Publications

The contractile nature of skeletal muscle tissue makes it especially attractive for powering biohybrid actuators. Significant efforts have been dedicated to the improvement and control of contraction force, going one step forward toward the automation of these biohybrid platforms. Herein, 3D-bioengineered skeletal muscle tissues are integrated with organic transistor-based sensors to define a soft bioactuator with real-time force monitoring capabilities. The muscle tissue is electrically stimulated while the organic sensor ensures transduction of the exerted force into an electrical signal that allows direct monitoring of the bioactuator performance. Sensor calibration is carried out to define its sensitivity at different biasing conditions: as opposed to standard, two-terminal piezoresistive devices, transistor-based strain sensors show tunable sensitivity by acting on the voltage applied to a third terminal-the gate. A complete evaluation of sensing performances is provided, demonstrating that real-time monitoring is effective under different conditions, including stimulation signal frequency and chemical modulation of the bioactuator contraction, demonstrating its potential use as a drug testing platform. In the reported results, the way is paved for a complete exploitation of organic devices in soft robotic applications and to the development of novel biohybrid machines in bioengineering and biomedicine. The integration of sensing elements in bioengineered actuators is key to obtain real-time information about their performance and further control/automation. By coupling flexible organic field-effect transistor to a skeletal muscle actuator we demonstrate the feasibility to record in real-time its contractile behavior when stimulated by electrical pulses, showing both high sensitivity absence of cross talk between stimulation and readout.image (c) 2024 WILEY-VCH GmbH

JTD Keywords: Bioengineerings, Flexible electronics, Muscle-based actuators, Organic field-effect transistors, Soft robotic

Transcutaneous devices such as dental implants frequently fail due to infections at their interfaces with epithelial tissues. These infections are facilitated by the lack of integration between the devices and the surrounding soft tissues. This study aims to improve epithelial integration through surface modification of a transcutaneous implant material (polyetheretherketone (PEEK)). The modification involved covalent bonding of collagen via two distinct methods: (1) nonselective binding through any primary amines present on collagen using carbodiimide-based coupling and (2) site-specific binding to the free amine on the N-terminus of collagen molecules. The second approach preserves active sites responsible for interacting with integrins, crucial for epithelial cell adhesion, located near the C terminus. Both conjugation methods resulted in similar amounts of immobilized collagen; yet, surfaces with 2-PCA-based collagen conjugation exhibited 4 times more free amines. This indicates that fewer amines were used for conjugation in these samples, confirming that 2-PCA selectively binds collagen only through the N-terminus amines. Collagen-conjugated surfaces significantly enhanced HaCaT epithelial cell viability and adhesion compared to unmodified PEEK. Furthermore, 2-PCA-based conjugation resulted in a 2-fold increase in beta 4 subunit gene expression of integrin alpha 6 beta 4 (a key epithelial cell adhesion marker), higher integrin beta 4 immunofluorescence (IF) intensity, and over a 30% improvement in cell retention following mechanical detachment, compared to nonselective conjugation. These findings suggest that selective collagen conjugation on PEEK surfaces increases the accessibility of collagen domains responsible for binding with integrin receptors, which in turn improves epithelial cell attachment, offering a promising strategy for reducing infections and enhancing the longevity of transcutaneous devices.

JTD Keywords: Cell-adhesion, Conjugation, Domains, Fibroblasts, Fibronectin, Integrin, Matrix, Protein, Selective protein conjugation, Soft tissue integration, Strategies, Titanium surfaces, Transcutaneous implants

Skeletal muscle tissue represents an attractive powering component for biohybrid robots, as traditional actuators used in the soft robotic context often rely on complex mechanisms and lack scalability at small dimensions. This article proposes a monolithic biohybrid flexure mechanism actuated by a bioengineered skeletal muscle tissue. The design leverages the contractile properties of a bioengineered skeletal muscle to produce a bending motion in a monolithic, tubular mechanism made of a soft and biocompatible silicone blend. This structure integrates two cylindrical pillars that facilitate force transmission from the bioengineered muscle tissue. Performance assessments reveal excellent contractile and stable behavior upon electrical stimulation, compared to current biohybrid actuation systems, with enhanced performance as the mechanism's internal and external diameters decrease. Finite-element simulations further reveal distinct force-displacement responses in mechanisms with different flexural rigidity. This innovative, scalable, and easy-to-fabricate design represents a significant step forward in the development of novel biohybrid machines.

JTD Keywords: Bioactuator, Biohybrid robotics, Flexible skeleton, Microfabrication, Muscle contraction, Muscle tissue engineering, Soft robotic

Unjamming transitions from a solid-like to a fluid-like state are a gateway to breast epithelial cancer invasion. However, the mechanical interplay between phase transitions and dimension transitions, in particular wetting, remains elusive, despite being critical for understanding the onset of metastatic dissemination. This study shows that unjamming, mediated by the RAB5A GTPase, alters carcinoma spheroid fluidity, rigidity, and rewires adhesion mechanics to drive supracellular active wetting as a new mode of tumor expansion. Spheroid fluidification enhances the selective expression of integrin subunits and increases focal adhesion dynamics, inducing a fluid-like spreading behavior on specific matrix ligands. Notably, nanoscale regulation of integrin clustering can select for distinct phase transitions at the collective scale upon wetting. In this framework, fluidized spheroids polarize into cohesive "supracells", and maintain a stiff peripheral actin bundle as measured by nanomechanical mapping. Furthermore, a combination of Brillouin microscopy and 2.5D traction force analysis reveals a mechanical switch within the spheroid core, characterized by significant cell softening and a reduction in compressive forces exerted on the substrate, thereby mimicking the wetting of a liquid droplet. These findings establish unjamming-driven active wetting as a key mechanism to comprehend the molecular and biophysical underpinnings of solid tumor invasion.

