Дисертації: "HYDROGEL NANOFIBERS"

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Ahmadi, Mojtaba. "Mechanics of Surface Instabilities of Soft Nanofibers and Nonlinear Contacts of Hydrogels." Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/31861.

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The research of this dissertation is formulated in two fields, i.e., the theoretical and computational studies of circumferential wrinkling on soft nanofibers and the swelling mechanics study of a bi-layered spherical hydrogel containing a hard core. Continuous polymer nanofibers have been massively produced by means of the low-cost, top-down electrospinning technique. As a unique surface instability phenomenon, surface wrinkling in circumferential direction is commonly observed on soft nanofibers in electrospinning. In this study, a theoretical continuum mechanics model is developed to explore the mechanisms of circumferential wrinkling on soft nanofibers under uniaxial stretching. The model is able to examine the effects of elastic properties, surface energy, and fiber radius on the critical axial stretch to trigger circumferential wrinkling and to discover the threshold fiber radius to initiate spontaneous wrinkling. In addition, nonlinear finite element method (FEM) is further adopted to predict the critical mismatch strain to evoke circumferential wrinkling in core-shell polymer nanofibers containing a hard core, as a powerful computational tool to simulate controllable wrinkling on soft nanofibers via co-electrospinning polymer nanofibers incorporated with nanoparticles as the core. The studies provide rational understanding of surface wrinkling in polymer nanofibers and technical approaches to actively tune surface morphologies of polymer nanofibers for particular applications, e.g. high-grade filtration, oil-water separation, polymer nanocomposites, wound dressing, tissue scaffolding, drug delivery, and renewable energy harvesting, conversion, and storage, etc. Furthermore, hydrogels are made of cross-linked polymer chains that can swell significantly when imbibing water and exhibit inhomogeneous deformation, stress, and, water concentration fields when the swelling is constrained. In this study, a continuum mechanics field theory is adopted to study the swelling behavior of a bi-layered spherical hydrogel containing a hard core. The problem is reduced into a two-point boundary value problem of a 2nd-order nonlinear ordinary differential equation (ODE) and solved numerically. Effects of material properties on the deformation, stress, and water concentration fields of the hydrogel are examined. The study offers a rational route to design and regulate hydrogels with tailorable swelling behavior for practical applications in drug delivery, leakage blocking, etc.

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GUPTA, PREETI. "HYDROGEL BASED WOUND DRESSING MATERIAL." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18806.

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Weak mechanical strength of hydrogels in wet condition limits their use for load bearing applications. Their mechanical strength can be raised by grafting them over some support or by converting them into nanofibrous form. Present thesis is focused on the preparation of poly (acrylamide-co-acrylic acid) hydrogel grafted over cotton fabric using two different cross-linkers i.e. PEG and MBAAm for making medicated dressing and nanofibers of hydrogel of poly (acrylamide-co-acrylic acid). FTIR was used to confirm the insertion of cross-links into the polymer chains. Grafting of uniform hydrogel layer on cotton surface and formation of hydrogel nanofibers were confirmed by using SEM. The average fibre diameter was found to be 275±94.5 nm. Swelling of composite prepared using PEG followed first-order kinetic model at acidic and neutral pH whereas second-order kinetic model at pH 8.5 while that prepared using MBAAm followed second-order kinetic equation at all the pHs studied. The kinetics of swelling was also governed by Peppas model at all pHs. Release of drug from both the composites was studied in phosphate buffers having pH 5.5,7 and 8.5 at 37±0.1°C and observed that it was fastest in phosphate buffer having pH 7. On fitting drug release data into different models, it was observed that drug release was diffusion controlled and followed Fickian diffusion mechanism in case of composite prepared by using PEG as cross-linker whereas it was controlled by diffusion as well as chain relaxation in case of composite prepared by using MBAAm. Mechanical testing using Universal Testing Machine supported a higher mechanical strength of the hydrogel composite as compared to its film. Swelling behaviour of Nanofibrous mats was found to be highest at neutral pH and it followed second order kinetics at all pHs. The drug release kinetics was further evaluated and found that it took place by Fickian diffusion (n < 0.5) and followed second order release kinetics. Antimicrobial tests were performed to show the effectiveness of drug loaded within the hydrogel samples.

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Sato, Tabata Do Prado. "Desenvolvimento de biomateriais à base de quitosana : matriz de fibras eletrofiadas para regeneração tecidual e de hidrogel coacervado para entrega controlada de fármaco /." São José dos Campos, 2019. http://hdl.handle.net/11449/191168.

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Orientador: Alexandre Luiz Souto Borges
Coorientador: Artur José Monteiro Valente
Banca: Bruno Vinícius Manzolli Rodrigues
Banca: Fernanda Alves Feitosa
Banca: Lafayette Nogueira Júnior
Banca: Eduardo Shigueyuki Uemura
Resumo: Os atuais avanços no desenvolvimento de biomateriais caminham para 2 áreas promissoras: a de regeneração tecidual e a de entrega controlada de fármacos. Assim, o presente estudo objetivou a síntese e caracterização de diferentes matrizes (fibras e hidrogel) à base de quitosana, a fim de se obter materiais biomiméticos para atuação em ambas áreas. Para regeneração, delineou-se a síntese de um arcabouço de fibras de quitosana com e sem cristais de nanohidroxiapatita onde, para isso, foram eletrofiadas soluções de quitosana (Ch) e de quitosana com nanohidroxiapatita (ChHa). Os espécimes de Ch apresentaram maior homogeneidade e maior diâmetro médio de fibras (690 ± 102 nm) que ChHa (358 ± 49 nm). No teste de viabilidade celular e na atividade da fosfatase alcalina não houve diferença estatística entre os grupos experimentais (Ch e ChHa), porém ambos diferiram do grupo controle (p < 0,001). Para o âmbito de liberação de fármacos, sintetizou-se, pela técnica de emulsão, dois tipos de hidrogéis: o primeiro, uma mistura da fase aquosa da solução de Ch (1 mL) e da solução de DNA (1 mL) (1:1) e o segundo, mistura da fase aquosa da solução de Ch (1 mL) e solução de Pectina (1 mL) (1:1). Ambas misturas foram realizadas em álcool benzílico (5 mL) com instrumento de dispersão de alto desempenho (31-34000 rpm min-1 por 5 min). Após a obtenção dos géis, 20mg de cada grupo foram imersos em uma solução aquosa de Própolis Verde (PV), na concentração de 70 μg/mL por 2 h e a cinética de liberação... (Resumo completo, clicar acesso eletrônico abaixo)
Current advances in biomaterial development are moving to 2 promising areas: tissue regeneration and controlled drug delivery. Thus, the present study aimed the synthesis and characterization of different matrices (fibers and hydrogel) based on chitosan, in order to obtain biomimetic materials for performance in both areas. For regeneration, the synthesis of a scaffold of chitosan fibers with and without nanohydroxyapatite crystals was delineated, where chitosan (Ch) and chitosan with hydroxyapatite (ChHa) solutions were electrospun. Ch specimens presented higher homogeneity and larger mean fiber diameter (690±102nm) than ChHa (358 ± 49nm). In the cell viability test and alkaline phosphatase activity there was no statistical difference between the experimental groups. (Ch and ChHa), but both differed from the control group (p < 0,001). For the drug release scope, two types of hydrogels were synthesized by the emulsion technique: the first, a mixture of the aqueous phase of Ch solution (1 mL) and DNA solution (1 mL) (1:1) and the second, mixture of the aqueous phase of the Ch solution (1mL) and Pectin solution (1 mL) (1:1). Both mixtures were performed in benzyl alcohol (5 mL) with high performance dispersion instrument (31-34000 rpm min-1 for 5 min). After obtaining the gels, 20mg from each group were immersed in an aqueous solution of Propolis Green (PV), at a concentration of 70 µg/mL for 2 h and the release kinetics of PV were analyzed at 25 and 37oC in water and artificial saliva. The obtained specimens were lyophilized and then physically-chemically characterized. The presence of pectin and DNA was confirmed by FTIR. PV sorption induced a significant modification of the gel surface. A phase separation was found between chitosan and DNA. Encapsulation efficiency did not change significantly between 25 and 37oC. The release kinetics in water or saliva presented a two-step mechanism. And the biological results...
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Philip, Diana Liz. "The Influence of Synthetic Microenvironments in Determining Stem Cell Fate." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627669247178055.

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Baddour, Joelle. "An Approach to Lens Regeneration in Mice Following Lentectomy and the Implantation of a Biodegradable Hydrogel Encapsulating Iris Pigmented Tissue in Combination with Basic Fibroblast Growth Factor." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335916825.

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McCaldin, Simon Roger. "Hydrogen storage in graphitic nanofibres." Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/11568/.

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There is huge need to develop an alternative to hydrocarbons fuel, which does not produce CO2 or contribute to global warming - 'the hydrogen economy' is such an alternative, however the storage of hydrogen is the key technical barrier that must be overcome. The potential of graphitic nanofibres (GNFs) to be used as materials to allow the solid-state storage of hydrogen has thus been investigated. This has been conducted with a view to further developing the understanding of the mechanism(s) of hydrogen storage in GNFs and modifying the material structure to maximise the amount of hydrogen that can be reversibly stored in the material. GNFs were synthesised using chemical vapour deposition (CVD) with careful control of temperature and gas mixture to create predominately herringbone GNFs from both Iron and Nickel catalysts. Within this, it was found that once GNF growth has been initiated under certain conditions, alteration of those conditions does not alter the fundamental structure of the GNF synthesised, but can increase the carbon yield, although reorientation of the surfaces was observed. The GNFs synthesised were subsequently chemically (acid washed and CO2 oxidised) and thermally treated to remove the residual CVD catalyst and alter their surface structures in an attempt to allow dihydrogen molecules to penetrate and adsorb onto the internal graphene layers. However, it was found that after initial growth, the surface layers of the GNFs became re-orientated parallel to the fibre axis - representing a large energy barrier to adsorption onto the surfaces of the internal graphene layers. By careful use and control of conditions, this re-orientated layer can be removed to yield GNFs with cleaned surfaces. Once GNFs with cleaned edges had been synthesised, these were modified to remove oxygen species from their surfaces. To further develop the understanding of the potential hydrogen uptake mechanisms, Pd particles were introduced to the GNF surfaces to act as catalyst gateways. By carefully controlling the variables of the incipient wetness process, a variety of morphologies and structures were synthesised. This allowed the precise determination of the hydrogen uptake mechanism occurring in samples by Kubas binding, Dissociation or Spill-over mechanisms. All of the GNFs created have had their hydrogen uptake capacities precisely determined using a Sieverts apparatus designed and constructed by the author. None of the samples were found to adsorb any significant levels of hydrogen (>0.1 wt%), regardless of the treatments applied to them – this result has been discussed in light of the existing claims for high hydrogen uptake in GNFs made within the literature. The conclusion of this thesis is that no hydrogen uptake capacity could be observed in the GNFs synthesised during the project, however, the development of the uptake mechanisms and GNF structures has led to suggested modifications that may yield GNFs suitable for storing large quantities of hydrogen (i.e. in excess of US-DOE targets).

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Haji, Aminoddin, Komeil Nasouri, Ahmad Mousavi Shoushtari, and Ali Kaflou. "Reversible Hydrogen Storage in Electrospun Composite Nanofibers." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35201.

