and modeling (micromechanics) approach. Longitudinal acoustic waves are sent in longitudinal (superior-inferior, axial) as well as transverse (circumferential) direction through millimeter-sized samples containing this vertebral cortex, and corresponding wave velocities agree very well with recently identified 'universal' compositional and acoustic characteristics (J Theor Biol 287:115, 2011), which are valid for a large data base comprising different bones from different species and different organs. This provides evidence that the 'universal' organization patterns inherent to all the bone tissues of the aforementioned data base also hold for vertebral bone. Consequently, an experimentally validated model covering the mechanical effects of this organization patterns (J Theor Biol 244:597, 2007, J Theor Biol 260:230, 2009) gives access to the complete elasticity tensor of human lumbar vertebral bone tissue, as a valuable input for structural analyses aiming at patient-specific fracture risk assessment, e.g. based on the Finite Element Method.

Keywords: Human vertebra, Micromechanics, Tissue elasticity, Ultrasonics

Veeregowda, D. H., van der Mei, H. C., de Vries, J., Rutland, M. W., Valle-Delgado, J. J., Sharma, P. K., Busscher, H. J., (2012). Boundary lubrication by brushed salivary conditioning films and their degree of glycosylation Clinical Oral Investigations 16, (5), 1499-1506

Objectives: Toothbrushing, though aimed at biofilm removal, also affects the lubricative function of adsorbed salivary conditioning films (SCFs). Different modes of brushing (manual, powered, rotary-oscillatory or sonically driven) influence the SCF in different ways. Our objectives were to compare boundary lubrication of SCFs after different modes of brushing and to explain their lubrication on the basis of their roughness, dehydrated layer thickness, and degree of glycosylation. A pilot study was performed to relate in vitro lubrication with mouthfeel in human volunteers. Materials and methods: Coefficient of friction (COF) on 16-h-old SCFs after manual, rotary-oscillatory, and sonically driven brushing was measured using colloidal probe atomic force microscopy (AFM). AFM was also used to assess the roughness of SCFs prior to and after brushing. Dehydrated layer thicknesses and glycosylation of the SCFs were determined using X-ray photoelectron spectroscopy. Mouthfeel after manual and both modes of powered brushing were evaluated employing a split-mouth design. Results: Compared with unbrushed and manually or sonically driven brushed SCFs, powered rotary-oscillatory brushing leads to deglycosylation of the SCF, loss of thickness, and a rougher film. Concurrently, the COF of a powered rotary-oscillatory brushed SCF increased. Volunteers reported a slightly preferred mouthfeel after sonic brushing as compared to powered rotating-oscillating brushing. Conclusion: Deglycosylation and roughness increase the COF on SCFs. Clinical relevance: Powered rotary-oscillatory brushing can deglycosylate a SCF, leading to a rougher film surface as compared with manual and sonic brushing, decreasing the lubricative function of the SCF. This is consistent with clinical mouthfeel evaluation after different modes of brushing.

Keywords: AFM, Friction, Glycosylation, Salivary conditioning film, Toothbrushing, XPS

Ambrosio, L., Guarino, V., Sanginario, V., Torricelli, P., Fini, M., Ginebra, M.P., Planell, J.A., Giardino, R., (2012). Injectable calcium-phosphate-based composites for skeletal bone treatments Biomedical Materials 7, (2), 1-10

Alpha-tricalcium-phosphate-based bone cements hydrolyze and set, producing calcium-deficient hydroxyapatite. They can result in an effective solution for bone defect reconstruction due to their biocompatibility, bioactivity and adaptation to shape and bone defect sizes, together with an excellent contact between bone and graft. Moreover, the integration of hydrogel phase based on poly(vinyl alcohol) (PVA) to H-cem–composed of

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2012). Electrochemical behaviour of mixed LB films of ubiquinone - DPPC Journal of Electroanalytical Chemistry 669, 6-13

The structure and the electrochemical behaviour of Langmuir and Langmuir-Blodgett (LB) films of the biological ubiquinone-10 (UQ) and a mixture of dipalmytoilphosphatidylcholine (DPPC) and UQ at the molar ratios DPPC:UQ 5:1 and 10:1 have been investigated. The surface pressure-area isotherms of the Langmuir films and the AFM images of the LB films show the formation of a monolayer in the DPPC:UQ mixture till a certain surface pressure is attained, and then at higher surface pressures the UQ is progressively expelled. The cyclic voltammograms of DPPC:UQ LB films formed on indium tin oxide, ITO, at different surface pressures show one reduction and one oxidation peak at low surface pressures, but two or even more reduction and oxidations peaks at medium and high surface pressures. The electrochemical behaviour is correlated with the film structure.

Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett, Lipid monolayer, Modified ITO electrode, Ubiquinone

Noailly, Jérôme, Ambrosio, Luigi, Elizabeth Tanner, K., Planell, Josep, Lacroix, Damien, (2012). In silico evaluation of a new composite disc substitute with a L3–L5 lumbar spine finite element model European Spine Journal 21, (5), 675-687

When the intervertebral disc is removed to relieve chronic pain, subsequent segment stabilization should restore the functional mechanics of the native disc. Because of partially constrained motions and the lack of intrinsic rotational stiffness ball-on-socket implants present many disadvantages. Composite disc substitutes mimicking healthy disc structures should be able to assume the role expected for a disc substitute with fewer restrictions than ball-on-socket implants. A biomimetic composite disc prototype including artificial nucleus fibre-reinforced annulus and endplates was modelled as an L4–L5 disc substitute within a L3–L5 lumbar spine finite element model. Different device updates, i.e. changes of material properties fibre distributions and volume fractions and nucleus placements were proposed. Load- and displacement-controlled rotations were simulated with and without body weight applied. The original prototype reduced greatly the flexibility of the treated segment with significant adjacent level effects under displacement-controlled or hybrid rotations. Device updates allowed restoring large part of the global axial and sagittal rotational flexibility predicted with the intact model. Material properties played a major role, but some other updates were identified to potentially tune the device behaviour against specific motions. All device versions altered the coupled intersegmental shear deformations affecting facet joint contact through contact area displacements. Loads in the bony endplates adjacent to the implants increased as the implant stiffness decreased but did not appear to be a strong limitation for the implant biomechanical and mechanobiological functionality. In conclusion, numerical results given by biomimetic composite disc substitutes were encouraging with greater potential than that offered by ball-on-socket implants.

Keywords: Medicine

Llorens, F., Del Rio, J. A., (2012). Unraveling the neuroprotective mechanisms of PrPC in excitotoxicity Prion 6, (3), 245-251

Knowledge of the natural roles of cellular prion protein (PrPC) is essential to an understanding of the molecular basis of prion pathologies. This GPIanchored protein has been described in synaptic contacts, and loss of its synaptic function in complex systems may contribute to the synaptic loss and neuronal degeneration observed in prionopathy. In addition, Prnp knockout mice show enhanced susceptibility to several excitotoxic insults, GABAA receptor-mediated fast inhibition was weakened, LTP was modified and cellular stress increased. Although little is known about how PrPC exerts its function at the synapse or the downstream events leading to PrPCmediated neuroprotection against excitotoxic insults, PrPC has recently been reported to interact with two glutamate receptor subunits (NR2D and GluR6/7). In both cases the presence of PrPC blocks the neurotoxicity induced by NMDA and Kainate respectively. Furthermore, signals for seizure and neuronal cell death in response to Kainate in Prnp knockout mouse are associated with JNK3 activity, through enhancing the interaction of GluR6 with PSD-95. In combination with previous data, these results shed light on the molecular mechanisms behind the role of PrPC in excitotoxicity. Future experimental approaches are suggested and discussed.