JTD Keywords: Adhesion, Biophysics, Dynamics, Epithelia, Integrin, Mechanobiology, Mechanotransduction, Mesenchymal transitions, Paxillin, Rab5a-mediated breast carcinoma fluidification, Snai, Softening, Spheroid wetting, Supracellular motilit

Biohybrid actuators leveraging living muscle tissue offer the potential to replicate natural motion for biomedical and robotic applications. However, challenges such as limited force output and inefficient force transfer at tissue interfaces persist. The myotendinous junction, a specialized interface connecting muscle to the tendon, plays a critical role in efficient force transmission for movement. Engineering muscle-tendon units in vitro is essential for replicating native musculoskeletal functions in biohybrid actuators. Here, we present a three-dimensionally bioprinted system integrating skeletal muscle tissue with tendon-mimicking anchors containing fibroblasts, forming a biomimetic interdigitated myotendinous junction. Using computational models, we optimized muscle geometries to enhance deformation and force generation. The engineered system improved mechanical stability, myofiber maturation, and force transmission, generating contractile forces of up to 350 micronewtons over a 3-month period. This work highlights how biomimetic designs and mechanical optimization can advance bioactuator technologies for applications in medicine and robotics.

JTD Keywords: Fabrication, Fibrinoge, Fibroblasts, Interleukin-6, Proliferation, Skeletal-muscle, Soft, Stiffness, Stimulation, Tissue

Kidney stones are some of the most common urinary diseases, affecting 12% of the population. The high prevalence and recurrence of this disease urges the development of more targeted and effective treatment with lower side effects and less invasiveness avoiding recurrence and prolonged drug administration. Particularly for recurring stone formers, the current methods of persistent drug treatment and repetitive surgeries for stone removal are unsatisfying solutions that bring a huge burden to the patients and healthcare systems. For these reasons, a delivery strategy that provides drug administration at the disease site through active, wireless transport is urgently needed to improve urinary tract disease treatment. A wireless treatment of kidney stones is proposed with the help of flexible, magnetically steered, enzymatically active robots. These robots are designed to navigate in the urinary tract and locally dissolve the stones by action of embedded urease. The robots are made of millimeter-sized, gelatin-based polymer strips with embedded micromagnets and encapsulated urease which constantly converts urea to increase urinary pH. This study demonstrates enhanced stone dissolution and the robots' magnetic navigation through the different parts of a 3D printed human urinary tract model. A clinical ultrasound system allows real-time localization of the robots. This research proposes a less invasive and more targeted strategy for medical interventions in the urinary tract with potential to circumvent surgery in case of uric acid kidney stones, which is relevant especially in the light of high prevalence and recurrence of kidney stones.

JTD Keywords: Enzymatic, Kidney stones, Magnetic, Microrobots, Renal stones, Soft robot

We report the fabrication and characterization of a highly sensitive pressure sensor that has been successfully tested using 3D-bioprinted skeletal muscle tissue. The proposed pressure sensor consists of two assembled 3D printed specimens, which were obtained using 60/40 v/v poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) / poly(ethylene glycol) diacrylate (PEGDA) mixture, placed between two indium tin oxidecoated polyethylene terephthalate (PET-ITO) films. The printed specimens were shaped with a serrated structure, improving the sensitivity of the contact when pressed against PET-ITO film. Initially, the performance of the fabricated pressure sensor was tested using light cylindrical weights, which corresponded to pressures ranging from 0.99 to 14.71 kPa, and as prove of concept, carefully pressing with the finger (from 2.91 to 6.81 kPa). As the sensitivity and fast response of sensor were compatible with detection of soft muscle contractions, 3D-bioprinted skeletal muscle bioactuators were manufactured using myoblast cells. The contractions of the bioactuators, which were induced using electrical stimulation, exerted a pressure of 1.5 kPa only that was clearly and precisely detected by the sensor. Overall, the potential application of proposed pressure sensor for wearable and biomedical devices is evidenced by demonstrating its fast response time (< 50 ms) and sensitivity.

JTD Keywords: 4-ethylenedioxythiophene), Bioactuator, Healt, Hydrogels, Poly(3, Poly(ethylene glycol) diacrylate, Raman-spectroscopy, Soft electronics, Wearable electronic

In this work, we report a direct measurement of the forces exerted by a tubulin/kinesin active nematic gel as well as its complete rheological characterization, including the quantification of its shear viscosity, lb and its activity parameter, a. For this, we develop a method that allows us to rapidly photo -polymerize compliant elastic inclusions in the continuously remodeling active system. Moreover, we quantitatively settle longstanding theoretical predictions, such as a postulated relationship encoding the intrinsic time scale of the active nematic in terms of n and a. In parallel, we infer a value for the nematic elasticity constant, K, by combining our measurements with the theorized scaling of the active length scale. On top of the microrheology capabilities, we demonstrate strategies for defect encapsulation, quantification of defect mechanics, and defect interactions, enabled by the versatility of the microfabrication strategy that allows to combine elastic motifs of different shapes and stiffnesses that are fabricated in situ.

