The controllable design of magnetic nanocarriers is essential for advanced in vivo applications such as magnetic resonance image-guided therapeutic delivery and alternating magnetic field-induced remote release of drugs. This work describes the fabrication of polymer-stabilized nanoparticles encapsulating imaging and therapeutic agents and delineates relationships among materials parameters and response. The effect of aggregation of magnetic iron oxide nanoparticles in aqueous suspension was characterized using a well-defined core-corona complex comprised of a superparamagnetic magnetite nanoparticle stabilized by terminally-anchored poly(N-isopropylacrylamide) (PNIPAM) corona. The modified Vagberg density distribution model was employed to verify that the complexes were individually dispersed prior to aggregation and was found to accurately predict the intensity-weighted hydrodynamic diameter in water. Aggregation of the complexes was systematically induced by heating the suspension above the lower critical solution temperature (LCST) of the polymer, and substantial increase in the NMR transverse relaxation rates was noted. Controlled clusters of primary iron oxide nanoparticles stabilized by the biodegradable block copolymer, poly(ethylene oxide-b-D,L-lactide) were fabricated by a scalable, rapid precipitation technique using a multi-inlet vortex mixer. Quantitative control over iron oxide loading, up to 40 wt%, was achieved. Correlations between particle parameters and transverse relaxivities were studied within the framework of the analytical models of transverse relaxivity. The experimental relaxivities typically agreed to within 15% with the values predicted using the analytical models and cluster size distributions derived from cryo-transmission electron microscopy. Hydrophilic-core particles assembled using the poly(ethylene oxide-b-acrylate) copolymer and at similar primary nanoparticle sizes and loadings had considerably higher transverse (r2) and longitudinal (r1) relaxivities, with r2s approaching the theoretical limit for ~ 8 nm magnetite. Block copolymer nanoparticles comprised of poly(D,L-lactide) and poly(butylene oxide) cores were utilized to encapsulate the poorly water-soluble antiretroviral drug, ritonavir, at therapeutically-useful loadings. Controlled size distributions were achieved by incorporation of homopolymer additives, poly(L-lactide) or poly(butylene oxide) during the nanoparticle preparation process. Nanoparticles either co-encapsulating a highly hydrophobic polyester poly(oxy-2,2,4,4-tetramethyl-1,3-cyclobutanediyloxy-1,4-cyclohexanedicarbonyl) within the core or possessing crosslinkable groups around the core were also successfully fabricated for potential sustained release of ritonavir from block copolymer carriers. / Ph. D.

La préparation de formulations à libération contrôlée est le domaine des sciences pharmaceutiques qui vise à modifier l’environnement immédiat des principes actifs pour en améliorer l’efficacité et l’innocuité. Cet objectif peut être atteint en modifiant la cinétique de circulation dans le sang ou la distribution dans l’organisme. Le but de ce projet de recherche était d’étudier le profil pharmacocinétique (PK) de différentes formulations liposomales. L’analyse PK, généralement employée pour représenter et prédire les concentrations plasmatiques des médicaments et de leurs métabolites, a été utilisée ici pour caractériser in vivo des formulations sensibles au pH servant à modifier la distribution intracellulaire de principes actifs ainsi que des liposomes destinés au traitement des intoxications médicamenteuses. Dans un premier temps, la PK d’un copolymère sensible au pH, à base de N-isopropylacrylamide (NIPAM) et d’acide méthacrylique (MAA) a été étudiée. Ce dernier, le p(NIPAM-co-MAA) est utilisé dans notre laboratoire pour la fabrication de liposomes sensibles au pH. L’étude de PK conduite sur les profils de concentrations sanguines de différents polymères a défini les caractéristiques influençant la circulation des macromolécules dans l’organisme. La taille des molécules, leur point de trouble ainsi que la présence d’un segment hydrophobe à l’extrémité des chaînes se sont avérés déterminants. Le seuil de filtration glomérulaire du polymère a été évalué à 32 000 g/mol. Finalement, l’analyse PK a permis de s’assurer que les complexes formés par la fixation du polymère à la surface des liposomes restaient stables dans le sang, après injection par voie intraveineuse. Ces données ont établi qu’il