The aim of this study was to investigate the molecular interactions of the anti-cancer drug Doxorubicin (DOX) with poly(methacrylic acid) grafted starch nanoparticles (PMAA-g-St). In order to fully understand the DOX/PMAA-g-St system, we conducted in-depth studies on DOX dimer dissociation and DOX/PMAA-g-St binding interactions using various techniques such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and fluorescence and absorption spectroscopy. Based on our experimental results, we developed a quantitative thermodynamic model with relevant parameters such as dissociation constant, Kd, as well as enthalpy of binding, ΔH, in order to explain DOX/PMAA-g-St interactions. In addition, we also studied the effect of environmental factors such as pH and NaCl on DOX self-association and DOX/PMAA-g-St complex formation. In conclusion, the combination of results obtained from various techniques as well as the multispecies equilibrium model, enables us to interpret quantitatively the data of drug loading onto and release from polymeric nanoparticles.

La diffusion Raman exaltée de surface (SERS) est utilisée pour la mise au point d’un biocapteur capable de détecter des pesticides dans l’eau, en se basant sur le suivi de l’activité enzymatique de l’Acétylcholinestérase (ACHE). Les nanoparticules d’or sont utilisées comme substrats SERS actifs. Le signal Raman exalté de l’analyte est optimisé en testant plusieurs types de nanoparticules.Le Raman SERS a permis la détection directe du Paraoxon (PO) et du carbaryl (CA) et la possibilité de suivi de l’activité de l’ACHE. En absence d'inhibiteurs, la molécule d’acétylcholine (ATC) est transformée en acide acétique et en choline par l’enzyme ACHE. La mesure de l’activité de l’ACHE repose sur le suivi des concentrations en ATC car sa transformation est inhibée en présence de pesticides. Il a été ainsi possible d’établir une relation linéaire entre la concentration de pesticides et l’exaltation du signal Raman de l’ATC non transformé. La méthode a permis la détection du PO et du CA, avec une limite de détection beaucoup plus faible que la détection directe. Ce biocapteur basé sur l’activité de l’ACHE a ensuite été utilisé pour l'évaluation d’autres polluants (inhibiteurs d’ACHE) comme les additifs contenus dans les plastiques notamment. Enfin, nous avons développé une seconde approche qui consistait à mesurer l’activité de l’ACHE en utilisant la diffusion dynamique de la lumière. En effet, nous avons montré que les paramètres physicochimiques (agrégation) des AuNPs en contact avec certaines molécules, sont fortement influencés par l’activité enzymatique de l’ACHE. C’est ce phénomène d’instabilité qui nous a permis de distinguer entre les deux cas : absence et présence de PO. / Surface-enhanced Raman scattering (SERS) was used to develop a biosensor for the detection of pesticides through the monitoring of the enzymatic activity of acetylcholinesterase (ACHE). Gold nanoparticles (AuNPs) were used as an active SERS substrate. The enhanced Raman signal of the analyte is optimized by testing several types of nanoparticles. Raman SERS allowed the direct detection of Paraoxon (PO) and carbaryl (CA) pesticides and the possibility of follow-up of the activity of the ACHE. In the absence of inhibitors, the acetylcholine (ATC) is transformed into acetic acid and choline by the enzyme ACHE. The measurement of ACHE activity is performed through the monitoring of ATC concentrations because its transformation is inhibited in the presence of pesticides. Results showed a linear correlation between the concentration of pesticides and the SERS signal of the untransformed ATC. The method was optimized for the quantification of paraoxon and carbaryl with a limit of quantification much lower than the one obtained with a direct detection. Their identification was also possible using chemometrics. This biosensors, based on the ACHE activities, was applied to the evaluation of emergent pollutants: additives of commercial polymers. Our results suggested that most of the tested polymers contained molecules that act as inhibitors of the ACHE. Finally, we propose another very simple approach to measure the ACHE activity using dynamic light scattering measurements. We found that the physicochemical parameters (aggregation) of AuNPs were strongly influenced by the enzymatic activity of ACHE when in contact with specified molecules, allowing to detect the presence of PO.