JTD Keywords: Dynamics, Hydrogel, Micro fabricatio, Micro fabrication, Motio, Rheology, Soft active matter, Topological defects

Introducing SimpliPyTEM, a Python library and accompanying GUI that simplifies the post-acquisition evaluation of transmission electron microscopy (TEM) images, helping streamline the workflow. After an imaging session, a folder of image and/or video files, typically containing low contrast and large file size 32-bit images, can be quickly processed via SimpliPyTEM into high-quality, high-contrast.jpg images with suitably sized scale bars. The app can also generate HTML or PDF files containing the processed images for easy viewing and sharing. Additionally, SimpliPyTEM specifically focuses on in situ TEM videos, an emerging field of EM involving the study of dynamic processes whilst imaging. The package allows fast data processing into preview movies, averages, image series, or motion-corrected averages. The accompanying Python library offers many standard image processing methods, all simplified to a single command, plus a module to analyse particle morphology and population. This latter application is particularly useful for life sciences investigations. User-friendly tutorials and clear documentation are included to help guide users through the processing and analysis. We invite the EM community to contribute to and further develop this open-source package.

JTD Keywords: Image processing, computer-assisted, Microscopy, electron, transmission, Mobile applications, Software

The intestine is a complex tissue with a characteristic three-dimensional (3D) crypt-villus architecture, which plays a key role in the intestinal function. This function is also regulated by the intestinal stroma that actively supports the intestinal epithelium, maintaining the homeostasis of the tissue. Efforts to account for the 3D complex structure of the intestinal tissue have been focused mainly in mimicking the epithelial barrier, while solutions to include the stromal compartment are scarce and unpractical to be used in routine experiments. Here we demonstrate that by employing an optimized bioink formulation and the suitable printing parameters it is possible to produce fibroblast-laden crypt-villus structures by means of digital light projection stereolithography (DLP-SLA). This process provides excellent cell viability, accurate spatial resolution, and high printing throughput, resulting in a robust biofabrication approach that yields functional gut mucosa tissues compatible with conventional testing techniques.Copyright © 2023 Elsevier B.V. All rights reserved.

JTD Keywords: 3d microstructure, barrier, cells, epithelial-stromal interactions, gelma-pegda soft hydrogels, growth, hydrogel, intestinal mucosa model, methacrylamide, microfabrication, proliferation, scaffold, stereolithography, 3d bioprinting, 3d microstructure, Epithelial-stromal interactions, Fibroblasts, Gelma-pegda soft hydrogels, Intestinal mucosa model

The formation of a biological seal around the neck of titanium (Ti) implants is critical for ensuring integration at the gingival site and for preventing bacterial colonization that may lead to periimplantitis. This process is guided by activated fibroblasts, named myofibroblasts, which secrete extracellular matrix (ECM) proteins and ECM-degrading enzymes resolving the wound. However, in some cases, Ti is not able to attract and activate fibroblasts to a sufficient extent, which may compromise the success of the implant. Fibronectin (FN) is an ECM component found in wounds that is able to guide soft tissue healing through the adhesion of cells and attraction of growth factors (GFs). However, clinical use of FN functionalized Ti implants is problematic because FN is difficult to obtain, and is sensitive to degradation. Herein, functionalizing Ti with a modified recombinant heparin binding II (HBII) domain of FN, mutated to include an Arg-Gly-Asp (RGD) sequence for promoting both fibroblast adhesion and GF attraction, is aimed at. The HBII-RGD domain is able to stimulate fibroblast adhesion, spreading, proliferation, migration, and activation to a greater extent than the native HBII, reaching values closer to those of full-length FN suggesting that it might induce the formation of a biological sealing.© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.

JTD Keywords: alpha-4-beta-1, beta, cell-binding, collagen, extracellular-matrix, fibroblast activation, fibronectin, growth factors, integrins, metalloproteinases, myofibroblasts, proliferation, soft-tissue integration, titanium, Biological-activities, Fibroblast activation, Titanium

Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology is supported by numerous experimental and theoretical investigations in recent years. In this review, first, a brief introduction to the key ideas of surface curvature in the context of biological systems is given and the challenges that arise when measuring surface curvature are discussed. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent. On the other hand, summarizing current findings also shows that both single cells and entire cell sheets, tissues or organisms respond to curvature by modulating their shape and their migration behavior. Finally, the interplay between the distribution of morphogens or micro-organisms and the emergence of curvature across length scales is addressed with examples demonstrating these key mechanistic principles of morphogenesis. Overall, this review highlights that curved interfaces are not merely a passive by-product of the chemical, biological, and mechanical processes but that curvature acts also as a signal that co-determines these processes.© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.

JTD Keywords: biological systems, butterfly wing scales, cubic membranes, extracellular-matrix, geometry, mechanotransduction, membrane curvature, morphogenesis, neotissue growth, pattern-formation, soft materials, surface curvature, tissue-growth, Biological systems, Collective cell-migration, Surface curvature

Research with soft materials, that is, polymeric gels, colloidal suspensions, liquid crystals, and most biomaterials often involves the need for microfabrication of confinement channels, cells, and lab-on-a-chip devices. Photolithography techniques are often chosen, as they offer the combination of versatility, precision, and quick delivery demanded by researchers. Beyond fabrication, stimulus-responsive systems, such as photosensitivity biomaterials, are the object of broad study within a very interdisciplinary community. Here, we show that a standard laboratory microscope can be quickly and economically transformed into a powerful maskless photofabrication/photoexcitation station using off-the-shelf DMD development modules and simple optomechanical components allowing real time observation of the fabrication process.