était possible de synthétiser un polymère pouvant être adéquatement éliminé par filtration rénale et que les liposomes sensibles au pH préparés avec celui-ci demeuraient intacts dans l’organisme. En second lieu, l’analyse PK a été utilisée dans le développement de liposomes possédant un gradient de pH transmembranaire pour le traitement des intoxications médicamenteuses. Une formulation a été développée et optimisée in vitro pour capturer un médicament modèle, le diltiazem (DTZ). La formulation liposomale s’est avérée 40 fois plus performante que les émulsions lipidiques utilisées en clinique. L’analyse PK des liposomes a permis de confirmer la stabilité de la formulation in vivo et d’analyser l’influence des liposomes sur la circulation plasmatique du DTZ et de son principal métabolite, le desacétyldiltiazem (DAD). Il a été démontré que les liposomes étaient capables de capturer et de séquestrer le principe actif dans la circulation sanguine lorsque celui-ci était administré, par la voie intraveineuse. L’injection des liposomes 2 minutes avant l’administration du DTZ augmentait significativement l’aire sous la courbe du DTZ et du DAD tout en diminuant leur clairance plasmatique et leur volume de distribution. L’effet de ces modifications PK sur l’activité pharmacologique du médicament a ensuite été évalué. Les liposomes ont diminué l’effet hypotenseur du principe actif administré en bolus ou en perfusion sur une période d’une heure. Au cours de ces travaux, l’analyse PK a servi à établir la preuve de concept que des liposomes possédant un gradient de pH transmembranaire pouvaient modifier la PK d’un médicament cardiovasculaire et en diminuer l’activité pharmacologique. Ces résultats serviront de base pour le développement de la formulation destinée au traitement des intoxications médicamenteuses. Ce travail souligne la pertinence d’utiliser l’analyse PK dans la mise au point de vecteurs pharmaceutiques destinés à des applications variées. À ce stade de développement, l’aspect prédictif de l’analyse n’a pas été exploité, mais le côté descriptif a permis de comparer adéquatement diverses formulations et de tirer des conclusions pertinentes quant à leur devenir dans l’organisme. / Drug delivery is the field of pharmaceutical sciences which focuses on altering the immediate environment of drug molecules to improve their efficacy and safety. Drug delivery systems can potentiate the effect of active principles or alleviate their side effects by modifying their circulation profiles and/or biodistribution. The objective of this research project was to investigate the role of pharmacokinetic (PK) analysis in the development of novel drug delivery systems. PK analysis is generally applied to describe and predict the blood concentration profiles of low molecular weight drugs and their metabolites. Nevertheless, it is herein used to characterize the circulation of 2 liposomal formulations: pH-sensitive liposomes designed to alter the intracellular distribution of drugs and liposomes with transmembrane pH gradient for drug detoxification. The first series of experiments were designed to study the circulation kinetics of a pH-sensitive polymer prepared with N-isopropylacrylamide (NIPAM) and methacrylic acid (MAA). The copolymer p(NIPAM-co-MAA) is used in our laboratory to prepare serum-stable, PEGylated, pH-sensitive liposomes. The circulation profiles of polymers with different characteristics were characterized. The parameters which impacted the fate of the macromolecules were the length of the polymer chain, its cloud point and the presence of a hydrophobic anchor at one extremity of the molecule. The glomerular filtration cut-off of the polymer was determined to be around 32,000 g/mol. PK analysis allowed to conclude that the complexes prepared by anchoring the polymer on the surface of the liposomes remained stable in the bloodstream. This data established that pH-sensitive vesicular formulations could be produced using a polymer which could be excreted through renal filtration. It also confirmed that the formulation remained intact in the bloodstream. The second part of this work involved the development of liposomes with a transmembrane pH gradient designed to treat cardiovascular drug intoxications. Liposomes were designed and optimized in vitro to capture a model cardiovascular drug, diltiazem (DTZ). In vitro, the liposome uptake capacity was 40-fold higher than the lipid emulsion used in the clinic. PK analysis was used to verify the stability of the formulation