Keywords: Prion protein, Excitotoxicity, Neuroprotection, Glutamate receptors, Synapse, prionopathy

Tsapikouni, T., Garreta, E., Melo, E., Navajas, D., Farré, R., (2012). A bioreactor for subjecting cultured cells to fast-rate intermittent hypoxia Respiratory Physiology & Neurobiology 182, (1), 47-52

High frequency intermittent hypoxia is one of the most relevant injurious stimuli experienced by patients with obstructive sleep apnea (OSA). Given that the conventional setting for culturing cells under intermittent hypoxia conditions is limited by long equilibration times, we designed a simple bioreactor capable of effectively subjecting cultured cells to controlled high-frequency hypoxic/normoxic stimuli. The bioreactor's operation is based on exposing cells to a medium that is bubbled with the appropriate mixture of gases into two separate containers, and from there it is directed to the cell culture dish with the aid of two bidirectional peristaltic pumps. The device was tested on human alveolar epithelial cells (A549) and mouse melanoma cells (B16-F10), subjecting them to patterns of intermittent hypoxia (20s at 5% O 2 and 50s at 20% O 2), which realistically mimic OSA of up to severe intensity as defined by the apnea hypopnea index. The proposed bioreactor can be easily and inexpensively assembled and is of practical use for investigating the effects of high-rate changes in oxygen concentration in the cell culture medium.

Keywords: Hypoxia-reoxygenation, Obstructive sleep apnea, Oxygen partial pressure

Pegueroles, M., Tonda-Turo, C., Planell, J. A., Gil, F. J., Aparicio, C., (2012). Adsorption of fibronectin, fibrinogen, and albumin on TiO2: Time-resolved kinetics, structural changes, and competition study Biointerphases 7, (48), 13

An understanding of protein adsorption process is crucial for designing biomaterial surfaces. In this work, with the use of a quartz-crystal microbalance with dissipation monitoring, we researched the following: (a) the kinetics of adsorption on TiO2 surfaces of three extensively described proteins that are relevant for metallic implant integration [i.e., albumin (BSA), fibrinogen (Fbg), and fibronectin (Fn)]; and (b) the competition of those proteins for adsorbing on TiO2 in a two-step experiment consisted of sequentially exposing the surfaces to different monoprotein solutions. Each protein showed a different process of adsorption and properties of the adlayer-calculated using the Voigt model. The competition experiments showed that BSA displaced larger proteins such as Fn and Fbg when BSA was introduced as the second protein in the system, whereas the larger proteins laid on top of BSA forming an adsorbed protein bi-layer when those were introduced secondly in the system.

Keywords: QCM, Human plasma fibronectin, Induced conformational-changes, Von-willebrand-factor, BSA, Protein adsortion, Polymer surfaces, Solid-surfaces, Viscoelastic properties, Globular-proteins

Mesquita, J., Solà, J., Fiz, J. A., Morera, J., Jané, R., (2012). All night analysis of time interval between snores in subjects with sleep apnea hypopnea syndrome Medical and Biological Engineering and Computing 50, (4), 373-381

Sleep apnea-hypopnea syndrome (SAHS) is a serious sleep disorder, and snoring is one of its earliest and most consistent symptoms. We propose a new methodology for identifying two distinct types of snores: the so-called non-regular and regular snores. Respiratory sound signals from 34 subjects with different ranges of Apnea-Hypopnea Index (AHI = 3.7-109.9 h -1) were acquired. A total number of 74,439 snores were examined. The time interval between regular snores in short segments of the all night recordings was analyzed. Severe SAHS subjects show a shorter time interval between regular snores (p = 0.0036, AHI cp: 30 h -1) and less dispersion on the time interval features during all sleep. Conversely, lower intra-segment variability (p = 0.006, AHI cp: 30 h -1) is seen for less severe SAHS subjects. Features derived from the analysis of time interval between regular snores achieved classification accuracies of 88.2 % (with 90 % sensitivity, 75 % specificity) and 94.1 % (with 94.4 % sensitivity, 93.8 % specificity) for AHI cut-points of severity of 5 and 30 h -1, respectively. The features proved to be reliable predictors of the subjects' SAHS severity. Our proposed method, the analysis of time interval between snores, provides promising results and puts forward a valuable aid for the early screening of subjects suspected of having SAHS.

Keywords: Sleep apnea, Snore sounds, Snore time interval

Solà, J., Fiz, J. A., Morera, J., Jané, R., (2012). Multiclass classification of subjects with sleep apnoea-hypopnoea syndrome through snoring analysis Medical Engineering and Physics 34, (9), 1213-1220

The gold standard for diagnosing sleep apnoea-hypopnoea syndrome (SAHS) is polysomnography (PSG), an expensive, labour-intensive and time-consuming procedure. Accordingly, it would be very useful to have a screening method to allow early assessment of the severity of a subject, prior to his/her referral for PSG. Several differences have been reported between simple snorers and SAHS patients in the acoustic characteristics of snoring and its variability. In this paper, snores are fully characterised in the time domain, by their sound intensity and pitch, and in the frequency domain, by their formant frequencies and several shape and energy ratio measurements. We show that accurate multiclass classification of snoring subjects, with three levels of SAHS, can be achieved on the basis of acoustic analysis of snoring alone, without any requiring information on the duration or the number of apnoeas. Several classification methods are examined. The best of the approaches assessed is a Bayes model using a kernel density estimation method, although good results can also be obtained by a suitable combination of two binary logistic regression models. Multiclass snore-based classification allows early stratification of subjects according to their severity. This could be the basis of a single channel, snore-based screening procedure for SAHS.

Keywords: Bayes classifier, Kernel density estimation, Sleep apnoea, Snoring

Gallach, D., Torres-Costa, V., García-Pelayo, L., Climent-Font, A., Martín-Palma, R. J., Barreiros-Das-Santos, M., Sporer, C., Samitier, J., Manso, M., (2012). Properties of bilayer contacts to porous silicon Applied Physics A: Materials Science and Processing 107, (2), 293-300

The aim of the present work is the growth by PVD techniques and ulterior characterization of electrical contacts to columnar porous silicon (PSi) as an approach to reliable PSi sensor devices. Contacts consist of a NiCr (40:60) and Au bilayer on the PSi surface deposited by magnetron sputtering. These structures show a good adhesion to the rough surface of columnar PSi. The morphology of these electrical contacts is characterized by electron microscopy and their crystalline structure by X-ray diffraction. Compositional profiles are determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy, which demonstrate that the infiltration of NiCr into the PSi is at the origin of the metallic thin film adhesion improvement. I-V characteristics and impedance spectroscopy measurements show that this configuration provides rectifying electrical contacts to PSi, for which a simple equivalent circuit based on one resistor and two capacitors can be modeled. These results further support the use of PSi electrical structures for sensing purposes.

Marco, S., Gutierrez-Galvez, A., (2012). Signal and data processing for machine olfaction and chemical sensing: A review IEEE Sensors Journal 12, (11), 3189-3214

Signal and data processing are essential elements in electronic noses as well as in most chemical sensing instruments. The multivariate responses obtained by chemical sensor arrays require signal and data processing to carry out the fundamental tasks of odor identification (classification), concentration estimation (regression), and grouping of similar odors (clustering). In the last decade, important advances have shown that proper processing can improve the robustness of the instruments against diverse perturbations, namely, environmental variables, background changes, drift, etc. This article reviews the advances made in recent years in signal and data processing for machine olfaction and chemical sensing.

Keywords: Chemical sensors, Electronic nose, Intelligent sensors, Measurement techniques, Sensor arrays, Sensor systems

Fazel Zarandi, M. H., Avazbeigi, M., (2012). A multi-agent solution for reduction of bullwhip effect in fuzzy supply chains Journal of Intelligent and Fuzzy Systems 23, (5), 259-268

In this paper, we present a new Multi-Agent System for reduction of the bullwhip effect in fuzzy supply chains. First, we show that a supply chain that uses an optimal ordering policy without data sharing among echelons still suffers from the bullwhip effect. Then, we propose the multi-agent solution to manage and reduce the bullwhip effect. The proposed multi-agent system includes four different types of agents in which each agent has its own list of actions. The proposed Multi-agent System applies a new Tabu Search algorithm for fuzzy rule generation, and a new data filtering algorithm for extraction of the bullwhip-free data from supply chain data warehouse. We validate the multi-agent system under different conditions and discuss how the system responds to different factors. The results show that the proposed multi-agent system reduces the bullwhip effect significantly in a rational time.