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Composite nanofibers containing single-walled carbon nanotubes (SWNT) were prepared by using elec-trospinning technique and hydrogen adsorption/desorption isotherms were carried out by a Sieverts appa-ratus at room temperature. The SEM analysis of the nanofibers revealed that the deformation of the nano-fiber increases with increasing SWNT concentration. The diameter of neat nanofibers was below 200 nm and had smooth surface. The surface of the composite nanofibers was rough even by adding low quantity of SWNT. The hydrogen storage results showed an improvement in the adsorption capacity with increasing the SWNT content in composite nanofibers. These nanofibers were evacuated again to remove the ad-sorbed hydrogen at room temperature. Moreover, even though specific surface area and total pore volume were important factors for increasing the capacity of hydrogen adsorption. Finally, maximum adsorption capacity was 0.29 wt % in case of nanofibers with 10 wt % SWNT under 30 bar at 298 K. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35201

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Guo, Yuanhao. "Reinforcement of Hydrogels by Nanofiber Network." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1367237415.

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Yang, Xianpeng. "Strong Cellulose Nanofiber Composite Hydrogels via Interface Tailoring." Kyoto University, 2020. http://hdl.handle.net/2433/253333.

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Mushi, Ngesa Ezekiel. "Chitin nanofibers, networks and composites : Preparation, structure and mechanical properties." Doctoral thesis, KTH, Biokompositer, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155528.

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Chitin is an important reinforcing component in load-bearing structures in many organisms such as insects and crustaceans (i.e. shrimps, lobsters, crabs etc.). It is of increasing interest for use in packaging materials as well as in biomedical applications. Furthermore, biological materials may inspire the development of new man-made material concepts. Chitinmolecules are crystallized in extended chain conformations to form nanoscale fibrils of about 3 nm in diameter. In the present study, novel materialshave been developed based on a new type of chitin nanofibers prepared from the lobster exoskeleton. Improved understanding about effects of chitin from crustaceans and chitin material preparation on structure is provided through Atomic Force Microscopy(AFM) (paper I&II), Scanning Transmission Electron Microscopy(STEM) (paper I&II), X-Ray Diffraction (XRD), Intrinsic Viscosity, solid state 13C Nuclear Magnetic Resonance (NMR) (paper II), Field Emission Scanning Electron Microscopy(FE-SEM) (paper I, II, III, IV & V), Ultraviolet-Visible Spectrophotometryand Dynamic Light Scattering (DLS) (paper III). The presence of protein was confirmed through colorimetric method(paper I & II). An interesting result from the thesis is the new features of chitin nanofiber including small diameter, high molar mass or nanofiber length,and high purity. The structure and composition of the nanofibers confirms this (paper I & II). Furthermore, the structure and properties of the corresponding materials confirm the uniqueness of the present nanofibers: chitin membrane (I & II), polymer matrix composites (III),and hydrogels (paper IV). Improved mechanical properties compared with typical data from the literature were confirmed for chitin nanofiber membranes in paper II, chitin-chitosan polymer matrix composites in paper III, and chitin hydrogel in paper IV. Mechanical tests included dynamic mechanical analysis and uniaxial tensile tests. Mechanical properties of chitin hydrogels were evaluated based onrheological and compression properties (paper IV). The values were the highest reported for this kind of chitin material. Furthermore, the relationships between materials structure and properties were analyzed. For membranes and polymer matrix nanocomposites, the degree of dispersion is an important parameter. For the hydrogels, the preparation procedure is very simple and has interesting practical potential. Chitin-binding characteristics of cuticular proteins areinteresting fornovel bio-inspired material development. In the present work(paper V), chitin nanofibers with newfeaturesincluding high surface area and low protein content were combined with resilin-like protein possessing the chitin-binding characteristics. Hydrated chitin-resilin nanocomposites with similar composition as in rubber-like insect cuticles were prepared. The main objective was to improve understanding on the role of chitin-binding domain on mechanical properties. Resilin is a rubber-like protein present in insects. The exon I (comprising 18 N-terminal elastic repeat units) together with or without the exon II (a typical cuticular chitin-binding domain) from the resilin gene CG15920 found in Drosophila melanogasterwere cloned and the encoded proteins were expressed as soluble products in Escherichia coli.Resilin-like protein with chitin-binding domain (designated as ResChBD) adsorbedin significant amount to chitin nanofiber surface andprotein-bound cuticle-like soft nanocomposites were formed. Although chitin bindingwas taking place only in proteinswith chitin-binding domain, the global mechanical behavior of the hydrated chitin-resilin nanocomposites was not so sensitive to this chitin-resilin interaction. In summary, chitin is an interesting material component with high potential as mechanical reinforcement in a variety of nanomaterials. The present study reports the genesisof novel chitin nanofibers and outlines the basic relationships between structure and properties for materials based on chitin. Future work should be directed towards both bio-inspired studies of the nanocomposite chitin structures in organisms, as well as the industrial applications of chitin waste from the food industry. Chitin nanofibers can strengthen the properties of materials, andprovide optical transparency as well as biological activities such as antimicrobial properties.

QC 20141110

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Way, Amanda E. "Stimuli-Responsive Nanofiber Composite Materials: From Functionalized Cellulose Nanocrystals to Guanosine Hydrogels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1390388160.

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Rick, Helene Sylvia. "Nanocarving of Titania Surfaces Using Hydrogen Bearing Gases." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7116.

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An investigation of surface structures formed on polycrystalline and single crystal TiO2 (titania) samples having under gone various heat treatments in a controlled hydrogen bearing atmosphere was conducted. The study included the recreation and examination of the process discovered by Sehoon Yoo at Ohio State University to form nanofibers on the surface of polycrystalline TiO2 disks. Fibers were formed by heating samples to 700??in a 5%H2 95%N2 gas stream. The nanofibers formed during this processes are approximately 5-20 nanometers in diameter and can be 100??f nanometers long. The fibers do not actually grow on the surface, but are what remain of the surface as the material around them is removed by the gas stream V i.e., nanocarving. The mechanism of fiber formation and the effect of varying experimental parameters remained unknown and were explored within this study. This included changing gas composition, flow rate, and changes in sample preparation. The effect of isovalent doping and impurities within the starting powder were examined. Sintering temperature and time was investigated to determine the effect of grain size and surface morphologies prior to nanocarving. The effect of elevated temperature and 5%H2 95%N gas on the surface of TiO2 single-crystal wafers was also investigated. Test methods include Thermogravimetric Analysis (TGA), Mass Spectrometry (MS), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) analysis.

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Buchtová, Nela. "Hydrogels nanocomposites : élaboration et études physico-chimiques." Nantes, 2012. http://archive.bu.univ-nantes.fr/pollux/show.action?id=b40fc44d-8633-4004-b01c-839f1f2d383f.

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Les hydrogels à base d’un dérivé cellulosique silanisé : hydroxypropylméthylcellulose silanisé (HPMC-Si) ont été développés en tant que biomatériaux pour une application en ingénierie tissulaire du cartilage articulaire. La dérivatisation inorganique par une fonction siloxane d’un polysaccharide permet d’obtenir un gel injectable polycondensant in situ. L’objectif de cette thèse était de disperser des nanofibres de silice (NFs) au sein de ces hydrogels afin d’améliorer leurs caractéristiques rhéologiques et mécaniques. A 3 wt% de NFs, les hydrogels nanocomposites possèdent un module en compression 5 fois supérieur à celui de l’hydrogel pur et restent cytocompatibles avec des chondrocytes et des cellules souches. De manière parallèle, un travail sur la compréhension de la structure du polysaccharide silanisé lui-même ainsi que sur la description de la structure, la morphologie et la dynamique de l’eau dans les hydrogels d’HPMC-Si a été réalisé. Il a été déterminé que l’eau confinée dans les hydrogels d’HPMC-Si est présente sous deux formes : l’eau d’hydratation et l’eau dite « bulk ». L’eau d’hydratation est en interaction avec les parties hydrophiles du polymère via les liaisons hydrogène, tandis que l’eau « bulk » se comporte comme de l’eau volumique classique. Les mesures des coefficients de diffusion montrent qu’à 300 K, les molécules d’eau « bulk » diffusent sur les distances de l’ordre de 10 μm sans être affectées par la présence du réseau polymère. Nous pensons donc que les hydrogels d’HPMC-Si ont une morphologie hiérarchisée, avec des pores de taille micrométrique dont les parois sont constituées de maillage nanométrique d’HPMC-Si
The hydrogels based on a cellulosic derivative, silanized hydroxypropyl methylcellulose (Si-HPMC), are developed as biomaterials for applications in articular cartilage tissue engineering. The inorganic derivatization of a polysaccharide utilizing a silane function provides an injectable gel which can polycondense in situ. Moreover, dispersion of silica nanofibers within the hydrogels enhances their rheological and mechanical properties. With 3 wt% of nanofibers the nanocomposite hydrogel’s compressive modulus is 5 times higher than that of the pure hydrogel. Such a nanocomposite hydrogel remains cytocompatible with respect to chondrocytes and human stem cells. At the same time, a study on silanized polysaccharide structure as well as a description of the structure and morphology of the gel, then a study of the water dynamics in the Si-HPMC hydrogels are realised. The water confined in Si-HPMC hydrogels is found to exist in two different forms: water of hydration and « bulk » water. The water of hydration interacts with the hydrophilic parts of the polymer by hydrogen bond formation, while the « bulk » water behaves as ordinary bulk water. The measurements of diffusion coefficient at 300 K show that the molecules of « bulk » water diffuse over distances in the order of 10 μm without being affected by the polymer network presence. Thus, the Si-HPMC hydrogels seem to have a hierarchically organized morphology with micrometer sized pores whose pore walls are made of a nanometric mesh

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Bambalaza, Sonwabo Elvis. "Fabrication of metal-organic frameworks with application-specific properties for hydrogen storage application." University of Western Cape, 2019. http://hdl.handle.net/11394/7727.

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Philosophiae Doctor - PhD
The application of porous materials into industrial hydrogen (H2) storage systems is based on their use in combination with high-pressure cylinders. The processing of metal-organic frameworks (MOF) powders into shaped forms is therefore imperative in order to counteract the adverse effects of poor packing of powders in cylinders. The fabrication of shaped MOFs has, however, been shown to be accompanied by compromised properties such as surface areas, gravimetric and volumetric H2 capacities, and also the working/deliverable H2 capacities in comparison to MOF powders.

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Mellot, Gaëlle. "Combinaison de la chimie supramoléculaire et de la PISA contrôlée par RAFT pour synthétiser des nanofibres dans l'eau." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS245.pdf.