in vivo, and to assess the impact of the liposomes on the plasma concentration of DTZ and its principal active metabolite, deacetyl-diltiazem (DAD). It was shown that the vesicles were able to capture and sequester DTZ and DAD. Injection of liposomes 2 min prior to administration of DTZ significantly increased the area under the plasma-concentration vs. time curve of both DTZ and DAD, while lowering their clearance and volume of distribution. The impact of the changes in PK on the pharmacological effect of the drug was also investigated. Liposomes tempered the hypotensive effect of the drug when the latter was administered via an intravenous bolus or a 1-h perfusion. Throughout this work, PK analysis proved to be an efficient tool to study the ability of transmembrane pH gradient liposomes to alter the blood circulation profiles of a cardiovascular drug, and to reduce its pharmacological effect. This proof of concept establishes firm ground for the further development of this colloidal formulation to treat drug intoxications. This work pointed out the relevance of PK analysis for the development of multi-purpose, colloidal drug delivery systems. At this stage, the predictive nature of the analysis was not exploited, but its descriptive properties allowed objective comparison of the circulation profiles of distinct systems and pertinent conclusions concerning their fate in vivo.

La préparation de formulations à libération contrôlée est le domaine des sciences pharmaceutiques qui vise à modifier l’environnement immédiat des principes actifs pour en améliorer l’efficacité et l’innocuité. Cet objectif peut être atteint en modifiant la cinétique de circulation dans le sang ou la distribution dans l’organisme. Le but de ce projet de recherche était d’étudier le profil pharmacocinétique (PK) de différentes formulations liposomales. L’analyse PK, généralement employée pour représenter et prédire les concentrations plasmatiques des médicaments et de leurs métabolites, a été utilisée ici pour caractériser in vivo des formulations sensibles au pH servant à modifier la distribution intracellulaire de principes actifs ainsi que des liposomes destinés au traitement des intoxications médicamenteuses. Dans un premier temps, la PK d’un copolymère sensible au pH, à base de N-isopropylacrylamide (NIPAM) et d’acide méthacrylique (MAA) a été étudiée. Ce dernier, le p(NIPAM-co-MAA) est utilisé dans notre laboratoire pour la fabrication de liposomes sensibles au pH. L’étude de PK conduite sur les profils de concentrations sanguines de différents polymères a défini les caractéristiques influençant la circulation des macromolécules dans l’organisme. La taille des molécules, leur point de trouble ainsi que la présence d’un segment hydrophobe à l’extrémité des chaînes se sont avérés déterminants. Le seuil de filtration glomérulaire du polymère a été évalué à 32 000 g/mol. Finalement, l’analyse PK a permis de s’assurer que les complexes formés par la fixation du polymère à la surface des liposomes restaient stables dans le sang, après injection par voie intraveineuse. Ces données ont établi qu’il était possible de synthétiser un polymère pouvant être adéquatement éliminé par filtration rénale et que les liposomes sensibles au pH préparés avec celui-ci demeuraient intacts dans l’organisme. En second lieu, l’analyse PK a été utilisée dans le développement de liposomes possédant un gradient de pH transmembranaire pour le traitement des intoxications médicamenteuses. Une formulation a été développée et optimisée in vitro pour capturer un médicament modèle, le diltiazem (DTZ). La formulation liposomale s’est avérée 40 fois plus performante que les émulsions lipidiques utilisées en clinique. L’analyse PK des liposomes a permis de confirmer la stabilité de la formulation in vivo et d’analyser l’influence des liposomes sur la circulation plasmatique du DTZ et de son principal métabolite, le desacétyldiltiazem (DAD). Il a été démontré que les liposomes étaient capables de capturer et de séquestrer le principe actif dans la circulation sanguine lorsque celui-ci était administré, par la voie intraveineuse. L’injection des liposomes 2 minutes avant l’administration du DTZ augmentait significativement l’aire sous la courbe du DTZ et du DAD tout en diminuant leur clairance plasmatique et leur volume de distribution. L’effet de ces modifications PK sur l’activité pharmacologique du médicament a ensuite été évalué. Les liposomes ont diminué l’effet hypotenseur du principe actif administré en