Keywords: Bullwhip effect, Bullwhip-free data, Decentralized decision making, Fuzzy rule base, Fuzzy supply chain, Fuzzy time series, Multi-agent system, Supply chain management

Azevedo, S., Diéguez, L., Carvalho, P., Carneiro, J. O., Teixeira, V., Martínez, E., Samitier, J., (2012). Deposition of ITO thin films onto PMMA substrates for waveguide based biosensing devices Journal of Nano Research 17, 75-83

Biosensors' research filed has clearly been changing towards the production of multifunctional and innovative design concepts to address the needs related with sensitivity and selectivity of the devices. More recently, waveguide biosensors, that do not require any label procedure to detect biomolecules adsorbed on its surface, have been pointed out as one of the most promising technologies for the production of biosensing devices with enhanced performance. Moreover the combination of optical and electrochemical measurements through the integration of transparent and conducting oxides in the multilayer structures can greatly enhance the biosensors' sensitivity. Furthermore, the integration of polymeric substrates may bring powerful advantages in comparison with silicon based ones. The biosensors will have a lower production costs being possible to disposable them after use ("one use sensor chip"). This research work represents a preliminary study about the influence of substrate temperature on the overall properties of ITO thin films deposited by DC magnetron sputtering onto 0,5 mm thick PMMA sheets.

Keywords: ITO thin films, PMMA sheets, Waveguide biosensing devices, Biosensing devices, Conducting oxides, Dc magnetron sputtering, Electrochemical measurements, Enhanced performance, Innovative design, ITO thin films, Multilayer structures, Overall properties, PMMA sheets, Polymeric substrate, Production cost, Sensor chips, Silicon-based, Substrate temperature, Biosensors, Deposition, Design, Film preparation, Optical multilayers, Thin films, Vapor deposition, Waveguides, Substrates

Lozano, M., Fiz, J.A., Jané, R., (2012). Análisis multicanal de sonidos respiratorios en acústica pulmonar: aplicación clínica en pacientes asmáticos Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

En este trabajo se ha visto que la evaluación de la potencia media de las señales de sonidos respiratorios antes y después de aplicar un fármaco broncodilatador puede reportar información importante sobre el estado y los cambios producidos en el sistema respiratorio. Se ha realizado y puesto a punto un protocolo de registro multicanal de acústica pulmonar mediante la colocación de 5 micrófonos de contacto: uno traqueal y cuatro micrófonos colocados en el tórax posterior. Mediante el análisis de las curvas intensidad-flujo respiratorio se han observado cambios significativos de intensidad a niveles de flujo elevados y en pacientes con una PBD negativa. Es en este grupo de pacientes, no respondedores, donde la técnica propuesta puede aportar información de interés clínico complementaria a la proporcionada por la espirometría clásica.

Giraldo, B.F., Gaspar, B.W., Caminal, P., Benito, S., (2012). Analysis of roots in ARMA model for the classification of patients on weaning trials Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 698-701

One objective of mechanical ventilation is the recovery of spontaneous breathing as soon as possible. Remove the mechanical ventilation is sometimes more difficult that maintain it. This paper proposes the study of respiratory flow signal of patients on weaning trials process by autoregressive moving average model (ARMA), through the location of poles and zeros of the model. A total of 151 patients under extubation process (T-tube test) were analyzed: 91 patients with successful weaning (GS), 39 patients that failed to maintain spontaneous breathing and were reconnected (GF), and 21 patients extubated after the test but before 48 hours were reintubated (GR). The optimal model was obtained with order 8, and statistical significant differences were obtained considering the values of angles of the first four poles and the first zero. The best classification was obtained between GF and GR, with an accuracy of 75.3% on the mean value of the angle of the first pole.

Keywords: Analytical models, Biological system modeling, Computational modeling, Estimation, Hospitals, Poles and zeros, Ventilation, Autoregressive moving average processes, Patient care, Patient monitoring, Pneumodynamics, Poles and zeros, Ventilation, ARMA model, T-tube test, Autoregressive moving average model, Extubation process, Mechanical ventilation, Optimal model, Patient classification, Respiratory flow signal, Roots, Spontaneous breathing, Weaning trials

Hernansanz, A., Zerbato, D., Gasperotti, L., Scandola, M., Casals, A., Fiorini, P., (2012). Assessment of virtual fixtures for the development of basic skills in robotic surgery International Journal of Computer Assisted Radiology and Surgery CARS 2012 Computer Assisted Radiology and Surgery , Springer (Pisa, Italy) 7 (Supplement 1) - Surgical Modelling, Simulation and Education, S186-S188

Teleoperation, by adequately adapting computer interfaces, can benefit from the knowledge on human factors and psychomotor models in order to improve the effectiveness and efficiency in the execution of a task. While scaling is one of the performances frequently used in teleoperation tasks that require high precision, such as surgery, this article presents a scaling method that considers the system dynamics as well. The proposed dynamic scaling factor depends on the apparent position and velocity of the robot and targets. Such scaling improves the performance of teleoperation interfaces, thereby reducing user's workload.

Keywords: Human-robot interaction, Throughput, Scaling functions, Motor control performance

Urra, O., Fiz, J.A., Abad, J., Jané, R., (2012). Beyond the reach of AHI: identifying key markers for improved systematic diagnosis of SAHS Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

Olivares, A.L., Perrault, C.M., Lacroix, D., (2012). Cell seeding optimization in 3D scaffold under dynamic condition: Computational and experimental methods The Proceedings of the 10th International Symposium on CMBBE 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering , ARUP (Berlin, Germany) SS12: In silico modelling of the spinal disc degeneration, 906-911

Proper cell density and spatial distribution in a 3D scaffold are essential to morphogenetic development of an engineered tissue. The aim of this study was to combine computational and experimental techniques to study cell seeding under dynamic conditions. Rapid prototyped poly-caprolactone scaffolds, 5 mm in diameter and 1.5 mm in height, were used in a custom-made microfluidic chamber, thus enabling live visualization of the seeding process. The scaffold morphologies were reconstructed from micro CT images and the fluid volume was created similar to the microfluidic chamber. Computationally cell motion was represented as spherical particles in a fluid medium using a multiphase Lagrangian formulation implemented in Ansys Fluent. Cells were dragged by the fluid flow and adhesion was quantified using wall film theory. Experimentally, fluorescent microspheres, 10 um in diameter, were used, and fluid flow was controlled with a syringe pump. Inlet fluid flow was applied at 0.15 mm/s, identical to the model condition. Live imaging of the seeding process in the microfluidic chamber enables to record particle trajectory and velocity and possible zone of cell adhesion. The computational simulation shows velocities (≈0.6mm/s) in agreement with the particles experiment. Particles distributions was similar and can be highlighted the scaffold design in fluid accessibility.

Chaparro, J., Giraldo, B.F., Caminal, P., Benito, S., (2012). Comportamiento de parámetros del patrón respiratorio en clasificadores para la predicción del proceso weaning Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

Toumanidou, T., Fortuny, G., Lacroix, D., Noailly, J., (2012). Constitutive modelling of the lumbar spine musculature The Proceedings of the 10th International Symposium on CMBBE 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering , ARUP (Berlin, Germany) SS12: In silico modelling of the spinal disc degeneration, 693-699

Spinal muscles provide stability of the trunk and transmit loading onto the vertebra and intervertebral discs. Current lumbar spine finite element models overlook such muscle contribution or suggest simplifications far from the reality. This study proposes to address this limitation by developing a novel active lumbar spine muscle model. A modified quasi-incompressible fibre-reinforced hyperelastic constitutive model was adopted for the passive and active behavior of the lumbar musculature. The constitutive relation was expressed in terms of muscle fibre, matrix deviatoric and volumetric stresses. A single unidirectional element was used to assess the model under 30% traction and 20% compression strains. For the active fibre stress, a parametric study defined suitable values for a strain-like parameter

Antelis, J.M., Montesano, L., Giralt, X., Casals, A., Minguez, J., (2012). Detection of movements with attention or distraction to the motor task during robot-assisted passive movements of the upper limb Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 6410-6413

Robot-assisted rehabilitation therapies usually focus on physical aspects rather than on cognitive factors. However, cognitive aspects such as attention, motivation, and engagement play a critical role in motor learning and thus influence the long-term success of rehabilitation programs. This paper studies motor-related EEG activity during the execution of robot-assisted passive movements of the upper limb, while participants either: i) focused attention exclusively on the task; or ii) simultaneously performed another task. Six healthy subjects participated in the study and results showed lower desynchronization during passive movements with another task simultaneously being carried out (compared to passive movements with exclusive attention on the task). In addition, it was proved the feasibility to distinguish between the two conditions.

