by Keyword: Film

Molina, BG, Ocón, G, Silva, FM, Iribarren, JI, Armelin, E, Alemán, C, (2023). Thermally-induced shape memory behavior of polylactic acid/ polycaprolactone blends European Polymer Journal 196, 112230

A study of the shape memory effect on extruded polylactic acid (PLA) and polycaprolactone (PCL) blends, which were transformed into films and movable components of articulated specimens by hot pressing and 3D printing, respectively, is presented. After characterizing their chemical structure by FTIR spectroscopy and their wetta-bility, the thermal properties and mechanical response of the blends were evaluated and compared with those of neat PLA and PCL. The blends exhibited very good interfacial adhesion between the phases, even though they are immiscible polymers. The thermoresponsive shape memory effects of neat PLA, neat PCL and PLA/PCL blends with different compositions (90/30, 70/30 and 50/50 w/w%) were evaluated considering three consecutive heating-cooling cycles. Comparison of the initial permanent state geometry with the geometries achieved after each heating-cooling cycle for both films and 3D printed specimens, evidenced that the 70/30 w/w% blend exhibited the best behavior. Thus, the blends obtained with such composition showed the maximum reversibility between the temporary and permanent states (i.e. highest shape recovery capability) and shape fixing of such two states.

JTD Keywords: 3d printing, Fibers, Films, Poly(lactic acid), Polycaprolactone, Polylactic acid, Polymer, Shape fixing, Shape-memory polymers, Unimolecular micelles

Campo-Pérez V, Alcàcer-Almansa J, Julián E, Torrents E, (2023). A High-Throughput Microtiter Plate Screening Assay to Quantify and Differentiate Species in Dual-Species Biofilms Microorganisms 11, 2244

Pathogenic bacteria form biofilms during infection, and polymicrobial biofilms are the most frequent manifestation. Biofilm attachment, maturation, and/or antibiotic sensitivity are mainly evaluated with microtiter plate assays, in which bacteria are stained to enable the quantification of the biomass by optical absorbance or fluorescence emission. However, using these methods to distinguish different species in dual-species or polymicrobial biofilms is currently impossible. Colony-forming unit counts from homogenized dual-species biofilms on selective agar medium allow species differentiation but are time-consuming for a high-throughput screening. Thus, reliable, feasible, and fast methods are urgently needed to study the behavior of polymicrobial and dual-species communities. This study shows that Pseudomonas aeruginosa and Burkholderia cenocepacia strains expressing specific fluorescent or bioluminescent proteins permit the more efficient study of dual-species biofilms compared to other methods that rely on measuring the total biomass. Combining fluorescence and bioluminescence measurements allows an independent analysis of the different microbial species within the biofilm, indicating the degree of presence of each one over time during a dual-species biofilm growth. The quantitative strategies developed in this work are reproducible and recommended for dual-species biofilm studies with high-throughput microtiter plate approaches using strains that can constitutively express fluorescent or bioluminescent proteins.

JTD Keywords: Biomass quantification, Burkholderia cenocepacia, Crystal violet, Dual-species biofilms, Pseudomonas aeruginosa

Gholami S, Rezvani A, Vatanpour V, Khoshravesh SH, Llorens J, Engel E, Castaño O, Cortina JL, (2023). Chlorine resistance property improvement of polyamide reverse osmosis membranes through cross-linking degree increment Science Of The Total Environment 889, 164283

Highly permeable polyamide reverse osmosis (RO) membranes are desirable for reducing the energy burden and ensuring future water resources in arid and semiarid regions. One notable drawback of thin film composite (TFC) polyamide RO/NF membranes is the polyamide's sensitivity to degradation by free chlorine, the most used biocide in water purification trains. This investigation demonstrated a significant increase in the crosslinking-degree parameter by the m-phenylenediamine (MPD) chemical structure extending in the thin film nanocomposite (TFN) membrane without adding extra MPD monomers to enhance the chlorine resistance and performance. Membrane modification was carried out according to monomer ratio changes and Nanoparticle embedding into the PA layer approaches. A new class of TFN-RO membranes incorporating novel aromatic amine functionalized (AAF)-MWCNTs embedded into the polyamide (PA) layer was introduced. A purposeful strategy was carried out to use cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) as an intermediate functional group in the AAF-MWCNTs. Thus, amidic nitrogen, connected to benzene rings and carbonyl groups, assembles a structure similar to the standard PA, consisting of MPD and trimesoyl chloride. The resulting AAF-MWCNTs were mixed in the aqueous phase during the interfacial polymerization to increase the susceptible positions to chlorine attack and improve the crosslinking degree in the PA network. The characterization and performance results of the membrane demonstrated an increase in ion selectivity and water flux, impressive stability of salt rejection after chlorine exposure, and improved antifouling performance. This purposeful modification resulted in overthrowing two tradeoffs; i) high crosslink density-water flux and ii) salt rejection-permeability. The modified membrane demonstrated ameliorative chlorine resistance relative to the pristine one, with twice the increase in crosslinking degree, more than four times the enhancement of the oxidation resistance, negligible reduction in the salt rejection (0.83 %), and only 5 L/m2.h flux loss following a rigorous static chlorine exposure of 500 ppm.h under acidic conditions. The excellent performance of new chlorine resistant TNF RO membranes fabricated via AAF-MWCNTs together with the facile membrane manufacturing process offered the possibility of postulating them in the desalination field, which could eventually help the current freshwater supply challenge.Copyright © 2023 Elsevier B.V. All rights reserved.

JTD Keywords: behavior, carbon nanotubes, desalination, interfacial polymerization, naclo resistance, nanocomposite, nanofiltration membrane, performance, polymerization, ro membranemodification, substrate, water, Antifouling, Desalination, Interfacial polymerization, Naclo resistance, Ro membrane modification, Thin-film composite

Fontana-Escartín, A, Lanzalaco, S, Bertran, O, Aradilla, D, Alemán, C, (2023). Aqueous alginate/MXene inks for 3D printable biomedical devices Colloids And Surfaces A-Physicochemical And Engineering Aspects 671, 131632

Electrochemically responsive hydrogel networks have been obtained usin g printable inks made of a biopolymer, alginate (Alg), and an inorganic 2D material , MXene (titaniu m carbide, Ti3C2Tx) nanosheets. While MXene offers an electrically conductive pathway for electron transfer and Alg provides an interconnected framework for ion diffusion, the printed nanocomposite results, after gelation, in an extended active interface for redox reactions, being an ideal framework to design and construct flexible devices for biomedical applications. In this work, after characterization, we demonstrate that hydrogels obtained by cross-linking printed Alg /MXene inks exhibit great potential for bioelectronics. More specifically, we prove that flexible Alg/MXene hydrogels act as self-supported electroactive electrodes for the electrochemical detection of bioanalytes, such as dopamine, with a performance similar to that achieved using more sophisticated electrodes, as for example those containing conducting poly-mers and electrocatalytic gold nanoparticles. In addition, Alg/MXene hydrogels have been successfully used to regulate the release of a previously loaded broad spectrum antibiotic (chloramphenicol) by electrical stimulation.

JTD Keywords: 3d-printing, Biomedical application s, Composites, Conducting polymers, Drug release, Electroresponsive hydrogels, Fabrication, Hydrogels, Platform, Sensors, Strategy, Surface, Thin-film, Titanium carbide

Liang Z, Nilsson M, Kragh KN, Hedal I, Alcàcer-Almansa J, Kiilerich RO, Andersen JB, Tolker-Nielsen T, (2023). The role of individual exopolysaccharides in antibiotic tolerance of Pseudomonas aeruginosa aggregates Frontiers In Microbiology 14, 1187708

The bacterium Pseudomonas aeruginosa is involved in chronic infections of cystic fibrosis lungs and chronic wounds. In these infections the bacteria are present as aggregates suspended in host secretions. During the course of the infections there is a selection for mutants that overproduce exopolysaccharides, suggesting that the exopolysaccharides play a role in the persistence and antibiotic tolerance of the aggregated bacteria. Here, we investigated the role of individual P. aeruginosa exopolysaccharides in aggregate-associated antibiotic tolerance. We employed an aggregate-based antibiotic tolerance assay on a set of P. aeruginosa strains that were genetically engineered to over-produce a single, none, or all of the three exopolysaccharides Pel, Psl, and alginate. The antibiotic tolerance assays were conducted with the clinically relevant antibiotics tobramycin, ciprofloxacin and meropenem. Our study suggests that alginate plays a role in the tolerance of P. aeruginosa aggregates toward tobramycin and meropenem, but not ciprofloxacin. However, contrary to previous studies we did not observe a role for Psl or Pel in the tolerance of P. aeruginosa aggregates toward tobramycin, ciprofloxacin, and meropenem.Copyright © 2023 Liang, Nilsson, Kragh, Hedal, Alcàcer-Almansa, Kiilerich, Andersen and Tolker-Nielsen.

JTD Keywords: aggregates, antibiotic tolerance, biofilm formation, extracellular matrix, genome, growth, lungs, molecular-mechanisms, mutations, polysaccharide, pseudomonas aeruginosa, psl, system, Aggregates, Antibiotic tolerance, Biofilm, Extracellular matrix, Pseudomonas aeruginosa, Small-colony variants

Fontana-Escartín A, Hauadi KE, Lanzalaco S, Pérez-Madrigal MM, Armelin E, Turon P, Alemán C, (2023). Smart Design of Sensor-Coated Surgical Sutures for Bacterial Infection Monitoring Macromolecular Bioscience 23, e2300024

Virtually, all implantable medical devices are susceptible to infection. As the main healthcare issue concerning implantable devices is the elevated risk of infection, different strategies based on the coating or functionalization of biomedical devices with antiseptic agents or antibiotics are proposed. In this work, an alternative approach is presented, which consists of the functionalization of implantable medical devices with sensors capable of detecting infection at very early stages through continuous monitoring of the bacteria metabolism. This approach, which is implemented in surgical sutures as a representative case of implantable devices susceptible to bacteria colonization, is expected to minimize the risk of worsening the patient's clinical condition. More specifically, non-absorbable polypropylene/polyethylene (PP/PE) surgical sutures are functionalized with conducting polymers using a combination of low-pressure oxygen plasma, chemical oxidative polymerization, and anodic polymerization, to detect metabolites coming from bacteria respiration. Functionalized suture yarns are used for real-time monitoring of bacteria growth, demonstrating the potential of this strategy to fight against infections.© 2023 Wiley-VCH GmbH.