bolus ou en perfusion sur une période d’une heure. Au cours de ces travaux, l’analyse PK a servi à établir la preuve de concept que des liposomes possédant un gradient de pH transmembranaire pouvaient modifier la PK d’un médicament cardiovasculaire et en diminuer l’activité pharmacologique. Ces résultats serviront de base pour le développement de la formulation destinée au traitement des intoxications médicamenteuses. Ce travail souligne la pertinence d’utiliser l’analyse PK dans la mise au point de vecteurs pharmaceutiques destinés à des applications variées. À ce stade de développement, l’aspect prédictif de l’analyse n’a pas été exploité, mais le côté descriptif a permis de comparer adéquatement diverses formulations et de tirer des conclusions pertinentes quant à leur devenir dans l’organisme. / Drug delivery is the field of pharmaceutical sciences which focuses on altering the immediate environment of drug molecules to improve their efficacy and safety. Drug delivery systems can potentiate the effect of active principles or alleviate their side effects by modifying their circulation profiles and/or biodistribution. The objective of this research project was to investigate the role of pharmacokinetic (PK) analysis in the development of novel drug delivery systems. PK analysis is generally applied to describe and predict the blood concentration profiles of low molecular weight drugs and their metabolites. Nevertheless, it is herein used to characterize the circulation of 2 liposomal formulations: pH-sensitive liposomes designed to alter the intracellular distribution of drugs and liposomes with transmembrane pH gradient for drug detoxification. The first series of experiments were designed to study the circulation kinetics of a pH-sensitive polymer prepared with N-isopropylacrylamide (NIPAM) and methacrylic acid (MAA). The copolymer p(NIPAM-co-MAA) is used in our laboratory to prepare serum-stable, PEGylated, pH-sensitive liposomes. The circulation profiles of polymers with different characteristics were characterized. The parameters which impacted the fate of the macromolecules were the length of the polymer chain, its cloud point and the presence of a hydrophobic anchor at one extremity of the molecule. The glomerular filtration cut-off of the polymer was determined to be around 32,000 g/mol. PK analysis allowed to conclude that the complexes prepared by anchoring the polymer on the surface of the liposomes remained stable in the bloodstream. This data established that pH-sensitive vesicular formulations could be produced using a polymer which could be excreted through renal filtration. It also confirmed that the formulation remained intact in the bloodstream. The second part of this work involved the development of liposomes with a transmembrane pH gradient designed to treat cardiovascular drug intoxications. Liposomes were designed and optimized in vitro to capture a model cardiovascular drug, diltiazem (DTZ). In vitro, the liposome uptake capacity was 40-fold higher than the lipid emulsion used in the clinic. PK analysis was used to verify the stability of the formulation in vivo, and to assess the impact of the liposomes on the plasma concentration of DTZ and its principal active metabolite, deacetyl-diltiazem (DAD). It was shown that the vesicles were able to capture and sequester DTZ and DAD. Injection of liposomes 2 min prior to administration of DTZ significantly increased the area under the plasma-concentration vs. time curve of both DTZ and DAD, while lowering their clearance and volume of distribution. The impact of the changes in PK on the pharmacological effect of the drug was also investigated. Liposomes tempered the hypotensive effect of the drug when the latter was administered via an intravenous bolus or a 1-h perfusion. Throughout this work, PK analysis proved to be an efficient tool to study the ability of transmembrane pH gradient liposomes to alter the blood circulation profiles of a cardiovascular drug, and to reduce its pharmacological effect. This proof of concept establishes firm ground for the further development of this colloidal formulation to treat drug intoxications. This work pointed out the relevance of PK analysis for the development of multi-purpose, colloidal drug delivery systems. At this stage, the predictive nature of the analysis was not exploited, but its descriptive properties allowed objective comparison of the circulation profiles of distinct systems and pertinent conclusions concerning their fate in vivo.