Keywords: Electrodes, Electroencephalography, Induction motors, Medical treatment, Robot sensing systems, Time frequency analysis, Biomechanics, Cognition, Electroencephalography, Medical robotics, Medical signal detection, Medical signal processing, Patient rehabilitation, Attention, Cognitive aspects, Desynchronization, Engagement, Motivation, Motor learning, Motor task, Motor-related EEG activity, Physical aspects, Robot-assisted passive movement detection, Robot-assisted rehabilitation therapies, Upper limb

Muñoz, L. M., Casals, A., (2012). Dynamic scaling interface for assisted teleoperation IEEE International Conference on Robotics and Automation (ICRA) , IEEE (Minnesota, USA) , 4288-4293

Teleoperation, by adequately adapting computer interfaces, can benefit from the knowledge on human factors and psychomotor models in order to improve the effectiveness and efficiency in the execution of a task. While scaling is one of the performances frequently used in teleoperation tasks that require high precision, such as surgery, this article presents a scaling method that considers the system dynamics as well. The proposed dynamic scaling factor depends on the apparent position and velocity of the robot and targets. Such scaling improves the performance of teleoperation interfaces, thereby reducing user's workload.

Keywords: Human-robot interaction, Motor control performance, Scaling functions, Throughput

Garde, A., Laguna, P., Giraldo, B.F., Jané, R., Sörnmo, L., (2012). Ensemble-based time alignment of biomedical signals Proceedings BSI 2012 7th International Workshop on Biosignal Interpretation (BSI 2012) , IEEE (Como, Italy) W3: METHODS FOR BIOMEDICAL SIGNAL PROCESSING ENHANCEMENT, 307-310

In this paper, the problem of time alignment is revisited by adopting an ensemble-based approach with all signals jointly aligned. It is shown that the maximization of an eigenvalue ratio is synonymous to maximizing the signal-to-jitter-and-noise ratio. Since optimization of this criterion is extremely time consuming, a relaxed optimization procedure is introduced which converges much more quickly. Using simulations based on respiratory flow signals, the results suggest that the time delay error variance of the new method is much lower than that obtained with the well-known Woody’s method.

Keywords: Time alignment, Signal ensemble, Subsample precision, Eigenvalue decomposition

Garde, A., Giraldo, B.F., Jané, R., Latshang, T.D., Turk, A.J., Hess, T., Bosch, M-.M., Barthelmes, D., Hefti, J.P., Maggiorini, M., Hefti, U., Merz, T.M., Schoch, O.D., Bloch, K.E., (2012). Estudio de la respiración periódica en el ascenso a altitudes extremas a partir de la señal de volumen respiratorio Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

La respiración periódica (PB) a gran altitud comparte aspectos fisiopatológicos con la apnea, la respiración Cheyne-Stokes y la PB en pacientes con insuficiencia cardiaca. Cuantificar las inestabilidades del control respiratorio puede proporcionar información relevante de los mecanismos fisiológicos que las producen, y ayudar en las actuaciones terapéuticas. Bajo la hipótesis de que en altitudes extremas la PB puede aparecer incluso durante actividad física, el objetivo es identificar la PB y evaluar el efecto de aclimatación a partir de la caracterización del patrón respiratorio mediante la señal de volumen respiratorio. Se analizaron los datos obtenidos de 34 montañeros sanos ascendiendo al Muztagh Ata, China (7,546m). Sus señales se etiquetaron visualmente como, respiración periódica (PB=40) y no periódica (nPB=371). El patrón respiratorio se caracterizó a partir de parámetros extraídos de la densidad espectral de potencia de la señal de volumen respiratorio. Los mejores resultados clasificando PB y nPB se obtuvieron con Pm (potencia de modulación) y R (ratio entre potencia de modulación y respiración) con una precisión del 80.3% y un área bajo la curva de 84.5%. SaO2 y el número de ciclos periódicos de respiración aumentaron significativamente con la aclimatación (p-valor<0.05). A menor SaO2 se observó una mayor Pm y frecuencia respiratoria, (correlación negativa, p-valor<0.01), y una mayor Pm en periodos etiquetados como PB con > 5 ciclos respiratorios periódicos, (correlación positiva, p-valor<0.01). Estos resultados demuestran que la caracterización espectral de la señal de volumen respiratorio permite identificar los efectos de la hipoxia hipobárica en el control de la respiración.

Torres, A., Sarlabous, L., Fiz, J.A., Jané, R., (2012). Evaluación de diferentes algoritmos adaptativos para la atenuación de la interferencia cardiaca en señales mecanomiográficas simuladas Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

El estudio de la señal mecanomiográfica del músculo diafragma (MMGdi) es una técnica utilizada para evaluar el esfuerzo muscular respiratorio. El estudio de la relación entre los parámetros de amplitud y frecuencia de esta señal con el esfuerzo respiratorio realizado es de gran interés para investigadores y médicos debido a su potencial de diagnóstico sobre la función muscular respiratoria. Las señales MMGdi se ven afectas por una componente interferente correspondiente a la actividad vibratoria cardíaca o interferencia mecanocardiográfica (MCG). Para reducir o atenuar esta actividad se puede utilizar una cancelación adaptativa de interferencias (CAI). En este trabajo se ha evaluado el esquema de CAI propuesto mediante una señal MMGdi sintética generada con amplitud y frecuencia controlada a la que se le ha añadido ruido MCG real adquirido durante apnea. El coeficiente de correlación de Pearson (r) entre la amplitud y la frecuencia teóricas, y la amplitud y la frecuencia evaluadas mediante el RMS y la frecuencia media del espectro, respectivamente, disminuye considerablemente cuando se añade el ruido cardíaco a la señal MMGdi sintética: pasa de 0.95 a 0.87 para la amplitud, y de 0.97 a 0.76 para la frecuencia. Con los algoritmos de CAI propuestos el efecto del ruido MCG sobre la actividad MMGdi se reduce considerablemente (r de 0.93 para la amplitud y 0.97 para la frecuencia media). El método de CAI propuesto en este trabajo es una técnica adecuada para atenuar la interferencia MCG en señales MMGdi.

Sarlabous, L., Torres, A., Fiz, J. A., Morera, J., Jané, R., (2012). Evaluation and adaptive attenuation of the cardiac vibration interference in mechanomyographic signals Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 3400-3403

The study of the mechanomyographic signal of the diaphragm muscle (MMGdi) is a promising technique in order to evaluate the respiratory muscles effort. The relationship between amplitude and frequency parameters of this signal with the respiratory effort performed during respiration is of great interest for researchers and physicians due to its diagnostic potentials. However, MMGdi signals are frequently contaminated by a cardiac vibration or mechanocardiographic (MCG) signal. An adaptive noise cancellation (ANC) can be used to reduce the MCG interference in the recorded MMGdi activity. In this paper, it is evaluated the proposed ANC scheme by means of a synthetic MMGdi signal with a controlled MCG interference. The Pearson's correlation coefficient (PCC) between both root mean square (RMS) and mean frequency (fm) of the synthetic MMGdi signal are considerably reduced with the presence of cardiac vibration noise (from 0.95 to 0.87, and from 0.97 to 0.76, respectively). With the ANC algorithm proposed the effect of the MCG noise on the amplitude and frequency of MMG parameters is reduced considerably (PCC of 0.93 and 0.97 for the RMS and fm, respectively). The ANC method proposed in this work is an interesting technique to attenuate the cardiac interference in respiratory MMG signals. Further investigation should be carried out to evaluate the performance of the ANC algorithm in real MMGdi signals.