JTD Keywords: Dmd, Microscopy, Photolithography, Soft matter

The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the “device”/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant – as a model percutaneous device – placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists. © 2022 The Authors

JTD Keywords: amino-acid-sequence, bioinspired surfaces, cell-secreted protein, growth-factor receptor, hemidesmosome, integrin beta-4 subunit, junctional epithelium, keratinocyte-derived chemokine, laminin-binding integrins, marginal bone loss, percutaneous device, percutaneous implant, pressure wound therapy, soft-tissue integration, Bioinspired surfaces, Bullous-pemphigoid antigen, Hemidesmosome, Junctional epithelium, Percutaneous device, Percutaneous implant

Hydroxyapatite nanoparticles are popular tools in bone regeneration, but they have also been used for gene delivery and as anticancer drugs. Understanding their mechanism of action, particularly for the latter application, is crucial to predict their toxicity. To this end, we aimed to elucidate the importance of nanoparticle membrane interactions in the cytotoxicity of MG-63 cells using two different types of nanoparticles. In addition, conventional techniques for studying nanoparticle internalisation were evaluated and compared with newer and less exploited approaches. Hydroxyapatite and magnesium-doped hydroxyapatite nanoparticles were used as suspensions or compacted as specular discs. Comparison between cells seeded on the discs and those supplemented with the nanoparticles allowed direct interaction of the cell membrane with the material to be ruled out as the main mechanism of toxicity. In addition, standard techniques such as flow cytometry were inconclusive when used to assess nanoparticles toxicity. Interestingly, the use of intracellular calcium fluorescent probes revealed the presence of a high number of calcium-rich vesicles after nanoparticle supplementation in cell culture. These structures could not be detected by transmission electron microscopy due to their liquid content. However, by using cryo-soft X-ray imaging, which was used to visualise the cellular ultrastructure without further treatment other than vitrification and to quantify the linear absorption coefficient of each organelle, it was possible to identify them as multivesicular bodies, potentially acting as calcium stores. In the study, an advanced state of degradation of the hydroxyapatite and magnesium-doped hydroxyapatite nanoparticles within MG-63 cells was observed. Overall, we demonstrate that the combination of fluorescent calcium probes together with cryo-SXT is an excellent approach to investigate intracellular calcium, especially when found in its soluble form.Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.

JTD Keywords: adsorption, cryo-soft x-ray tomography, cytotoxicity, expression, flow cytometry, internalisation, intracellular calcium, magnesium, nano, nanomaterials, nanoparticles, proliferation, protein corona, ultrastructure, Calcium-phosphate nanoparticles, Cryo-soft x-ray tomography, Flow cytometry, Hydroxyapatite, Internalisation, Intracellular calcium, Nanoparticles

Tuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers. © The Author(s) 2022.

JTD Keywords: blends, compressibility, crosslink density, cure characteristics, ethylene propylene diene monomer, focused ion beam, mechanical-properties, morphology, natural-rubber, particles, scanning acoustic microscopy, scanning electron microscopy, sulfur, thermal-stability, vulcanization, Composite soft materials, Cross-link densities, Crosslink density, Crosslinking, Density (specific gravity), Ethylene, Ethylene propylene diene monomer, Flory-rehner, Focused ion beam - scanning electron microscopy, Focused ion beam-scanning electron microscopies, Ii-vi semiconductors, Monomers, Moving die rheometers, Physical and mechanical properties, Propylene, Relaxation analysis, Rubber, Scanning acoustic microscopy, Scanning electron microscopy, Stress relaxation, Sulfur contents, Temperature scanning stress relaxations, Zinc oxide

JTD Keywords: biomimetics, living machines, Biomimetics, Living machines, Soft machines

Unlike the attachment of soft epithelial skin tissue to penetrating solid natural structures like fingernails and teeth, sealing around percutaneous/permucosal devices such as dental implants is hindered by inflammation and epidermal down growth. Here, we employed a dual keratinocyte-adhesive peptide and anti-inflammatory biomolecule coating on titanium to promote oral epithelial tissue attachment. For minimizing inflammation-triggered epidermal down growth, we coated pristine and oxygen plasma pre-treated polished titanium (pTi) with conjugated linoleic acid (CLA). Further, in order to aid in soft tissue attachment via the formation of hemidesmosomes, adhesive structures by oral keratinocytes, we coated the anionic linoleic acid (LA) adsorbed titanium with cationic cell adhesive peptides (CAP), LamLG3, a peptide derived from Laminin 332, the major extracellular matrix component of the basement membrane in skin tissue and Net1, derived from Netrin-1, a neural chemoattractant capable of epithelial cell attachment via alpha 6 beta 4 integrins. The dual CLA-CAP coatings on pTi were characterized by X-ray photoelectron spectroscopy and dynamic water contact angle measurements. The proliferation of human oral keratinocytes (TERT-2/OKF6) was accelerated on the peptide coated titanium while also promoting the expression of Col XVII and beta-4 integrin, two markers for hemidesmosomes. Simultaneously, CLA coating suppressed the production of inducible nitric oxide synthase (anti-iNOS); a pro-inflammatory M1 marker expressed in lipopolysaccharide (LPS) stimulated murine macrophages (RAW 264.7) and elevated expression of anti-CD206, associated to an anti-inflammatory M2 macrophage phenotype. Taken together, the dual keratinocyte-adhesive peptide and anti-inflammatory biomolecule coating on titanium can help reduce inflammation and promote permucosal/peri-implant soft tissue sealing.

JTD Keywords: Adhesives, Animal, Animals, Anti-inflammatories, Anti-inflammatory agents, Antiinflammatory agent, Biomolecules, Bone, Cell adhesion, Cell-adhesives, Coatings, Conjugated linoleic acid, Conjugated linoleic-acid, Contact angle, Hemidesmosome, Hemidesmosomes, Human, Humans, Hydroxyapatite, Inflammation, Integrins, Keratinocyte, Keratinocytes, Linoleic acid, Macrophages, Mice, Mouse, Nitric oxide, Oral implants, Pathology, Peptides, Skin tissue, Soft tissue, Supplementation, Surface properties, Surface property, Tissue, Titania, Titanium, X ray photoelectron spectroscopy

The use of broadly neutralizing antibodies against human immunodeficiency virus type 1 (HIV-1) has been shown to be a promising therapeutic modality in the prevention of HIV infection. Understanding the b12-gp120 binding mechanism under physiological conditions may assist the development of more broadly effective antibodies. In this work, the main conformations and interactions between the receptor-binding domain (RBD) of spike glycoprotein gp120 of HIV-1 and the IgG1-b12 mAb are studied. Accelerated molecular dynamics (aMD) and ab initio hybrid molecular dynamics have been combined to determine the most persistent interactions between the most populated conformations of the antibody-antigen complex under physiological conditions. The results show the most persistent receptor-binding mapping in the conformations of the antibody-antigen interface in solution. The binding-free-energy decomposition reveals a small enhancement in the contribution played by the CDR-H3 region to the b12-gp120 interface compared to the crystal structure.