A proteína P21 do Trypanosoma cruzi participa no processo de infecção da célula hospedeira, desse modo é de grande importância: elucidar as vias de sinalização induzidas pela proteína, bem como caracterizar a nível molecular e estrutural a P21. O que vai auxiliar no entendimento da função biológica da P21 e sua participação no processo de infecção. A P21 recombinante é expressa Escherichia coli em sua maioria na fração insolúvel. Visando aumento de proteína na fração solúvel, foi realizada a clonagem do gene da P21 em vetor pSMT3, bem como testes de expressão subsequentes em diferentes cepas de expressão de E. coli, em vetor pET-28 e pSMT3 e variadas condições de expressão e lise celular. Desse modo obtiveram-se as condições que permitissem uma maior concentração da P21 na fração solúvel. A expressão foi realizada no vetor pET-28, cepa BL21, a 37°C com meio 2xYT a 0.5 mM de IPTG, utilizando a técnica de sonicação como lise. A P21 foi purificada em cromatografia de afinidade e posteriormente em coluna de exclusão molecular. Foram realizados estudos de modelagem por homologia levaram a elaborar a hipótese de que a P21 tem a função de inibidor de serinoprotease do tipo kunitz. Posteriormente essa hipótese foi confirmada com ensaios de avaliação da atividade inibitória da P21 frente à tripsina, quimiotripsina e elastase neutrofílica, o qual a P21 mostrou capaz de inibir a elastase neutrofílica. Estudos com espalhamento dinâmico da luz (DLS) revelaram que as amostras testadas de P21 contém diferentes concentrações de agregados de alto peso molecular em todos os pHs avaliados. Outras medidas foram realizadas para avaliar o estado de agregação da P21 de acordo com a temperatura e verificou-se que entre 32-52 °C, a proteína apresenta menor raio hidrodinâmico, indicando menor agregação nesse intervalo. Estudos de dicroísmo circular revelaram que a P21 apresenta por volta de 20% de α hélice, 32% de folha-β, 22% de volta e 23 % estrutura randômica. De acordo com a curva de desnaturação referente ao espectro de CD obtido, a P21 se mostra desnaturada a partir de 64°C. / The Trypanosoma cruzi protein P21 participates in the host cell infection process, but its specific function is poorly described. Thus it is important to elucidate the signaling pathways induced by the protein and characterize the P21 at the structural and molecular levels, as a contribution towards the understanding of the P21 biological function and its role in the infection process. The Escherichia coli recombinant P21 is expressed mostly in the insoluble fraction. Aiming to increase protein in the soluble fraction, we performed the cloning of the P21 gene in pSMT3 vector and subsequent expression tests in different expression strains of E. coli in pET-28 and pSMT3 vectors and varied expression conditions and cell lysis. Thus we obtained conditions that allow a greater concentration of the P21 in the soluble fraction. The expression vector was performed using vector pET-28, in Bl21 strain at 37°C in 2xYT culture medium with 0.5 mM IPTG, using the sonication technique in cell lysis. The recombinant P21 was purified by Ni affinity chromatography and subsequently a molecular exclusion column. We performed homology modeling studies which led to assume that P21 can be a serinprotease inhibitor of Kunitz type. Furthermore, this hypothesis was confirmed in the experiments testing the P21 inhibitory activity against the trypsin, chymotrypsin and elastase. We found the P21 exclusively inhibit neutrophil elastase. Studies using dynamic light scattering (DLS) revealed that the samples containing P21 contained large molecular weigth aggregates in different concentrations at all evaluated pHs. Others measurements were performed to assess the P21 aggregation state according to the temperature and we found that between 32-52 °C the protein had a smaller hydrodynamic radius, indicating less aggregation in this range. Circular dichroism (CD) studies revealed that P21 has about 20% α-helix, 32% β, -sheet, 22% turn and 23% of random structure. According to the denaturation curve for the CD spectrum obtained, the P21 was denatured from 64°C.