Here, we report on a new temperature responsive polymer brush system with a terminal “click” functionality. Bifunctionalized poly(N-isopropylacrylamide) (PNiPAAm) with distinct functional end groups was synthesized by atom transfer radical polymerization (ATRP) and grafted to a modified silicon substrate. The presence of the active terminal alkyne functionality is validated using an azide-modified rhodamine B (N3-RhB) via copper(I) catalyzed alkyne–azide cycloaddition (CuAAC). The optical properties and swelling dynamics of an N3-RhB modified PNiPAAm brush are analyzed in dry state and in situ by VIS-spectroscopic ellipsometry (SE). The best-fit results are obtained using a Gaussian oscillator model and are confirmed by UV/VIS-spectroscopy. We observed evidence of interactions between the aromatic residues of the dye and the PNiPAAm amide groups, which significantly affect the swelling behavior of the modified polymer brush. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Here, we report on a new temperature responsive polymer brush system with a terminal “click” functionality. Bifunctionalized poly(N-isopropylacrylamide) (PNiPAAm) with distinct functional end groups was synthesized by atom transfer radical polymerization (ATRP) and grafted to a modified silicon substrate. The presence of the active terminal alkyne functionality is validated using an azide-modified rhodamine B (N3-RhB) via copper(I) catalyzed alkyne–azide cycloaddition (CuAAC). The optical properties and swelling dynamics of an N3-RhB modified PNiPAAm brush are analyzed in dry state and in situ by VIS-spectroscopic ellipsometry (SE). The best-fit results are obtained using a Gaussian oscillator model and are confirmed by UV/VIS-spectroscopy. We observed evidence of interactions between the aromatic residues of the dye and the PNiPAAm amide groups, which significantly affect the swelling behavior of the modified polymer brush. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Made available in DSpace on 2014-12-17T15:42:31Z (GMT). No. of bitstreams: 1 BrunaVL_TESE.pdf: 4965695 bytes, checksum: f511eb063b5cd567f364bc0ec9385727 (MD5) Previous issue date: 2014-05-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Sustainable development is a major challenge in the oil industry and has aroused growing interest in research to obtain materials from renewable sources. Carboxymethylcellulose (CMC) is a polysaccharide derived from cellulose and becomes attractive because it is water-soluble, renewable, biodegradable and inexpensive, as well as may be chemically modified to gain new properties. Among the derivatives of carboxymethylcellulose, systems have been developed to induce stimuli-responsive properties and extend the applicability of multiple-responsive materials. Although these new materials have been the subject of study, understanding of their physicochemical properties, such as viscosity, solubility and particle size as a function of pH and temperature, is still very limited. This study describes systems of physical blends and copolymers based on carboxymethylcellulose and poly (N-isopropylacrylamide) (PNIPAM), with different feed percentage compositions of the reaction (25CMC, 50CMC e 75CMC), in aqueous solution. The chemical structure of the polymers was investigated by infrared and CHN elementary analysis. The physical blends were analyzed by rheology and the copolymers by UV-visible spectroscopy, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential. CMC and copolymer were assessed as scale inhibitors of calcium carbonate (CaCO3) using dynamic tube blocking tests and chemical compatibility tests, as well as scanning electron microscopy (SEM). Thermothickening behavior was observed for the 50 % CMC_50 % PNIPAM and 25 % CMC_75 % PNIPAM physical blends in aqueous solution at concentrations of 6 and 2 g/L, respectively, depending on polymer concentration and composition. For the copolymers, the increase in temperature and amount of PNIPAM favored polymer-polymer interactions through hydrophobic groups, resulting in increased turbidity of polymer solutions. Particle size decreased with the rise in copolymer PNIPAM content as a function of pH (3-12), at 25 ?C. Larger