JTD Keywords: antibody, complex, functionals, gp120 envelope glycoprotein, hiv, immunodeficiency-virus, noncovalent interactions, simulations, software integration, Ab initio, Accelerated molecular dynamics, Accelerated molecular-dynamics, Antibodies, Antigens, Binding energy, Binding mechanisms, Computational studies, Crystal structure, Diseases, Free energy, Hiv infection, Human immunodeficiency virus, Molecular dynamics, Neutralizing antibodies, Physiological condition, Physiology, Receptor-binding domains, Therapeutic modality, Viruses

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

JTD Keywords: brain, composite hydrogel, dynamic mechanical analysis, elastography, hardness, hydrogels, in-vitro, liver, materials, mechanical-properties, mimicking, soft tissues, tissue scaffolding, viscoelasticity, warner-braztler shear test, warner–braztler shear test, Dynamic mechanical analysis, Hardness, Hydrogels, Materials, Mimicking, Soft tissues, Tissue scaffolding, Viscoelastic characterization, Viscoelasticity, Warner–braztler shear test

[Figure: see text].

JTD Keywords: activation, cell extrusion, contraction, drives, homeostasis, interface, junctions, kinase, tension, Adhesion, Article, Cell membranes, Chemical activation, Cytology, E-cadherin, Epithelial monolayers, Epithelium, Homoeostasis, Human, Mechanical instabilities, Monolayers, Morphological transformations, Morphology, Normal tissue, Oncogenics, Soft substrates, Substrates, Tissue, Tissue mechanics, Tissue morphology, Tumor development

Multifunctional hydrogels are a class of materials offering new opportunities for interfacing living organisms with machines due to their mechanical compliance, biocompatibility, and capacity to be triggered by external stimuli. Here, we report a dual magnetic- and electric-stimuli-responsive hydrogel with the capacity to be disassembled and reassembled up to three times through reversible cross-links. This allows its use as an electronic device (e.g., temperature sensor) in the cross-linked state and spatiotemporal control through narrow channels in the disassembled state via the application of magnetic fields, followed by reassembly. The hydrogel consists of an interpenetrated polymer network of alginate (Alg) and poly(3,4-ethylenedioxythiophene) (PEDOT), which imparts mechanical and electrical properties, respectively. In addition, the incorporation of magnetite nanoparticles (Fe3O4 NPs) endows the hydrogel with magnetic properties. After structural, (electro)chemical, and physical characterization, we successfully performed dynamic and continuous transport of the hydrogel through disassembly, transporting the polymer-Fe3O4 NP aggregates toward a target using magnetic fields and its final reassembly to recover the multifunctional hydrogel in the cross-linked state. We also successfully tested the PEDOT/Alg/Fe3O4 NP hydrogel for temperature sensing and magnetic hyperthermia after various disassembly/re-cross-linking cycles. The present methodology can pave the way to a new generation of soft electronic devices with the capacity to be remotely transported.

JTD Keywords: conductive hydrogel, constructs, magnetic field, magnetite nanoparticle, nanoindentation, soft electronics, spatiotemporal control, Conductive hydrogel, Conductive hydrogels, Magnetic field, Magnetite nanoparticle, Soft electronics, Spatiotemporal control

Cell response to force regulates essential processes in health and disease. However, the fundamental mechanical variables that cells sense and respond to remain unclear. Here we show that the rate of force application (loading rate) drives mechanosensing, as predicted by a molecular clutch model. By applying dynamic force regimes to cells through substrate stretching, optical tweezers, and atomic force microscopy, we find that increasing loading rates trigger talin-dependent mechanosensing, leading to adhesion growth and reinforcement, and YAP nuclear localization. However, above a given threshold the actin cytoskeleton softens, decreasing loading rates and preventing reinforcement. By stretching rat lungs in vivo, we show that a similar phenomenon may occur. Our results show that cell sensing of external forces and of passive mechanical parameters (like tissue stiffness) can be understood through the same mechanisms, driven by the properties under force of the mechanosensing molecules involved. Cells sense mechanical forces from their environment, but the precise mechanical variable sensed by cells is unclear. Here, the authors show that cells can sense the rate of force application, known as the loading rate, with effects on YAP nuclear localization and cytoskeletal stiffness remodelling.