Keywords: Adaptive filters, Frequency modulation, Interference, Muscles, Noise cancellation, Vibrations, Cardiology, Medical signal processing, Muscle, Signal denoising, ANC algorithm, MCG interference, Pearson correlation coefficient, Adaptive noise cancellation, Cardiac vibration interference, Cardiac vibration noise, Diaphragm muscle, Mechanocardiographic signal, Mechanomyographic signals, Respiratory muscles effort

Serra, T., Navarro, M., Planell, J. A., (2012). Fabrication and characterization of biodegradable composite scaffolds for tissue engineering Innovative Developments in Virtual and Physical Prototyping 5th International Conference on Advanced Research and Rapid Prototyping (ed. Margarida, T., Ferreira, D.), Taylor & Francis (Leiria, Portugal) VR@P, 67-72

In this study, polylactic acid (PLA) and polyethylene glycol (PEG) were combined with soluble CaP glass particles and processed by rapid prototyping to obtain fully biodegradable structures for Tissue Engineering applications. The obtained 3D biodegradable structures were characterized in terms of their architecture and mechanical properties. The scaffold morphology, internal micro-architecture and mechanical properties were evaluated using Scanning Electron Microscopy (SEM), micro-computed tomography (micro-CT) and mechanical testing, respectively. Well defined structures with pore size of 350-400μm (in the axial view), struts width of approximately 70-80μm, and a porosity ranging between 60-65% were obtained. The combination RP and PLA/PEG/CaP glass turned into promising fully degradable, mechanically stable, bioactive and biocompatible composite scaffolds for TE.

Keywords: Axial view, Biodegradable composites, Composite scaffolds, Glass particles, Mechanically stable, Micro architectures, Micro computed tomography (micro-CT), Poly lactic acid, Scaffold morphology, Tissue engineering applications, Well-defined structures, Bioactive glass, Mechanical properties, Mechanical testing, Polyethylene glycols, Polymer blends, Rapid prototyping, Scaffolds (biology), Scanning electron microscopy, Computerized tomography

Bartra, A., Meca, P., Guamán, A., Pardo, A., Marco, S., Montesi, A., (2012). A feasability study of drowsiness detection using driving behaviour parameters IEEE Conference Publications IEEE Intelligent Vehicles Symposium (2012) , IEEE (Alcala de Henares, Spain) , 111-116

One of the main causes of car accidents is drowsiness. There have been many studies regarding driving monitoring systems in the past few years, although most of them are focused in simulator environments. This paper presents a system to detect drowsiness patterns in real driving environments, where many external conditions need to be taken into account. Initial tests were done in simulator, followed by tests in real vehicles. Although two different approaches have been developed, this paper is focused in the inadequate driving identification based on the steering movements. Its sub-modules are also presented, with a special focus on the active driving detector.

Keywords: -----

Ruiz, C., Noailly, J., Lacroix, D., (2012). Material discontinuities create fluid flow instabilities in intervertebral disc poroelastic finite element models The Proceedings of the 10th International Symposium on CMBBE 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering , ARUP (Berlin, Germany) SS12: In silico modelling of the spinal disc degeneration, 142-147

Fluid flow predictions are important in intervertebral disc models to explore the mechanobiology and biomechanics of the tissue. Poroelastic models are used in this sense, but the results from applying physiological load rates may present instabilities. Four IVD models including the annulus fibrosus, the nucleus pulposus, and the endplates were used with different mesh sizes under physiological extension and axial rotational loads. Simulations indicated that oscillations were caused by numerical instability of the pore pressure derivation at material discontinuities. Applying local refinement only was not enough to eliminate the instabilities. Indeed, mesh refinements had to be local and material-dependent, and had to be supplemented by the creation of a material transition zone, including exponentially interpolated material properties between the nucleus and the annulus.

Malandrino, A., Noailly, J., Lacroix, D., (2012). Mechanical effect on metabolic transport and cell viability in the intervertebral disc The Proceedings of the 10th International Symposium on CMBBE 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering , ARUP (Berlin, Germany) SS12: In silico modelling of the spinal disc degeneration, 248-253

The degeneration process in the intervertebral disc (IVD) is linked to progressive cell death and to mechanical factors. Therefore, the inclusion of cell viability criteria coupled with disc mechanics in a computational model would enable to get a better understanding of the degeneration process in IVD. A recently developed finite element (FE) model of the L4-L5 IVD based on poromechanics and IVD metabolism (Malandrino et al., 2011) was modified to include an exponential decay of cells over time below critical glucose and pH levels. The implementation was verified against in vitro literature data on cell viability. Viability criteria were used in the IVD model where diffusions of glucose, oxygen and lactate accounted for predicted porosity and volume changes. Subtissue-specific mechanical properties and cell concentrations were modelled. Daily compressive phases (standing and resting) were applied. Metabolite boundary concentrations were reduced at the endplates to induce critical conditions within the IVD. Solutions with and without mechanical coupling were compared. Critical glucose rather than pH levels were relevant to cell viability far away from the solute supply. Deformation couplings increased glucose in the disc centre so that cells stopped dying up to 10 hours earlier over two days simulated when mechanical deformations were considered. These results can help in the understanding of coupled mechanical and biological factors. If metabolite supply is disturbed, as it could happen during endplate calcification or circulatory diseases, a local accelerated cell death in the disc centre may occur in absence of tissue compliance. This study highlights the need to restore both nutritional and mechanical factors in order to favour cell viability along regenerative treatments.

Chaparro, J.A., Giraldo, B.F., Caminal, P., Benito, S., (2012). Performance of respiratory pattern parameters in classifiers for predict weaning process Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 4349-4352

Weaning trials process of patients in intensive care units is a complex clinical procedure. 153 patients under extubation process (T-tube test) were studied: 94 patients with successful trials (group S), 38 patients who failed to maintain spontaneous breathing and were reconnected (group F), and 21 patients with successful test but that had to be reintubated before 48 hours (group R). The respiratory pattern of each patient was characterized through the following time series: inspiratory time (TI), expiratory time (TE), breathing cycle duration (TTot), tidal volume (VT), inspiratory fraction (TI/TTot), half inspired flow (VT/TI), and rapid shallow index (f/VT), where f is respiratory rate. Using techniques as autoregressive models (AR), autoregressive moving average models (ARMA) and autoregressive models with exogenous input (ARX), the most relevant parameters of the respiratory pattern were obtained. We proposed the evaluation of these parameters using classifiers as logistic regression (LR), linear discriminant analysis (LDA), support vector machines (SVM) and classification and regression tree (CART) to discriminate between patients from groups S, F and R. An accuracy of 93% (98% sensitivity and 82% specificity) has been obtained using CART classification.

Keywords: Accuracy, Indexes, Logistics, Regression tree analysis, Support vector machines, Time series analysis, Autoregressive moving average processes, Medical signal processing, Pattern classification, Pneumodynamics, Regression analysis, Sensitivity, Signal classification, Support vector machines, Time series, SVM, T-tube testing, Autoregressive models-with-exogenous input, Autoregressive moving average models, Breathing cycle duration, Classification-and-regression tree, Expiratory time, Extubation process, Half inspired flow, Inspiratory fraction, Inspiratory time, Intensive care units, Linear discriminant analysis, Logistic regression, Rapid shallow index, Respiratory pattern parameter performance, Sensitivity, Spontaneous breathing, Support vector machines, Tidal volume, Time 48 hr, Time series, Weaning process classifiers

Garde, A., Giraldo, B.F., Jané, R., Latshang, T.D., Turk, A.J., Hess, T., Bosch, M-.M., Barthelmes, D., Hefti, J.P., Maggiorini, M., Hefti, U., Merz, T.M., Schoch, O.D., Bloch, K.E., (2012). Periodic breathing during ascent to extreme altitude quantified by spectral analysis of the respiratory volume signal Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 707-710