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Les nanofibres polymères constituent un type de matériaux particulièrement intéressant puisqu’elles peuvent être utilisées dans diverses applications (e.g. stabilisation d’émulsions Pickering, renforcement mécanique de films polymères, biomédical, catalyse). Malgré le développement de différentes méthodes de préparation des nanofibres, il n’existe actuellement aucune méthode robuste et polyvalente permettant la formation de nanofibres, directement dans l’eau et à un taux de solide élevé. Dans cette optique, nous avons choisi de combiner la PISA contrôlée par RAFT et la chimie supramoléculaire, en introduisant un motif associatif de type bis- ou trisurée dans la structure d’un macro-agent RAFT afin de favoriser la formation de nanofibres lors du processus de polymérisation. En effet, ces motifs urée sont capables de s’associer via des liaisons hydrogène de manière unidirectionnelle conduisant à la formation d’assemblages filamentaires. Lors de la PISA dans l’eau, ces liaisons peuvent ainsi prévaloir sur le paramètre d’empilement et forcer la formation de fibres. Nous avons tout d’abord prouvé ce concept en synthétisant par PISA dans l’eau une série de copolymères amphiphiles à base de poly(N,N-diméthylacrylamide) et de poly(acrylate de 2-méthoxyéthyle) fonctionnalisés en bout de chaine par un motif bis-urée aliphatique. L’étude de la morphologie des nano-objets obtenus a mis en évidence la formation de fibres dans une large gamme de conditions expérimentales. Nous avons ensuite évalué la robustesse et la polyvalence de notre stratégie en faisant varier la nature chimique et la taille des blocs polymères
Nanofibers are particularly interesting structures since they can be used in numerous applications (e.g. stabilization of Pickering emulsions, reinforcement of water-based coatings, biomedical applications, catalysis). Despite the development of various preparation methods of nanofibers, there is nowadays no method allowing the formation of fibers of different natures, directly in water, at high solids contents. In this context, we have combined RAFT-mediated PISA and supramolecular chemistry by introducing a bis- or trisure a sticker in the structure of a macro-RAFT to favor the formation of nanofibers during the PISA process. It is known that such urea stickers can form unidirectional hydrogen bonding leading to the formation of filamentous assemblies. During the aqueous PISA process, hydrogen bonding should thus overrule the packing parameter predictions and drive the PISA toward the fiber morphology in robust experimental conditions. We proved our concept by synthesizing a series of aliphatic bisurea-functionalized amphiphilic copolymers made of poly(N,N-dimethylacrylamide) and poly(2-methoxyethyl acrylate) by aqueous PISA. The study of the obtained nano-objects morphologies in water highlighted the formation of fibers in a broad range of experimental conditions. Finally, we investigated the robustness and the versatility of our strategy by varying the chemical nature and the size of the polymer blocks

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Meltz, Freda-Jean. "Amphiphilic electrospun fibres of poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers as a means to controlling electrospun fibre morphology and obtaining nanofibre hydrogels." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86620.

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Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Novel poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers were synthesised by conventional free radical reactions using a poly(dimethylsiloxane) macromonomer. The polymers were electrospun to investigate how the fibre morphology can be modified by manipulating the electrospinning solution parameters, and to determine the possibility of using the polymers as new materials for the production of polymer nanofibre hydrogels. The electrospinning solution parameters were varied by electrospinning the highly amphiphilic copolymers in solvents with variable solvent qualities. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FE–SEM) was used to investigate the fibre morphology. Internal morphology was studied using a freeze fracture technique prior to FE-SEM imaging. It is revealed that the polymers in this study does not form any fine structure or pores even when self-assembled structures are present in the solution. Attempts were made to visualise any self-assembled structures of films produced from dilute solutions using TEM. Further studies included investigating the fibres properties, primarily with regards to their rate and extent of moisture and water uptake. The fibres showed hydrogel behaviour and the PDMS content were found to have an impact on the hydrogel stability. Post electrospinning crosslinking of the nanofibres was also explored.
AFRIKAANSE OPSOMMING: Unieke ent-kopolimere wat bestaan uit poli(metielakrielsuur) (PMAS) en poli(dimetielsiloksaan) (PDMS) is gesintetiseer deur middel van 'n “ent-deur” vryeradikaalkopolimerisasie. 'n PDMS makromonomeer is vir hierdie doel gebruik. Die polimere is geëlektrospin om vesels te vorm. Die doel was om die invloed van verkillende strukture in oplossing op die veselmorfologie te bepaal. Die moontlikheid om hierdie nanovesels as gels te gebruik is ook ondersoek. Die amfifiliese kopolimere is geëlektrospin uit die oplossing waarin dit wisselende oplosbaarheid toon. Skandeer elektron mikroskopie (SEM) is gebruik om die morfologie te ondersoek. Die interne morfologie van die vesels is ondersoek deur die vesels te vries en in die gevriesde toestand te breek. Die studie het getoon dat geen strukture op, of binne, die vesels vorm nie, selfs al moes daar assosiasie tussen segmente van die polimere gewees het. Hierdie tipe assosiasies sou strukture in die oplossing tot gevolg gehad het. 'n Poging is aangewend om die strukture in oplossing te visualiseer deur transmissie elektron mikroskopie (TEM) van dun films te ondersoek. Films is vanaf verdunde oplossings gevorm. Ander studies het ingesluit om die eienskappe van die vesels te ondersoek, met die fokus op hoeveel en hoe vinnig die vesels waterdamp en water kon absorbeer. Die vesels het soos 'n gel reageer. Hierdie gedrag is beïnvloed deur die hoeveelheid PDMS wat 'n definitiewe invloed op die stabiliteit van die gel gehad het. Kruisverbindings van die vesels, nadat dit geëlektrospin is, is ook ondersoek.

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17

Dzurická, Lucia. "Příprava a charakterizace krytů ran." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414181.

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The diploma thesis if focused on the study of bioactive hydrogél and nanofiber wound dressings composed of natural biopolymers, which were functionalized by active compounds in the form of analgesic, antibiotics and enzymes. Hydrogél wound dressings were constituted from alginate and chitosan and nanofibers were created from polyhydroxybutyrate. The following 7 active compounds were selected to be added to the wound dressings: ampicillin, streptomycin, ibuprofen, papain, bromelain, collagenase and trypsin. In the theoretical part the structure of the skin and types of wound injuries were described. This part also talks about types of wound dressing and their applications, as well as treatment of skin wounds using enzymes and compounds with analgesic and antimicrobial properties. In addition, this section describes safety assays, in particular cytotoxicity assays on human cells. At the beginning of the experimental part, the process of preparation of hydrogél wound dressing was optimised. Subsequently, the dressings were enriched with active compounds and the rate of gradual releasing of the substances into model environment was monitored. In the case of enzymes, their proteolytic activity was also tested after their incorporation to the wound dressings. Furthermore, the prepared bioactive wound dressings were analyzed for possible cytotoxic effect on human keratinocytes. Finally, the wound dressing with combined content of active substances was created and also characterized for the rate of substance release, proteolytic activity and cytotoxicity. Antimicrobial activity of this wound dressings, against two selected strains of microorganisms: Escherichia coli and Staphylococcus epidermidis, was also evaluated.

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18

Oliveira, Natália Maira Braga 1987. "Reação de deslocamento de gás d'Água sobre catalisadores de cobre e níquel suportados em alumina e nanofibra de carbono." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266717.

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Orientadores: Gustavo Paim Valença, Ricardo Vieira
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-21T00:05:40Z (GMT). No. of bitstreams: 1 Oliveira_NataliaMairaBraga_M.pdf: 2188373 bytes, checksum: 7d467de1163b278869ab8a52ee898f4f (MD5) Previous issue date: 2012
Resumo: A reação de deslocamento de gás d'água, também conhecida como water gas shift reaction (WGSR), é muito utilizada na produção de hidrogênio, por meio da conversão do monóxido de carbono em CO2 e da água em H2. No presente trabalho, catalisadores de cobre e níquel suportados em alumina ou nanofibras de carbono (NFC) foram utilizados para estudo da WGSR. Os catalisadores foram preparados através da impregnação de nitrato do metal nos suportes, sendo 5% em massa o valor nominal de teor metálico empregado. Os materiais foram secados, calcinados e caracterizados através de Microscopia Eletrônica de Varredura (MEV), Difração de Raios X (DRX), Adsorção Física de Nitrogênio e Espectrometria de Emissão Óptica por Plasma Indutivamente Acoplado (ICP OES). Depois de calcinados, os catalisadores foram carregados no reator, reduzidos e então testados na WGSR a baixas temperaturas (125 - 300 °C). Os gases que saíram do reator foram analisados online por Cromatografia Gasosa (CG). Houve produção de CO2, H2 e, provavelmente, de coque em pequenas quantidades. A pressão parcial de CO variou entre 4,64 e 11,35 kPa, e a pressão parcial de água variou entre 20,01 e 47,44 kPa. As condições de reação mais favoráveis para 5% Cu/Al2O3 foram pH2O = 38,64 kPa e pCO = 11,35 kPa, em todas as temperaturas reacionais empregadas. Já para 5% Cu/NFC as condições mais favoráveis foram pH2O = 20,01 kPa e pCO = 6,56 kPa, correspondendo a uma razão molar H2O:CO de 3,05. Outra variável testada foi corrente elétrica aplicada em 5% Ni/NFC, com o objetivo de verificar sua influência na atividade do catalisador. Entretanto, diferentes intensidades de corrente elétrica (entre -1,4 e 1,4 A) não alteraram a taxa ou a seletividade da WGSR. Dentre os catalisadores testados, 5% Cu/Al2O3 foi o mais ativo em todas as condições reacionais, devido à alta dispersão das partículas metálicas no suporte. Níquel suportado em Al2O3 se mostrou pouco ativo, porque as partículas metálicas estavam muito dispersas e, provavelmente, não foram reduzidas pelo H2. Ni/NFC e Cu/NFC apresentaram baixas conversões de CO, devido à hidrofobicidade do suporte. A energia de ativação aparente calculada para a WGSR foi de 86,05 kJ/mol para 5% Cu/Al2O3 e de 69,80 kJ/mol para 5% Cu/NFC. O mecanismo de reação proposto para Cu/NFC foi redox de cooperação e as ordens aparentes de reação obtidas foram 0,64 em relação ao CO e aproximadamente zero em relação à água
Abstract: The water gas shift reaction (WGSR) is widely used in the production of hydrogen, by the conversion of carbon monoxide into CO2 and of water into H2. In the present work, copper and nickel catalysts supported on alumina or carbon nanofibers (CNF) were used to study the WGSR. The catalysts were prepared by impregnating metal nitrate in the supports, with a nominal mass metallic content of 5%. The solids were dried, calcined and characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Nitrogen Adsorption and Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES). After calcination, the catalysts were loaded into the reactor, reduced and then tested in the WGSR at low temperatures (125 - 300 °C). The gases from reactor were analyzed online by Gas Chromatography (GC). The products were CO2, H2 and, probably, small amounts of coke. The CO partial pressure varied between 4.64 and 11.35kPa, and the water partial pressure varied between 20.01 and 47.44 kPa. The most favorable reaction conditions for 5% Cu/Al2O3 were pH2O = 38.64 kPa and pCO = 11.35 kPa, for all reaction temperatures used in this work. For 5% Cu/CNF the most favorable conditions were pH2O = 20.01kPa and pCO = 6.56 kPa, corresponding to a molar ratio H2O:CO of 3.05. In a different experiment, electrical current was used in the 5% Ni/CNF bed, in order to verify its influence on the catalyst activity. The electrical current was varied between -1.4 and 1.4 A and no change was observed in the rate or selectivity of the WGSR. Among the catalysts tested, 5%Cu/Al2O3 was the most active under all conditions used in this work, due to the high dispersion of the metal particles on the support. Nickel supported on Al2O3, under reaction conditions studied, was less active, because the metal particles were widely dispersed and, probably, were not reduced by H2. Ni/CNF and Cu/CNF had low CO conversions, due to the support hydrophobicity. The apparent activation energy calculated for the WGSR was 86.05kJ/mol for 5% Cu/Al2O3 and 69.80 kJ/mol for 5% Cu/CNF. For Cu/CNF a co-operative redox reaction mechanism was proposed, and apparent reaction orders were 0.64 in relation to CO and approximately zero in relation to water
Mestrado
Desenvolvimento de Processos Químicos
Mestra em Engenharia Química

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19

Wychowaniec, Jacek. "Designing nanostructured peptide hydrogels containing graphene oxide and its derivatives for tissue engineering and biomedical applications." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/designing-nanostructured-peptide-hydrogels-containing-graphene-oxide-and-its-derivatives-for-tissue-engineering-and-biomedical-applications(409e60a2-ed17-45bf-ab6c-b76ede937a67).html.