JTD Keywords: Actin cytoskeleton, Actin filament, Actin-filament, Adhesion, Animal, Animals, Atomic force microscopy, Breathing, Cell, Cell adhesion, Cell culture, Cell nucleus, Cells, cultured, Cytoplasm, Extracellular-matrix, Fibroblast, Fibroblasts, Fibronectin, Frequency, Gene knockdown, Gene knockdown techniques, Genetics, Germfree animal, Integrin, Intracellular signaling peptides and proteins, Knockout mouse, Lung, Male, Mechanotransduction, Mechanotransduction, cellular, Metabolism, Mice, Mice, knockout, Microscopy, atomic force, Mouse, Optical tweezers, Paxillin, Physiology, Primary cell culture, Pxn protein, mouse, Rat, Rats, Rats, sprague-dawley, Respiration, Signal peptide, Softening, Specific pathogen-free organisms, Sprague dawley rat, Stress, Substrate, Substrate rigidity, Talin, Talin protein, mouse, Tln1 protein, mouse, Tln2 protein, mouse, Traction, Transmission, Ultrastructure, Yap-signaling proteins, Yap1 protein, rat

This book constitutes the proceedings of the )th International Conference on Biomimetic and Biohybrid Systems, Living Machines 2020, held in Freiburg, Germany, in July 2020. Due to COVID-19 pandemic the conference was held virtually. The 32 full and 7 short papers presented in this volume were carefully reviewed and selected from 45 submissions. They deal with research on novel life-like technologies inspired by the scientific investigation of biological systems, biomimetics, and research that seeks to interface biological and artificial systems to create biohybrid systems.

JTD Keywords: Artificial intelligence, Soft robotics, Biomimetics, Insect navigation, Synthetic nervous system, Computer vision, Bio-inspired materials, Visual homing, Locomotion+, Image processing, Intelligent robots, Human-robot interaction, Machine learning, Snake robot, Mobile robots, Robotic systems, Drosophila, Robots, Sensors, Signal processing

EMG signals reflect the neuromuscular activation patterns related to the execution of a certain movement or task. In this work, we focus on reaching and grasping (R&G) movements in rats. Our objective is to develop an automatic algorithm to detect the onsets and offsets of muscle activity and use it to study muscle latencies in R&G maneuvers. We had a dataset of intramuscular EMG signals containing 51 R&G attempts from 2 different animals. Simultaneous video recordings were used for segmentation and comparison. We developed an automatic onset/offset detector based on the ratio of local maxima of Teager-Kaiser Energy (TKE). Then, we applied it to compute muscle latencies and other features related to the muscle activation pattern during R&G cycles. The automatic onsets that we found were consistent with visual inspection and video labels. Despite the variability between attempts and animals, the two rats shared a sequential pattern of muscle activations. Statistical tests confirmed the differences between the latencies of the studied muscles during R&G tasks. This work provides an automatic tool to detect EMG onsets and offsets and conducts a preliminary characterization of muscle activation during R&G movements in rats. This kind of approaches and data processing algorithms can facilitate the studies on upper limb motor control and motor impairment after spinal cord injury or stroke.

JTD Keywords: Muscles, Electromyography, Rats, Low pass filters, Microsoft Windows, Band-pass filters

Generating complex, human-like behaviour in a humanoid robot like the iCub requires the integration of a wide range of open source components and a scalable cognitive architecture. Hence, we present the iCub-HRI library which provides convenience wrappers for components related to perception (object recognition, agent tracking, speech recognition, touch detection), object manipulation (basic and complex motor actions) and social interaction (speech synthesis, joint attention) exposed as a C++ library with bindings for Java (allowing to use iCub-HRI within Matlab) and Python. In addition to previously integrated components, the library allows for simple extension to new components and rapid prototyping by adapting to changes in interfaces between components. We also provide a set of modules which make use of the library, such as a high-level knowledge acquisition module and an action recognition module. The proposed architecture has been successfully employed for a complex human-robot interaction scenario involving the acquisition of language capabilities, execution of goal-oriented behaviour and expression of a verbal narrative of the robot's experience in the world. Accompanying this paper is a tutorial which allows a subset of this interaction to be reproduced. The architecture is aimed at researchers familiarising themselves with the iCub ecosystem, as well as expert users, and we expect the library to be widely used in the iCub community.

JTD Keywords: Robotics, iCub Humanoid, YARP, Software architecture, C++, Python, Java, Human-robot interaction

This book constitutes the proceedings of the 7th International Conference on Biomimetic and Biohybrid Systems, Living Machines 2018, held in Paris, France, in July 2018. The 40 full and 18 short papers presented in this volume were carefully reviewed and selected from 60 submissions. The theme of the conference targeted at the intersection of research on novel life-like technologies inspired by the scientific investigation of biological systems, biomimetics, and research that seeks to interface biological and artificial systems to create biohybrid systems.

JTD Keywords: Artificial neural network, Bio-actuators, Bio-robotics, Biohybrid systems, Biomimetics, Bipedal robots, Earthoworm-like robots, Robotics, Decision-making, Tactile sensing, Soft robots, Locomotion, Insects, Sensors, Actuators, Robots, Artificial intelligence, Neural networks, Motion planning, Learning algorithms

Background: Most stroke survivors continue to experience motor impairments even after hospital discharge. Virtual reality-based techniques have shown potential for rehabilitative training of these motor impairments. Here we assess the impact of at-home VR-based motor training on functional motor recovery, corticospinal excitability and cortical reorganization. Objective: The aim of this study was to identify the effects of home-based VR-based motor rehabilitation on (1) cortical reorganization, (2) corticospinal tract, and (3) functional recovery after stroke in comparison to home-based occupational therapy. Methods: We conducted a parallel-group, controlled trial to compare the effectiveness of domiciliary VR-based therapy with occupational therapy in inducing motor recovery of the upper extremities. A total of 35 participants with chronic stroke underwent 3 weeks of home-based treatment. A group of subjects was trained using a VR-based system for motor rehabilitation, while the control group followed a conventional therapy. Motor function was evaluated at baseline, after the intervention, and at 12-weeks follow-up. In a subgroup of subjects, we used Navigated Brain Stimulation (NBS) procedures to measure the effect of the interventions on corticospinal excitability and cortical reorganization. Results: Results from the system?s recordings and clinical evaluation showed significantly greater functional recovery for the experimental group when compared with the control group (1.53, SD 2.4 in Chedoke Arm and Hand Activity Inventory). However, functional improvements did not reach clinical significance. After the therapy, physiological measures obtained from a subgroup of subjects revealed an increased corticospinal excitability for distal muscles driven by the pathological hemisphere, that is, abductor pollicis brevis. We also observed a displacement of the centroid of the cortical map for each tested muscle in the damaged hemisphere, which strongly correlated with improvements in clinical scales. Conclusions: These findings suggest that, in chronic stages, remote delivery of customized VR-based motor training promotes functional gains that are accompanied by neuroplastic changes. Trial Registration: International Standard Randomized Controlled Trial Number NCT02699398 (Archived by ClinicalTrials.gov at https://clinicaltrials.gov/ct2/show/NCT02699398?term=NCT02699398&rank=1)