High altitude periodic breathing (PB) shares some common pathophysiologic aspects with sleep apnea, Cheyne-Stokes respiration and PB in heart failure patients. Methods that allow quantifying instabilities of respiratory control provide valuable insights in physiologic mechanisms and help to identify therapeutic targets. Under the hypothesis that high altitude PB appears even during physical activity and can be identified in comparison to visual analysis in conditions of low SNR, this study aims to identify PB by characterizing the respiratory pattern through the respiratory volume signal. A number of spectral parameters are extracted from the power spectral density (PSD) of the volume signal, derived from respiratory inductive plethysmography and evaluated through a linear discriminant analysis. A dataset of 34 healthy mountaineers ascending to Mt. Muztagh Ata, China (7,546 m) visually labeled as PB and non periodic breathing (nPB) is analyzed. All climbing periods within all the ascents are considered (total climbing periods: 371 nPB and 40 PB). The best crossvalidated result classifying PB and nPB is obtained with Pm (power of the modulation frequency band) and R (ratio between modulation and respiration power) with an accuracy of 80.3% and area under the receiver operating characteristic curve of 84.5%. Comparing the subjects from 1st and 2nd ascents (at the same altitudes but the latter more acclimatized) the effect of acclimatization is evaluated. SaO2 and periodic breathing cycles significantly increased with acclimatization (p-value <; 0.05). Higher Pm and higher respiratory frequencies are observed at lower SaO2, through a significant negative correlation (p-value <; 0.01). Higher Pm is observed at climbing periods visually labeled as PB with >; 5 periodic breathing cycles through a significant positive correlation (p-value <; 0.01). Our data demonstrate that quantification of the respiratory volum- signal using spectral analysis is suitable to identify effects of hypobaric hypoxia on control of breathing.

Keywords: Frequency domain analysis, Frequency modulation, Heart, Sleep apnea, Ventilation, Visualization, Cardiology, Medical disorders, Medical signal processing, Plethysmography, Pneumodynamics, Sensitivity analysis, Sleep, Spectral analysis, Cheyne-Stokes respiration, Climbing periods, Dataset, Heart failure patients, High altitude PB, High altitude periodic breathing, Hypobaric hypoxia, Linear discriminant analysis, Pathophysiologic aspects, Physical activity, Physiologic mechanisms, Power spectral density, Receiver operating characteristic curve, Respiratory control, Respiratory frequency, Respiratory inductive plethysmography, Respiratory pattern, Respiratory volume signal, Sleep apnea, Spectral analysis, Spectral parameters

Colomer-Farrarons, J., Miribel-Català , P., Juanola-Feliu, E., Samitier, J., (2012). A proof-of-concept of a multi-harvesting power source in a low-voltage CMOS technology IEEE Computer Society 2012 IEEE International Conference on Green Computing and Communications, Conference on Internet of Things, and Conference on Cyber, Physical and Social Computing , IEEE (Besancon, France) , 655-659

This paper presents a view of the state of the art in the field of energy harvesting solutions focused on discrete to integrated solutions in the range of low-power generation, from a few microwatts to several nanowatts. A view of commercial solutions to the new trends in new self-powered smart sensors operating without the use of any kind of battery will be presented. A specific solution developed in our laboratory will be used as an example of application.

Keywords: Electric power generation, Energy scavenging, Low-power electronics, Power conditioning

Sarlabous, L., Torres, A., Fiz, J.A., Jané, R., (2012). Reducción de interferencia cardíaca en señales MMG diafragmáticas registradas durante un protocolo de carga incremental sostenida mediante el algoritmo RLS Libro de Actas XXX CASEIB 2012 XXX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB2012) , Sociedad Española de Ingeniería Biomédica (San Sebastián, Spain) , 1-4

En este trabajo se aplicó el filtrado adaptativo empleando el algoritmo RLS para reducir la interferencia de origen cardíaco en las señales mecanomiográficas diafragmáticas (MMGdi) registras durante un protocolo de carga incremental sostenida. La señal MMGdi fue dividida en tramos con y sin ruido cardíaco, CRC y SRC, respectivamente. En cada tramo se estudio el comportamiento de la densidad espectral de potencia (DEP), y los parámetros de amplitud RMS y ARV para cada una de las cargas inspiratorias que conforman el test. Los resultados obtenidos, empleando filtro adaptativo de orden =50, con el algoritmo RLS y valores de - = 1, permiten reducir considerablemente la interferencia cardíaca en las señales MMGdi.

Mesquita, J., Poree, F., Carrault, G., Fiz, J. A., Abad, J., Jané, R., (2012). Respiratory and spontaneous arousals in patients with Sleep Apnea Hypopnea Syndrome Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 6337-6340

Sleep in patients with Sleep Apnea-Hypopnea Syndrome (SAHS) is frequently interrupted with arousals. Increased amounts of arousals result in shortening total sleep time and repeated sleep-arousal change can result in sleep fragmentation. According to the American Sleep Disorders Association (ASDA) an arousal is a marker of sleep disruption representing a detrimental and harmful feature for sleep. The nature of arousals and its role on the regulation of the sleep process raises controversy and has sparked the debate in the last years. In this work, we analyzed and compared the EEG spectral content of respiratory and spontaneous arousals on a database of 45 SAHS subjects. A total of 3980 arousals (1996 respiratory and 1984 spontaneous) were analyzed. The results showed no differences between the spectral content of the two kinds of arousals. Our findings raise doubt as to whether these two kinds of arousals are truly triggered by different organic mechanisms. Furthermore, they may also challenge the current beliefs regarding the underestimation of the importance of spontaneous arousals and their contribution to sleep fragmentation in patients suffering from SAHS.

Keywords: Adaptive filters, Correlation, Databases, Electroencephalography, Hospitals, Sleep apnea, Electroencephalography, Medical signal processing, Pneumodynamics, Sleep, EEG spectral content, Organic mechanism, Respiratory, Sleep apnea hypopnea syndrome, Sleep fragmentation, Spectral content, Spontaneous arousal

Amigo, L. E., Fernandez, Q., Giralt, X., Casals, A., Amat, J., (2012). Study of patient-orthosis interaction forces in rehabilitation therapies IEEE Conference Publications 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob) , IEEE (Roma, Italy) , 1098-1103

The design of mechanical joints that kinematically behave as their biological counterparts is a challenge that if not addressed properly can cause inadequate forces transmission between robot and patient. This paper studies the interaction forces in rehabilitation therapies of the elbow joint. To measure the effect of orthosis-patient misalignments, a force sensor with a novel distributed architecture has been designed and used for this study. A test-bed based on an industrial robot acting as a virtual exoskeleton that emulates the action of a therapist has been developed and the interaction forces analyzed.

Keywords: Force, Force measurement, Force sensors, Joints, Medical treatment, Robot sensing systems, Force sensors, Medical robotics, Patient rehabilitation, Biological counterparts, Distributed architecture, Elbow joint, Force sensor, Inadequate forces transmission, Industrial robot, Mechanical joints design, Orthosis-patient misalignments, Patient-orthosis interaction forces, Rehabilitation therapies, Robot, Test-bed, Virtual exoskeleton

Hernansanz, A., Amat, J., Casals, A., (2012). Virtual Robot: A new teleoperation paradigm for minimally invasive robotic surgery IEEE Conference Publications 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob) , IEEE (Roma, Italy) , 749-754

This paper presents a novel teleoperation paradigm, the Virtual Robot (VR), focused on facilitating the surgeon tasks in minimally invasive robotic surgery. The VR has been conceived to increase the range of applicability of traditional master slave teleoperation architectures by means of an automatic cooperative behavior that assigns the execution of the ongoing task to the most suitable robot. From the user's point of view, the VR internal operation must be automatic and transparent. A set of evaluation indexes have been developed to obtain the suitability of each robot as well as an algorithm to determine the optimal instant of time to execute a task transfer. Several experiments demonstrate the usefulness of the VR, as well as indicates the next steps of the research.