JTD Keywords: adhesion, biofilm, conducting polymers, contamination, derivatives, detections, functionalized sutures, nadh, poly(3,4-ethylenedioxythiophene), Bacteria growth, Conducting polymers, Detections, Functionalized sutures, Monofilament, Nadh

Rubio-Canalejas, A, Admella, J, Pedraz, L, Torrents, E, (2023). Pseudomonas aeruginosa Nonphosphorylated AlgR Induces Ribonucleotide Reductase Expression under Oxidative Stress Infectious Conditions Msystems 8, e0100522

The emergence of multidrug-resistant bacteria is a serious problem worldwide. Pseudomonas aeruginosa is a pathogen that causes severe infections because it can form a biofilm that protects it from immune system mechanisms such as the production of oxidative stress. Ribonucleotide reductases are essential enzymes which synthesize deoxyribonucleotides used in the replication of DNA.

JTD Keywords: algr, biofilm, galleria mellonella, nrdj, oxidative stress, Gene-expression, Ribonucleotide reductase

Resina, Leonor, El Hauadi, Karima, Sans, Jordi, Esteves, Teresa, Ferreira, Frederico Castelo, Pérez-Madrigal, Maria M., Alemán, Carlos, (2023). Electroresponsive and pH-Sensitive Hydrogel as Carrier for Controlled Chloramphenicol Release Biomacromolecules 24, 1432-1444

Multiresponsive hydrogels, which are smart soft materials that respond to more than one external stimulus, have emerged as powerful tools for biomedical applications, such as drug delivery. Within this context and with the aim of eliminating the systematic administration of antibiotics, special attention is being paid to the development of systems for controlled delivery of antibiotic for topical treatment of bacterial infections. In this work, an electro-chemo responsive hydrogel able to release chloramphenicol (CAM), a broad spectrum antibiotic also used for anticancer therapy, is proposed. This has been prepared by grafting poly(acrylic acid) (PAA) to sodium alginate (Alg) and in situ encapsulation of poly(3,4-ethylenedioxythiophene) nanoparticles loaded with CAM (PEDOT/CAM NPs), which were obtained by emulsion polymerization. Although the response to electrical stimuli of PEDOT was the main control for the release of CAM from PEDOT/CAM NPs, the release by passive diffusion had a relatively important contribution. Conversely, the passive release of antibiotic from the whole engineered hydrogel system, Alg-g-PAA/PEDOT/CAM, was negligible, whereas significant release was achieved under electrostimulation in an acid environment. Bacterial tests and assays with cancer cells demonstrated that the biological activity of CAM remained after release by electrical stimulation. Notably, the successful dual-response of the developed hydrogel to electrical stimuli and pH changes evidence the great prospect of this smart material in the biomedical field, as a tool to fight against bacterial infections and to provide local cancer treatment.

JTD Keywords: drug-delivery, films, growth, nanoparticles, Cancer stem-cells

Munoz-Galan, H, Aleman, C, Perez-Madrigal, MM, (2023). Beyond biology: alternative uses of cantilever-based technologies Lab On A Chip 23, 1128-1150

Microcantilever-based platforms are presented as versatile lab-on-chip devices for advanced applications spanning from material characterization and environmental monitoring to energy.

JTD Keywords: mechanical-properties, micromechanical cantilever, photothermal spectroscopy, sensitive detection, silicon cantilevers, solid-liquid interface, surface-stress, thin-films, vapor detection, Nanomechanical thermal-analysis

Huetter, Larissa, Kyndiah, Adrica, Gomila, Gabriel, (2023). Analytical Physical Model for Electrolyte Gated Organic Field Effect Transistors in the Helmholtz Approximation Advanced Theory And Simulations 6, 2200696

Sanmukh, Swapnil Ganesh, Admella, Joana, Moya-Andérico, Laura, Fehér, Tamás, Arévalo-Jaimes, Betsy Verónica, Blanco-Cabra, Núria, Torrents, Eduard, (2023). Accessing the In Vivo Efficiency of Clinically Isolated Phages against Uropathogenic and Invasive Biofilm-Forming Escherichia coli Strains for Phage Therapy Cells 12, 344

Escherichia coli is one of the most common members of the intestinal microbiota. Many of its strains are associated with various inflammatory infections, including urinary or gut infections, especially when displaying antibiotic resistance or in patients with suppressed immune systems. According to recent reports, the biofilm-forming potential of E. coli is a crucial factor for its increased resistance against antibiotics. To overcome the limitations of using antibiotics against resistant E. coli strains, the world is turning once more towards bacteriophage therapy, which is becoming a promising candidate amongst the current personalized approaches to target different bacterial infections. Although matured and persistent biofilms pose a serious challenge to phage therapy, they can still become an effective alternative to antibiotic treatment. Here, we assess the efficiency of clinically isolated phages in phage therapy against representative clinical uropathogenic and invasive biofilm-forming E. coli strains. Our results demonstrate that irrespective of host specificity, bacteriophages producing clear plaques with a high burst size, and exhibiting depolymerizing activity, are good candidates against biofilm-producing E. coli pathogens as verified from our in vitro and in vivo experiments using Galleria mellonella where survival was significantly increased for phage-therapy-treated larvae.

JTD Keywords: antibiotic resistance, assay, bacteriophage, bacteriophages, biofilm-forming potential, infection, inflammatory infections, mechanisms, Galleria-mellonella, Intestinal microflora

Webster-Wood, VA, Guix, M, Xu, NW, Behkam, B, Sato, H, Sarkar, D, Sanchez, S, Shimizu, M, Parker, KK, (2023). Biohybrid robots: recent progress, challenges, and perspectives Bioinspiration & Biomimetics 18, 15001

The past ten years have seen the rapid expansion of the field of biohybrid robotics. By combining engineered, synthetic components with living biological materials, new robotics solutions have been developed that harness the adaptability of living muscles, the sensitivity of living sensory cells, and even the computational abilities of living neurons. Biohybrid robotics has taken the popular and scientific media by storm with advances in the field, moving biohybrid robotics out of science fiction and into real science and engineering. So how did we get here, and where should the field of biohybrid robotics go next? In this perspective, we first provide the historical context of crucial subareas of biohybrid robotics by reviewing the past 10+ years of advances in microorganism-bots and sperm-bots, cyborgs, and tissue-based robots. We then present critical challenges facing the field and provide our perspectives on the vital future steps toward creating autonomous living machines.

JTD Keywords: biohybrid, cyborg, Biohybrid, Cell, Cyborg, Delivery, Fabrication, Flight, Insect, Living machines, Muscle activities, Muscular thin-films, Nanoparticles, Stimulation, Tissue

Moussa, Dina G., Sharma, Ashok K., Mansour, Tamer A, Witthuhn, Bruce, Perdigão, Jorge, Rudney, Joel D., Aparicio, Conrado, Gomez, Andres, (2022). Functional signatures of ex-vivo dental caries onset Journal Of Oral Microbiology 14, 2123624

The etiology of dental caries remains poorly understood. With the advent of next-generation sequencing, a number of studies have focused on the microbial ecology of the disease. However, taxonomic associations with caries have not been consistent. Researchers have also pursued function-centric studies of the caries microbial communities aiming to identify consistently conserved functional pathways. A major question is whether changes in microbiome are a cause or a consequence of the disease. Thus, there is a critical need to define conserved functional signatures at the onset of dental caries.Since it is unethical to induce carious lesions clinically, we developed an innovative longitudinal ex-vivo model integrated with the advanced non-invasive multiphoton second harmonic generation bioimaging to spot the very early signs of dental caries, combined with 16S rRNA short amplicon sequencing and liquid chromatography-mass spectrometry-based targeted metabolomics.For the first time, we induced longitudinally monitored caries lesions validated with the scanning electron microscope. Consequently, we spotted the caries onset and, associated with it, distinguished five differentiating metabolites - Lactate, Pyruvate, Dihydroxyacetone phosphate, Glyceraldehyde 3-phosphate (upregulated) and Fumarate (downregulated). Those metabolites co-occurred with certain bacterial taxa; Streptococcus, Veillonella, Actinomyces, Porphyromonas, Fusobacterium, and Granulicatella, regardless of the abundance of other taxa.These findings are crucial for understanding the etiology and dynamics of dental caries, and devising targeted interventions to prevent disease progression.© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

JTD Keywords: bacteria, biofilms, children, dental caries, generation, genomics, longitudinal model, metabolism, metabolomics, microscopy, non-invasive bioimaging, oral microbiome, plaque, restorations, signatures, Dental caries, Field-emission sem, Signatures

García-Torres, Jose, Lázaro, Carmen, Sylla, Dioulde, Lanzalaco, Sonia, Ginebra, Maria-Pau, Alemán, Carlos, (2022). Combining 2D organic and 1D inorganic nanoblocks to develop free-standing hybrid nanomembranes for conformable biosensors Journal Of Nanostructure In Chemistry ,

We report a simple approach to fabricate free-standing perforated 2D nanomembranes hosting well-ordered 1D metallic nanostructures to obtain hybrid materials with nanostructured surfaces for flexible electronics. Nanomembranes are formed by alternatively depositing perforated poly(lactic acid) (PLA) and poly(3,4-ethylenedioxythiophene) layers. Copper metallic nanowires (NWs) were incorporated into the nanoperforations of the top PLA layer by electrodeposition and further coated with silver via a transmetallation reaction. The combination of 2D polymeric nanomembranes and aligned 1D metallic NWs allows merging the flexibility and conformability of the ultrathin soft polymeric nanomembranes with the good electrical properties of metals for biointegrated electronic devices. Thus, we were able to tailor the nanomembrane surface chemistry as it was corroborated by SEM, EDX, XPS, CV, EIS and contact angle. The obtained hybrid nanomembranes were flexible and conformable showing sensing capacity towards H2O2 with good linear concentration range (0.35–10 mM), sensitivity (120 µA cm?2 mM?1) and limit of detection (7 ?m). Moreover, the membranes showed good stability, reproducibility and selectivity towards H2O2.