JTD Keywords: Stroke, Movement disorder, Recovery of function, neuroplasticity, Transcranial magnetic stimulation, Physical therapy, Hemiparesis, Computer applications software

It has been experimentally observed that cells exhibit a fluidisation process when subjected to a transient stretch, with an eventual recovery of the mechanical properties upon removal of the applied deformation. This fluidisation process is characterised by a decrease of the storage modulus and an increase of the phase angle. We propose a rheological model which is able to reproduce this combined mechanical response. The model is described in the context of continua and adapted to a cell-centred particle system that simulates cell–cell interactions. Mechanical equilibrium is coupled with two evolution laws: (i) one for the reference configuration, and (ii) another for the porosity or polymer density. The first law depends on the actual strain of the tissue, while the second assumes different remodelling rates during porosity increase and decrease. The theory is implemented on a particle based model and tested on a stretching experiment. The numerical results agree with the experimental measurements for different stretching magnitudes.

JTD Keywords: Cell remodelling, Cell rheology, Fluidisation, Softening, Viscoelasticity

A simple method for constructing versatile ordered biotin/avidin arrays on UV-curable perfluoropolyethers (PFPEs) is presented. The goal is the realization of a versatile platform where any biotinylated biological ligands can be further linked to the underlying biotin/avidin array. To this end, microcontact arrayer and microcontact printing technologies were developed for photobiotin direct printing on PFPEs. As attested by fluorescence images, we demonstrate that this photoactive form of biotin is capable of grafting onto PFPEs surfaces during irradiation. Bioaffinity conjugation of the biotin/avidin system was subsequently exploited for further self-assembly avidin family proteins onto photobiotin arrays. The excellent fouling release PFPEs surface properties enable performing avidin assembly step simply by arrays incubation without PFPEs surface passivation or chemical modification to avoid unspecific biomolecule adsorption. Finally, as a proof of principle biotinylated heparin was successfully grafted onto photobiotin/avidin arrays.

JTD Keywords: Antifouling, Heparin, Malaria, Microcontact arrayer, Microcontact printing, Micropatterning, Perfluoropolyether, Photobiotin, Polymers, Soft lithography

The characterization of the mechanical properties of soft materials has been traditionally performed through uniaxial tensile tests. Nevertheless, this method cannot be applied to certain extremely soft materials, such as biological tissues or cells that cannot be properly subjected to these tests. Alternative non-destructive tests have been designed in recent years to determine the mechanical properties of soft biological tissues. One of these techniques is based on the use of atomic force microscopy (AFM) to perform nanoindentation tests. In this work, we investigated the mechanical response of soft biological materials to nanoindentation with spherical indenters using finite element simulations. We studied the responses of three different material constitutive laws (elastic, isotropic hyperelastic and anisotropic hyperelastic) under the same process and analyzed the differences thereof. Whereas linear elastic and isotropic hyperelastic materials can be studied using an axisymmetric simplification, anisotropic hyperelastic materials require three-dimensional analyses. Moreover, we established the limiting sample size required to determine the mechanical properties of soft materials while avoiding boundary effects. Finally, we compared the results obtained by simulation with an estimate obtained from Hertz theory. Hertz theory does not distinguish between the different material constitutive laws, and thus, we proposed corrections to improve the quantitative measurement of specific material properties by nanoindentation experiments.

JTD Keywords: AFM, Cell mechanics, FEM, Nanoindentation, Soft-tissue

Novel strategies to heal discogenic low back pain could highly benefit from comprehensive biophysical studies that consider both mechanical and biological factors involved in intervertebral disc degeneration. A decrease in nutrient availability at the bone-disc interface has been indicated as a relevant risk factor and as a possible initiator of cell death processes. Mechanical behaviour of both healthy and degenerated discs could highly interact with cell death in these compromised situations. In the present study, a mechano-transport finite element model was used to investigate the nature of mechanical effects on cell death processes via load-induced metabolic transport variations. Cycles of static sustained compression were chosen to simulate daily human activity. Healthy and degenerated cases were simulated as well as a reduced supply of solutes and an increase in solute exchange area at the bone-disc interface. Results showed that a reduction in metabolite concentrations at the bone-disc boundaries induced cell death, even when the increased exchange area was simulated. Slight local mechanical enhancements of glucose in the disc centre were capable of decelerating cell death but occurred only with healthy mechanical properties. However, mechanical deformations were responsible for a worsening in terms of cell death in the inner annulus, a disadvantaged zone far from the boundary supply with both an increased cell demand and a strain-dependent decrease of diffusivity. Such adverse mechanical effects were more accentuated when degenerative properties were simulated. Overall, this study paves the way for the use of biophysical models for a more integrated understanding of intervertebral disc pathophysiology.