A β2GPI é uma glicoproteína que circula livre ou em lipoproteínas. Adsorve em superfícies negativas, tem efeitos anticoagulantes e moduladores da inflamação. Neste trabalho caracterizou-se a interação de moléculas da proteína entre si e com superfícies lipídicas. O SDS-PAGE e o imunoblot da β2GPI identificaram monômeros, dímeros e oligômeros. Técnicas de espalhamento de luz (estático, dinâmico, Raios-X) revelaram que β2GPI forma soluções aquosas de macroagregados anisométricos. Seca sobre mica, a β2GPI forma elipsóides prolatos, observáveis por microscopia de força atômica. A forma e o tamanho das partículas dependeram de pH e concentração de proteína. A interação entre a β2GPI e superfícies lipídicas foi estudada por microgravimetria. Superfícies de fosfatidilcolina pura adsorveram β2GPI mais fracamente do que ouro ou misturas com fosfatidilserina. A adsorção de lipoproteínas artificiais à β2GPI foi dependente de pH. Sugere-se que os efeitos biológicos da β2GPI sejam mediados por interações proteína-proteína e proteína-lipídio, e dependentes de pH. / β2GPI is a blood glycoprotein circulating free or bound to lipoproteins. β2GPI adsorbs to negatively charged surfaces, acting as anticoagulant and modulator of inflammation. This work was designed to characterize the interaction between protein molecules and among protein molecules and lipid surfaces. The β2GPI SDS-PAGE and immunoblot revealed monomer, dimer and oligomers. Light scattering methods (static, dynamic and X-ray) showed that β2GPI generates aqueous solutions of anisometric macroaggregates. Atomic force microscopy showed that β2GPI dried on muscovite surfaces assembles itself in prolate ellipsoids. The particle shape and size depended both on the pH and protein concentration. The interaction among β2GPI and lipid surfaces was studied by microgravimetry. β2GPI adsorption to pure phosphatidylcholine was weaker than to gold or phosphatidylcholine/phosphatidylserine surfaces. Artificial lipoproteins adsorbed to β2GPI in a pH dependent manner. Results suggest that β2GPI biological effects could be mediated by protein-protein interactions and lipid surface binding, and pH dependent.