JTD Keywords: biointegrated sensors, designs, electronics, fabrication, free-standing films, h2o2, metallic nanowires, nanoparticles, nanowires, sensor, skin, Hydrogen-peroxide, Perforated nanomembranes

Moreira, VB, Aleman, C, Rintjema, J, Bravo, F, Kleij, AW, Armelin, E, (2022). A Biosourced Epoxy Resin for Adhesive Thermoset Applications Chemsuschem 15, e202102624

Biobased epoxy-derived raw materials will be essential for future coating and adhesive designs in industry. Here, a facile approach is reported towards the incorporation of limonene into an epoxy-functionalized polycarbonate and its crosslinking with a polyamine curing agent to obtain a thermoset material. For the first time, a solvent-borne adhesive with excellent film-forming, mechanical and adhesion strength properties is described.

JTD Keywords: adhesives, biobased epoxies, limonene, polycarbonate, Adhesives, Biobased epoxies, Biobased epoxy, Carbon-dioxide, Curing agents, Design in industries, Epoxides, Epoxy, Epoxy resins, Film adhesion, Film-forming, Functionalized, Limonene, Mechanical, Monomer, Monoterpenes, Oil, Oxide, Performance, Polyamines, Polycarbonate, Polycarbonates, Terpenes, Thermoset materials, Thermosets

Borras, N, Sanchez-Jimenez, M, Casanovas, J, Aleman, C, Perez-Madrigal, MM, (2022). Porous Poly(3,4-ethylenedioxythiophene)-Based Electrodes for Detecting Stress Biomarkers in Artificial Urine and Sweat Macromolecular Materials And Engineering 307,

When danger is perceived, the human body responds to overcome obstacles and survive a stressful situation; however, sustained levels of stress are associated with health disorders and diminished life quality. Hence, stress biomarkers are monitored to control stress quantitatively. Herein, a porous sensor (4l-COP/p) composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (COP), which is prepared in a four-layered fashion to detect dopamine (DA) and serotonin (5-HT), is presented. Specifically, the detection is conducted in phosphate-buffered saline (PBS), as well as artificial urine and sweat, by applying cyclic voltammetry. The limit of detection values obtained are as low as 5.7 x 10(-6) and 1.4 x 10(-6) m for DA and 5-HT, respectively, when assessed individually in artificial urine. When mixed in PBS, 4l-COP/p detects both biomarkers with a resolution of 0.18 V and a sensitivity of 40 and 30 mu A mm(-1) for DA and 5-HT, respectively. Additionally, by theoretical calculations, the interaction pattern that each stress biomarker establishes with the PEDOT outer layer is elucidated. Whereas DA interacts with the pi-system of PEDOT, 5-HT forms specific hydrogen bonds with the conducting polymer chains. The resolution value obtained depends upon such interactions. Overall, 4l-COP/p electrodes display potential as stress sensing devices for healthcare technologies.

JTD Keywords: Artificial body fluids, Boron-doped diamond, Cortisol, Cyclic voltammetry, Dopamine, Multilayered films, Paper, Saliva, Selective detection, Sensor, Sensors, Serotonin, Serum

Rubio-Canalejas, A, Baelo, A, Herbera, S, Blanco-Cabra, N, Vukomanovic, M, Torrents, E, (2022). 3D spatial organization and improved antibiotic treatment of a Pseudomonas aeruginosa-Staphylococcus aureus wound biofilm by nanoparticle enzyme delivery Frontiers In Microbiology 13, 959156

Chronic wounds infected by Pseudomonas aeruginosa and Staphylococcus aureus are a relevant health problem worldwide because these pathogens grow embedded in a network of polysaccharides, proteins, lipids, and extracellular DNA, named biofilm, that hinders the transport of antibiotics and increases their antimicrobial tolerance. It is necessary to investigate therapies that improve the penetrability and efficacy of antibiotics. In this context, our main objectives were to study the relationship between P. aeruginosa and S. aureus and how their relationship can affect the antimicrobial treatment and investigate whether functionalized silver nanoparticles can improve the antibiotic therapy. We used an optimized in vitro wound model that mimics an in vivo wound to co-culture P. aeruginosa and S. aureus biofilm. The in vitro wound biofilm was treated with antimicrobial combinatory therapies composed of antibiotics (gentamycin and ciprofloxacin) and biofilm-dispersing free or silver nanoparticles functionalized with enzymes (alpha-amylase, cellulase, DNase I, or proteinase K) to study their antibiofilm efficacy. The interaction and colocalization of P. aeruginosa and S. aureus in a wound-like biofilm were examined and detailed characterized by confocal and electronic microscopy. We demonstrated that antibiotic monotherapy is inefficient as it differentially affects the two bacterial species in the mixed biofilm, driving P. aeruginosa to overcome S. aureus when using ciprofloxacin and the contrary when using gentamicin. In contrast, dual-antibiotic therapy efficiently reduces both species while maintaining a balanced population. In addition, DNase I nanoparticle treatment had a potent antibiofilm effect, decreasing P. aeruginosa and S. aureus viability to 0.017 and 7.7%, respectively, in combined antibiotics. The results showed that using nanoparticles functionalized with DNase I enhanced the antimicrobial treatment, decreasing the bacterial viability more than using the antibiotics alone. The enzymes alpha-amylase and cellulase showed some antibiofilm effect but were less effective compared to the DNase I treatment. Proteinase K showed insignificant antibiofilm effect. Finally, we proposed a three-dimensional colocalization model consisting of S. aureus aggregates within the biofilm structure, which could be associated with the low efficacy of antibiofilm treatments on bacteria. Thus, designing a clinical treatment that combines antibiofilm enzymes and antibiotics may be essential to eliminating chronic wound infections.

JTD Keywords: antimicrobial therapies, biofilm, chronic infection, nanoparticle, Antimicrobial therapies, Biofilm, Chronic infection, In-vitro, Matrix, Model, Nanoparticle, Wound healing

Babeli I, Puiggalí-Jou A, Roa JJ, Ginebra M-P, García-Torres J, Alemán C, (2021). Hybrid conducting alginate-based hydrogel for hydrogen peroxide detection from enzymatic oxidation of lactate International Journal Of Biological Macromolecules 193, 1237-1248

A conducting nanocomposite hydrogel is developed for the detection of L-lactate. The hydrogel is based on a mixture of alginate (Alg) and poly(3,4-ethylenedioxythiophene) (PEDOT), which is loaded with gold nanoparticles (GNP). In this novel hydrogel, Alg provides 3D structural support and flexibility, PEDOT confers conductivity and sensing capacity, and GNP provides signal amplification with respect to simple voltammetric and chronoamperometric response. The synergistic combination of the properties provided by each component results in a new flexible nanocomposite with outstanding capacity to detect hydrogen peroxide, which has been used to detect the oxidation of L-lactate. The hydrogel detects hydrogen peroxide with linear response and limits of detection of 0.91 ?M and 0.02 ?M by cyclic voltammetry and chronoamperometry, respectively. The hydrogel is functionalized with lactate oxidase, which catalyzes the oxidation of L-lactate to pyruvate, forming hydrogen peroxide. For L-lactate detection, the functionalized biosensor works in two linear regimes, one for concentrations lower than 5 mM with a limit of detection of 0.4 mM, and the other for concentrations up to 100 mM with a limit of detection of 3.5 mM. Because of its linear range interval, the developed biosensor could be suitable for a wide number of biological fluids. © 2021

JTD Keywords: biosensor, dehydrogenase, enzymatic oxidation, films, hardness, indentation, lactate oxidase, Biosensor, Elastic-modulus, Enzymatic oxidation, Lactate, Lactate oxidase, Reacciones enzimáticas

Prieto, Alejandro, Bernabeu, Manuel, Sánchez-Herrero, José Francisco, Pérez-Bosque, Anna, Miró, Lluïsa, Bäuerl, Christine, Collado, Carmen, Hüttener, Mário, Juárez, Antonio, (2021). Modulation of AggR levels reveals features of virulence regulation in enteroaggregative E. coli Commun Biol 4, 1295

Enteroaggregative Escherichia coli (EAEC) strains are one of the diarrheagenic pathotypes. EAEC strains harbor a virulence plasmid (pAA2) that encodes, among other virulence determinants, the aggR gene. The expression of the AggR protein leads to the expression of several virulence determinants in both plasmids and chromosomes. In this work, we describe a novel mechanism that influences AggR expression. Because of the absence of a Rho-independent terminator in the 3?UTR, aggR transcripts extend far beyond the aggR ORF. These transcripts are prone to PNPase-mediated degradation. Structural alterations in the 3?UTR result in increased aggR transcript stability, leading to increased AggR levels. We therefore investigated the effect of increased AggR levels on EAEC virulence. Upon finding the previously described AggR-dependent virulence factors, we detected novel AggR-regulated genes that may play relevant roles in EAEC virulence. Mutants exhibiting high AggR levels because of structural alterations in the aggR 3?UTR show increased mobility and increased pAA2 conjugation frequency. Furthermore, among the genes exhibiting increased fold change values, we could identify those of metabolic pathways that promote increased degradation of arginine, fatty acids and gamma-aminobutyric acid (GABA), respectively. In this paper, we discuss how the AggR-dependent increase in specific metabolic pathways activity may contribute to EAEC virulence.

JTD Keywords: aggregative adherence, arginine metabolism, biofilm formation, escherichia-coli, gene-expression, messenger-rna, operon, persistent diarrhea, untranslated region, Fimbria-i expression

Hidouri S, Errachid AH, Baussels J, Korpan YI, Ruiz-Sanchez O, Baccar ZM, (2021). Potentiometric sensing of histamine using immobilized enzymes on layered double hydroxides Journal Of Food Science And Technology-Mysore 58, 2936-2942

Diamine oxydase and peroxidase have been co-immobilized onto layered double hydroxide (LDH) thin films for the development of real-time histamine biosensors. The chosen LDH materials are Mg2AlCO3, Mg4FeCl and Ca2AlCl. Prepared bi-enzymatic hybrid nanomaterials are capable of detecting histamine through the electrochemical oxidation of H(2)O(2)and are used as the sensitive membrane for potentiometric microelectrode. Histamine biosensors developed in this work have fast response of less than 20 s, are sensitive and selective, with a large dynamic range of 10(-8)-10(-3) M and a limit of detection of less than 10(-8) M. The detection limit of the developed bi-enzymatic biosensors is relatively higher than those corresponding with gas and liquid chromatography, which are still considered as the reference methods. Finally, the reproducibility, the specificity and the storage stability of the biosensors were studied.