JTD Keywords: Boundary conditions, Cell nutrition, Cell viability, Computational analysis, Intervertebraldisc, Softtissuebiomechanics

We resort to non-linear viscoelasticity to develop a truss element able to model reversible softening in lung epithelial tissues undergoing transient stretch. Such a Maxwell truss element is built by resorting to a three-noded element whose mid-node is kinematically constrained to remain on the line connecting the end-nodes. The whole mechanical system undergoes an additive decomposition of the strains along the truss direction where the total contribution of the mid-node is accounted for by using a null-space projection and static condensation techniques. Assembling of such line-elements in 3D networks allows us to model extended regions of living tissues as well as their anisotropies.

JTD Keywords: Maxwell, Null-space, Reversible softening, Truss, Viscoelasticity

A method for the simultaneous (bio)chemical and topographical patterning of enclosed structures in poly(dimethyl siloxane) (PDMS) is presented. The simultaneous chemical and topography transference uses a water-soluble chitosan sacrificial mold to impart a predefined pattern with micrometric accuracy to a PDMS replica. The method is compared to conventional soft-lithography techniques on planar surfaces. Its functionality is demonstrated by the transference of streptavidin directly to the surface of the three-dimensional PDMS structures as well as indirectly using streptavidin-loaded latex nanoparticles. The streptavidin immobilized on the PDMS is tested for bioactivity by coupling with fluorescently labeled biotin. This proves that the streptavidin is immobilized on the PDMS surface, not in the bulk of the polymer, and is therefore accessible for use as signaling/binding element in micro and bioengineering. The use of a biocompatible polymer and processes enables the technique to be used for the chemical patterning of tissue constructions.

JTD Keywords: Biotechnology, Chitosan, Microfabrication, MEMs, Soft lithography

Lower limb amputation is a severe psychological and physical event in a patient. A prosthetic solution can be provided but should respond to a patient-specific need to accommodate for the geometrical and biomechanical specificities. A new approach to calculate the stress-strain state at the interaction between the socket and the stump of five transfemoral amputees is presented. In this study the socket donning procedure is modeled using an explicit finite element method based on the patient-specific geometry obtained from CT and laser scan data. Over stumps the mean maximum pressure is 4 kPa (SD 1.7) and the mean maximum shear stresses are 1.4 kPa (SD 0.6) and 0.6 kPa (SD 0.3) in longitudinal and circumferential directions, respectively. Locations of the maximum values are according to pressure zones at the sockets. The stress-strain states obtained in this study can be considered more reliable than others, since there are normal and tangential stresses associated to the socket donning procedure.

JTD Keywords: Trans-tibial prosthesis, Knee residual limb, Pressure distribution, Transtibial amputees, Stump/socket interface, Mechanical conditions, Load-transfer, Soft-tissues, Stresses, Contact

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JTD Keywords: Soft lithography, Micro contact printing, Self-assembled monolayers, Soft Molding techniques

A new method for obtaining a three-dimensional volumetric reconstruction from a set of views improving the classical Shape from Silhouette method (SFS) is presented. SFS approaches can be easily accelerated through hardware and software techniques but they are very sensible to errors arising during calibration and segmentation processes so they present difficulties when dealing with real images. This paper proposes a new algorithm which uses the information about pixel segmentation uncertainty contained in each view in order to get a reliable 3D reconstruction of the scene. Aggregation of the projected uncertainties permits to classify scene's voxels by means of a decision rule but also makes it possible to create a three-dimensional confidence map of the scene. As a consequence, the regions where more information is needed can be foreseen. Sample reconstructions from real image sets are presented and evaluated.

JTD Keywords: Calibration, Image classification, Image reconstruction, Image segmentation, 3D reconstruction, Calibration process, Decision rule, Hardware technique, Pixel segmentation, Pixel-level certainty measures, Scene voxel classification, Segmentation process, Shape from silhouette method, Software technique, Three-dimensional confidence map, Three-dimensional volumetric reconstruction

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

A technique for imparting micro- and nano-structured topography into the surface of freestanding thin sheets of chitosan is described. Both micro- and nanometric surface structures have been produced using soft lithography. The soft lithography method, based on solvent evaporation, has allowed structures similar to 60 nm tall and similar to 500 X 500 nm(2) to be produced on freestanding similar to 0.5 mm thick sheets of the polymer when cured at 293 K, and structures similar to 400 nm tall and 5 X 5 mu m(2) to be produced when cured at 283 K. Nonstructured chitosan thin sheets (similar to 200 mu m thick) show excellent optical transmission properties in the visible portion of the electromagnetic spectrum. The structured sheets can be used for applications where optical microscopic analysis is required, such as cell interaction experiments and tissue engineering.

JTD Keywords: Chitin/chitosan, Microstructure, Nanotopography, Polymerization, Soft lithography

Micro- and nanoscale protein patterns have been produced via a new contact printing method using a nanoimprint lithography apparatus. The main novelty of the technique is the use of poly(methyl methacrylate) (PMMA) instead of the commonly used poly(dimethylsiloxane) (PDMS) stamps. This avoids printing problems due to roof collapse, which limits the usable aspect ratio in microcontact printing to 10:1. The rigidity of the PMMA allows protein patterning using stamps with very high aspect ratios, up to 300 in this case. Conformal contact between the stamp and the substrate is achieved because of the homogeneous pressure applied via the nanoimprint lithography instrument, and it has allowed us to print lines of protein similar to 150 nm wide, at a 400 nm period. This technique, therefore, provides an excellent method for the direct printing of high-density sub-micrometer scale patterns, or, alternatively, micro-/nanopatterns spaced at large distances. The controlled production of these protein patterns is a key factor in biomedical applications such as cell-surface interaction experiments and tissue engineering.

JTD Keywords: Soft lithography, Cell-adhesion, Microstructures, Fabrication, Stability, Patterns