L’objectif de cette thèse est d’étudier expérimentalement les deformations de microcapsules dans un écoulement confiné. Les microcapsules sont composées d’albumine du sérum humain avec des concentrations de 5 à 20 [g/100mL]. Leur taille varie de 50 à 1000 [μm]. Les capsules sont injectées dans des écoulements de Poiseuille produits dans des canaux microfluidiques présentant deux sections différentes : circulaire ou carrée.La mesure des caractéristiques géométriques de microcapsules déformées couplée à des simulations numériques mène à la détermination du module de cisaillement surfacique. Cette caractéristique mécanique augmente fortement tant avec la taille qu’avec la concentration en protéine de la capsule, et plus précisément avec le produit de ces deux paramètres.Le fluide est ensemencé avec des microparticules pour mesurer l’écoulement induit par une capsule dans un capillaire cylindrique par la méthode de la vélocimétrie par suivi de particules. Les zones de recirculation et de perturbation sont alors déduites et comparées avec la simulation numérique d’un objet rigide dans un capillaire et présentant le profil donné par les expériences. Finalement un système original de visualisation optique est consacré à l’observation simultanée de la vue de côté et de la vue de face des capsules pour obtenir sa forme entière. Ceux-ci révèlent l’existence des plis tout autour de la membrane des capsules. Le seuil de formation et l’évolution de ces plis sont étudiés en fonction de la vitesse, de la taille et du confinement, dans des canaux de section circulaire ou carrée. / The objective of this thesis is to study experimentally microcapsule deformations in confined flows. The microcapsules are made of cross-linked proteins, the human serum albumin (HSA) with concentrations from 5 to 20 [g/100mL]. Their size vary from 50 to 1000 [μm]. Capsules are injected in Poiseuille flows generated within microfluidics channels with two different cross sections geometries : circular or square.The measurement of geometrical characteristics of deformed microcapsules coupled with numerical simulations leads to the determination of the surface shear modulus. This mechanical characteristic increases strongly with both the size and the protein concentration of the capsule, and more precisely with the product of these two parameters.The flow is seeded with microparticles to measure the induced flow of a capsule in a cylindrical capillary by particle tracking velocimetry. The recirculation and perturbation zones are then deduced and compared with numerical simulation of a rigid body flowing in a capillary. Finally an original system of optical visualization is dedicated to the simultaneous observation of the side and the front view of the capsules to get its whole shape. These reveal radial wrinkles all around capsules membrane. The formation threshold and the evolution of these wrinkles are studied as function of the capsule velocity and size and the confinement within capillaries with circular or square cross–section.

Made available in DSpace on 2014-12-17T14:13:33Z (GMT). No. of bitstreams: 1 ElquioEO_TESE.pdf: 1649953 bytes, checksum: 1098cd34b1d3e6c9a180949d25fa8185 (MD5) Previous issue date: 2010-06-07 / Universidade Federal do Rio Grande do Norte / The aim of this work was to perform the extraction and characterization of xylan from corn cobs and prepare xylan-based microcapsules. For that purpose, an alkaline extraction of xylan was carried out followed by the polymer characterization regarding its technological properties, such as angle of repose, Hausner factor, density, compressibility and compactability. Also, a low-cost and rapid analytical procedure to identify xylan by means of infrared spectroscopy was studied. Xylan was characterized as a yellowish fine powder with low density and poor flow properties. After the extraction and characterization of the polymer, xylan-based microcapsules were prepared by means of interfacial crosslinking polymerization and their characterization was performed in order to obtain gastroresistant multiparticulate systems. This work involved the most suitable parameters of the preparation of microcapsules as well as the study of the process, scale-up methodology and biological analysis. Magnetic nanoparticles were used as a model system to be encapsulated by the xylan microcapsules. According to the results, xylan-based microcapsules were shown to be resistant to several conditions found along the gastrointestinal tract and they were able to avoid the early degradation of the magnetic nanoparticles / O presente trabalho teve como objetivo a extra??o e caracteriza??o do pol?mero de xilana a partir de res?duos de sabugo de milho e a produ??o de microc?psulas a partir deste pol?mero. O primeiro passo foi a extra??o da xilana em meio alcalino e caracteriza??o deste pol?mero quanto as suas propriedades tecnol?gicas (?ngulo de repouso, fator de Hausner, densidade, compressibilidade e compactabilidade), bem como a elabora??o de uma procedimento r?pido e barato para a identifica??o deste pol?mero atrav?s de espectroscopia de absor??o na regi?o do infravermelho. O pol?mero de xilana foi caracterizado como sendo um p? de cor amarelada de baixa densidade e com propriedades de escoamento pouco favor?veis. Ap?s a obten??o e caracteriza??o do pol?mero, microc?psulas de xilana foram preparadas atrav?s da reticula??o polim?rica interfacial e caracterizadas a fim de se obter sistemas multiparticulados gastroresistentes. O trabalho foi delineado buscando-se os melhores fatores na t?cnica de prepara??o das microc?psulas, assim como o estudo do processo, aumento de escala e avalia??o biol?gica. Nanopart?culas magn?ticas foram utilizadas como sistema modelo a ser encapsulado pelas microc?psulas ? base de xilana. Os resultados obtidos demonstraram que as microc?psulas de xilana s?o resistentes ?s diversas condi??es encontradas ao longo do trato gastrintestinal e foram capazes de evitar a degrada??o pr?via das nanopart?culas magn?ticas in vitro