JTD Keywords: Biogenic-amines, Biosensor, Diamine oxidase, Film, Fish, Histamine, Hybrid nanomaterial, Immobilization, Layer double hydroxide, Potentiometric biosensor, Specificity

Cendra MdM, Torrents E, (2021). Pseudomonas aeruginosa biofilms and their partners in crime Biotechnology Advances 49, 107734

Pseudomonas aeruginosa biofilms and the capacity of the bacterium to coexist and interact with a broad range of microorganisms have a substantial clinical impact. This review focuses on the main traits of P. aeruginosa biofilms, such as the structural composition and regulatory networks involved, placing particular emphasis on the clinical challenges they represent in terms of antimicrobial susceptibility and biofilm infection clearance. Furthermore, the ability of P. aeruginosa to grow together with other microorganisms is a significant pathogenic attribute with clinical relevance; hence, the main microbial interactions of Pseudomonas are especially highlighted and detailed throughout this review. This article also explores the infections caused by single and polymicrobial biofilms of P. aeruginosa and the current models used to recreate them under laboratory conditions. Finally, the antimicrobial and antibiofilm strategies developed against P. aeruginosa mono and multispecies biofilms are detailed at the end of this review.

JTD Keywords: aeruginosa models, antibiotic-resistance, antimicrobials, bacterial biofilms, biofilms, c-di-gmp, chronic infections, enterococcus-faecalis, extracellular dna, in-vitro, lectin pa-iil, p, p. aeruginosa models, polymicrobial, polymicrobial interactions, staphylococcus-aureus, Antimicrobials, Biofilms, Chronic infections, P. aeruginosa models, Polymicrobial, Pseudomonas aeruginosa, Urinary-tract-infection

Vilela D, Blanco-Cabra N, Eguskiza A, Hortelao AC, Torrents E, Sanchez S, (2021). Drug-Free Enzyme-Based Bactericidal Nanomotors against Pathogenic Bacteria Acs Applied Materials & Interfaces 13, 14964-14973

The low efficacy of current conventional treatments for bacterial infections increases mortality rates worldwide. To alleviate this global health problem, we propose drug-free enzyme-based nanomotors for the treatment of bacterial urinary-tract infections. We develop nanomotors consisting of mesoporous silica nanoparticles (MSNPs) that were functionalized with either urease (U-MSNPs), lysozyme (L-MSNPs), or urease and lysozyme (M-MSNPs), and use them against nonpathogenic planktonic Escherichia coli. U-MSNPs exhibited the highest bactericidal activity due to biocatalysis of urea into NaHCO3 and NH3, which also propels U-MSNPs. In addition, U-MSNPs in concentrations above 200 μg/mL were capable of successfully reducing 60% of the biofilm biomass of a uropathogenic E. coli strain. This study thus provides a proof-of-concept, demonstrating that enzyme-based nanomotors are capable of fighting infectious diseases. This approach could potentially be extended to other kinds of diseases by selecting appropriate biomolecules.

JTD Keywords: biofilms, carbonate, e. coli, enzymatic nanomotors, infections, lysozyme, micromotors, nanomachines, proteins, self-propulsion, Biofilms, E. coli, Eliminate escherichia-coli, Enzymatic nanomotors, Infections, Nanomachines, Self-propulsion

Puiggalí-Jou A, Ordoño J, del Valle LJ, Pérez-Amodio S, Engel E, Alemán C, (2021). Tuning multilayered polymeric self-standing films for controlled release of L-lactate by electrical stimulation Journal Of Controlled Release 330, 669-683

© 2020 Elsevier B.V. We examine different approaches for the controlled release of L-lactate, which is a signaling molecule that participates in tissue remodeling and regeneration, such as cardiac and muscle tissue. Robust, flexible, and self-supported 3-layers films made of two spin-coated poly(lactic acid) (PLA) layers separated by an electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) layer, are used as loading and delivery systems. Films with outer layers prepared using homochiral PLA and with nanoperforations of diameter 146 ± 70 experience more bulk erosion, which also contributes to the release of L-lactic acid, than those obtained using heterochiral PLA and with nanoperforations of diameter 66 ± 24. Moreover, the release of L-lactic acid as degradation product is accelerated by applying biphasic electrical pulses. The four approaches used for loading extra L-lactate in the 3-layered films were: incorporation of L-lactate at the intermediate PEDOT layer as primary dopant agent using (1) organic or (2) basic water solutions as reaction media; (3) substitution at the PEDOT layer of the ClO4− dopant by L-lactate using de-doping and re-doping processes; and (4) loading of L-lactate at the outer PLA layers during the spin-coating process. Electrical stimuli were applied considering biphasic voltage pulses and constant voltages (both negative and positive). Results indicate that the approach used to load the L-lactate has a very significant influence in the release regulation process, affecting the concentration of released L-lactate up to two orders of magnitude. Among the tested approaches, the one based on the utilization of the outer layers for loading, approach (4), can be proposed for situations requiring prolonged and sustained L-lactate release over time. The biocompatibility and suitability of the engineered films for cardiac tissue engineering has also been confirmed using cardiac cells.

JTD Keywords: biphasic voltage pulse, cardiac tissue regeneration, cardiomyocytes proliferation, conducting polymer, nanoperforated films, sustained delivery, Biphasic voltage pulse, Cardiac tissue regeneration, Cardiomyocytes proliferation, Conducting polymer, Nanoperforated films, Sustained delivery

Keridou I, Franco L, del Valle LJ, Martínez JC, Funk L, Turon P, Puiggalí J, (2021). Hydrolytic and enzymatic degradation of biobased poly(4-hydroxybutyrate) films. Selective etching of spherulites Polymer Degradation And Stability 183

© 2020 Hydrolytic degradation of poly(4-hydroxybutyrate) (P4HB) films has been studied considering media of different pH values (i.e., 3, 7 and 10) and temperatures (i.e., 37 and 55 °C). Enzymatic degradation has also been evaluated at physiological conditions using two different lipases: Pseudomonas cepacia and Rhizopus oryzae. Different bulk and surface erosion mechanisms with random chain scissions and successive removal of monomer units have been supported through weight loss measurements, molecular weight determinations by GPC and NMR spectroscopy and changes on thermal properties by DSC. Thermal annealing during exposure to different media and even degradation influenced on the melting temperature and crystallinity of samples, as well as on the lamellar geometrical parameters as evaluated by SAXS. Enzymatic degradation was ideal to selectively eliminate the amorphous regions and highlight the spherulitic morphology. Presence of ringed textures were therefore evident in bright field optical micrographs in addition to SEM images, namely observations under polarized light was not necessary to distinguish the presence of banded spherulites. Rhizopus oryzae was revealed to be the most suitable enzyme to crop out the P4HB spherulites that form part of the initial smooth surfaces of solvent casting films. After determining the appropriate activity and exposure time, the presence of rings constituted by cooperative C-shaped edge-on lamellae and flat-on lamellae was highlighted.

JTD Keywords: biodegradable polymers, enzymatic degradation, films, hydrolytic degradation, microstructure, thermal properties, Biodegradable polymers, Enzymatic degradation, Films, Hydrolytic degradation, Microstructure, Poly(4-hydroxybutyrate), Thermal properties

Abramov A, Maiti B, Keridou I, Puiggalí J, Reiser O, Díaz DD, (2021). A pH-Triggered Polymer Degradation or Drug Delivery System by Light-Mediated Cis/Trans Isomerization of o-Hydroxy Cinnamates Macromolecular Rapid Communications 42, e2100213

A new methodology for the pH-triggered degradation of polymers or for the release of drugs under visible light irradiation based on the cyclization of ortho-hydroxy-cinnamates (oHC) to coumarins is described. The key oHC structural motif can be readily incorporated into the rational design of novel photocleavable polymers via click chemistry. This main-chain moiety undergoes a fast photocleavage when irradiated with 455 nm light provided that a suitable base is added. A series of polyethylene glycol-alt-ortho-hydroxy cinnamate (polyethylene glycol (PEG)(n)-alt-oHC)-based polymers are synthesized and the time-dependent visible-light initiated cleavage of the photoactive monomer and polymer is investigated in solution by a variety of spectroscopic and chromatographic techniques. The photo-degradation behavior of the water-soluble poly(PEG(2000)-alt-oHC) is investigated within a broad pH range (pH = 2.1-11.8), demonstrating fast degradation at pH 11.8, while the stability of the polymer is greatly enhanced at pH 2.1. Moreover, the neat polymer shows long-term stability under daylight conditions, thus allowing its storage without special precautions. In addition, two water-soluble PEG-based drug-carrier molecules (mPEG(2000)-oHC-benzhydrol/phenol) are synthesized and used for drug delivery studies, monitoring the process by UV-vis spectroscopy in an ON/OFF intermittent manner.

JTD Keywords: coumarins, drug delivery, e/z-double bond isomerization, o-hydroxy cinnamates, polymer degradation, Aliphatic compounds, Antioxidant activity, Antitumor, Chromatographic techniques, Chromatography, Cis/trans isomerization, Controlled drug delivery, Coumarin derivatives, Coumarins, Drug delivery, Drug delivery system, E/z-double bond isomerization, Films, Hydrogels, Image enhancement, Light, Long term stability, O-hydroxy cinnamates, Particles, Photoactive monomers, Photodegradation, Polyethylene glycols, Polyethylenes, Polymer degradation, Responsive polymers, Salts, Structural motifs, Synthesis (chemical), Targeted drug delivery, Visible light photocatalysis, Visible-light irradiation

Molina, B. G., Lopes-Rodrigues, M., Estrany, F., Michaux, C., Perpète, E. A., Armelin, E., Alemán, C., (2020). Free-standing flexible and biomimetic hybrid membranes for ions and ATP transport Journal of Membrane Science 601, 117931

The transport of metabolites across robust, flexible and free-standing biomimetic membranes made of three perforated poly (lactic acid) (pPLA) layers, separated by two anodically polymerized conducting layers of poly (3,4-ethylenedioxythiophene-co-3-dodecylthiophene), and functionalized on the external pPLA layers with a voltage dependent anion channel (VDAC) protein, has been demonstrated. The three pPLA layers offer robustness and flexibility to the bioactive platform and the possibility of obtaining conducing polymer layers by in situ anodic polymerization. The incorporation of dodecylthiophene units, which bear a 12 carbon atoms long linear alkyl chain, to the conducting layers allows mimicking the amphiphilic environment offered by lipids in cells, increasing 32% the efficiency of the functionalization. Electrochemical impedance measurements in NaCl and adenosine triphosphate (ATP) solutions prove that the integration of the VDAC porin inside the PLA perforations considerably increases the membrane conductivity and is crucial for the electrolyte diffusion. Such results open the door for the development of advanced sensing devices for a broad panel of biomedical applications.