Keywords: Cameras, Collision avoidance, Indexes, Joints, Robots, Surgery, Trajectory, Medical robotics, Surgery, Telerobotics, VR internal operation, Automatic cooperative behavior, Evaluation indexes, Master slave teleoperation architectures, Minimally invasive robotic surgery, Task transfer, Virtual robot

Ranaldo, Gabriella, Richaud-Patin, Yvonne, Lombardo, Angelo, Grosso, Chantal, Talmon, Maria, Raya, Angel, Naldini, Luigi, Schinco, Piercarla, Follenzi, Antonia, (2012). A novel iPSC-based strategy to correct the bleeding phenotype in Hemophilia A Molecular Therapy 15th Annual Meeting of the American Society of Gene and Cell Therapy (ASGCT) , Nature Publishing group (Philadelphia, USA) 20, S251-S251

Hemophilia A (HA) is an X-linked bleeding disorder caused by mutations in the coagulation factor VIII (FVIII) gene. Currently, there is no defi nitive cure. Therefore, cell and gene therapy may represent powerful solutions for the permanent treatment of HA. Reprogramming of genetically corrected somatic cells can be used to generate high amount of autologous, disease-free induced Pluripotent Stem Cells (iPSC), which can be then differentiated into progenitor cells relevant for gene and cell therapy applications. Towards this goal, we fi rst generated iPSC from human fi broblasts derived from healthy donors by retroviral transduction with four factors (OCT4, KLF4, SOX2 and c-MYC). These cells were phenotypically similar to human embryonic stem cells (hESC): colonies were compact, uniform and with defi ned borders when grown on feeder cells and expressed specifi c stem cell markers such as alkaline phosphatase, Nanog, Oct3/4, Sox2, TRA-1-60, TRA-1-81 and SSEA 3/4. iPSC were competent for differentiation into cell types of the three germ layers. Importantly, iPSC differentiated into endothelial cells (EC), a cell type that, when transplanted in HA mice, allows correcting the hemorrhagic phenotype of this model. iPSC can differentiate into EC acquiring a typical endothelial-like morphology with increased expression of CD31, KDR and FVIII. Moreover, after differentiation these cells were amenable to gene transfer by LV expressing the clotting human B-domain-deleted FVIII (hBDD-FVIII) under control of an endothelial-specifi c VE-cadherin promoter. Using this method we obtained iPSC, but they cannot be used for future therapeutic approach for the risk of reactivation of the reprogramming genes in the iPSC progeny. Thus, we recently reprogrammed human and mouse fi broblasts with a Cre-excisable LV expressing OCT4, KLF4 and SOX2. One month after transduction, colonies displayed a hESC-like morphology and stained positive for embryonic stem cell markers. RT-PCR and WB analyses showed activation of the endogenous reprogramming factors in iPSC. Given these results, we reprogrammed HA mouse fi broblasts into iPSC both before and after correction with a LV expressing hBDD-FVIII under control of the PGK promoter. Importantly, corrected iPSC expressed detectable BDD-FVIII in reprogrammed cells that were differentiated in EC. However, in hemophilic patients, to harvest fi broblasts from skin biopsies is risky; for this reason, we utilized peripheral blood cells as an easy-to-access source of cells and reprogrammed mononuclear cells from donors and hemophilic patients with HA. After genetic correction with LV and Cre-mediated excision of the reprogramming vector, the iPSC will be differentiated into EC and transplanted into NOD-SCID HA mice. Overall, these data will be instrumental to assess the engraftment, the proliferation and the levels of FVIII expression from differentiated, gene corrected and reprogramming factor free iPSC to confi rm the suitability of this approach for hemophilia gene-cell-therapy.

Sanmartí, M., Iavicoli, P., Samitier, J., (2012). Biosensors for diagnostic based on olfactory receptors Nanomedicine in Diagnostics (ed. Rozlosnik, N.), Science Publishers (Jersey, UK) , 120-150

Trepat, Xavier, Chen, Zaozao, Jacobson, Ken, (2012). Cell Migration Comprehensive Physiology (ed. Terjung, Ron), John Wiley & Sons, Inc. (Hoboken, USA) 2, 2369–2392

Cell migration is fundamental to establishing and maintaining the proper organization of multicellular organisms. Morphogenesis can be viewed as a consequence, in part, of cell locomotion, from large-scale migrations of epithelial sheets during gastrulation, to the movement of individual cells during development of the nervous system. In an adult organism, cell migration is essential for proper immune response, wound repair, and tissue homeostasis, while aberrant cell migration is found in various pathologies. Indeed, as our knowledge of migration increases, we can look forward to, for example, abating the spread of highly malignant cancer cells, retarding the invasion of white cells in the inflammatory process, or enhancing the healing of wounds. This article is organized in two main sections. The first section is devoted to the single-cell migrating in isolation such as occurs when leukocytes migrate during the immune response or when fibroblasts squeeze through connective tissue. The second section is devoted to cells collectively migrating as part of multicellular clusters or sheets. This second type of migration is prevalent in development, wound healing, and in some forms of cancer metastasis.

Navarro, M., Planell, J. A., (2012). Composite scaffolds for bone tissue engneering Encyclopedia of Composites (ed. Nicolais, L., Borzacchiello, A., Lee, S. M.), John Wiley & Sons (New Jersey, USA) , 544-558

Muñoz, L. M., Ponsa, P., Casals, A., (2012). Design and development of a guideline for ergonomic haptic interaction Advances in Intelligent and Soft Computing (ed. Hippe, Z.S. , Kulikowski, J.L. , Mroczek, Teresa), Springer (Chennai, India) 99, 15-29

The main goal of this chapter is to propose a guideline for human-robot systems focused on ergonomic haptic interaction. With this aim, this model presents several main parts: a set of heuristic indicators in order to identify the attributes of the haptic interaction, the relationship between indicators, the human task and the haptic interface requirements and finally an experimental task procedure and a qualitative performance evaluation metrics in the use of haptic interfaces. The final goal of this work is the study of possible applications of haptics in regular laboratory conditions, in order to improve the analysis, design and evaluation of human task over haptic interfaces in telerobotic applications.

Zaffino, R.L., Pardo, W.A., Mir, M., Samitier, J., (2012). Electrochemical DNA biosensors at the nanoscale Biosensors and Cancer (ed. Preedy, V.R., Patel, V.), Science Publishers (London, UK) , 62-84

Pecheva, E., Pramatarova, L., Hikov, T., Hristova, K., Altankov, G., Montgomery, P., Hanawa, T., (2012). Electrodeposition of hydroxyapatite-nanodiamond composite coating on metals, interaction with proteins and osteoblast-like cells Electrodeposition: Properties, processes and applications (ed. Udit Surya Mohanty), Nova Publishers (Hauppauge, USA) Electrical Engineering Developments, 233-253

Hydroxyapatite (HA) is the main component of human bones, a highly bioactive and biocompatible material; however, it has poor mechanical properties. Carbon-based coatings are found to significantly improve the mechanical properties of apatite, increase its adhesion, prevent metal ion release from metal implants and inhibit the formation of fibrous tissue and blood clotting upon implantation. In this chapter, homogeneous nanodiamond-reinforced hydroxyapatite (HA-ND) composite coating with improved mechanical strength and ductility was developed to enhance the biological properties of deposited by electrodeposition from simulated body fluid with dispersed nanodiamond particles. Study of the initial interaction of osteoblast-like MG-63 cells revealed that cells attached well on all plain samples (HA-ND, pure HA and stainless steel). However, precoating with fibronectin (FN) even at low adsorption concentrations (1mg/ml) strongly improved cell adhesion and preferentially spreading on the HA-ND samples as indicated by the flattened cell morphology and pronounced vinculin positive focal adhesions. This effect correlates with the observed higher affinity for FN. Moreover, osteoblasts tended to rearrange both adsorbed and secreted FN in a fibril-like pattern, suggesting improved FN matrix organization on HA-ND samples.

Castaño, O., Eltohamy, M., Kim, H. W., (2012). Electrospinning technology in tissue regeneration Nanotechnology in Regenerative Medicine - Methods and Protocols (Methods in Molecular Biology) (ed. Navarro, M., Planell, J. A.), Springer (New York, USA) 811, 127-140

Electrospinning is one of the most versatile and effective tools to produce nanostructured fibers in the biomedical science fields. The nanofibrous structure with diameters from tens to hundreds of nanometers largely mimics the native extracellular matrix (ECM) of many tissues. Thus far, a range of compositions including polymers and ceramics and their composites/hybrids have been successfully applied for generating electrospun nanofibers. Different processing tools in electrospinning set-ups and assemblies are currently developed to tune the morphology and properties of nanofibers. Herein, we demonstrate the electrospinning process and the electrospun biomaterials for specific use in tissue regeneration with some examples, involving different material combinations and fiber morphologies.