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Progress in biomedicine requires the design of functional biomaterials, in particular, 3-dimensional (3D) scaffolds. Shear thinning, β-sheet based peptide hydrogels have attracted wide interest due to their potential use in tissue engineering and biomedical applications as 3D functional scaffolds. The emergence of carbon nanomaterials has also opened the door for the construction of increasingly functional hybrid hydrogels built from nanofibres and graphene-based materials using non-covalent physical interactions. The relationship between peptide molecular structure and the formed hydrogel is important for understanding the material response to shear. In particular, the physicochemical properties of peptide based biomaterials will affect the feasibility of injecting them during medical procedures. In the first part of this work, four peptides: FEFKFEFK (F8), FKFEFKFK (FK), KFEFKFEFK (KF8) and KFEFKFEFKK (KF8K) (F - phenylalanine, E - glutamic acid, K - lysine) were designed and used at identical charge to explore the effect of lysine rich β-sheet self-assembling sequences on the shear thinning behaviour and final properties of bulk hydrogels. By varying the peptide sequence design and concentration of the peptide, the tendency of the nanofibres formed to aggregate and the balance of nanofibre junction strength versus fibre cohesive strength could be explored. This allowed the existing theory of the shear thinning behaviour of this class of materials to be extended. The relationship between molecular structures of nanofibres forming the 3D network and the nano-filler is critical to understand in order to design tuneable and functional materials. In the next part of the work, three rationally designed β-sheet peptides, which form hydrogels: VEVKVEVK (V8), FEFKFEFK (F8) and FEFEFKFE (FE) (V - valine) and five graphene-based materials: graphene oxide (GO), reduced graphene oxide (rGO), three graphene-polymer hybrid flakes: GO with polydiallyldimethylammonium chloride (GO/PDADMAC), rGO with PDADMAC (rGO/PDADMAC) and rGO with polyvinylpyrrolidone (rGO/PVP) were used to form a selection of hybrid hydrogels. Graphene derivatives of the lateral flake sizes of 16.8 ± 10.1 µm were used. Various interactions between the graphene flakes and the peptides were observed that affected the overall mechanical properties of the hydrogels. Electrostatic interactions and pie-pie stacking, when phenylalanine residues are present, were shown to play a key role in determining the dispersion of graphene materials in the peptide hydrogels and stiffness of the hybrid materials. In particular, FE with reduced graphene oxide (rGO) and FE with rGO covered with polydiallyldimethylammonium chloride (PDADMAC) thin film formed double network-like hybrid hydrogels due to strong formation of peptide nanofibrillar bridges between adjacent rGO flakes. This corresponded to the 3- and 4-fold increase in the storage modulus (Gꞌ) of these hydrogels in comparison to controls. FE hydrogels with homogeneus dispersions of graphene oxide (GO) and reduced graphene oxide (rGO) are further shown to be suitable for 3D culture of human mesenchymal stem cells (hMSCs) with no cytotoxicity. These results focus attention on the importance of understanding interactions between the nano-filler and the nanofibrillar network in forming hybrid hydrogels with tuneable mechanical and biological properties, and demonstrates the possibility of using these materials as 3D cell culture scaffolds for biomedical purposes. Furthermore, graphene oxide (GO) itself is currently used in a number of processes of technological relevance such as wet spinning, injection moulding or inkjet printing to form graphene fibres, composites and printed conductors. Typically, such processes utilise well-aligned layered GO liquid crystal (LC) structures in aqueous dispersions. Flow and confinement encountered during processing affects the alignment and stability of this phase. In the final part of this work, the alignment of GOLCs of two lateral flake sizes (42.1 ± 29.4 µm and 15.5 ± 7.5 µm) were probed under a wide range of rotational shear flow conditions that overlap with the manufacturing processes defined by angular speeds from 0.08 to 8 rad.s-1 (and corresponding maximum shear rates from 0.1 s-1 to 100 s-1), in real-time, using shear induced polarized light imaging and small angle X-ray scattering, both coupled with an in-situ rheometer (Rheo-SIPLI and Rheo-SAXS, respectively). Under certain conditions, a unique pattern in Rheo-SIPLI: a Maltese cross combined with shear banding was observed. This phenomenon is unique to GO flakes of sufficiently large lateral size. The structure formed is attributed to a helical flow arising from a combination of shear flow and Taylor-vortex type flow, which is reinforced by a mathematical model. The orientations prescribed by this model are consistent with anomalous rheopecty oberved in Rheo-SIPLI and an anomolous scattering pattern in Rheo-SAXS. With the current trend towards producing ultra-large GO flakes, evidence that the flow behaviour changes from a Couette flow to a Taylor vortex flow was provided, which would lead to undesired, or alternatively, controllable alignment of GO flakes for a variety of applications, including aligned structures for biomedical purposes.

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20

Hodde, Dorothee Verfasser], Hermann [Akademischer Betreuer] [Wagner, and Gary [Akademischer Betreuer] Brook. "The development of a novel orientated nanofibre-containing hydrogel scaffold : in vitro studies of cell-substrate interactions and its application in vivo for peripheral nerve repair / Dorothee Hodde ; Hermann Wagner, Gary Brook." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1158498594/34.

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21

Hodde, Dorothee [Verfasser], Hermann [Akademischer Betreuer] Wagner, and Gary [Akademischer Betreuer] Brook. "The development of a novel orientated nanofibre-containing hydrogel scaffold : in vitro studies of cell-substrate interactions and its application in vivo for peripheral nerve repair / Dorothee Hodde ; Hermann Wagner, Gary Brook." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1158498594/34.

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22

Marangoni, Tomas. "Non-covalent nanostructuration of chromophoric organic materials." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7852.

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2010/2011
In the last few decades materials possessing well-defined structural properties on the nanoscale and microscale have shown to be extremely promising for applications in several fields, such as microelectronics, biology, and solar cells fabrication. This is due to the fact that the manufacture of organic-based devices, for any kind of application, requires the development of reproducible protocols to engineer materials featuring precise structural properties. To improve control on the nanoscale level, both bottom-up and top-down approaches have been intensively exploited to date. Although nowadays the second is still predominant at applicative level, Moore’s law foresees its final limit in a few years. In this context strong hope is coming from the possibility to control, in a defined way, the assembly of opportunely functionalized molecules, called building blocks, through the exploitation of particular type of non-covalent interactions. For this purpose the key concepts proper of the supramolecular chemistry has been revealed to be extremely promising for the preparation of nano-aggregates provided with well defined structural and functional properties. In this context one of the factors that crucially affects the process of nanostructuration through non-covalent interactions is the geometrical and structural property of the single building blocks used. Indeed, the geometric structure of molecules can considerably influence their ability to self-organize into more complex objects and therefore by an accurate development of the structural characteristic of the single molecular module it will be possible to tune the structure and the properties of the final material. Unfortunately in this context, even if great efforts have been undertaken by the scientific community to prepare well defined nanostructures through a supramolecular approach, the possibility to perfectly control the transmission of the geometrical informations from the molecular level to the final nanostructure still remains a partially unresolved task due to the high number of physical and chemical variables correlated to the self-assembly/self-organization process. The aim of this thesis consists into the design and synthesis of a novel library of molecules, equipped with desired molecular functionalities, which by means of hydrogen bonding interactions can self-assemble and generate different types of nanostructured materials that can be studied at the geometrical and morphological level by means of the combined use of different microscopic techniques such as Transmission Electron Microscopy (TEM) or Atomic Force Microscopy (AFM). Intrinsically, our goal is to shed further light on the structural features of the molecular recognition process, leading to the formation of the final nanostructured material, giving the maximum importance to the investigation of the transfer of geometrical informations from the single building block to the final nanostructure. In the first part of Chapter 1, the reader is introduced to the basic principle regarding the engineering of nanostructured materials through the different types of non-covalent interactions (hydrogen bonds, electrostatic, aromatic-aromatic and coordinative interactions) with a particular emphasis on the operative procedure developed in the last ten years. In the second part of the chapter instead, the attention is focused on the detailed description of the design and preparation of the nanostructuration process of the material through hydrogen bonds systems. In Chapter 2, the first part of the experimental work of this thesis is introduced. In this context the synthesis of a molecular library of building blocks able to self-assembly via heterocomplementary H-bonds interactions and self-organize into different types of nanostructure if thermally stimulated, is reported. As for our precedent studies on the subject, the molecular modules used feature complementary terminal H-bonding sites, namely 2,6-di(acetylamino)pyridyl) and uracil moieties, which are connected to different aromatic units through linear ethynyl spacers. The peculiarity of the building blocks adopted for this study is centred on the fact that they possess as H-bonds recognition units uracil moieties protected with the tert-butyloxycarbonyl (BOC) group at the level of their imidic nitrogen. Due to the thermal instability of the BOC groups, the heating of the modules results into the cleavage of this protective group, inducing in this way the self-assembly process between the complementary building blocks. The first part of the chapter guides the reader through the synthetic pathway adopted for the preparation and the spectroscopic characterization of the single building blocks, but also through the investigation of the different aspects of the thermal induced self-assembly process, such as the BOC deprotection phenomena and the molecular recognition process. In the second part of the chapter instead, great space will be given to the investigation of the microscopic characterization of the nanostructured morphologies by means of TEM and AFM. In order to have more detailed informations of the nanostructuration process not only the molecular geometry of the single building blocks was studied but also additional physical and chemical factors, such as the solvent composition or the temperature and concentration used, were taken in consideration to obtain the final nanostructure. A further development of the previous work is reported in Chapter 3, in which the self-assembly and self-organization behaviour of axially chiral building blocks based on binaphthol core is studied The principal task of this project regards the investigation of the transmission mechanism of chiral informations from the single building block to the resulting nano-object obtained by the self-assembly process. In the first part of this chapter the synthetic pathway toward the preparation of the single building blocks is discussed and their self-assembly mechanism in solution, is elucidated by means of different spectroscopic techniques, such as 1H-NMR, UV-Visible and Circular-Dichroism spectroscopy. The second part of the chapter is instead focused on the morphological aspects of the self-organized nanostructures deriving from the assembly of the chiral building blocks. In this context the morphology and the geometrical aspects of the resulting nanostructured materials were investigated by means of different microscopy techniques such as TEM and AFM. Moreover, a detailed evaluation of the morphological changes affecting the structure of the nanomaterial in relation with the solvent composition (i.e polarity) is performed, in order to determine at the same time the best conditions necessary for the preparation of nanostructures provided with a controlled shape and to shed some light on the organization mechanism. As last topic performed during this thesis, in Chapter 4 the supramolecular polymerization process was exploited in order to prepare nanostructured material provided with a certain degree of functionality. For this purpose a template approach was used in order to create hybrid material based on the self-assembly of organic supramolecular polymers onto an electroactive support. In this work we decided to use as template nanomaterial Multi-Wall Carbon Nanotubes (MWCNTs), due to their outstanding electronical properties, and high aspect ratio character that makes them excellent candidate for any eventual application in nanoelectronic devices. Unfortunately the main drawback of this kind of nanomaterial is their low solubility in almost any organic solvent that decreases drastically their applicability. To avoid this drawback, we decided therefore to functionalize the pristine MWCNT following a supramolecular approach. For this purpose a series of di-porphyrin derivatives, able to form a supramolecular polymer through axial coordination, are synthesized. The ability of these compounds to produce polymers by coordination with the bidentate ligand 1,2-(4-(bispyridyl))-ethane was evaluated by means of different spectroscopic techniques, such as UV-Visible and Fluorescence spectroscopy, whereas the morphological aspects of the nanostructure resulting from their self-organization was studied by AFM images. Finally the obtained supramolecular polymers were used to prepare highly soluble MWCNTs, provided at the same time of a large number of antenna systems that can be of high importance for the preparation of nanoelectronic devices. All the nanostructured systems described in this thesis provide a remarkable series of examples of the tremendous potential that the supramolecular approach possess for the fabrication of molecular devices of new generation, which are hardly achievable using the miniaturizing methods that are nowadays the most exploited.
XXIV Ciclo
1984

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23

Joshi, Jyotsna. "Engineering the Micro-Environment Niche of Human Bone Marrow-Derived Mesenchymal Stem Cells for Enhanced Cardiac Tissue Regeneration." Cleveland State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu1543925924170549.