JTD Keywords: Conducting polymers, Membrane proteins, Membranes, Polylactic acid, Self-supported films

Blanco-Cabra, N., Vega-Granados, K., Moya-Andérico, L., Vukomanovic, M., Parra, A., Álvarez De Cienfuegos, L., Torrents, E., (2019). Novel oleanolic and maslinic acid derivatives as a promising treatment against Bacterial biofilm in nosocomial infections: An in vitro and in vivo study ACS Infectious Diseases 5, (9), 1581-1589

Oleanolic acid (OA) and maslinic acid (MA) are pentacyclic triterpenic compounds that abound in industrial olive oil waste. These compounds have renowned antimicrobial properties and lack cytotoxicity in eukaryotic cells as well as resistance mechanisms in bacteria. Despite these advantages, their antimicrobial activity has only been tested in vitro, and derivatives improving this activity have not been reported. In this work, a set of 14 OA and MA C-28 amide derivatives have been synthesized. Two of these derivatives, MA-HDA and OA-HDA, increase the in vitro antimicrobial activity of the parent compounds while reducing their toxicity in most of the Gram-positive bacteria tested, including a methicillin-resistant Staphylococcus aureus-MRSA. MA-HDA also shows an enhanced in vivo efficacy in a Galleria mellonella invertebrate animal model of infection. A preliminary attempt to elucidate their mechanism of action revealed that these compounds are able to penetrate and damage the bacterial cell membrane. More significantly, their capacity to reduce antibiofilm formation in catheters has also been demonstrated in two sets of conditions: a static and a more challenged continuous-flow S. aureus biofilm.

JTD Keywords: Antibiofilm, Galleria mellonella, In vitro and in vivo antimicrobials, Maslinic and oleanolic acids, Natural products, Staphylococcus aureus

Cendra, Maria del Mar, Blanco-Cabra, Núria, Pedraz, Lucas, Torrents, Eduard, (2019). Optimal environmental and culture conditions allow the in vitro coexistence of Pseudomonas aeruginosa and Staphylococcus aureus in stable biofilms Scientific Reports 9, (1), 16284

The coexistence between species that occurs in some infections remains hard to achieve in vitro since bacterial fitness differences eventually lead to a single organism dominating the mixed culture. Pseudomonas aeruginosa and Staphylococcus aureus are major pathogens found growing together in biofilms in disease-affected lungs or wounds. Herein, we tested and analyzed different culture media, additives and environmental conditions to support P. aeruginosa and S. aureus coexistence in vitro. We have unraveled the potential of DMEM to support the growth of these two organisms in mature cocultured biofilms (three days old) in an environment that dampens the pH rise. Our conditions use equal initial inoculation ratios of both strains and allow the stable formation of separate S. aureus microcolonies that grow embedded in a P. aeruginosa biofilm, as well as S. aureus biofilm overgrowth when bovine serum albumin is added to the system. Remarkably, we also found that S. aureus survival is strictly dependent on a well-characterized phenomenon of oxygen stratification present in the coculture biofilm. An analysis of differential tolerance to gentamicin and ciprofloxacin treatment, depending on whether P. aeruginosa and S. aureus were growing in mono- or coculture biofilms, was used to validate our in vitro coculture conditions.

JTD Keywords: Applied microbiology, Biofilms

Crespo, Anna, Blanco-Cabra, N., Torrents, Eduard, (2018). Aerobic vitamin B12 biosynthesis is essential for pseudomonas aeruginosa class II ribonucleotide reductase activity during planktonic and biofilm growth Frontiers in Microbiology 9, (986), Article 986

P. aeruginosa is a major pathogenic bacterium in chronic infections and is a model organism for studying biofilms. P. aeruginosa is considered an aerobic bacterium, but in the presence of nitrate, it also grows in anaerobic conditions. Oxygen diffusion through the biofilm generates metabolic and genetic diversity in P. aeruginosa growth, such as in ribonucleotide reductase activity. These essential enzymes are necessary for DNA synthesis and repair. Oxygen availability determines the activity of the three-ribonucleotide reductase (RNR) classes. Class II and III RNRs are active in the absence of oxygen; however, class II RNRs, which are important in P. aeruginosa biofilm growth, require a vitamin B12 cofactor for their enzymatic activity. In this work, we elucidated the conditions in which class II RNRs are active due to vitamin B12 concentration constraints (biosynthesis or environmental availability). We demonstrated that increased vitamin B12 levels during aerobic, stationary and biofilm growth activate class II RNR activity. We also established that the cobN gene is essentially responsible for B12 biosynthesis under planktonic and biofilm growth. Our results unravel the mechanisms of dNTP synthesis by P. aeruginosa during biofilm growth, which appear to depend on the bacterial strain (laboratory-type or clinical isolate).

JTD Keywords: Vitamin B12, Adenosylcobalamin, Ribonucleotide Reductases, Pseudomonas aeruginosa, NrdJ, Bacterial growth, Biofilm,Anaerobiosis

Hüttener, Mário, Prieto, Alejandro, Espelt, Joan, Bernabeu, Manuel, Juárez, Antonio, (2018). Stringent response and AggR-dependent virulence regulation in the enteroaggregative escherichia coli strain 042 Frontiers in Microbiology 9, (717), Article 717

Virulence expression in the enteroaggregative E. coli strain 042 requires the transcriptional activator AggR. We show in this report that, as reported for other virulence factors, the nucleotide second messenger (p)ppGpp is needed for a high expression level of AggR. As expected from these findings, expression of AggR-activated genes such as the AafA pilin subunit is downregulated in the absence of (p)ppGpp. Considering the fact that biofilm formation in strain 042 requires the AafA protein, biofilm development in strain 042 is impaired in derivatives that lack either the AggR protein, the virulence plasmid that encodes AggR (pAA2) or the ability to synthesize (p)ppGpp. These results show a direct correlation between (p)ppGpp, expression of AggR and biofilm development in strain 042.

JTD Keywords: (p)ppGpp, AggR, EAEC, Biofilm, AAF/II

Crespo, Anna, Pedraz, Lucas, Astola, Josep, Torrents, Eduard, (2016). Pseudomonas aeruginosa exhibits deficient biofilm formation in the absence of class II and III ribonucleotide reductases due to hindered anaerobic growth Frontiers in Microbiology 7, Article 688

Chronic lung infections by the ubiquitous and extremely adaptable opportunistic pathogen Pseudomonas aeruginosa correlate with the formation of a biofilm, where bacteria grow in association with an extracellular matrix and display a wide range of changes in gene expression and metabolism. This leads to increased resistance to physical stress and antibiotic therapies, while enhancing cell-to-cell communication. Oxygen diffusion through the complex biofilm structure generates an oxygen concentration gradient, leading to the appearance of anaerobic microenvironments. Ribonucleotide reductases (RNRs) are a family of highly sophisticated enzymes responsible for the synthesis of the deoxyribonucleotides, and they constitute the only de novo pathway for the formation of the building blocks needed for DNA synthesis and repair. P. aeruginosa is one of the few bacteria encoding all three known RNR classes (Ia, II, and III). Class Ia RNRs are oxygen dependent, class II are oxygen independent, and class III are oxygen sensitive. A tight control of RNR activity is essential for anaerobic growth and therefore for biofilm development. In this work we explored the role of the different RNR classes in biofilm formation under aerobic and anaerobic initial conditions and using static and continuous-flow biofilm models. We demonstrated the importance of class II and III RNR for proper cell division in biofilm development and maturation. We also determined that these classes are transcriptionally induced during biofilm formation and under anaerobic conditions. The molecular mechanism of their anaerobic regulation was also studied, finding that the Anr/Dnr system is responsible for class II RNR induction. These data can be integrated with previous knowledge about biofilms in a model where these structures are understood as a set of layers determined by oxygen concentration and contain cells with different RNR expression profiles, bringing us a step closer to the understanding of this complex growth pattern, essential for P. aeruginosa chronic infections.

JTD Keywords: Pseudomonas aeruginosa, Ribonucleotide Reductases, Vitamin B 12, Anaerobic metabolism, Biofilm formation, DNA Synthesis, Oxygen diffusion, nrd genes.

Baelo, Aida, Levato, Riccardo, Julián, Esther, Crespo, Anna, Astola, José, Gavaldà, Joan, Engel, Elisabeth, Mateos-Timoneda, Miguel Angel, Torrents, Eduard, (2015). Disassembling bacterial extracellular matrix with DNase-coated nanoparticles to enhance antibiotic delivery in biofilm infections Journal of Controlled Release 209, 150-158

Abstract Infections caused by biofilm-forming bacteria are a major threat to hospitalized patients and the main cause of chronic obstructive pulmonary disease and cystic fibrosis. There is an urgent necessity for novel therapeutic approaches, since current antibiotic delivery fails to eliminate biofilm-protected bacteria. In this study, ciprofloxacin-loaded poly(lactic-co-glycolic acid) nanoparticles, which were functionalized with DNase I, were fabricated using a green-solvent based method and their antibiofilm activity was assessed against Pseudomonas aeruginosa biofilms. Such nanoparticles constitute a paradigm shift in biofilm treatment, since, besides releasing ciprofloxacin in a controlled fashion, they are able to target and disassemble the biofilm by degrading the extracellular DNA that stabilize the biofilm matrix. These carriers were compared with free-soluble ciprofloxacin, and ciprofloxacin encapsulated in untreated and poly(lysine)-coated nanoparticles. DNase I-activated nanoparticles were not only able to prevent biofilm formation from planktonic bacteria, but they also successfully reduced established biofilm mass, size and living cell density, as observed in a dynamic environment in a flow cell biofilm assay. Moreover, repeated administration over three days of DNase I-coated nanoparticles encapsulating ciprofloxacin was able to reduce by 95% and then eradicate more than 99.8% of established biofilm, outperforming all the other nanoparticle formulations and the free-drug tested in this study. These promising results, together with minimal cytotoxicity as tested on J774 macrophages, allow obtaining novel antimicrobial nanoparticles, as well as provide clues to design the next generation of drug delivery devices to treat persistent bacterial infections.