Este estudo reúne os principais resultados de fluorescência estática e resolvida no tempo sobre a interação da porfirina meso-tetrakis (4-metilpiridil), na forma de base livre (TMPyP) e complexada com Zn2+ (ZnTMPyP), com vesículas de fosfolipídio. Adicionalmente foram utilizadas as técnicas de potencial zeta e espalhamento de luz dinâmico (DLS, do inglês \"dynamic light scattering\"). As vesículas de fosfolipídio foram formadas por dois conjuntos de fosfolipídios: saturados e insaturados. O primeiro grupo é formado pela mistura dos fosfolipídios zwiteriônico 1,2-dipalmitoil-sn-glicero-3-fosfocolina (DPPC) e aniônico 1,2-dipalmitoil-sn-3-glicero-[fosfo-rac-(1- glicerol)] (DPPG), a diferentes razões molares. Os estudos utilizando tais sistemas foram realizados abaixo (25oC) e acima (50oC) da temperatura de transição de fase gel-líquido cristalino destes fosfolipídios (~ 41oC). O segundo grupo é formado pela mistura dos fosfolipídios zwiteriônico 1-palmitoil-2-oleoil-sn-glicero-3-fosfocolina (POPC) e aniônico 1-palmitoil-2-oleoil-sn-glicero-3-fosfo(1-rac-glicerol) (POPG). Como a transição de fase destes dois fosfolipídios ocorre a temperaturas negativas, todos os experimentos foram realizados a 25oC (vesículas no estado líquido cristalino). Todos os sistemas foram preparados através do método de extrusão para a obtenção de vesículas grandes unilamelares (LUV, do inglês \"large unilamellar vesicles\"). As análises dos dados de fluorescência indicaram que a atração eletrostática entre os substituíntes (positivamente carregados) das porfirinas TMPyP e ZnTMPyP e o grupo das cabeças polares (camada de Stern) das vesículas de fosfolipídio desempenha um papel fundamental na associação da porfirina. A distribuição da TMPyP entre o meio aquoso (tampão) e as vesículas de fosfolipídio foi evidenciada pela coexistência de um tempo de vida de fluorescência mais curto (~ 5 ns) e outro mais longo (~ 9-11 ns), respectivamente. Baseado nos valores das constantes pré-exponenciais, estudos adicionais mostram que a distribuição acima é afetada pela concentração de sal na solução. Os resultados de supressão de fluorescência com o supressor iodeto de potássio (KI) indicaram que ambas porfirinas estão localizadas, preferencialmente, na região da camada de Stern. Este resultado foi confirmado pelos estudos de potencial zeta e de DLS, os quais mostraram uma neutralização parcial das cargas negativas na superfície das vesículas devido à associação da porfirina. / This study presents time-resolved and steady-state fluorescence results on the interaction of the meso-tetrakis (4-methylpyridil) porphyrin, in free base form (TMPyP), and complexed with Zn2+ (ZnTMPyP), with phospholipid vesicles. Zeta potential and dynamic light scattering (DLS) techniques were also used. Phospholipid vesicles were formed by two phospholipid systems: saturated and unsaturated. The first group is a mixture of zwiterionic dipalmitoyl-sn-glycero-3-phosphocoline (DPPC) and anionic 1,2-dipalmitoyl-sn-3-glycero-[phospho-rac-(1-glycerol)] (DPPG) phospholipids, at different molar ratios. Measurements were performed bellow (25oC) and above (50oC) the main gel-liquid crystalline phase transition temperature (~ 41oC). The second group is constituted by a mixture of zwiterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocoline (POPC) and anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho(1-rac-glycerol) (POPG) phospholipids, at different molar ratios. Since the gel-liquid crystalline phase transition of these phospholipids occurs at a very low temperature value, all experiments were performed at 25oC (liquid crystalline state vesicles). All phospholipid systems were prepared through the extrusion method in order to obtain large unilamellar vesicles (LUV). The fluorescence data analyses indicated that the electrostatic attraction between the porphyrin substituents (positively charged) and the polar head groups of the phospholipid vesicles (Stern layer) plays an important role on the porphyrin binding affinity. The distribution of TMPyP between the aqueous medium (buffer) and the phospholipid vesicles was characterized by the coexistence of a shorter (~ 5 ns) and a longer (~ 9-11 ns) fluorescence lifetimes, respectively. Based on the pre- exponential values, additional time-resolved experiments showed a redistribution of the porphyrin at increasing salt concentration. The quenching studies, using potassium iodide (KI) as quencher, indicated that both TMPyP and ZnTMPyP are preferentially located at the Stern layer region. This result is in agreement with the zeta potential and DLS findings, which demonstrated a partial neutralization of the negative charges at the vesicle surface due to the porphyrin association.