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24

Belda, Marín Cristina. "Silk bionanocomposites : design, characterization and potential applications." Thesis, Compiègne, 2020. http://www.theses.fr/2020COMP2570.

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Les « bionanocomposites » à base de soie sont des matériaux qui suscitent un intérêt croissant dans de nombreuses applications, et en particulier dans le domaine biomédical, de par leur capacité à combiner les propriétés de la fibroïne (biodégradabilité, biocompatibilité et propriétés mécaniques intéressantes) et celles des nanoparticules (NP). L’objectif de ce travail est de (i) développer une méthode efficace, et « facile » à mettre en oeuvre, permettant l’élaboration de plusieurs types de bionanocomposites de soie ; (ii) fournir une caractérisation approfondie pour une meilleure compréhension de l’interface soie/NP ; et (iii) présenter des applications pertinentes en relation avec les propriétés spécifiques de ces bionanocomposites. Pour ce faire, les NP, d’or (Au NP), d’argent (Ag NP) et d’oxyde de fer (IONP) ont été utilisées en raison de leurs propriétés bien connues. L’élaboration de bionanocomposites à base de soie, tels que les tissus électrofilées, hydrogels, aérogels, éponges et structures imprimés en 3D est décrite. Une caractérisation approfondie, y compris des mesures in situ (pendant la formation du gel) et des analyses ex situ (une fois le gel formé), des hydrogels de soie montre qu’aucune différence significative n’est observée dans la structure de l’hydrogel, alors que la biocompatibilité des matériaux est préservée. Enfin, une application potentielle pour chaque « bionanocomposite » est présentée. Dans une perspective biomédicale, les hydrogels soie-Ag NP montrent une activité antibactérienne significative. Les hydrogels soie-IONP, implantés dans le cerveau d’un rat et suivis par imagerie de résonance magnétique (IRM), montrent l’induction d’une procédure de régénération du cerveau pendant au moins 3 mois. Dans une perspective liée à la dépollution, les hydrogels soie-Au NP montrent des performances remarquables dans la catalyse de la réaction de réduction du bleu de méthylène par le borohydrure de sodium
Silk-based bionancompoistes have attracted a growing interest in numerous applications, particularly in the biomedical field, owing to their ability to combine the specific properties of silk fibroin (biodegradability, biocompatibility and interesting mechanical properties) and nanoparticles (NPs). This work aims to (i) develop a straightforward, yet efficient, methodology to design various silk bionanocomposite materials; (ii) provide an in-depth characterization regarding the silk/NPs interface and (iii) provide potential applications which are relevant for the use of these bionanocompoistes. To this end, gold (Au NPs), silver (Ag NPs) and iron oxide (IONPs) NPs are used as model nanomaterials due to their well-known properties. The successful design of silk bionancocomposite electrospun mats, hydrogels, cryogels, sponges and 3D printed structures is described. An in-depth characterization, including in situ (during hydrogel formation) and ex situ (once hydrogel is formed), of silk hydrogel bionanocomposites do not reveal any noticeable structural changes of silk hydrogels, while their biocompatibility is not impacted by the incorporation of NPs. Finally, a potential application for each bionanocomposite is presented. In a biomedical perspective, silk-Ag NPs hydrogels bionanocomposites show significant antibacterial activity. Silk-IONPs hydrogel bionanocomposites are implanted into rat’s brain allowing a good monitoring of the implant by magnetic resonance imaging and inducing a brain regeneration process up to 3 months. In depollution perspective, silk-Au NPs hydrogel bionanocomposites show remarkable ability to adsorb and catalyze the reduction of methylene blue dye by sodium borohydride

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25

Balášová, Patricie. "Příprava a charakterizace moderních krytů ran." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449701.

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This diploma thesis is focused on the study of bioactive wound dressings. During the thesis, hydrogel, lyophilized and nanofiber wound dressings were prepared. Hydrogel and lyophilized wound dressings were prepared on basis of two polysaccharides – alginate and chitosan. Nanofiber wound dressings were prepared by spinning polyhydroxybutyrate. All prepared wound dressings were enriched with bioactive substances, which represented analgesics (ibuprofen), antibiotics (ampicillin) and enzymes (collagenase). Into hydrogel and lyophilized wound dressings were all the mentioned active substances incorporated, whereas nanofiber wound dressings were only with ibuprofen and ampicillin prepared. The theoretical part deals with the anatomy and function of human skin. There was explained the process of wound healing and also there were introduced available modern wound dressings. The next chapter of the theoretical part deals with materials for preparing wound dressings (alginate, chitosan, polyhydroxybutyrate) and with active substances, which were used during the experimental part of this thesis. In the theoretical part, the methods of preparation of nanofiber wound dressings and also the methods of cytotoxicity testing used in this work were presented. The first part of the experimental part of this thesis was focused on preparing already mentioned wound dressings. Then, their morphological changes over time and also the gradual release of incorporated active substances into the model environment were monitored. The gradual release of ampicillin was monitored not only spectrophotometrically, but also by ultra-high-performance chromatography. In wound dressings, in which collagenase was incorporated, was also the final proteolytic activity of this enzyme monitored. The effect of the active substances was observed on three selected microorganisms: Escherichia coli, Staphylococcus epidermidis and Candida glabrata. The cytotoxic effect of the active substances on the human keratinocyte cell line was monitored by MTT test and LDH test. A test for monitoring the rate of wound healing – a scratch test – was also performed.

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26

"Electrospinning of Bioactive Dex-PAA Hydrogel Fibers." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.9078.

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abstract: In this work, a novel method is developed for making nano- and micro- fibrous hydrogels capable of preventing the rejection of implanted materials. This is achieved by either (1) mimicking the native cellular environment, to exert fine control over the cellular response or (2) acting as a protective barrier, to camouflage the foreign nature of a material and evade recognition by the immune system. Comprehensive characterization and in vitro studies described here provide a foundation for developing substrates for use in clinical applications. Hydrogel dextran and poly(acrylic acid) (PAA) fibers are formed via electrospinning, in sizes ranging from nanometers to microns in diameter. While "as-electrospun" fibers are continuous in length, sonication is used to fragment fibers into short fiber "bristles" and generate nano- and micro- fibrous surface coatings over a wide range of topographies. Dex-PAA fibrous surfaces are chemically modified, and then optimized and characterized for non-fouling and ECM-mimetic properties. The non-fouling nature of fibers is verified, and cell culture studies show differential responses dependent upon chemical, topographical and mechanical properties. Dex-PAA fibers are advantageously unique in that (1) a fine degree of control is possible over three significant parameters critical for modifying cellular response: topography, chemistry and mechanical properties, over a range emulating that of native cellular environments, (2) the innate nature of the material is non-fouling, providing an inert background for adding back specific bioactive functionality, and (3) the fibers can be applied as a surface coating or comprise the scaffold itself. This is the first reported work of dex-PAA hydrogel fibers formed via electrospinning and thermal cross-linking, and unique to this method, no toxic solvents or cross-linking agents are needed to create hydrogels or for surface attachment. This is also the first reported work of using sonication to fragment electrospun hydrogel fibers, and in which surface coatings were made via simple electrostatic interaction and dehydration. These versatile features enable fibrous surface coatings to be applied to virtually any material. Results of this research broadly impact the design of biomaterials which contact cells in the body by directing the consequent cell-material interaction.
Dissertation/Thesis
Ph.D. Bioengineering 2011

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27

Hsieh, Hsiu-ling, and 謝秀伶. "The electrospun nanofibers from hydrogel copolymers with Ag particles and their antimicrobial and deodorizing application." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/b7v6s6.

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碩士
國立臺北科技大學
有機高分子研究所
102
Electrospinning technique is novel nanotechnology in recent years, a wide range of source materials and the manufacturing process is simple, has a trait can be prepared quickly and directly into nano-fiber material, there is no limit to the tradition fiber manufacturing process. In recent years has become a very important topic of polymer engineering research. The fine structure of the polymer determines the scope of application of the finished product, and in addition to the nature of the material itself order to various factors in the process of change will also affect the fine structure of the polymer. Studies using Poly (HEMA-co-NMA) copolymers as the main blending silver nitrate to make and has antibacterial deodorizing. Formed by the electrostatic spinning of nano fiber web film. Then testing include SEM, UV light reduction, crosslinked, immersed, antibacterial test and deodorizing test. The study successfully using Poly (HEMA-co-NMA) copolymer as the main polymer (HEMA of superabsorbent group, and NMA of chemical crosslinking group), according to the UV light by blending a silver nitrate is reduced to give containing different proportions nano fibers are not woven silver nanoparticles. By regulating different electrospinning operating parameters (different solution concentrations, the amount of added solvent Methanol, electro-spinning velocity), heating temperature, and controlling nano fiber thickness, to obtain diverse morphology and fiber fineness range of 100 ~ 1000 nm nano fibers. With JIS L1902: 2008 bacteria absorption, antibacterial test (Staphylococcus aureus & Escherichia coli) and FTTS-FA-018-2008 deodorizes test. The results of this study, when increasing concentration of the silver nanoparticles, and Staphylococcus aureus antibacterial activity values rise, then adding 3% of silver nanoparticles, getting a maximum inhibition value of 5.2 (S) and maximum sterilization value of 3.1 (L). When adding 3% of silver nanoparticles , the Escherichia coli antibacterial activity value was rise, can reach a maximum inhibition value 6.9 (S) , sterilization value 3.4 (L), and after 24 hours of deodorizing rate was up to 30% , has the characteristics of environmental protection and low cost. Future, the nano-fibers in the film expect to medical supplies and biochemical raw materials such as clothing.

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28

Antunes, Jerome Bruno. "Materiais capazes de transportar e libertar colagenase para o tratamento de lesões cutâneas: síntese e caracterização." Master's thesis, 2019. http://hdl.handle.net/1822/73711.