JTD Keywords: Pseudomonas aeruginosa, Biofilm, Ciprofloxacin, DNase I, Nanoparticles

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone Biochimica et Biophysica Acta - Biomembranes , 1848, (6), 1341-1351

The photosynthesis is the process used by plants and bacteria cells to convert inorganic matter in organic thanks to the light energy. This process consist on several steps, being one of them the electronic transport from the photosystem II to the cytochrome thanks to plastoquinone-9 (PQ). Here we prepare membranes that mimic the characteristics and composition of natural photosynthetic cell membranes and we characterize them in order to obtain the PQ molecules position in the membrane and their electrochemical behaviour. The selected galactolipid is digalactosyldiacylglycerol (DGDG) that represents the 30% of the thylakoid membrane lipid content. The results obtained are worthful for several science fields due to the relevance of galactolipids as anti-algal, anti-viral, anti-tumor and anti-inflammatory agents and the antioxidant and free radical scavenger properties of prenylquinones. Both pure components (DGDG and PQ) and the DGDG:PQ mixtures have been studied using surface pressure-area isotherms. These isotherms give information about the film stability and indicate the thermodynamic behaviour of the mixture and their physical state. The Langmuir-Blodgett (LB) film has been transferred forming a monolayer that mimics the bottom layer of the biological membranes. This monolayer on mica has been topographically characterized using AFM and both the height and the physical state that they present have been obtained. Moreover, these monolayers have been transferred onto ITO that is a hydrophilic substrate with good optical and electrical features, so that, it is suitable for studying the electrochemical behaviour of these systems and it is a good candidate for energy producing devices.

JTD Keywords: Biomimetic membrane, Digalactosyldiacylglycerol, Electron transfer, LangmuirBlodgett film, Modified ITO electrode, Plastoquinone

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Electrochemistry of LB films of mixed MGDG: UQ on ITO Bioelectrochemistry , 104, 26-34

The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being kRapp(I)=2.2·10-5s-1, kRapp(II)=5.1·10-14 kOapp(I)=3.3·10-3s-1 and kOapp(II)=6.1·10-6s-1, respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.

JTD Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett film, Modified ITO electrode, Monogalactosyldiacylglycerol, Ubiquinone

Barniol-Xicota, M., Escandell, A., Valverde, E., Julián, E., Torrents, E., Vázquez, S., (2015). Antibacterial activity of novel benzopolycyclic amines Bioorganic and Medicinal Chemistry , 23, (2), 290-296

Staphylococcus aureus, especially strains resistant to multiple antibiotics, is a major pathogen for humans and animals. In this paper we have synthesized and evaluated the antibacterial activity of a new series of benzopolycyclic amines. Some of them exhibited μM MIC values against Staphylococcus aureus and other bacteria, including methicillin-resistant S. aureus MRSA. Compound 8 that displayed a good selectivity index, showed to be active in eliminating bacterial cells forming a preexisting biofilm.

JTD Keywords: Antibacterials, Minimal biofilm inhibitory concentration, Polycyclic compounds, Staphylococcus aureus

Pérez-Madrigal, M. M., Giannotti, M. I., Del Valle, L. J., Franco, L., Armelin, E., Puiggalí, J., Sanz, F., Alemán, C., (2014). Thermoplastic polyurethane:polythiophene nanomembranes for biomedical and biotechnological applications ACS Applied Materials & Interfaces 6, (12), 9719-9732

Nanomembranes have been prepared by spin-coating mixtures of a polythiophene (P3TMA) derivative and thermoplastic polyurethane (TPU) using 20:80, 40:60, and 60:40 TPU:P3TMA weight ratios. After structural, topographical, electrochemical, and thermal characterization, properties typically related with biomedical applications have been investigated: swelling, resistance to both hydrolytic and enzymatic degradation, biocompatibility, and adsorption of type I collagen, which is an extra cellular matrix protein that binds fibronectin favoring cell adhesion processes. The swelling ability and the hydrolytic and enzymatic degradability of TPU:P3TMA membranes increases with the concentration of P3TMA. Moreover, the degradation of the blends is considerably promoted by the presence of enzymes in the hydrolytic medium, TPU:P3TMA blends behaving as biodegradable materials. On the other hand, TPU:P3TMA nanomembranes behave as bioactive platforms stimulating cell adhesion and, especially, cell viability. Type I collagen adsorption largely depends on the substrate employed to support the nanomembrane, whereas it is practically independent of the chemical nature of the polymeric material used to fabricate the nanomembrane. However, detailed microscopy study of the morphology and topography of adsorbed collagen evidence the formation of different organizations, which range from fibrils to pseudoregular honeycomb networks depending on the composition of the nanomembrane that is in contact with the protein. Scaffolds made of electroactive TPU:P3TMA nanomembranes are potential candidates for tissue engineering biomedical applications.

JTD Keywords: Bioactive platform, Biodegradable blend, Collaged adsorption, Scaffolds, Tissue engineering, Ultrathin films

Gomila, G., Gramse, G., Fumagalli, L., (2014). Finite-size effects and analytical modeling of electrostatic force microscopy applied to dielectric films Nanotechnology 25, (25), 255702 (11)

A numerical analysis of the polarization force between a sharp conducting probe and a dielectric film of finite lateral dimensions on a metallic substrate is presented with the double objective of (i) determining the conditions under which the film can be approximated by a laterally infinite film and (ii) proposing an analytical model valid in this limit. We show that, for a given dielectric film, the critical diameter above which the film can be modeled as laterally infinite depends not only on the probe geometry, as expected, but mainly on the film thickness. In particular, for films with intermediate to large thicknesses (>100 nm), the critical diameter is nearly independent from the probe geometry and essentially depends on the film thickness and dielectric constant following a relatively simple phenomenological expression. For films that can be considered as laterally infinite, we propose a generalized analytical model valid in the thin-ultrathin limit (<20-50 nm) that reproduces the numerical calculations and the experimental data. Present results provide a general framework under which accurate quantification of electrostatic force microscopy measurements on dielectric films on metallic substrates can be achieved.

JTD Keywords: Dielectric constant, Dielectric films, Electrostatic force microscopy, Quantification, Analytical models, Electric force microscopy, Electrostatic force, Film thickness, Permittivity, Probes, Substrates, Ultrathin films, Accurate quantifications, Electrostatic force microscopy, Finite size effect, Lateral dimension, Metallic substrate, Numerical calculation, Polarization forces, Quantification, Dielectric films

Torrent-Burgués, J., Cea, P., Giner, I., Guaus, E., (2014). Characterization of Langmuir and Langmuir-Blodgett films of an octasubstituted zinc phthalocyanine Thin Solid Films , 556, 485-494

In this work we report the fabrication of Langmuir and Langmuir-Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl)phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (π-A) and surface potential (ΔV-A) isotherms as well as UV-vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air-water interface together with UV-vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The π-A and ΔV-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9 mN/m and a multilayer formation at surface pressures around 19-20 mN/m; at a surface pressure around 27 mN/m a disordered collapse of the film occurs. In addition, AFM images of LB films at π = 10 mN/m and π = 20 mN/m show a monomolecular and a multilayered film, respectively. The comparison of the UV-vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV-vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the random distribution in solution. The UV-vis Reflection spectra are also consistent with multilayer formation at surface pressures around 19-20 mN/m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB film which is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular organizations.

JTD Keywords: Atomic Force Microscopy, Electrochemistry, Langmuir-Blodgett, Multilayers, Optical spectroscopy techniques, Zinc phthalocyanine, Atomic force microscopy, Electrochemistry, Interfaces (materials), Isotherms, Multilayers, Nitrogen compounds, Optical multilayers, Organic polymers, Zinc compounds, Brewster angle microscopy, Characterization techniques, Electrochemical behaviour, Langmuir and langmuir-blodgett films, Langmuir-blodgett, Optical spectroscopy techniques, UV-Vis Reflection Spectroscopy, Zinc phthalocyanines, Langmuir Blodgett films

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.

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

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.

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

Azevedo, S., Diéguez, L., Carvalho, P., Carneiro, J. O., Teixeira, V., Martínez, Elena, 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.

JTD 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

Simao, C., Mas-Torrent, M., Crivillers, N., Lloveras, V., Artés, Juan Manuel, Gorostiza, Pau, Veciana, Jaume, Rovira, C., (2011). A robust molecular platform for non-volatile memory devices with optical and magnetic responses Nature Chemistry , 3, (5), 359-364

Bistable molecules that behave as switches in solution have long been known. Systems that can be reversibly converted between two stable states that differ in their physical properties are particularly attractive in the development of memory devices when immobilized in substrates. Here, we report a highly robust surface-confined switch based on an electroactive, persistent organic radical immobilized on indium tin oxide substrates that can be electrochemically and reversibly converted to the anion form. This molecular bistable system behaves as an extremely robust redox switch in which an electrical input is transduced into optical as well as magnetic outputs under ambient conditions. The fact that this molecular surface switch, operating at very low voltages, can be patterned and addressed locally, and also has exceptionally high long-term stability and excellent reversibility and reproducibility, makes it a very promising platform for non-volatile memory devices.