amounts of CMC result in a stronger effect of pH on particle size, indicating pH-responsive behavior. Thus, 25CMC was not affected by the change in pH, exhibiting similar behavior to PNIPAM. In addition, the presence of acidic or basic additives influenced particle size, which was smaller in the presence of the additives than in distilled water. The results of zeta potential also showed greater variation for polymers in distilled water than in the presence of acids and bases. The lower critical solution temperature (LCST) of PNIPAM determined by DLS corroborated the value obtained by UV-visible spectroscopy. SAXS data for PNIPAM and 50CMC indicated phase transition when the temperature increased from 32 to 34 ?C. A reduction in or absence of electrostatic properties was observed as a function of increased PNIPAM in copolymer composition. Assessment of samples as scale inhibitors showed that CMC performed better than the copolymers. This was attributed to the higher charge density present in CMC. The SEM micrographs confirmed morphological changes in the CaCO3 crystals, demonstrating the scale inhibiting potential of these polymers / O desenvolvimento sustent?vel ? um dos principais desafios da ind?stria do petr?leo, que tem despertado crescente interesse por pesquisas para obten??o de novos materiais provenientes de fontes renov?veis. A carboximetilcelulose (CMC) ? um polissacar?deo derivado da celulose, que se destaca por ser sol?vel em ?gua, renov?vel, biodegrad?vel, de baixo custo e por apresentar possibilidades de modifica??es em sua estrutura qu?mica. Dentre os derivados de carboximetilcelulose, alguns sistemas t?m sido desenvolvidos para induzir propriedades est?mulos-responsivos e ampliar a aplicabilidade desses materiais multirresponsivos. Embora esses novos materiais sejam atualmente objeto de estudo, a compreens?o de suas propriedades f?sico-qu?micas, tais como viscosidade, solubilidade e tamanho de part?culas em fun??o do pH e temperatura ainda ? muito limitada. Esta tese descreve sistemas de misturas f?sicas e copol?meros ? base de carboximetilcelulose e poli (Nisopropilacrilamida) (PNIPAM) com diferentes composi??es percentuais de alimenta??o reacional (25CMC, 50CMC e 75CMC), em solu??o aquosa. A estrutura qu?mica dos pol?meros foi investigada por infravermelho e an?lise elementar CHN. As misturas f?sicas foram analisadas por reologia e os copol?meros foram analisados por UV-vis?vel, espalhamento de raios-X a baixos ?ngulos (SAXS), espalhamento de luz din?mico (DLS) e potencial zeta. CMC e copol?mero foram avaliados como inibidores de incrusta??o de carbonato de c?lcio (CaCO3) usando os testes de compatibilidade qu?mica e precipita??o din?mica em capilar, assim como a microscopia eletr?nica de varredura (MEV). As misturas f?sicas 50% CMC_50% PNIPAM e 25% CMC_75% PNIPAM em solu??o aquosa, nas concentra??es de 6 e 2 g/L, respectivamente, apresentaram comportamento termoviscosificante dependente da concentra??o de pol?mero e da composi??o. Para os copol?meros, o aumento da quantidade de PNIPAM e da temperatura favoreceu as intera??es pol?mero-pol?mero atrav?s dos grupos hidrof?bicos, resultando no aumento da turbidez das solu??es polim?ricas. O tamanho das part?culas diminuiu com o aumento do teor de PNIPAM na composi??o dos copol?meros em fun??o do pH (3-12), a 25 ?C. Maiores quantidades de CMC resultaram em um efeito mais forte do pH nos tamanhos das part?culas, exibindo um comportamento pH-responsivo. Assim, 25CMC n?o foi afetada pela mudan?a de pH, apresentando comportamento similar a PNIPAM. Al?m disso, a presen?a de aditivos de car?ter ?cido ou b?sico influenciou no tamanho das part?culas, que foram menores na presen?a desses aditivos do que em ?gua destilada. Os resultados de potencial zeta tamb?m sofreram maior varia??o para os pol?meros em ?gua destilada do que na presen?a de ?cidos e bases. A temperatura consoluta inferior (LCST) da PNIPAM determinada por DLS foi concordante com o valor obtido por UV-visible. Os dados de SAXS mostraram para PNIPAM e 50CMC uma transi??o de fase quando a temperatura aumentou de 32 para 34 ?C. Um aumento do car?ter polieletrol?tico foi observado em fun??o do aumento da CMC na composi??o dos copol?meros. A avalia??o das amostras como inibidores de incrusta??o mostrou que a CMC apresenta um melhor desempenho do que o copol?mero. Isto foi atribu?do a maior densidade de cargas presente na CMC. As micrografias do MEV confirmaram mudan?as morfol?gicas dos cristais de CaCO3, indicando o potencial desses pol?meros para inibi??o de incrusta??o