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Dissertação de mestrado em Química Têxtil
Os danos causados à pele podem trazer consequências nefastas e afetar a homeostasia do organismo. Nesse sentido, é fundamental desenvolver sistemas que auxiliem o processo de cicatrização e evitem a proliferação de microrganismos invasores. Uma nova era de dispositivos biocompatíveis de matriz têxtil, mais eficientes no tratamento das lesões cutâneas e com a capacidade de transporte e libertação controlada de substâncias bioativas, é capaz de proporcionar uma resposta terapêutica mais célere do que os tratamentos convencionais. Por sua vez, os hidrogéis e as nanofibras podem ser materiais biocompatíveis que permitem mimetizar a matriz extracelular de forma a proporcionar um microambiente favorável para a regeneração tecidual. No presente trabalho foram sintetizados hidrogéis e nanofibras com a capacidade de transportar e libertar colagenase para o tratamento de lesões cutâneas. Para isso, foram sintetizados hidrogéis à base de hidroxipropilmetilcelulose (HPMC) e ciclodextrinas (βCD ou HPβCD). Foram também produzidas nanofibras de policaprolactona (PCL) pela técnica de electrospinning. Os materiais desenvolvidos foram caracterizados através de técnicas de FTIR, DSC e TGA. A caracterização química demonstrou a presença dos principais grupos químicos nos diversos componentes dos materiais. A avaliação dos perfis térmicos através do DSC permite visualizar dois picos endotérmicos, relativos à desidratação e ao intervalo de fusão, para cada um dos materiais analisados e a análise de TGA demonstra uma única fase degradação térmica tanto nos hidrogéis como nas nanofibras. A sua capacidade de inchaço também foi avaliada em diferentes condições de pH, apresentando o hidrogel de HPMC-HPβCD a maior retenção de água em qualquer das condições estudadas. Por sua vez, o hidrogel de HPMC-βCD mostrou ser o menos sensível a variações de pH do meio. No caso das nanofibras de PCL, foi ainda feita uma análise microscópica usando um microscópio eletrónico de varrimento (SEM). As fibras produzidas apresentaram-se uniformes e homogéneas, com diâmetros compreendidos entre 110 e 137nm sem enzima e entre 195 a 200nm quando incorporada a colagenase na solução do polímero. Nos hidrogéis a colagenase foi incorporada por adsorção. Os dois hidrogéis apresentaram capacidade de adsorção enzimática semelhante. Os estudos de libertação controlada efetuados permitiram concluir que quer nos hidrogéis quer nas nanofibras, a colagenase ficou fortemente retida na estrutura polimérica.
Skin damage can have harmful consequences and affect the body's homeostasis. For this reason, it is essential to develop systems that help the healing process and prevent the proliferation of invasive microorganisms. A new era of biocompatible textile matrix devices, more efficient in the treatment of skin lesions and able for transport and controlled release of bioactive substances, can provide a faster therapeutic response than conventional treatments. On the other hand, hydrogels and nanofibers can be biocompatible materials that mimic the extracellular matrix in order to provide a favorable microenvironment for tissue regeneration. In the present work hydrogels and nanofibers were synthesized with the ability to transport and release collagenase for the treatment of skin lesions. Thus, hydrogels based on hydroxypropyl methylcellulose (HPMC) and cyclodextrins (βCD or HPβCD) were synthesized. Polycaprolactone (PCL) nanofibres were also produced by the electrospinning technique. The developed materials were characterized by FTIR, DSC and TGA techniques. The chemical characterization revealed the presence of the main chemical groups in the various components of the materials. The evaluation of the thermal profiles by DSC technique showed two endothermic peaks, related to dehydration and melting range, for both analyzed materials and the TGA technique demonstrated a single thermal degradation phase in both hydrogels and nanofibers. Its swelling capacity was assessed in different pH conditions, with the HPMC-HPβCD hydrogel showing the highest water retention in all of the studied conditions. On the other hand, the HPMC-βCD hydrogel was the least sensitive to pH variations. For the PCL nanofibers, a microscopic analysis was also performed using a scanning electron microscope (SEM). The produced fibers were uniform and homogeneous, with diameters between 110 and 137nm without enzyme and between 195 and 200nm when collagenase was incorporated into the polymer solution. The collagenase was incorporated by adsorption in the hydrogels. Both hydrogels presented similar enzymatic adsorption capacity. Controlled release studies showed that collagenase was strongly retained in the polymeric structures studied.

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29

Chang, Ju-Szu, and 張如斯. "The exploration of morphology and heavy metal-ion adsorption of electrospun nanofibers form hydrogel copolymers blending with algae." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/s5jtaw.

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碩士
國立臺北科技大學
有機高分子研究所
102
The development of technology to bring increasingly severe negative impact on the environment, along with industrial and commercial development, emissions of waste water are also increasingly proliferated. In this study, given the many experimental sewage waste generated in institutions, acid waste containing organic solvents and heavy metals and other ingredients, if an overflow occurs upset when there is an immediate risk of harm, to be covered by the chemisorption of cotton acid containing heavy metals, alkaline liquid, proper follow-up treatment after adsorption to do to improve the quality of the environment. In this study, electrospinning and cross-linking of two processing technology, successfully prepared a series of Copolymer Poly (HEMA-co-MNA) ( HEMA with NMA segment containing different proportions ) electrospun nanofibers. Explore processed into parameters (polymer concentration, process flow rates, the use of solvents), and cross-linked changes in the proportions of the different segments of its nano- fiber morphology. SEM observation using different crosslinking conditions under which the water of the changes in fiber morphology found high levels NMA (10: 1 and 10 : 3) large degree of crosslinking , the crosslinked HEMA can not return to the fiber was dissolved in water , sustain a cylindrical fiber structure . Blending and use of algae in Poly (HEMA-co-MNA) copolymers, the use of a polymer prepared by electrospinning nanofibers containing algae, the study of heavy metal adsorption behavior. In the ICP-OES spectrometer tests, found to contain algae nano fibers with high specific surface area, within 10 minutes adsorption trend, and can quickly reach saturation adsorption within 2 hours, remove excellent efficiency of heavy metals. Algae changed its adsorption characteristics of heavy metals Pb, Cd, Ni, and environmental factors (initial pH, time, initial concentration of heavy metals), etc., will have a different impact absorption. Therefore, in this study the preparation of polymer nanofibers containing algae, not only with the biological adsorption principle to reduce environmental pollution adsorption of heavy metal waste, also showed rapid adsorption of heavy metals in the waste of performance, the future will be made of acid, alkali environmental chemisorption cotton, used in the related fields.

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30

HUEI-SYUAN, LIN, and 林慧宣. "Making Bi-layered composite scaffold with 3D plotted Alginate hydrogel and Chitosan / polyvinyl alcohol nanofibers for tissue repair." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/zfhaxr.

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碩士
國立臺北科技大學
化學工程研究所
104
3D printing technology produces scaffolds with interconnected pores. They facilitate cell growth, nutrient and metabolic waste transportation. Electro spun method produces nanofibers with large surface area and pore structure, mimicking the extracellular matrix. Combing 3D printing technology and electro spun technology to manufacture skin dressing composites. Electro spun material selection chitosan and polyvinyl alcohol are all biodegradable material, and use concentrated acetic acid (90 vol %) as a solvent. It can effectively reduce the surface tension，increase the charge density, form nanofibers. Improving mechanical properties by glutaraldehyde vapor cross-linked nanofibers as the skin surface. 3D printing material choice alginate hydrogel with calcium chloride crosslinked to form gelled as the dermal layer. And finally bonding two kinds of product biological with glue to form composite. Compared composites material with 3D molded alginate hydrogel scaffold, composites material scaffolds have a higher tensile strength, low degradation rate, swelling rate and water vapor permeability. Composites material value slightly above but below lidless container moisture permeability values. It also has good growth on the biocompatibility.

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31

Mashao, Gloria. "Polyaniline-zeolitic imidazolate framework composite nanofibers for hydrogen gas sensing application." Thesis, 2019. http://hdl.handle.net/10386/3149.

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Thesis(M.Sc.(Chemistry)) -- University of Limpopo, 2019
The quest for renewable, sustainable and environmentally compatible energy sources have been on-going for decades. Green technology such as hydrogen fuel cell has attained much attention as an alternative energy carrier to carbon-based fuels owing to its renewability and cleanliness. However, hydrogen gas feed to the fuel cell can easily be ignited if its concentration is above 4 wt.% at room temperature. Thus, hydrogen safety mechanisms such as hydrogen sensors are vital to guarantee people‘s safety in the hydrogen infrastructure. Sensors based on metals and metal oxides have been widely applied for hydrogen gas detection. Nonetheless, these materials are only sensitive to hydrogen gas at elevated temperatures (˃ 100 °C) and they also possess low surface area (< 20 m2/g). Hence in this work, we present polyaniline (PANI) doped with cobalt-based zeolitic benzimidazolate framework (CoZIF) and zinc-ZIF to fabricate (PANI-CoZIF and PANIZnZIF) composite nanofibers as effective electrocatalysts for hydrogen gas sensing application. The composites were synthesised through chemical oxidative polymerisation of aniline monomer in the presence of 3.6 wt.% CoZIF and ZnZIF, respectively. The structural properties of the synthesised materials were studied using Ultraviolet visible (UV-vis), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy and simultaneous thermal analysis (STA). FTIR, Raman and XRD studies showed successful synthesis of CoZIF, ZnZIF and their composites. Furthermore, the studies indicated the co-existence of both CoZIF and ZnZIF in the PANI matrix upon composites formation, indicated by reduction in crystalline size, decrease in band gap and increase in thermal stability. as compared to the neat PANI. Morphological characteristics of the prepared samples were investigated usingscanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with both energy dispersive spectroscopy and X-ray (EDS/EDX). PANICoZIF revealed the grafting of CoZIF on to the surface of PANI matrix while PANI-ZnZIF composite showed that PANI is wrapping the cube nanofiber-like structures of ZnZIF also supported by selected area electron diffraction (SAED). Cyclic voltammetry (CV), Tafel analysis and turn over frequencies (TOFs) were performed to study the electrochemical performance of the synthesised materials through hydrogen evolution reaction (HER) for gas sensing. Both composites presented drastic enhancement in the catalytic H2 evolution at 0.033 mol.L-1 H2SO4 with the Tafel slope of 160 mV/dec and exchange current density of 3.98 A.m-2 for PANI-CoZIF composite, while the Tafel slope and exchange current density for PANIZnZIF composite were 246 mV/dec and 5.01 A.m-2, respectively. Moreover, the TOFs of the PANI-CoZIF composite (0,117 mol H2.s-1) was higher as compared to neat PANI (0.040 mol H2.s-1). The TOF values for PANI and PANI-ZnZIF composite were 0.04 and 0.45 mol H2.s-1, respectively. In addition, the chronoamperometric (CA) results exhibited the significant improvement in the electrochemical hydrogen sensing ability of PANI-CoZIF and PANI-ZnZIF composites with higher current response and sensitivity values of 12 and 10.8 µA.mmol.L-1 H2, respectively. The composites exhibited faster steady state response time of 5 s for PANI-CoZIF composite and 4 s for PANI-ZnZIF composite accompanied by lower detection limit (5.27 µmol.L-1) as compared to the neat PANI matrix. The high electrochemical current response is due to extraordinary specific surface area, more accessible active sites available for the electrolyte provided by CoZIF and ZnZIF and high conductivity supplied by PANI. These results proved that the PANI-CoZIF and PANI- ZnZIF composites are suitable electrocatalytic materials for hydrogen gas sensing application through HER in acidic medium. These results further suggest that the safety of people in mining sectors and other industries can be addressed through simple electrocatalytic gas sensing systems.