JTD Keywords: Self-assembled monolayers, Chromophore-based monolayers, Ultrathin platinum films, Carbon free-radicals, Per-million levels, Polychlorotriphenylmethyl radicals, Electron-transfer, Surface, Logic, Quantification

Sjoberg, B. M., Torrents, E., (2011). Shift in ribonucleotide reductase gene expression in pseudomonas aeruginosa during infection Infection and Immunity , 79, (7), 2663-2669

The roles of different ribonucleotide reductases (RNRs) in bacterial pathogenesis have not been studied systematically. In this work we analyzed the importance of the different Pseudomonas aeruginosa RNRs in pathogenesis using the Drosophila melanogaster host-pathogen interaction model. P. aeruginosa codes for three different RNRs with different environmental requirements. Class II and III RNR chromosomal mutants exhibited reduced virulence in this model. Translational reporter fusions of RNR gene nrdA, nrdJ, or nrdD to the green fluorescent protein were constructed to measure the expression of each class during the infection process. Analysis of the P. aeruginosa infection by flow cytometry revealed increased expression of nrdJ and nrdD and decreased nrdA expression during the infection process. Expression of each RNR class fits with the pathogenicities of the chromosomal deletion mutants. An extended understanding of the pathogenicity and physiology of P. aeruginosa will be important for the development of novel drugs against infections in cystic fibrosis patients.

JTD Keywords: Broad-host-range, Anaerobic growth, Drosophila-melanogaster, Bacterial biofilms, Escherichia-coli, Cystic-fibrosis, Model host, Virulence, Promoter, Vectors

Caballero-Briones, F., Palacios-Padrós, A., Sanz, Fausto, (2011). CuInSe2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies Electrochimica Acta 56, (26), 9556-9567

p-Type semiconducting copper indium diselenide thin films have been prepared onto In2O3:Sn substrates by a recently developed pulse electrodeposition method that consists in repeated cycles of three potential application steps. The Cu–In–Se electrochemical system and the related single component electrolytes were studied by cyclic voltammetry to identify the electrode processes and study the deposition processes. In situ atomic force microscopy measurements during the first 100 deposition cycles denote a continuous nucleation and growth mechanism. Particles removed by film sonication from some of the films were characterized by transmission electron microscopy and determined to consist in nanoscopic and crystalline CuInSe2. The remaining film is still crystalline CuInSe2, as assessed by X-ray diffraction. The chemical characterization by combined X-ray photoelectron spectroscopy, X-ray fluorescence and inductively coupled plasma optical emission spectroscopy, showed that films were Cu-poor and Se-poor. Raman characterization of the as-grown films showed that film composition varies with film thickness; thinner films are Se-rich, while thicker ones have an increased Cu–Se content. Different optical absorption bands were identified by the analysis of the UV–NIR transmittance spectra that were related with the presence of CuInSe2, ordered vacancy compounds, Se, Cu2−xSe and In2Se3. The photoelectrochemical activity confirmed the p-type character and showed a better response for the films prepared with the pulse method.

JTD Keywords: CuInSe2, Solar cells, Electrodeposition, Optical properties, As-deposited films, ITO substrate

Comelles, J., Estevez, M., Martinez, E., Samitier, J., (2010). The role of surface energy of technical polymers in serum protein adsorption and MG-63 cells adhesion Nanomedicine: Nanotechnology Biology and Medicine , 6, (1), 44-51

Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. However, novel applications in the biosensor field require materials to be compatible with cell growth and at the same time be suitable for technological processing. Technological polymers are key materials in the fabrication of disposable parts and other sensing elements. As such, it is essential to characterize the surface properties of technological polymers, especially after processing and sterilization. It is also important to understand how technological polymers affect cell behavior when in contact with polymer materials. Therefore, the aim of this research was to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly (methyl methacrylate), polystyrene, and poly(dimethylsiloxane). Glass was used as the control material. From the Clinical Editor: Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. The aim of this research is to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly(methylmethacrylate) (PMMA), polystyrene (PS), and poly(dimethylsiloxane) (PDMS).

JTD Keywords: Thin-films, Poly(methyl methacrylate), Osteoblast adhesion, Electron-microscopy, Fibronectin, Polystyrene, Oly(dimethylsiloxane), Biocompatibility, Hydroxyapatite, Behavior

Fumagalli, L., Gramse, G., Esteban-Ferrer, D., Edwards, M. A., Gomila, G., (2010). Quantifying the dielectric constant of thick insulators using electrostatic force microscopy Applied Physics Letters , 96, (18), 183107

Quantitative measurement of the low-frequency dielectric constants of thick insulators at the nanoscale is demonstrated utilizing ac electrostatic force microscopy combined with finite-element calculations based on a truncated cone with hemispherical apex probe geometry. The method is validated on muscovite mica, borosilicate glass, poly(ethylene naphthalate), and poly(methyl methacrylate). The dielectric constants obtained are essentially given by a nanometric volume located at the dielectric-air interface below the tip, independently of the substrate thickness, provided this is on the hundred micrometer-length scale, or larger.

JTD Keywords: Borosilicate glasses, Finite element analysis, Insulating thin films, Mica, Nanostructured materials, Permittivity, Polymers, Scanning probe microscopy

Caballero-Briones, F., Palacios-Padros, A., Calzadilla, O., Sanz, F., (2010). Evidence and analysis of parallel growth mechanisms in Cu2O films prepared by Cu anodization Electrochimica Acta 55, (14), 4353-4358

We have studied the preparation of Cu2O films by copper anodization in a 0.1 M NaOH electrolyte. We identified the potential range at which Cu dissolution takes place then we prepared films with different times of exposure to this potential. The morphology, crystalline structure, band gap. Urbach energy and thickness of the films were studied. Films prepared with the electrode unexposed to the dissolution potential have a pyramidal growth typical of potential driven processes, while samples prepared at increasing exposure times to dissolution potential present continuous nucleation, growth and grain coalescence. We observed a discrepancy in the respective film thicknesses calculated by coulometry, atomic force microscopy and optical reflectance. We propose that anodic Cu2O film formation involves three parallel mechanisms (i) Cu2O nucleation at the surface, (ii) Cu+ dissolution followed by heterogeneous nucleation and (iii) Cu+ and OH- diffusion through the forming oxide and subsequent reaction in the solid state.

JTD Keywords: Cuprous oxide, Anodic films, Reflectance, Thickness, Band gap, Urbach tail parameter, Dissolution, Growth mechanism

Caballero-Briones, F., Artes, J. M., Diez-Perez, I., Gorostiza, P., Sanz, F., (2009). Direct observation of the valence band edge by in situ ECSTM-ECTS in p-type Cu2O layers prepared by copper anodization Journal of Physical Chemistry C 113, (3), 1028-1036

Polycrystalline Cu2O layers have been selectively grown by electrochemical anodization of polycrystalline Cu electrodes in an alkaline medium (pH 12.85). Uniform layers with thicknesses around 100 nm have been obtained. Using electrochemical impedance spectroscopy, it was concluded that the Cu2O films behave as a p-type semiconductor. The Mott-Schottky plot gives a value for the flat band potential of U-FB = -255 mV vs silver/silver chloride electrode (SSC), an estimated carrier density N-A = 6.1 x 10(17) cm(-3), and the space charge layer width was calculated to be W-SCL = 9 nm at a band bending of 120 mV. The electronic structure of the Cu vertical bar Cu2O vertical bar electrolyte interface was for the first time probed by in situ electrochemical tunneling spectroscopy. The use of in situ electrochemical scanning tunneling microscopy allows us to directly observed the valence band edge and determine its position against the absolute energy scale to be E-VB = -4.9 eV. Finally, we constructed a quantitative electronic diagram of the Cu vertical bar Cu2O vertical bar electrolyte interface, where the positions of the valence and conduction band edges are depicted, as well as the edge of the previously reported electronic subband.

JTD Keywords: 0.1 m NaOH, Electrochemical tunneling spectroscopy, Cuprous-oxide films, Anodic-oxidation, Electronic-structure, Alkaline-solution, Aqueous-solution, Initial-stages, Passive film, Thin-films

Caballero, D., Samitier, J., Errachid, A., (2009). Submerged nanocontact printing (SnCP) of thiols Journal of Nanoscience and Nanotechnology , 9, (11), 6478-6482

Biological patterned surfaces having sub-micron scale resolution are of great importance in many fields of life science and biomedicine. Different techniques have been proposed for surface patterning at the nanoscale. However, most of them present some limitations regarding the patterned area size or are time-consuming. Micro/nanocontact printing is the most representative soft lithography-based technique for surface patterning at the nanoscale. Unfortunately, conventional micro/nanocontact printing also suffers from problems such as diffusion and stamp collapsing that limit pattern resolution. To overcome these problems, a simple way of patterning thiols under liquid media using submerged nanocontact printing (SnCP) over large areas (similar to cm(2)) achieving nanosize resolution is presented. The technique is also low cost and any special equipment neither laboratory conditions are required. Nanostructured poly(dimethyl siloxane) stamps are replicated from commercially available digital video disks. SnCP is used to stamp patterns of 200 nm 1-octadecanethiol lines in liquid media, avoiding ink diffusion and stamp collapsing, over large areas on gold substrates compared with conventional procedures. Atomic force microscopy measurements reveal that the patterns have been successfully transferred with high fidelity. This is an easy, direct, effective and low cost methodology for molecule patterning immobilization which is of interest in those areas that require nanoscale structures over large areas, such as tissue engineering or biosensor applications.

JTD Keywords: Submerged Nanocontact Printing, Replica Molding, Nanopatterning, Large Area, Dip-pen nanolithography, High-aspect-ratio, Soft lithography, Submicronscale, Nanoimprint lithography, Thin-film, Surfaces, Fabrication, Proteins, Nanofabrication

Baccar, Z. M., Caballero, D., Zine, N., Jaffrezic-Renault, N., Errachid, A., (2009). Development of urease/layered double hydroxides nanohybrid materials for the urea detection: Synthesis, analytical and catalytic characterizations Sensor Letters 6th Maghreb-Europe Meeting on Materials and Their Applications for Devices and Physical, Chemical and Biological Sensors , AMER SCIENTIFIC PUBLISHERS (Rabat, Morocco) 7, (5), 676-682

We developed new hybrid nanomaterials, urease/LDH (layered double hydroxides), for the urea detection. The LDH that were prepared by co-precipitation in constant pH and in ambient temperature are hydrotalcites (Mg2Al, Mg3Al) and zaccagnaite (Zn2Al and Zn3Al). The immobilization of urease in these various layered hybrid materials is realized by auto-assembly. The structures of hosted matrices were studied by X-ray diffraction, Absorbance Infrared spectroscopy in ATR mode and Atomic Force Microscopy (AFM). These techniques allowed the characterisation of the urease immobilization and its interactions with LDH chemical groups. The urease was adsorbed and its morphology was conserved in its new environment. Furthermore, the study of catalytic parameters of Urease/LDH biomembranes and of the kinetics reaction of urea hydrolysis shows a good conformation of the enzyme in hydrotalcite matrices and that the affinity is similar to free urease.

