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Title: Methodological detection solution scaffolds response to mechanical stress, depending on the degree of hydration Objectives: Determining the extent of lateral deformation u scaffolds made of PVA polymer electrospinning technique. Identify the extent of differences in transverse deformation for different groups of nanofiber scaffolds made of PVA polymer electrospinning technique. Methods: Research scaffolds, we used a measuring device μ-tester, which has two jaws. For the measurement, we chose uniaxial tension test in -tester and record the fluorescence microscope was used with HD camera Olympus 320 for online video recording. Results: The results of this study showed that the ratio of the samples U: L and crosslinking time affects the degree of lateral deformation of the samples scaffolds. Samples scaffolds are compressible, some groups even reached the limits of incompressibility 0.5 Poisson's ratio. Keywords: Poisson, Poisson's ratio, scaffold, nanofiber scaffold, scaffold hydrated, electrospun scaffold, lateral deformation

De nouveaux électrocatalyseurs avec nanofilm de platine pour la réaction de réduction de l'oxygène avec application dans des piles à combustible à membrane échangeuse de protons ont été développés. Ces catalyseurs comprennent des films minces de platine déposés sur des réseaux de nanofibres de carbone. Des supports de nanofibres de carbone et de nanobrosse ont été préparés par électrofilage suivi de traitements thermiques pour la stabilisation et la graphitisation. Une méthode innovante d’électrodéposition pulsée à surpotentiel élevé a été développée pour le dépôt de nanofilm de platine sur des supports de nanofibres de carbone et de nanobrosse, ainsi que sur du graphite pyrolytique hautement orienté dont la planéité permet de caractériser le dépôt avec microscopie à force et électronique. Ces approches ont conduit à des électrodes en nanofibres autosupportées avec une porosité qui a été accordée à un matériau de plus en plus dense d'un côté à l'autre, où le côté présentant la plus grande surface était utilisé pour déposer du platine. Les électrodes ont été caractérisées ex situ en utilisant voltampérométrie cyclique, en démontrant une activité plus élevée pour la réaction de réduction de l'oxygène et une durabilité contre des cycles de tension plus élevée que les catalyseurs classiques au platine sur carbone. Ces électrodes ont été assemblés directement avec une membrane et une anode et caractérisés in situ dans une pile à combustible. Des films minces de platine ont également été préparés à la surface des nanofibres de nickel en utilisant le nouvelle approche de l'échange galvanique assisté par micro-ondes ; divers paramètres expérimentaux ont été étudiés pour déterminer leur effet sur l'échange et la morphologie du platine. Les fibres de nickel@platine résultantes ont présenté une électroactivité élevée pour la réaction de réduction d'oxygène et ont été caractérisées comme des électrocatalyseurs non supportés à la cathode d'un assemblage d'électrodes à membrane; des travaux supplémentaires sont nécessaires pour les stabiliser contre la perte de nickel de l’électrocatalyseur vers l’électrolyte. / Novel platinum thin film electrocatalysts for the oxygen reduction reaction of proton exchange membrane fuel cells were developed. These catalysts comprise platinum thin films deposited on carbon nanofibrous webs. Carbon nanofibres and nanobrush supports were prepared by electrospinning followed by thermal treatments for stabilisation and graphitisation. An innovative pulsed high overpotential electrodeposition method was developed to deposit platinum thin films both on carbon nanofibre and nanobrush supports, and also on highly oriented pyrolytic graphite, the planarity of which allowed detailed characterisation of the conformity, contiguity and thickness of the platinum films using atomic force and electron microscopy. These approaches led to self-standing nanofibre electrodes with porosity that was tuned to increasingly dense material from one side to the other, where the side presenting highest surface area was used to deposit platinum. The electrodes were characterised ex situ using cycling voltammetry where they demonstrated higher activity for the oxygen reduction reaction and greater durability on voltage cycling than conventional platinum on carbon catalysts. They were also assembled directly with a membrane and anode and characterised in situ in a single fuel cell. Thin platinum films were also prepared at the surface of nickel nanofibres using a novel approach to galvanic exchange assisted by microwaves, and a range of experimental parameters was investigated to determine their effect on the extent of exchange and the resulting platinum morphology. While the resulting nickel@platinum core@shell fibres demonstrated high electroactivity for the oxygen reduction reaction and were characterised as unsupported electrocatalysts at the cathode of a membrane electrode assembly, further work is required to stabilise them against nickel leaching from the catalyst to the electrolyte.

Skeletal muscle injuries and muscle degenerative diseases pose significant challenges to the healthcare. Surgical interventions are restricted due to tissue availability, donor site morbidity and alterations to tissue biomechanics. Current cell-based therapies are hindered by low survival and long-term engraftment for the transplanted cells due to the lack of appropriate supportive microenvironment (cell niche) in the injured muscle. Therefore, there is a critical need for developing strategies that provide cellular and structural support in the regeneration of functional muscle. In the present work, a bioengineered cell niche mimicking the native skeletal muscle microenvironment has been developed for skeletal muscle regenerative engineering. It is hypothesized that the bioengineered scaffolds with appropriate structural and cell instructive properties will support myoblast alignment and function, as well as promote the myogenic responses in clinically relevant skeletal muscle injuries. The current work utilized a three-pronged approach to design biomaterial scaffolds to aid in skeletal muscle regeneration. In the first part, aligned poly(lactide-co-glycolide) (PLGA) fiber scaffolds mimicking the oriented muscle fiber microenvironment with fiber diameters of 335±154 nm (nanoscale), 1352±225 nm (microscale) and 3013±531 nm (microscale) were fabricated and characterized. Myoblasts were found to respond to fiber diameter as observed from the differences in cell alignment, cell elongation, cell spreading area, proliferation and differentiation. <i>In vivo</i> study demonstrated the potential of using microscale fiber scaffolds to improve myogenic potential in the <i>mdx</i> mouse model. In the second part, we designed, synthesized, and characterized an implantable glycosaminoglycan-based composite hydrogel consisting of hyaluronic acid, chondroitin sulfate and polyethylene glycol (HA-CS) with tailored structural and mechanical properties for skeletal muscle regeneration applications. We demonstrated that HA-CS hydrogels provided a suitable microenvironment for <i>in vitro</i> myoblast proliferation and differentiation. Furthermore, <i>in vivo</i> studies using a volumetric muscle loss model in the mouse quadriceps showed that HA-CS hydrogels integrated with the surrounding host tissue and facilitated <i>de novo</i> myofiber generation, angiogenesis, nerve innervation and minimized scar tissue formation. In the third part, we investigated the effects of PC12 secreted signaling factors in modulating C2C12 myoblast behavior. We showed that PC12 conditioned media modulated myoblast proliferation and differentiation in both 2D culture and 3D aligned electrospun fiber scaffold system in a dose dependent manner. We also demonstrated the biomimetic HA-CS hydrogel system enabled 3D encapsulation of PC12 cells secreting signaling factors and promoted survival and proliferation of myoblasts in co-culture. Further proteomics analysis identified a total of 2088 protein/peptides from the secretome of the encapsulated PC12 cells and revealed the biological role and overlapping functions of nerve secreted proteins for skeletal muscle regeneration, potentially through regulating myoblast behavior, nerve function, and angiogenesis. These set of experiments not only provide critical insight on exploiting the interactions between muscle cells and their microenvironment, but they also open new avenues for developing advanced bioengineered scaffolds for regenerative engineering of skeletal muscle tissues.<br>

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