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32

Huang, Ching-Ting, and 黃敬婷. "Biofunctional Nanofibers and Supramolecular Hydrogels of Naphthalimide-based Peptides." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/jqjq6a.

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碩士
國立交通大學
材料科學與工程學系所
103
Adhesive peptide sequences within many ECM proteins have been discovered via competitive adhesion assays and mutagenesis experiment. In our laboratory, Novel hydrogels based on Naphthalimide with peptide sequences DGEA, IKVAV, GFF, and FFG have been synthesized. This thesis has three-fold. In the first part, DGEA-containing peptides hydrogelators based on naphthalimide are developed. The DGEA tetra-peptide sequence is the shortest collagen type I-derived motif recognized by the collagen-binding integrin 21. Also, the materials have significant differences in their fluorescence intensity because of the capping group, 1,8-Naphthalimide-N-acetic acid and 4-Nitro-1,8-Naphthalimide-N-acetic acid. In the second part, small molecule hydrogels containing IKVAV polypeptide induced self-assembly to form nanofiber gel was synthesized. The IKVAV peptide sequence is located in the α-1 chain of laminin responsible for cell adhesion and neurite outgrowth. We reduce the molecular weight of IKVAV-containing hydrogelator and toward a better material that fits the Atomic economy and Green chemistry. In the last one, we capped peptide sequences, GFF and FFG with aromatic group, naphthalimide, and compared the cell viability of NI-GFF and NI-FFG. We also tested the cell viability of 4-Nitro-1,8-naphthalimide, NO2-FDGEA and NO2-FIKVAV to know whether if the cytotoxicity of the materials can be improved by conjugating the peptide sequences.

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33

Saraswat, Sushil Kumar. "Thermocatalytic decomposition of methane to COx free hydrogen and carbon nanofibers." Thesis, 2012. http://localhost:8080/xmlui/handle/12345678/3418.

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34

Shie, Tzung-Ying, and 謝宗穎. "Electrospun Titanium Dioxide Nanofibers for Hydrogen Production by UV-Induced Water Splitting." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41665463924912818950.

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碩士
國立成功大學
材料科學及工程學系碩博士班
95
Titanium dioxide nanofibers fabricated by the polymer-assisted electrospinning technique were utilized in the photo-induced water splitting applications. A sol-gel solution formulated by titanium-tetraisopropoxide (TTIP) and poly(vinylpyrrolidone) (PVP) in an ethanol medium was ejected under a strong electrical field. Accompanied by the solvent evaporation and the solidification, highly charged polymer jet induces the formation of nanofibers collected on the grounded electrode as s uniform thin film. Calcination process was carried out afterward to encourage the crystallization and the phase transformation of titania, along with the thermal decomposition of polymer domains. Different diameter of TiO2 nanofibers were easily collected by sol-gel recipes and electrospinning parameters. Structures and other characterizations of titania nanofibers were investigated and discussed in this research work. Water splitting performance of electrospun TiO2 nanomaterials was studied and compared with Degussa P-25 TiO2. Activities of photocatalytic hydrogen production revealed the strong relationship with specific surface area of different titania samples. Meanwhile, UV-visible spectra of electrospun TiO2 nanofibers suggested the significant light harvesting effect caused by the nanostructured titania nanomaterials. Thickness-dependent photoresponses of these electrospun homogeneously deposited on FTO-coated glass slides also showed the proportional increases with the applied bias and the irradiation. More importantly, the steadily photocurrent increases as a function of titania film thicknesses indicated the efficiency enhancement by macroporous electrospun titania materials in the hydrogen production applications.

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35

Fu, Amy Hau Yu. "Mitigating Scarring and Inflammation during Corneal Wound Healing using Nanofiber-Hydrogel Scaffolds." Thesis, 2015. https://thesis.library.caltech.edu/8893/1/AmyFu2015_Thesis.pdf.

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Due to the universal lack of donor tissue, there has been emerging interest in engineering materials to stimulate living cells to restore the features and functions of injured organs. We are particularly interested in developing materials for corneal use, where the necessity to maintain the tissue’s transparency presents an additional challenge. Every year, there are 1.5 – 2 million new cases of monocular blindness due to irregular healing of corneal injuries, dwarfing the approximately 150,000 corneal transplants performed. The large gap between the need and availability of cornea transplantation motivates us to develop a wound-healing scaffold that can prevent corneal blindness.

To develop such a scaffold, it is necessary to regulate the cells responsible for repairing the damaged cornea, namely myofibroblasts, which are responsible for the disordered and non-refractive index matched scar that leads to corneal blindness. Using in vitro assays, we identified that protein nanofibers of certain orientation can promote cell migration and modulate the myofibroblast phenotype. The nanofibers are also transparent, easy to handle and non-cytotoxic. To adhere the nanofibers to a wound bed, we examined the use of two different in situ forming hydrogels: an artificial extracellular matrix protein (aECM)-based gel and a photo-crosslinkable heparin-based gel. Both hydrogels can be formed within minutes, are transparent upon gelation and are easily tunable.

Using an in vivo mouse model for epithelial defects, we show that our corneal scaffolds (nanofibers together with hydrogel) are well-tolerated (no inflammatory response or turbidity) and support epithelium regrowth. We developed an ex vivo corneal tissue culture model where corneas that are wounded and treated with our scaffold can be cultured while retaining their ability to repair wounds for up to 21 days. Using this technique, we found that the aECM-based treatment induced a more favorable wound response than the heparin-based treatment, prompting us to further examine the efficacy of the aECM-based treatment in vivo using a rabbit model for stromal wounds. Results show that treated corneas have fewer myofibroblasts and immune cells than untreated ones, indicating that our corneal scaffold shows promise in promoting a calmer wound response and preventing corneal haze formation.

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36

Chou, Yi-Feng, and 周宜鋒. "Surface Modification of Electrospun Hyaluronic Acid and Its Derivatives Nanofiber on Silicone Hydrogel Membrane." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/13704155289460017035.

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碩士
中原大學
生物醫學工程研究所
98
Abstract Silicone hydrogel contact lenses have high oxygen transmissibility that makes them suitable for extended wear, but their hydrophobic surfaces cause discomfort to the cornea during extended wear. This study aims to adjust the hydrophobic characteristics of the silicone hydrogel by combining siloxane-containing monomers of (trimethyl-siloxy)silyl-propyl methacrylate (TRIS) with hydrophilic monomers, such as 2-hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone. A crosslinking agent and a photoinitiator were also used to fabricate the silicone membrane. Hyaluronic acid (HA) was mixed with polyvinyl pyrrolidone (PVP) to form fibrous membranes using the electrospinning technique. Glycidyl methacrylate-hyaluronic acid (GMHA) was successfully synthesized. Proton nuclear magnetic resonance spectrra showed that the GMHA proton signals were present at 5.6 and 6.1 ppm, representing the vinyl functional group. A solution of GMHA with PVP was used to form fibers by electrospinning. When TRIS was increased by 30-50 vol%, the water content of TRIS-based silicone hydrogel decreased from 35 to 28%. The elastic modulus increased from 0.8 MPa to 4.4 MPa after treatment. The transmittance of the silicone membrane was about 80-95%T. The contact angle at the surface of the silicone membrane was about 92-103o. Scanning electron microscopy analysis showed that the HA-PVP fiber diameters were in the range of 100-680 nm at 25 oC and in the range of 140-770 nm at 50 oC. When silicone membranes were coated with HA-PVP fibers using a physical adsorption procedure, the contact angle decreased from 62 o to77o. In contrast, chemical modification of silicon membranes through ozone treatment and coating with electrospun GMHA-PVP yielded contact angles of 59-77o. Therefore, the techniques presented here have successfully improved the hydrophilic characteristics of a silicon hydrogel membrane.

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37

Chen, Yu-hsiang, and 陳禹翔. "Nanocomposite comprising gold nanoparticles and polyaniline nanofibers via one-step synthesis for sensing hydrogen peroxide." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/27338859093148764273.

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Анотація:

碩士
國立成功大學
化學工程學系碩博士班
96
The first part of the the dissertation is on the characterization of the nanocomposite comprising gold nanoparticles and polyaniline nanofibers. Au nanoparticles were generated along with the simultaneous formation of polyaniline（PANI）nanofibers using interfacial polymerization route. Scanning electron microscopic（SEM）revealed that PANI possesses nanofiber structure. The nanofiber structure of PANI acts as not only reducing agent but also matrix to prevent the aggregation of gold nanoparticles. Transmission electron microscopic（TEM）results revealed that particle size of gold nanoparticles is at ca. 10-30 nm which is consistent with the result from the calculation by x-ray diffraction pattern （XRD）. X-ray photoelectron spectroscopy（XPS）and Fourier transform infrared spectroscopy（FTIR）results showed that there were more side products and higher oxidized states for the nanocomposite synthesized by using HAuCl4 as oxidant. On the second part of the dissertation, we extended our work to study the electrochemical sensing properties of the prepared nanocomposite for hydrogen peroxide. The nanocomposite comprising gold nanoparticles and PANI nanofibers possess the sensing ability for hydrogen peroxide. Furthermore, the optimal operation of the nanocomposite for sensing hydrogen peroxide is at pH 7.5. The hydrogen peroxide sensor shows a linear calibration curve over the range from 2.5×10-7 to 2×10-3 M, with a slope and detection limit（S/N=3）of 9.53 μA/mM and 2.5×10-7 M, respectively. In addition, the hydrogen peroxide sensor possesses a fast response time（6 sec）for sensing hydrogen peroxide.

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38

Guincho, Pedro Batalha. "Novel pectin and nanocellulose based bioinks for 3D bioprinting applications." Master's thesis, 2021. http://hdl.handle.net/10773/30763.