Made available in DSpace on 2014-12-17T14:16:25Z (GMT). No. of bitstreams: 1 AcariliaES_Dissert_01.pdf: 1640327 bytes, checksum: 9c4568aff953d538d26000691eb0407d (MD5) Previous issue date: 2009-03-10 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Colon-specific drug delivery systems have attracted increasing attention from the pharmaceutical industry due to their ability of treating intestinal bowel diseases (IBD), which represent a public health problem in several countries. In spite of being considered a quite effective molecule for the treatment of IBD, mesalazine (5-ASA) is rapidly absorbed in the upper gastrointestinal tract and its systemic absorption leads to risks of adverse effects. The aim of this work was to develop a microparticulate system based on xylan and Eudragit? S- 100 (ES100) for colon-specific delivery of 5-ASA and evaluate the interaction between the polymers present in the systems. Additionaly, the physicochemical and rheological properties of xylan were also evaluated. Initially, xylan was extracted from corn cobs and characterized regarding the yield and rheological properties. Afterwards, 10 formulations were prepared in different xylan and ES100 weight ratios by spray-drying the polymer solutions in 0.6N NaOH and phosphate buffer pH 7.4. In addition, 3 formulations consisting of xylan microcapsules were produced by interfacial cross-linking polymerization and coated by ES100 by means of spray-drying in different polymer weight ratios of xylan and ES100. The microparticles were characterized regarding yield, morphology, homogeneity, visual aspect, crystallinity and thermal behavior. The polymer interaction was investigated by infrared spectroscopy. The extracted xylan was presented as a very fine and yellowish powder, with mean particle size smaller than 40μm. Regarding the rheological properties of xylan, they demonstrated that this polymer has a poor flow, low density and high cohesiveness. The microparticles obtained were shown to be spherical and aggregates could not be observed. They were found to present amorphous structure and have a very high thermal stability. The yield varied according to the polymer ratios. Moreover, it was confirmed that the interaction between xylan and ES100 occurs only by means of physical aggregation / Sistemas c?lon-espec?ficos t?m atra?do o interesse da ind?stria farmac?utica devido ? possibilidade de tratarem enfermidades, como as doen?as inflamat?rias intestinais (DII), que compreendem um problema de sa?de p?blica em muitos pa?ses. Apesar de ser considerada uma mol?cula bastante eficiente para o tratamento das DII, a mesalazina (5-ASA) ? rapidamente absorvida no trato gastrintestinal superior e sua absor??o sist?mica leva ? incid?ncia de s?rios efeitos adversos. Este trabalho teve como objetivos produzir um sistema polim?rico microparticulado ? base de xilana e Eudragit? S-100 (ES100) para libera??o c?lon-espec?fica de 5-ASA e avaliar a intera??o entre os pol?meros constituintes do sistema, al?m de aprofundar a caracteriza??o f?sico-qu?mica e tecnol?gica da xilana. A xilana foi extra?da a partir de sabugos de milho e caracterizada quanto ao rendimento, granulometria, cristalinidade, propriedades reol?gicas e comportamento t?rmico. Em seguida, 10 formula??es contendo 5-ASA foram preparadas em diferentes propor??es de xilana e ES100 atrav?s da secagem por aspers?o das solu??es polim?ricas com NaOH 0,6N ou tamp?o-fosfato pH 7,4, como solvente. Al?m disso, 3 formula??es constitu?das de microc?psulas de xilana produzidas por reticula??o polim?rica interfacial foram revestidas por ES100 atrav?s de secagem por aspers?o em diferentes propor??es polim?ricas e empregando-se NaOH 0,6N ou tamp?o-fosfato pH 7,4, como solvente. As micropart?culas foram avaliadas quanto ao rendimento, morfologia, granulometria, homogeneidade, aspecto visual, cristalinidade e comportamento t?rmico. A intera??o entre os pol?meros foi investigada atrav?s da espectroscopia na regi?o do infravermelho e de an?lises t?rmicas. A xilana extra?da apresentou-se como um p? muito fino, com tamanho m?dio inferior a 40μm, e com colora??o opaca levemente amarelada. A avalia??o das propriedades reol?gicas da xilana permitiram a caracteriza??o desse pol?mero, em seu estado original de p?, como um material de baixa densidade, fluxo restrito e bastante coesivo. Foram obtidas micropart?culas esf?ricas e sem presen?a de agregados, com estrutura amorfa, em sua maior parte, e bastate est?veis a temperaturas elevadas. Al?m disso, confirmou-se que a intera??o entre xilana e ES100 ocorre apenas por agrega??o f?sica