Keywords: Ceramic, Composites, Electrospinning, Nanofi bers, Nanostructured fi bers, Polymer, Tissue regeneration

Noailly, J., Lacroix, D., (2012). Finite element modelling of the spine Biomaterials for Spinal Surgery - Part I: Fundamentals of Biomaterials for Spinal Surgery (ed. Ambrosio, L., Tanner, K. E.), Woodhead Publishing Ltd (Cambridge, UK) , 144-232

Abolmaesumi, Purang, Joskowicz, Leo, Navab, Nassir, Jannin, Pierre, Hernansanz, Albert, Zerbato, Davide, Gasperotti, Lorenza, Scandola, Michele, Fiorini, Paolo, Casals, Alicia, (2012). Improving the development of surgical skills with virtual fixtures in simulation Lecture Notes in Computer Science Information Processing in Computer-Assisted Interventions (ed. Abolmaesumi, P., Joskowicz, L., Navab, N., Jannin, P.), Springer Berlin Heidelberg (Chennai, India) 7330, 157-166

This paper focuses on the use of virtual fixtures to improve the learning of basic skills for laparoscopic surgery. Five virtual fixtures are defined, integrated into a virtual surgical simulator and used to define an experimental setup based on a trajectory following task. 46 subjects among surgeons and residents underwent a training session based on the proposed setup. Their performance has been logged and used to identify the effect of virtual fixtures on the learning curve from the point of view of accuracy and completion time. Virtual fixtures prove to be effective in improving the learning and affect differently accuracy and completion time. This suggests the possibility to tailor virtual fixtures on the specific task requirements.

Navarro, M., Planell, J. A., (2012). Is nanotechnology the key to unravel and engineer biological processes? Nanotechnology in Regenerative Medicine - Methods and Protocols (Methods in Molecular Biology) (ed. Navarro, M., Planell, J. A.), Springer (New York, USA) 811, 1-16

Regenerative medicine is an emerging field aiming to the development of new reparative strategies to treat degenerative diseases, injury, and trauma through developmental pathways in order to rebuild the architecture of the original injured organ and take over its functionality. Most of the processes and interactions involved in the regenerative process take place at subcellular scale. Nanotechnology provides the tools and technology not only to detect, to measure, or to image the interactions between the different biomolecules and biological entities, but also to control and guide the regenerative process. The relevance of nanotechnology for the development of regenerative medicine as well as an overview of the different tools that contribute to unravel and engineer biological systems are presented in this chapter. In addition, general data about the social impact and global investment in nanotechnology are provided.

Keywords: Nanotechnology, Regenerative medicine, Tissue engineering

Waters, C.M., Roan, E., Navajas, D., (2012). Mechanobiology in lung epithelial cells: Measurements, perturbations, and responses Comprehensive Physiology (ed. Terjung, Ron), John Wiley & Sons, Inc. (Hoboken, USA) 2, (1), 1-29

Epithelial cells of the lung are located at the interface between the environment and the organism and serve many important functions including barrier protection, fluid balance, clearance of particulate, initiation of immune responses, mucus and surfactant production, and repair following injury. Because of the complex structure of the lung and its cyclic deformation during the respiratory cycle, epithelial cells are exposed to continuously varying levels of mechanical stresses. While normal lung function is maintained under these conditions, changes in mechanical stresses can have profound effects on the function of epithelial cells and therefore the function of the organ. In this review, we will describe the types of stresses and strains in the lungs, how these are transmitted, and how these may vary in human disease or animal models. Many approaches have been developed to better understand how cells sense and respond to mechanical stresses, and we will discuss these approaches and how they have been used to study lung epithelial cells in culture. Understanding how cells sense and respond to changes in mechanical stresses will contribute to our understanding of the role of lung epithelial cells during normal function and development and how their function may change in diseases such as acute lung injury, asthma, emphysema, and fibrosis.

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Martínez, E., Pla, M., Samitier, J., (2012). Micro/nanopatterning of proteins using a nanoimprint-based contact printing technique Nanotechnology in Regenerative Medicine - Methods and Protocols (Methods in Molecular Biology) (ed. Navarro, M., Planell, J. A.), Springer (New York, USA) 811, 79-87

Micro and nanoscale protein patterning based on microcontact printing technique on large substrates have often resolution problems due to roof collapse of the poly(dimethylsiloxane) (PDMS) stamps used. Here, we describe a technique that overcomes these issues by using instead a stamp made of poly(methyl methacrylate) (PMMA), a much more rigid polymer that do not collapse even using stamps with very high aspect ratios (up to 300:1). Conformal contact between the stamp and the substrate is achieved because of the homogeneous pressure applied via the nanoimprint lithography instrument, and it has allowed us to print lines of protein 150 nm wide, at a 400 nm period. This technique, therefore, provides an excellent method for the direct printing of high-density submicrometer scale patterns, or, alternatively, micro/nanopatterns spaced at large distances.

Keywords: Microcontact printing, Nanoimprint lithography, Poly(methyl methacrylate), Protein

Garcia-Parajo, M. F., (2012). The role of nanophotonics in regenerative medicine Nanotechnology in Regenerative Medicine - Methods and Protocols (Methods in Molecular Biology) (ed. Navarro, M., Planell, J. A.), Springer (New York, USA) 811, 267-284

Cells respond to biochemical and mechanical stimuli through a series of steps that begin at the molecular, nanometre level, and translate finally in global cell response. Defects in biochemical- and/or mechanical-sensing, transduction or cellular response are the cause of multiple diseases, including cancer and immune disorders among others. Within the booming field of regenerative medicine, there is an increasing need for developing and applying nanotechnology tools to bring understanding on the cellular machinery and molecular interactions at the nanoscale. Nanotechnology, nanophotonics and in particular, high-resolution-based fluorescence approaches are already delivering crucial information on the way that cells respond to their environment and how they organize their receptors to perform specialized functions. This chapter focuses on emerging super-resolution optical techniques, summarizing their principles, technical implementation, and reviewing some of the achievements reached so far.

Keywords: Cell membrane organization, Nanophotonics, Near-field optical microscopy, Super-resolution optical microscopy

Redondo, L., Giannotti, M. I., Sanz, F., (2012). Stability of lipid bilayers as model membranes: Atomic force microscopy and spectroscopy approach Atomic force microscopy in liquid (ed. Baró, A. M., Reifenberger, R. G.), Wiley-VCH Verlag GmbH & Co.KGaA (Weinheim, Germany) Part I: General Atomic Force Microscopy, 259-284

van Zanten, T. S., Garcia-Parajo, M. F., (2012). Super-resolution near-field optical microscopy Comprehensive Biophysics (ed. Egelman, E. H.), Elsevier (Desdren, Germany) Volume 2: Biophysical Techniques for Characterization of Cells, 144-164

Near-field optical microscopy is a technique not limited by the laws of diffraction that enables simultaneous high-resolution fluorescence and topographic measurements at the nanometer scale. This chapter highlights the intrinsic advantages of near-field optics in the study of cellular structures. The first part of the chapter lays the foundations of the near-field concept and technical implementation of near-field scanning optical microscopy (NSOM), whereas the second part of the chapter focuses on applications of NSOM to the study of model membranes and cellular structures on the plasma membrane. The last part of the chapter discusses further directions of near-field optics, including optical antennas and fluorescence correlation spectroscopy approaches in the near-field regime.

Keywords: Biological membranes, Cell membrane nanoscale compartmentalization, Cellular nanodomains, Fluorescence correlation spectroscopy in reduced volumes, Immunoreceptor imaging, Lipid rafts, Near-field scanning optical microscopy, Optical nano-antennas, Shear force imaging, Single molecule detection, Super-resolution microscopy

Navarro, M., Planell, J. A., (2012). Nanotechnology in Regenerative Medicine Methods and Protocols (Methods in Molecular Biology) , Springer (New York, USA) 811, (811), 319


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