Dans un contexte général de valorisation alimentaire et non alimentaire du figuier de barbarie, nous nous sommes intéressés lors de cette étude à l'analyse morphologique de la pelure et des graines du fruit. Les polysaccharides pariétaux des différentes parois ont été isolés, purifiés, et leurs caractérisations ont été réalisées grâce aux méthodes chimiques ainsi qu'à la RMN haute résolution (1H et 13C) et en phase solide (CP/MAS). L'autre aspect du travail décrit la modification chimique des microfibrilles de cellulose. Il traite, dans un premier temps, de l'oxydation de la cellulose par le système TEMPO-NaOCl-NaBr et les conditions opératoires ont été optimisées dans le but de préparer des échantillons d'acide polyglucuroniques. La seconde étape met l'accent sur le greffage, via un couplage peptidique, du poly-N-isopropylacrylamide en vue d'élaborer des biopolymères thermostimulables à partir de la cellulose oxydée.

Diese Arbeit liefert die Grundlage für intelligente Beschichtungen aus kovalent gebundenen Polymeren, sogenannten Polymerbürsten, mit Schichtdicken von wenigen Nanometern. Durch ihre Fähigkeit die Oberflächeneigenschaften je nach Umgebungstemperatur, pH Wert und Zusammensetzung zu ändern, kann die Adsorption von Biomolekülen auf eine einzigartige Art und Weise kontrolliert und reguliert werden. Die zusätzliche Modifizierung der Polymerbürsten mit Elektronenstrahlen ermöglicht die Generierung von Gradienten und erweitert die Anwendungsmöglichkeiten in vielfältigen Bereichen der interdisziplinären Forschung, wie z.B. in Hinblick auf das Lab-on-Chip Design oder die Biomedizin. / Polymer brushes represent sensitive coatings with thicknesses of few nanometres and are interesting for interdisciplinary scientific research, e.g. for intelligent lab-on-chip design or biotechnology. It is demonstrated in this work, that polymer brushes are able to change their surface properties depending on the ambient conditions like solvent quality, temperature or pH value. This sensitivity highly influenced the adsorption of bio molecules. Especially mixed polymer brushes enabled the tuning of the adsorbed amount of various proteins and cells. To create surface gradients or structures in the different polymer brush surfaces, controlled electron beam modification was applied.

Diese Arbeit liefert die Grundlage für intelligente Beschichtungen aus kovalent gebundenen Polymeren, sogenannten Polymerbürsten, mit Schichtdicken von wenigen Nanometern. Durch ihre Fähigkeit die Oberflächeneigenschaften je nach Umgebungstemperatur, pH Wert und Zusammensetzung zu ändern, kann die Adsorption von Biomolekülen auf eine einzigartige Art und Weise kontrolliert und reguliert werden. Die zusätzliche Modifizierung der Polymerbürsten mit Elektronenstrahlen ermöglicht die Generierung von Gradienten und erweitert die Anwendungsmöglichkeiten in vielfältigen Bereichen der interdisziplinären Forschung, wie z.B. in Hinblick auf das Lab-on-Chip Design oder die Biomedizin. / Polymer brushes represent sensitive coatings with thicknesses of few nanometres and are interesting for interdisciplinary scientific research, e.g. for intelligent lab-on-chip design or biotechnology. It is demonstrated in this work, that polymer brushes are able to change their surface properties depending on the ambient conditions like solvent quality, temperature or pH value. This sensitivity highly influenced the adsorption of bio molecules. Especially mixed polymer brushes enabled the tuning of the adsorbed amount of various proteins and cells. To create surface gradients or structures in the different polymer brush surfaces, controlled electron beam modification was applied.

Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophores’ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the air–water–solid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution.