The cell plasma membrane is an interactive interface playing an important role in regulating cell-to-cell, cell-to-tissue contact, and cell-to-environment responses. This environment-responsive phospholipid layer consisting of multiple dynamically balanced macromolecules, such as membrane proteins, carbohydrate and lipids, is regarded as a promising platform for various surface engineering strategies. Through different chemical modification routes, we are able to incorporate various artificial materials into the cell surface for biomedical applications in small molecule and cellular therapeutics. In this dissertation, we establish two different cell coating techniques for applications of cell-mediated drug delivery and the localization of cell-based therapies to specific tissues. The first part of this dissertation establishes a membrane-associated hydrogel patch for drug delivery. The crosslinking of a grafted polymeric patch from a mammalian cell membrane is achieved through surface-mediated photolithographic polymerization. With the use of photomask, the formation of nanoparticle-loaded PEGDA hydrogel is controlled to deposit various geometric features on photoinitiator-immobilized surfaces. Through microarray patch patterning, we analyzed the influence of processing parameters on the accuracy of polymer patterning on a microarray. We then optimized the patterning approach for the formation of PEGDA patches on live A549 cells. In the second part of this dissertation, we study the use of tissue-adhesive coatings to improve the retention of therapeutic mesenchymal stem cells (MSCs) in the heart following intramyocardial or intravenous injection. MSCs were coated with antibodies against ICAM1 to adhere to CAM-overexpressed endothelium present in the heart following MI. Through intramyocardial or intravenous delivery, we observe higher number of coated cells retained in the heart over uncoated ones, supporting enhanced affinity for the inflamed endothelium near the infarct. We correlate the detachment force of antigen-interacted MSCs by a parallel laminar flow assay with the density of ICAM on the substrate and the density of anti-ICAM on the MSC surface. MSC retention on CAMmodified surfaces or activated HUVECs was significantly increased on antibody-coated groups (~90%) under physiologically hemodynamic forces (< 30dyne/cm2), compared to uncoated MSCs (~20%). Moreover, a dramatic reduction of immune cell quantity was observed after intravenous injection, indicating the enhanced immunoregulatory efficacy by systemically delivering ICAM-adhesive MSCs to the site of inflammation.

Le développement d'un nouveau système photo-initiateur 1 photoinitiateur capable d'absorber fortement la lumière dans la région de la lumière visible et de travailler sous irradiation LED a fait des progrès gratifiants. Ici, notamment l'azurant fluorescent en tant que classe de dérivés fluorophores, a été confirmé comme un Pl efficace pour la photopolymérisation radicalaire (FRP), l'un des principaux avantages est qu'ils peuvent travailler efficacement sous l'air, même à faible intensité lumineuse. Lorsqu'ils sont incorporés dans des systèmes photoinitiateurs multicomposants (en présence de sel d'iodonium (et éventuellement N-vinylcarbazole ou amine)), les dérivés du naphtalène-benzoxazole, des triazinylstilbènes sulfonés, du stilbène-biphényl sulfoné et du coumarinme inhibent d'excellentes capacités photoamorcantes pour la FRP des acrylates sous air. De plus, ils sont particulièrement efficaces pour la formation d'un réseau de polymères interpénétrés à travers une photopolymérisation cationique 1 radicale concomitante d'un mélange époxydes 1 acrylates.De plus, la substitution d'une certaine teneur en monomère acrylate avec de l'eau augmente positivement la conversion finale des fonctions acrylate polymérisables, spécialement formulée avec les systèmes initiateurs à base d'azurants hydrophiles. En outre, une formulation aqueuse d'acrylate contenant des systèmes d'amorçage à base d'azurants a permis la synthèse d'hydrogels assistée par LED. Cette méthode de synthèse consomme moins d'énergie et les hydrogels produits ont généralement une teneur élevée en eau. Et, l'étude des photopolymérisations qui se déroulent dans les mélanges acrylate 1 eau élargit les perspectives pour le polymère vert et la chimie organique. / The development of a new photoinitiator/photoinitiatng system being capable of strongly absorbing light in the visible-light region and working under LED irradiation has made gratifying advance. Herein, notably the fluorescent brightener as one class of fluorophore derivetives, has been confirmed as an efficient Pl for free radical photopolymerization (FRP), one of the major advantages is thalthey could efficiently work under air even exposure to a low LED light intensity. When incorporated into multicomponent photoinitiating systems (in the presence of iodonium salt (and optionally N-vinyl carbazole or amine)), the derivatives of naphthalene­ benzoxazole, sulfonated triazinylstilbenes, sulfonated stilbene-biphenyl and coumarinmexhibit quite excellent photoinitiating abilities for FRP of acrylates under air. Moreover, they are particularly efficient for the formation of interpenetrated polymer network through a concomitant cationic/radical photopolymerization of epoxides/acrylates blend.Additionally, substitution of a certain content of acrylate monomer with water is found to positively increase the final conversion of polymerizable acrylate functions, especially formulated with the hydrophilic brighteners-based initiating systems. Besides, an aqueous acrylate formulation containing brighteners-based initiating systems enabled the LED-assisted synthesis of hydrogels. This synthetic method is less energy-intensive and the hydrogels produced are typically of high water content. And, the investigation of photopolymerizations thal proceed in acrvlate/water blends broadens the perspectives for qreen polvmer and organic chemistry.

A celulose é o principal polímero derivado de fonte renovável de uso industrial tanto em termos de volume como em número de aplicações. A celulose é comercializada na forma de polpa, que se trata de uma commodity cuja principal aplicação é a indústria de papel e de derivados de celulose, tais como os seus éteres e ésteres. Com o advento das nanoceluloses, que podem ser obtidas diretamente da polpa química, se observa um expressivo aumento no interesse por esses materiais. A modificação superficial tanto das fibras (polpa) como das microfibrilas é de grande interesse, pois podem permitir a ampliação do uso desses materiais uma vez que suas propriedades poderiam ser modificadas. O desenvolvimento de métodos de modificação em meio aquoso da celulose em suspensão é de grande interesse em especial se realizado com o uso de agentes sustentáveis em contexto de química verde. Este trabalho visou a modificação da polpa de celulose por duas vias: química e física, realizadas inteiramente em meio aquoso e utilizando materiais de caráter renováveis. A modificação física da fibra de celulose \"never-dried\" foi feita pelo método de auto-montagem (Layer-by-Layer) com o par de polieletrólito quitosana / carboximetilcelulose (CH / CMC) em meio aquoso. Fibras modificadas foram submetidas à analise morfológica (MEV e microscopia confocal no método de absorção de dois fótons e EDS), propriedade mecânica (módulo elástico e limite de resistência à tração) e potencial zeta. O complexo CH / CMC depositado sobre as fibras apresentou uma espessura de aproximadamente 50 nm por camada e um aumento de aproximadamente 170% no limite de resistência a tração das folhas produzidos a partir das fibras, demonstrando uma forte interação fibra/polieletrólitos. Através da técnica de absorção de dois fótons foi possível identificar a deposição das camadas fora e dentro das fibras sem o uso de cromóforo. A modificação química da nanofibra de celulose foi feita pela enxertia de grupamentos furânicos na superfície da fibra, oxidada. Em seguida de uma reação com uma bismaleimida através da reação de \"click\" de Diels-Alder em meio aquoso. Os géis foram caracterizados por meio da técnica de calorimetria diferencial de varredura (DSC) e viscosimetria, com os quais pode-se verificar o efeito da termorreversibilidade uma vez que a 65°C ocorre gelificação do sistema e 95°C ocorre reversão do gel como resultado das reações DA e retro Diels-Alder. As modificações das fibras e nanofibras de celulose em meio aquoso foram bem-sucedidas, o que pode impulsionar o uso da polpa de celulose em novas aplicações originais como artefatos de papel fortes e géis biocompatíveis, visando a estratégia green chemistry. / Cellulose is the main polymer derived from renewable sources of industrial use, in terms of volume and number of applications. Cellulose is marketed in the pulp form, which is a commodity whose main application is the paper industry and derived from pulp, such as its ethers and esters. The advent of nanocelluloses, which can be obtained directly from the chemical pulp, there is an expressive increase in these materials. The superficial modification in fibers (pulp) and microfibrils is great interest, since they can allow the amplification of the use of these materials since their properties could be modified. The development of methods for modification of cellulose in aqueous suspension is of particular interest especially if carried out with sustainable agents in the context of green chemistry. This work aimed at the modification of the cellulose pulp by two routes: chemistry and physics, performed entirely in aqueous medium and using renewable character materials. The physical modification of the \"never-dried\" cellulose fiber was done by the self-assembly method (Layer-by-Layer) with the polyelectrolyte pair chitosan / carboxymethylcellulose (CH / CMC) in aqueous medium. Modified fibers were subjected to morphological analysis (SEM and confocal microscopy in two-photon absorption technique and EDS), mechanical properties (elastic modulus and tensile strength) and zeta potential. The CH / CMC complex deposited under the fibers had a thickness of approximately 50 nm per layer and an increase of approximately 170% in the tensile strength of the sheets in compare of unmodified fibers sheets, showing a strong interaction between fiber and polyelectrolyte. Through the technique of two-photon adsorption, it was possible to identify the layers deposition outside and inside the fibers without the use of chromophore. The chemical modification of the cellulose nanofiber was made by the grafting of furanic groups on the surface of the oxidized fiber. Following by reaction with a bismaleimide through the \"click\" reaction of Diels-Alder in aqueous medium. The thermoreversible hydrogels were characterized by differential scanning calorimetry (DSC) and viscosimetry, which the effect of thermoreversibility can be verified at 65 °C when the gelation of the system occurs and 95 °C gel reversion occurs because of DA and retro Diels-Alder reactions. Modifications of cellulose fibers and nanofibers in aqueous media have been successful, which may increase the use of cellulose pulp in novel applications such as strong paper artifacts and biocompatible gels, targeting the green chemistry strategy.

Les copolymères à blocs amphiphiles sont des macromolécules composées d'au moins un bloc hydrophile lié chimiquement à un ou plusieurs blocs hydrophobes. En milieu aqueux, ils s'auto-associent pour former des micelles dont les cœurs constitués des blocs hydrophobes sont protégés de l'eau par une couronne constituée des blocs hydrophiles hydratés. La majorité des copolymères à blocs amphiphiles génèrent dans l'eau des micelles " gelées " ne présentant aucun échange de chaînes entre elles. Ceci vient du fait que l'énergie nécessaire pour extraire un bloc hydrophobe du cœur des objets est beaucoup trop importante. Par conséquent, les caractéristiques des micelles sont plus contrôlées cinétiquement que thermodynamiquement. Pour diminuer cette énergie nous avons incorporé des unités hydrophile acide acrylique (AA) dans le bloc hydrophobe de poly(acrylate de n-butyle) (PnBA). L'incorporation de 50% molaire d'unités AA dans le bloc hydrophobe conduit à la formation d'agrégats pH-sensibles dans le cas du dibloc PAA-b-P(AA0.5-stat-nBA0.5) comme montré dans une étude antérieure. Cette thèse a consisté en une analyse quantitative de la dynamique d'auto-association de copolymères dibloc et tribloc amphiphiles à base d'acrylate de n-butyle et d'acide acrylique dont les blocs hydrophobes contiennent 50% d'unités hydrophiles réparties de manière statistique. Les copolymères à blocs ont été synthétisés par polymérisation radicalaire contrôlée par ATRP. L'influence de la concentration, du pH, de la température et de la force ionique sur la structure et les propriétés mécaniques des systèmes auto-assemblés a été systématiquement étudiée. Par diffusion statique de la lumière nous avons montré la présence d'une concentration d'agrégation critique (CAC) au-dessus de laquelle, des micelles de type étoile (dibloc) ou fleur (tribloc) sont formées par auto-association des blocs hydrophobes. A plus fortes concentrations, des interactions répulsives de type volume exclu apparaissent entre les micelles étoiles. Pour les micelles fleurs, à l'inverse des interactions attractives conduisent au pontage des fleurs jusqu'à l'obtention de réseaux tri-dimensionnels au-dessus de la concentration de percolation. Une attraction trop importante entre les fleurs peut même conduire à une séparation de phase à forte force ionique et bas pH. En diffusion dynamique de la lumière, nous avons montré que la formation des réseaux s'accompagnait de l'apparition d'un mode lent dont l'origine a été expliquée par un mouvement balistique d'hétérogénéités relaxées dans les systèmes. La vitesse de relaxation de ces hétérogénéités s'avèrent être dépendantes des propriétés mécaniques des hydrogels. La formation des réseaux et la dynamique d'échange des chaînes ont été étudiées par rhéologie. La viscosité augmente régulièrement avec la concentration jusqu'à la concentration de percolation où une augmentation brusque de la viscosité se produit et un temps de relaxation apparaît. Le temps de vie des ponts a été finement contrôlé et modulé sur plusieurs décades par modification du pH, de la température et de la force ionique. La formation in-situ des hydrogels nous a permis de mettre en évidence un phénomène de vieillissement des réseaux après leur formation avant d'atteindre un état stationnaire. Ce phénomène s'est traduit par une augmentation du temps de relaxation au cours du temps avant d'atteindre une valeur plateau. Ceci nous a également permis de comprendre pourquoi il était possible de générer des réseaux homogènes, par vieillissement, possédant une dynamique extrêmement lente voir nulle.

<p>In the presented work, immunosensors for detection of Aflatoxin B1 based on different immobilization platforms were studied. Synthesis of an electroactive hydrogel was also carried out. Aflatoxins are a group of mycotoxins that have deleterious effects on humans and are produced during fungal infection of plants or plant products. Electrochemical immunosensor for the determination of Aflatoxin B1 (AFB1) was developed with anti-aflatoxin B1 antibody immobilized on Pt electrodes modified with polyaniline (PANi) and polystyrene sulphonic acid (PSSA). Impedimetric analysis shows that the electron transfer resistances of Pt/PANi-PSSA electrode, Pt/PANi-PSSA/AFB1-Ab immunosensor and Pt/PANi-PSSA/AFB1-Ab incubated in BSA were 0.458, 720 and 1066 k&Omega / , respectively. These results indicate that electrochemical impedance spectroscopy (EIS) is a suitable method for monitoring the change in electron-transfer resistance associated with the immobilization of the antibody. Modelling of EIS data gave equivalent circuits which showed that the electron transfer resistance increased from 0.458 k&Omega / for Pt/PANi-PSSA electrode to 1066 k&Omega / for Pt/PANi-PSSA/AFB1-Ab immunosensor, indicating that immobilization of the antibody and incubation in BSA introduced an electron transfer barrier. The AFB1 immunosensor had a detection limit of 0.1 mg/L and a sensitivity of 869.6 k &Omega / L/mg.</p>

Certain hydrogel forming de novo proteins that utilize different crosslinking methods are studied experimentally on a rheometer. The stress reaxation modulus of CRC, a telechelic, triblock protein, is shown to be that of a stretched exponential function with a value of β ≅ 0.5. The insertion of an integrin binding domain and changes in pH within the range 6.5–8.5 are shown not to significantly affect the resulting rheological behavior. A selective chemical crosslinker is used on CRC hydrogel systems and is shown to change the rheological behavior of the system to that of a combination of a chemically and physically crosslinked system. Chemically crosslinked hydrogels composed of W6, a wheat gluten-based protein, demonstrate a storage modulus weakly dependent on the angular frequency that is much greater than the loss modulus, with a modulus concentration dependence of c^9/4.

Certain hydrogel forming de novo proteins that utilize different crosslinking methods are studied experimentally on a rheometer. The stress reaxation modulus of CRC, a telechelic, triblock protein, is shown to be that of a stretched exponential function with a value of β ≅ 0.5. The insertion of an integrin binding domain and changes in pH within the range 6.5–8.5 are shown not to significantly affect the resulting rheological behavior. A selective chemical crosslinker is used on CRC hydrogel systems and is shown to change the rheological behavior of the system to that of a combination of a chemically and physically crosslinked system. Chemically crosslinked hydrogels composed of W6, a wheat gluten-based protein, demonstrate a storage modulus weakly dependent on the angular frequency that is much greater than the loss modulus, with a modulus concentration dependence of c^9/4.

This thesis describes a number of novel experiments contributing to the understanding of protein adsorption from both a fundamental and applied perspective. The first three papers involve the use of the localized surface plasmon resonance of gold nanospheres to measure protein conformational dependencies during heat and acid denaturation. Thermal denaturation of BSA is shown to proceed differently depending on the size of nanosphere to which it is conjugated. Activation energies are extracted for thermal denaturing on nanoparticles. These energies decrease with decreasing radius of curvature. Under pH perturbation in the acid region, the multiple transition states of bulk BSA are suppressed, and only one apparent transition around pH 4 is evident. Smaller spheres (diameter < 20nm) do not exhibit any transition. A significant finding of all three studies is that the state and stability of BSA depends strongly upon local curvature. The last two papers investigate protein adsorption relevant to the biomaterial field. Investigation of protein adsorption to polyHEMA hydrogels is carried out using a quartz crystal microbalance. Single and mixed protein adsorption kinetics for BSA, lysozyme and lactoferrin are extracted and interpreted. Selected commercial cleaning solutions are shown to be no more effective than simple buffer solution. Examination of commercial lenses indicates that the morphology of adsorption is material dependent and that siloxane-based hydrogels only deposit low levels of protein. A unique fibril-like morphology is identified on galyfilcon A. Protein morphology is discussed in terms of bare lens morphology, roughness, and surface composition.

Cytotoxicity of Multi-Purpose Solutions (MPS) is commonly tested on cells using diluted MPS or extracts from MPS soaked contact lenses. There is evidence that lens type will affect uptake and release of compounds contained in MPS. To assess the cytotoxicity of agents contained in MPS that would be released by contact lens, an in vitro “onlay” model was used, whereby MPS soaked silicone hydrogel lenses were directly set onto a confluent monolayer of corneal cells. Chapter 4 describes the impact of MPS released from contact lenses on immortalized human corneal epithelial cells. MPS-soaked lens interactions with cells were characterized by studying cell viability, cell adhesion and caspase assays. In Chapter 5, mechanisms of cell death induced by exposure to MPS from contact lenses were determined through evaluation of apoptotic markers, such as activation of caspase 3 and 9. In Chapter 6, the impact of the physical properties of silicone hydrogel lenses, specifically surface treatments, on cytotoxicity of MPS were investigated. The development of methods for characterizing the release of MPS from lenses, using absorbance spectra, is also described. The results indicate that exposure to contact lenses soaked in Opti-Free Express (OFX) and ReNu not only induces cell death in vitro, but also has an adverse effect on adhesion phenotype, suggesting that the remaining cells may have a compromised epithelial structure. Borate- buffered MPS were found to be more cytotoxic than phosphate-buffered base solutions. Investigation of the mechanisms of cell death revealed that ReNu and OFX induced corneal epithelial cell death in vitro using different pathways, whereby ReNu induced a necrotic pathway while OFX-induced cell death was mediated by the intrinsic pathway of apoptosis. The in vitro model was also able to identify differences between silicone hydrogels with different surface treatments: the different surface treatments and chemistries of silicone hydrogels lens will affect the release profile of MPS and hence their potential cytotoxicity. By investigating the induction of cell death processes by solution-lens combinations in vitro, we aim to prevent potential adverse effects in the cornea, which may ultimately compromise various visual and barrier functions. The findings indicate the wealth of information in vitro cytotoxicity testing can provide when evaluating the toxicological profile of MPS.

This thesis describes a number of novel experiments contributing to the understanding of protein adsorption from both a fundamental and applied perspective. The first three papers involve the use of the localized surface plasmon resonance of gold nanospheres to measure protein conformational dependencies during heat and acid denaturation. Thermal denaturation of BSA is shown to proceed differently depending on the size of nanosphere to which it is conjugated. Activation energies are extracted for thermal denaturing on nanoparticles. These energies decrease with decreasing radius of curvature. Under pH perturbation in the acid region, the multiple transition states of bulk BSA are suppressed, and only one apparent transition around pH 4 is evident. Smaller spheres (diameter < 20nm) do not exhibit any transition. A significant finding of all three studies is that the state and stability of BSA depends strongly upon local curvature. The last two papers investigate protein adsorption relevant to the biomaterial field. Investigation of protein adsorption to polyHEMA hydrogels is carried out using a quartz crystal microbalance. Single and mixed protein adsorption kinetics for BSA, lysozyme and lactoferrin are extracted and interpreted. Selected commercial cleaning solutions are shown to be no more effective than simple buffer solution. Examination of commercial lenses indicates that the morphology of adsorption is material dependent and that siloxane-based hydrogels only deposit low levels of protein. A unique fibril-like morphology is identified on galyfilcon A. Protein morphology is discussed in terms of bare lens morphology, roughness, and surface composition.