JTD Keywords: Ldh hybrid nanomaterials, Surface properties, Urea biosensors, Urease thin films

Guaus, E., Torrent-Burgues, J., Zine, N., Errachid, A., (2009). Glassy carbon electrode modified with a langmuir-blodgett film of a thiomacrocyclic ionophore for Cu(II) recognition Sensor Letters 6th Maghreb-Europe Meeting on Materials and Their Applications for Devices and Physical, Chemical and Biological Sensors , AMER SCIENTIFIC PUBLISHERS (Rabat, Morocco) 7, (5), 1006-1011

Nanometric films of a thiomacrocyclic ionophore, 4-phenyl-4-sulfide-11(1- oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (ThM), have been deposited on the surface of a Glassy Carbon Electrode (GCE) by the Langmuir-Blodgett (LB) technique. The films have been characterised by using AFM. The influence of these modified electrodes (GCE-ThM) on the reduction of Cu(II) ions has been investigated by using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), and its sensor response has been checked. The CV and EIS responses of LB films on GCE indicate that these ThM films are sensitive to Cu(II) ions. The analysis by EIS of the interference of some other cations, as Mg(II) and Co(II), shows that LB films of ThM can be used for specific Cu(II) sensing applications.

JTD Keywords: Cu(II) sensor, Cyclic voltammetry, Electrochemical impedance spectroscopy, Langmuir-blodgett films

Caballero-Briones, F., Palacios-Padros, A., Pena, J. L., Sanz, F., (2008). Phase tailored, potentiodynamically grown P-Cu2-xTe/Cu layers Electrochemistry Communications , 10, (11), 1684-1687

In this work we successfully prepared p-type semiconducting Cu2-xTe layers on Cu substrates by applying a potential multistep signal. Spontaneously deposited tellurium layers were reduced in a single cathodic sweep. The X-ray diffraction characterization showed the presence of single-phased, crystalline Cu2-xTe in the weissite form. A further anodization step allows crystallization of several phases such as CU1.75Te, Cu0.664Te0.336 and CU7Te4. This type of sample was found to be photoactive. The prepared films are p-type and have carrier concentrations in the order of 10(21) CM-3, suitable for CdTe-CU2-xTe contacts.

JTD Keywords: Copper telluride, Electrochemical signal, XRD, Morphology, EIS, Photocurrent, Telluride thin-films, Solar cells, Deposition, Cu

Navarro, M., Benetti, E. M., Zapotoczny, S., Planell, J. A., Vancso, G. J., (2008). Buried, covalently attached RGD peptide motifs in poly(methacrylic acid) brush layers: The effect of brush structure on cell adhesion Langmuir 24, (19), 10996-11002

Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMAA) brush layers obtained from surface-attached iniferters in self-assembled monolayers to a gold surface. The tethered chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) motif. The modified brushes were extended by reinitiating the polymerization to obtain an additional layer of PMAA, thereby burying the peptide-functionalized segments inside the brush structure. Contact angle measurements and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the wettability and the chemical properties of these platforms. Time of flight secondary ion mass spectroscopy (TOF-SIMS) measurements were performed to monitor the chemical composition of the polymer layer as a function of the distance to the gold surface and obtain information concerning the depth of the RGD motifs inside the brush structure. The brush thickness was evaluated as a function of the polymerization (i.e.. UV-irradiation) time with atomic force microscopy (AFM) and ellipsometry. Cell adhesion tests employing human osteoblasts were performed on substrates with the RGD peptides exposed at the surface as well as covered by a PMAA top brush layer. Immunofluorescence studies demonstrated a variation of the cell morphology as a function of the position of the peptide units along the grafted chains.

JTD Keywords: Ion mass-spectrometry, Transfer radical polymerization, Asymmetric diblock copolymers, Arg-gly-asp, Swelling behaviour, Endothelial-cells, Thin-films, fibronectin, Surfaces, SIMS

Oncins, G., Torrent-Burgues, J., Sanz, F., (2008). Nanomechanical properties of arachidic acid Langmuir-Blodgett films Journal of Physical Chemistry C 112, (6), 1967-1974

The nanomechanical properties of Langmuir-Blodgett monolayers of arachidic acid extracted at surface pressures of 1, 15, and 35 mN/m and deposited on mica were investigated by atomic force microscopy, force spectroscopy, and lateral force microscopy. It was experimentally demonstrated that the arachidic acid molecular orientation depends on the extraction pressure. According to this, tilting angles of 50, 34, and 22 degrees with respect to the surface perpendicular were detected and identified as conformations that maximize van der Waals interactions between the arachidic acid alkyl chains. The vertical force needed to puncture the monolayers with the AFM tip strongly depends on the molecular tilting angles attained at different monolayer extraction surface pressures, obtaining values that range from 13.07 +/- 3.24 nN for 50 degrees to 22.94 +/- 5.49 nN for 22 degrees tilting angles. The different molecular interactions involved in the monolayer cohesion are discussed and quantitatively related to the experimental monolayer breakthrough forces. The friction measurements performed from low vertical forces up to monolayer disruption reveal the existence of three well-defined regimes: first, a low friction response due to the elastic deformation of the monolayer, which is followed by a sharp increase in the friction force due to the onset of a sudden plastic deformation. The last regime corresponds to the monolayer rupture and the contact between tip and substrate. The friction coefficient of the substrate is seen to depend on the monolayer extraction pressure, a fact that is discussed in terms of the relationship between the sample compactness and its rupture mechanism.

JTD Keywords: AFM, SAM, Reflection-absortion spectroscopy, Lipid-bilayers, Frictional-properies, Molecular-structure, Thermal behavior, Nanometer-scale, Chain-length, LB films

Guaus, E., Errachid, A., Torrent-Burgues, J., (2008). Voltammetric response of a glassy carbon electrode modified by a Langmuir-Blodgett film of a thiomacrocyclic compound Journal of Electroanalytical Chemistry , 614, (1-2), 73-82

A Langmuir-Blodgett (LB) film of a thiomacrocyclic (ThM) compound was deposited on the surface of a glassy carbon electrode (GCE) sheet, from a subphase containing Cu(II) ions. The study of the voltammetric response of this modified GCE when the ThM was bonded to Cu2+, showed that the films had the behaviour of confined species of an electrode surface, and that the current density of the voltammograms increased with the number of LB layers deposited. On the other hand, a LB film of the ThM compound was deposited on the surface of a GCE sheet from a subphase of pure water. When the voltammetric response of the GCE-ThM electrode was studied in a Cu2+-SO42- solution, it was found that a membrane model applies to describe the effect of the LB film on the GCE surface.

JTD Keywords: Modified electrodes, Langmuir-Blodgett films, Cyclic voltammetry, Permeation at LB films, Membrane model of a thin film

Mills, C. A., Pla, M., Martin, C., Lee, M., Kuphal, M., Sisquella, X., Martinez, E., Errachid, A., Samitier, J., (2007). Structured thin organic active layers and their use in electrochemical biosensors Measurement & Control , 40, (3), 88-91

Díez-Pérez, Ismael, Guell, Aleix Garcia, Sanz, Fausto, Gorostiza, Pau, (2006). Conductance maps by electrochemical tunneling spectroscopy to fingerprint the electrode electronic structure Analytical Chemistry , 78, (20), 7325-7329

We describe a methodology to perform reliable tunneling spectroscopy in electrochemical media. Sequential in situ tunneling spectra are recorded while the electrochemical potential of the electrode is scanned. Spectroscopic data are presented as conductance maps or conductograms that show the in situ electronic structure of an electrode surface while it undergoes an electrochemical reaction. The conductance map or conductogram represents the redox fingerprint of an electrode/liquid interface in a specific medium and can serve to predict its electrochemical behavior in a quantitative energy scale. The methodology is validated studying the reversible oxidation and passivity of an iron electrode in borate buffer, and we describe the main quantitative information that can be extracted concerning the semiconducting properties of the Fe passive film. This methodology is useful to study heterogeneous catalysis, electrochemical sensing and bioelectronic systems.

JTD Keywords: Passive film, Oxide-film, Stainless-steel, Iron, Microscope, Surfaces, STM, Probes

Díez-Pérez, Ismael, Vericat, Carolina, Gorostiza, Pau, Sanz, Fausto, (2006). The iron passive film breakdown in chloride media may be mediated by transient chloride-induced surface states located within the band gap Electrochemistry Communications , 8, (4), 627-632

Despite its tremendous scientific and economic impact, the mechanism that triggers metal passive film breakdown in the presence of aggressive ions remains under discussion. We have studied the iron passive film in chloride media using X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy and electrochemical tunneling spectroscopy (ECTS). Ex situ XPS reveal that the film consists exclusively of an Fe(III) oxide without chloride content. In situ ECTS has been used to build up conductance maps of the Fe electrode during its electrochemical oxidation in a borate buffer solution and its breakdown when the film is grown in the presence of chloride. This conductograms provide direct and in situ experimental evidence of chloride-induced surface states within the band gap of the oxide film (~3.3eV). These states enable new charge exchange pathways that allow hole capture at the surface of the n-type Fe(III) oxide. The blocking of VB processes that occurs in the iron passive film is no longer present in chloride media, and electrode corrosion can proceed through these new states. We propose a simple 3-step mechanism for the process, in which chloride anions form an oxidizing Fe(II) surface intermediate but do not participate directly in the reaction.

JTD Keywords: Electrochemical tunneling spectroscopy, Electronic band structure, Fe passive film, Aqueous chloride corrosion, Semiconductor decomposition, Interface states