La poudre de boehmite, précurseur de l’alumine utilisée pour la production de supports catalytiques variés, est produite suite à une étape de séchage par atomisation. Cet oxyhydroxyde d’aluminium est composé de particules anisotropes chargées. Ces dernières années, il a été ont montré que les propriétés physico-chimiques des suspensions avaient une influence sur les caractéristiques des poudres. La morphologie des grains (sphère creuse, tore…) ainsi que les propriétés des poudres (dispersibilité, résistance mécanique…) peuvent être modifiées en jouant sur les caractéristiques des suspensions.Ce travail de thèse porte sur la compréhension des liens entre les propriétés physico-chimiques et rhéologiques de suspensions de deux boehmites industrielles et les propriétés des grains obtenus après séchage. Dans une première partie, nous avons caractérisé les particules en suspension de ces deux boehmites grâce à une approche multi-technique (SAXS, DLS, MET). Une étude rhéologique des suspensions obtenues par stress osmotique a ensuite permis de construire précisément le diagramme de phase de ces deux boehmites dans le plan force ionique – fraction volumique. La diffusion des rayons X aux petits angles et la diffusion dynamique de la lumière ont été utilisées pour déterminer l’organisation structurale des suspensions. Enfin, des expériences de séchage suivies optiquement et par micro-tomographie X ont été réalisées sur des suspensions de boehmite afin d’étudier l’impact de la concentration et de la force ionique sur l’évolution de la goutte au cours du séchage. / In the catalyst supports industry, one important step of alumina powder production is the spray-drying of boehmite suspensions. This aluminium oxyhydroxyde is often used as precursor for various types of alumina catalyst supports. Boehmite is composed of anisotropic particles bearing an electric charge. In the past decade, it has been shown that the properties of the dry powder depend not only on the drying conditions but on physico-chemical properties of the sprayed suspensions. For instance, different grains morphologies (doughnut-shaped grains, hollow spheres,…) as well as various dry grains properties (textural properties, mechanical resistance,…) may be obtained by tuning the physico-chemical properties of the suspension.This study focus on the understanding of the links between the physico-chemical properties of suspensions of two industrial boehmites and the characteristics of the final dry grain. Since these two boehmites were not well-known, the first step of the study was to characterize boehmite particles present in suspension thanks to a multi-technical approach. A rheological study was performed on boehmite suspensions obtained thanks to osmotic stress to build precisely the phase diagrams of the both boehmites according to the system of ionic strength vs. volume fraction. Small angle X ray scattering and dynamic light scattering were used to investigate the existence of an orientational order of boehmite particles in suspension. Finally, drying experiments of boehmite suspensions were conducted on an optical set-up and on fast micro-tomography X, to examine the impact of both concentration and ionic strength on the evolution of the droplet during drying.

This thesis deals with the study of preparation and characterization of hyaluronan-micelle aggregates. The theoretical part deals with drug delivery systems, characterization of used materials and methods especially fluorescence spectroscopy, dynamic light scattering and turbidimetry. Methods of determination of measured data are summarized in the experimental section. The result section is divided into two subsections dedicated to different preparation methods of hyaluronan-surfactant complexes. Induced aggregates of hyaluronan with Septonex are characterized in terms of their origin and stability, and the results are compared with previously studied surfactants CTAB. In the second part are discussed so-called decorated micelles, their formation, properties and stability.

This diploma thesis deals with the preparation and characterization of negatively charged catanionic vesicular systems and their combination with selected polycations. The catanionic vesicular system was prepared by mixing of two oppositely charged surfactants SDS and CTAB. The negative charge as well as the stability of the vesicular system was provided by the incorporation of phosphatidic acid. Polycations, DEAE and TMC, have been selected for use in a pharmaceutical applications. Characterization of the prepared systems was performed by measuring DLS and ELS. The results indicate that we were able to prepare stable negatively charged vesicles that were eligible to non-covalently interact with selected polycations.

This master thesis deals with study of chitosan-lignohumate, chitosan-polystyrenesulfonate, chitosan-alginate and chitosan-carrageenan polyelectrolyte complexes. The work was motivated by research of finding suitable alternative substance for lignohumate. The molecular weights of substances were characterized using SEC-MALLS. A degree and a character of the interactions between polyelectrolyte were studied by isothermal titration calorimetry and dynamic light scattering method. The calorimetric experiments proved that decreasing concentration of samples causes decreasing of heat flow. The best calorimetric measurements were provided by adding chitosan into polymer solution. The interactions between chitosan and polyanions and influence of mixing order were proved also by measuring intensity of zeta potential, Z-average of particle size and turbidity. New chitosan-based materials have a big potential in agriculture and medicine.

This diploma thesis is focused on the determintaion of viscoelastic properties of agarose hydrogels containing different polyelectrolytes by microrheological and macrorheological techniques. From microrheological techniques the dynamic light scattering was used. Firstly, the influence of different polyelectrolyte volume was studied. Then the effect of variously charged polyelectrolyte and ionic strenght on microrheological properties of agarose hydrogels were determined. Classic rheology was used to compare the results obtained using the DLS microrheology method. Finally, the results from macro- and microrheology were correlated with each other.