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Анотація:

The implementation of personalized and efficient strategies for damaged tissue/organ replacement is becoming increasingly urgent, being observed significant advancements in the field of tissue engineering in recent years, namely in 3D bioprinting of functional living tissue analogues. This automatized technology allows a wide control over the cellular environment and the overall tissue organization. To obtain a fully developed and functional tissue/organ, the bioprinting method and the bioink need to have adequate properties and functionalities, for this reason, a thoughtful choice is crucial. Recently, there have been great developments in the field of bioinks for bioprinting applications. However, the developed bioinks still present several limitations, such as weak mechanical properties, low viability, or high production costs. In this context, the objective of this dissertation is the development of a pectinnanocellulose fibers hydrogel-based bioink laden with human keratinocyte cells (HaCaT cells) for 3D bioprinting. These biopolymers were chosen due to their great potential for 3D bioprinting applications. Pectin is biodegradable, hydrophilic, and can form hydrogels in the presence of divalent cations, such as calcium. Nanocellulose has also already demonstrated its potentialities in 3Dbioprinting, revealing excellent mechanical properties and biocompatibility. However, this combination of biopolymers has never been explored for 3Dbioprinting. The developed bioinks were characterized in terms of their rheology, chemical structure/composition, and morphology. Furthermore, the bioprinting parameters were optimized and the cytotoxicity of the hydrogels evaluated. Rheologically, the inks presented a shear-thinning behavior, which is extremely important for 3D bioprinting applications, furthermore, an increase of three levels of magnitude in viscosity and shear stress was observed after a pre-crosslinking procedure. The inks were able to be printed with the optimal result being obtained for the ink with the highest content of NFC and prereticulated with 1% (m/v) CaCl2, which allowed the printing of up to 8 layers without losing resolution. The fully-crosslinked hydrogels were considered noncytotoxic towards HaCaT cells, however higher cell viability values were observed for the hydrogels with higher NFC content. This study can be considered a great step towards the use of pectin-NFC-based bioinks in 3Dbioprinting applications.
A implementação de estratégias personalizadas e eficientes para a regeneração de tecidos/órgãos danificados é cada vez mais importante, enos últimos anos têm-se observado avanços significativos no campo da engenharia de tecidos, nomeadamente, na bio-impressão 3D de análogos de tecidos vivos funcionais. Esta tecnologia automatizada permite o controlo do ambiente celular e também da organização tecidular. Para que o tecido impresso seja funcional e adequado para a aplicação em causa, o método de bio-impressão e a biotinta necessitam de ter propriedades e funcionalidades adequadas, sendo a sua seleção um passo fundamental. Recentemente, tem havido um grande progresso no desenvolvimentode biotintas para aplicação em bio-impressão3D. Contudo, as biotintas desenvolvidas ainda apresentam diversas limitações, tais como fracas propriedades mecânicas, baixa viabilidade celular ou custos de produção elevados. Neste contexto, o objetivo destadissertação é o desenvolvimento de uma biotinta à base de um hidrogel de pectina e nanofibras de celulose (NFC) com incorporação de queratinócitos humanos (células HaCaT) para aplicação em bio-impressão 3D. Estes biopolímeros foram escolhidos devido às suas propriedades intrínsecas e ao seu potencial para impressão 3D. A pectina é biodegradável, hidrofílica e forma hidrogéis na presença de catiões divalentes, como o cálcio. A nanocelulose também já demonstrou as suas potencialidades, revelando excelentes propriedades mecânicas e biocompatibilidade. Contudo, a combinação de pectina e NFC nunca fui explorada no campo da bio-impressão 3D.As tintas desenvolvidas foram caraterizadas em termos da sua reologia, estrutura/composição química e morfologia. Adicionalmente, os parâmetros de impressão foram otimizados e a citotoxicidade dos hidrogéis avaliada. Reologicamente, as tintas apresentaram um comportamento pseudoplástico, que é extremamente importante para aplicações em bio-impressão 3D e, além disso, após pré-reticulação observou-se um aumento de três níveis de magnitude na viscosidade e tensão de cisalhamento. As tintas desenvolvidas têm aptidão para serem imprimidas, tendo o resultado mais promissor sido obtido para a tinta com maior quantidade de NFC e pré-reticulada com1%(m/v) de CaCl2. Nomeadamente, conseguiu-se imprimiraté8 camadas sem perder resolução. Os hidrogéis imprimidos mostraram ser não citotóxicos para as células HaCaT, contudo os valores de viabilidade celular mais elevados foram observados para os hidrogéis com maiores quantidades de nanocelulose. Este estudo considera-se como um grande passo em direção ao uso de biotintas baseadas em pectina e NFC embio-impressão3D.
Mestrado em Bioquímica

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39

楊立志. "Fabrication and Characterization of Multiwalled Carbon Nanotubes Dispersion to Hydrogen-Bonding System of Composite Nanofibers via Electrospinning." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/29152557955938681615.

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碩士
國立交通大學
應用化學系碩博士班
100
In this thesis, the poly(3-thiophene-triazole-diaminopyridin) (PTDAP) possessing triple hydrogen bonding sites were successfully synthesized through chemical oxidative polymerization. Following blending with the biocompatible poly(4-vinylbenzyl uracil) (PVBU), nano/micro nanofibers can be fabricated through electrospinning. These results indicate that the presence of the hydrogen-bonding system may improve the morphology, thermal stability, functionality and compatibility of nanofibers for applying in carbon nanotube dispersion, biomatrix, filter, or battery seperation. In addition, we incorporate the multiwalled carbon nanotubes (MWCNTs) into the PVBU/PTDAP hydrogen-bonding system and successfully fabricated bead-free composite nanofibers with diameter down to 500 nm. Under the hydrogen-bonding system, the thermal stability of the composite nanofibers is improved apparently. Fourier transform Raman (FT-Raman) spectra, transmission electron microscope (TEM) and standard four probe result indicate that the conjugated polymer block such as polythiophenes can form strong non-covalent π–π interactions with multiwalled carbon nanotube walls which prevents MWCNTs from aggregating and dispersion, while the triple hydrogen-bonding interaction between PTDAP and PVBU provide the de-bundled MWCNTs with a good solubility and stability in the organic solvents and host polymer matrices. TEM observation showed the MWCNTs were parallel and oriented along the axes of the nanofibers which increase the conduction of electrons and therefore significantly enhance the conductivity.

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"Multi-Hierarchical Self-Assembly of Collagen Mimetic Peptides into AAB Type Heterotrimers, Nanofibers and Hydrogels Driven by Charged Pair Interactions." Thesis, 2012. http://hdl.handle.net/1911/70377.

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Replicating the multi-hierarchical self-assembly of collagen (peptide chain to triple helix to nanofiber and, finally, to a hydrogel) has long attracted scientists, both from the fundamental science perspective of supramolecular chemistry and for the potential biomedical applications perceived in tissue engineering. In terms of triple helical formation, collagen is the most abundant protein in the human body with at least 28 types, yet research involving collagen mimetic systems has only recently began to consider the innate ability of collagen to control helix composition and register. Collagen triple helices can be homotrimeric or heterotrimeric and while some types of natural collagen form only one specific composition of helix, others can form multiple. It is critical to fully understand and, if possible, reproduce the control that native collagen has on helix composition and register. In terms of nanofiber formation, many approaches to drive the self-assembly of synthetic systems through the same steps as natural collagen have been partially successful, but none have simultaneously demonstrated all levels of structural assembly. In this work, advancements in the ability to control helix composition and replicate the multi-hierarchical assembly of collagen are described. Both positive and negative design for the assembly of AAB type collagen heterotrimers were utilized by promoting heterotrimer formation though the use of charged amino acids to form intra-helix electrostatic interactions, while simultaneously discouraging homotrimers, resulting in the identification of multiple peptide systems with full control over the composition of the resulting triple helix. Similar salt-bridged hydrogen bonds between charged residues were incorporated into nanofiber forming peptides, one of which successfully assembled into sticky-ended triple helices, nanofibers with characteristic triple helical packing visible in the solution state, and strong hydrogels that are degraded by collagenase at a similar rate to natural collagen. Together, these results provide a better understanding of the self-assembly of collagenous sequences as well as a novel design scheme for synthetic extracellular matrix mimetics with potential applications in regenerative medicine and drug delivery.

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Perlík, Martin. "Studium fotogenerace peroxidu vodíku polymerními nanovlákny s enkapsulovaným fotosensitizerem." Master's thesis, 2011. http://www.nusl.cz/ntk/nusl-298515.

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This study is dedicated to characterisation of photosensitisation properties of polymeric nanofibres with encapsulated photosentisitiser. Main goal of thesis is demonstration and study of H2O2 photoproduction. Photosensitizer used in this study was 5,10,15,20-meso-tetrafenylporfyrin (TPP), studied were also its complexes with Cu2+ a Ni2+ . Properties of nanofibers were examined using UV-Vis molecular absorption spectroscopy, fluorescence spectroscopy and electron microscopy (SEM).

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Bartneck, Matthias [Verfasser]. "Interactions of human primary immune cells with nanoparticles, two-dimensional micropatterns, hydrogels and three-dimensional nanofibres / vorgelegt von Matthias Bartneck." 2010. http://d-nb.info/1009776401/34.

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Maclean, Francesca. "Biomaterials to change astrocyte behaviour and morphology for brain repair." Phd thesis, 2017. http://hdl.handle.net/1885/135344.

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The incapacity of the central nervous system (CNS) to regenerate is a barrier to the effective treatment of neurodegenerative diseases and traumatic injuries. Of particular importance in treating traumatic injuries is the CNS’s inflammatory response, which is a complex response that does not effectively transition from the growth-inhibitory and protective phase to a growth supportive phase that would allow for tissue repair and remodelling. Therefore, the astrocyte response to injury presents a valuable therapeutic target as they perform both cytotrophic and cytotoxic functions, sometimes concomitantly, after injury. The chronic persistence of scar-forming astrocytes presents a significant barrier to regeneration and hence, functional recovery. As such, understanding how particular cues, and when they are presented, affect astrocyte behaviour is of interest in developing tissue engineering solutions for traumatic brain injury (TBI). Biomaterials present an attractive solution candidate as they can mimic the extracellular matrix of the brain, present biologically relevant cues, and facilitate cell growth. Through understanding how biomaterials and the cues they can present impact astrocyte behaviour and morphology, we seek to inform the future design of biomaterials to harness the cytotrophic aspects of astrocytes and their response to injury to improve reparative outcomes. In this thesis, the development and biological evaluation of nanofibrous biomaterial systems functionalized with galactose moieties or the anti-inflammatory polysaccharide, fucoidan are described. Electrospun poly(ε-caprolactone) nanofibre scaffolds were fabricated and functionalized with biologically relevant heparin (anti-inflammatory) and poly(L-lysine) (PLL), or the novel galactose-presenting poly(l-lysine)-lactobionic acid (PLL-LBA). The research reported here demonstrates the functionalization and materials characterization, as well as biological evaluation in vitro and in vivo to elucidate the impact of nanofibrous morphology and the galactose moieties on astrocytes in culture as well as after TBI. The galactose-presenting scaffold could maintain a reduced inflammatory profile of astrocytes in vitro and resulted in neuroprotection at 7 days post injury in mice. These findings were extended upon by transitioning to the Fmoc-capped self-assembled peptide (SAP) hydrogel, Fmoc-DIKVAV, which can effectively fill a brain lesion, whilst also providing bioactive cues on the surface of the nanofibres within the hydrogel. This system was co-assembled with fucoidan to present anti-inflammatory cues after TBI, where it was found that structural support and no additional functionalization was required to reduce the primary astrocyte scar by ~50% compared to the stab control 7 days post injury. The presentation of fucoidan on the fibrils of Fmoc-DIKVAV increased the organization of astrocytes within the primary scar and also altered the morphology of the astrocytes far away from the lesion site. This demonstrates the ability of fucoidan to alter the morphology, and potentially the phenotype of reactive astrocyte after injury. Finally, this SAP system was evaluated as a 3-dimensional (3D) cell culture environment to enhance the understanding of astrocyte behaviour in culture as well as after lipopolysaccharide (LPS) or interleukin-1α (IL-1α) stimulation. Fucoidan delivered via the hydrogel system significantly reduced the proliferation of LPS-stimulated astrocytes compared to soluble fucoidan or the control, and exposure to the hydrogel resulted in significant reorganization of astrocyte networks in vitro, which was also observed in vivo. Thus, this SAP hydrogel is promising as a 3D biomimetic cell culture environment for future studies of astrocytes. Here, we have engineered functionalized nanofibrous biomaterial scaffolds that can be used in vitro and in vivo to impact astrocyte behaviour and morphology after injury or stimulation. The results presented can be used to better inform the design of future tissue engineering strategies that can manipulate the inflammatory response to improve functional recovery outcomes.

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Дисертації з теми "HYDROGEL NANOFIBERS"

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