[pt] Atualmente a crescente demanda do uso de repelentes de insetos tem promovido a pesquisa de produtos mais eficazes e com uma maior durabilidade da ação repelente. O objetivo deste trabalho foi a obtenção de novas nanopartículas com propriedades interfaciais modificadas superficialmente com grupos funcionais catiônicos e polímeros aniônicos, com o intuito de melhorar a estabilidade de emulsões Pickering contendo um princípio ativo, N,N -dimetil-m-toluamida (DEET), comumente utilizado nos repelentes comerciais. A obtenção das nanopartículas incluiu a funcionalização inicial da superfície de nanopartículas de sílica comerciais com grupos amino secundários (R-NH2), seguido da introdução de grupos catiônicos de amônio quaternário (R-NR4 positivo) e posterior complexação eletrostática com polímeros aniônicos (poli(ácido acrílico), PAA, e poli(4-estireno sulfonato de sódio), PSS). As nanopartículas modificadas mostraram boa dispersabilidade em meio aquoso, favorecendo a estabilização de emulsões de tipo óleo em água (O/A). Os melhores resultados dos estudos de estabilidade no tempo das emulsões foram obtidos usando as nanopartículas catiônicas (SiNP-A,G) recobertas com PAA e com a mistura de polímeros (PAA mais PSS). As emulsões Pickering obtidas com as nanopartículas de sílica recobertas com PAA mostraram os melhores resultados na retardação da evaporação do DEET, com potencial uso para liberação lenta deste composto. / [en] Currently the increasing demand for insect repellent use has promoted research into more effective products and a longer repellent action. The objective of this work was to obtain new nanoparticles by surface modification with cationic functional groups and anionic polymers, with the aim of improving the stability of Pickering emulsions containing an active ingredient, N,N -diethyl-m-toluamide (DEET) commonly used in commercial repellents. The preparation of the nanoparticles included initial surface functionalization of commercial silica nanoparticles with secondary amino groups (R-NH2), followed by the introduction of cationic quaternary ammonium groups (R-NR4 positive) and subsequent electrostatic complexation with anionic polymers (poly (acrylic acid), PAA, and poly(sodium 4-styrenesulfonate), PSS). The modified nanoparticles showed good dispersibility in aqueous medium, favoring the stabilization of emulsions oil-in-water (O/W). The best results of the emulsion time stability studies were obtained using cationic silica nanoparticles (SiNP-A,G) covered with PAA and with the polymer mixture (PA plus PSS). The Pickering emulsions obtained with the cationic silica nanoparticles coated with PAA showed the best results in retarding DEET evaporation, with potential use for slow release of this compound.

Após o primeiro ano de transplante cardíaco (TC) o desenvolvimento da doença coronária do transplante se torna a principal causa de morbidade e mortalidade desses pacientes. Neste período, aproximadamente 40% dos pacientes com (TC) desenvolvem hiperlipidemias que contribuem para a gênese da doença coronária do transplante. Alterações no metabolismo lipídico, entre elas, no metabolismo dos quilomícrons e da lipoproteína de baixa densidade (LDL) já foram reportadas no pós transplante. Por outro lado, a concentração da lipoproteína de alta densidade (HDL) nesses pacientes é ainda controversa. Tem sido reportado que a avaliação somente da concentração da HDL não é o suficiente para avaliar todo o papel protetor, portanto aspectos funcionais da HDL devem ser testados. Neste estudo, a propriedade fundamental da HDL de receber lipídeos das outras lipoproteínas foi avaliada em pacientes com TC, através da lipoproteína artificial (LDE). Foi também avaliado o diâmetro da HDL e a sua enzima antioxidante, a paraxonase 1 (PON1). Foram estudados 20 pacientes com TC e 20 indivíduos normolipidêmicos pareados por sexo, idade e índice de massa corpórea. Amostras de sangue foram coletadas, após jejum de 12hs, para determinação do perfil lipídico, glicose, atividade da PON1, diâmetro da HDL e transferência de lipídeos da LDE para a HDL. A concentração de colesterol total e LDL-colesterol não foram diferentes entre os grupos, enquanto a concentração de HDL_colesterol foi menor no grupo TC (p=0.01). A concentração de triglicérides no TC foi aproximadamente 40% (p=0.001). A concentração de apo A-I e apo B foram similares entre os grupos. A glicose plasmática está aumentada nos pacientes transplantados (p=0.008). O diâmetro da HDL é menor nos pacientes do grupo TC quando comparados ao do grupo controle (p=0.047), enquanto a atividade da PON1 não diferiu entre os grupos. A transferência de colesterol e éster de colesterol da LDE para a HDL foi menor em pacientes com TC quando comparados aos controles (p= 0,045 and 0,003 respectivamente). Por outro lado, não encontramos diferenças entre os grupos na transferência de triglicérides e fosfolípides. Os resultados nos mostram que a transferência de colesterol e éster de colesterol está diminuída no TC. Como o éster de colesterol é o principal constituinte do núcleo da HDL, a menor transferência de colesterol para a HDL pode ter contribuído para o menor diâmetro da HDL observado neste grupo. Estas alterações no metabolismo da HDL podem potencialmente desestabilizar o pool de colesterol plasmático e o transporte reverso de colesterol. Este achado pode contribuir para o acelerado processo aterosclerótico que frequentemente ocorre nestes pacientes. / After the first year from the transplantation procedure transplant coronary heart disease becomes a major complication and the leading cause of late morbity and mortality of those patients. After the first year, roughly 40% of heart transplantation (HT) patients develop hyperlipidemias what is implicated in the genesis of transplant coronary heart disease. Alterations in plasma lipid metabolism such as disturbed chylomicron and low-density lipoprotein (LDL) metabolism were also reported. On the other hand, levels of high-densitylipoprotein (HDL) cholesterol are controversy in those patients. It has been perceived that the estimation of the lipoprotein concentration does not suffice to evaluate the overall HDL protective role and that the functional aspects of the lipoprotein should be tested. In this study, the fundamental property of HDL to receive lipids from other lipoproteins modeled by a artificial lipoprotein (LDE) was tested in HT patients, together with size and the HDL-associated antioxidant paraxonase 1 (PON 1). We studied 20 heart transplantation patients and 20 healthy normolipidemic subjects paired for sex, age and body mass index. Blood samples were collected after 12h fasting, for determination plasma lipids, glucose, paraxonase 1 activity, HDL size and transfer of lipids from LDE to HDL. The total cholesterol and LDL cholesterol concentration did not differ in the two groups, whereas HDL cholesterol was smaller in HT (p=0.01). Triglycerides were roughly 40% greater than those of the controls (p=0.001). Apo A-I e apo B concentration values were similar comparing HT patients with controls. Plasma glucose was greater in HT than in controls (p=0.008). HDL particle diameter was smaller in HT patients then in controls (p=0.047), whereas the activity of PON 1 is not different in both groups. The transfer of cholesterol and cholesteryl ester from LDE to HDL were smaller in HT patients than in controls (p= 0.045 and 0.003, respectively). On the other hand, there was no difference in the transfer of triglycerides and phospholipids between HT patients and controls. The results showed that the acceptance of cholesterol and cholesteryl esters by the HDL fraction is diminished in HT. Since cholesteryl ester constitute most of the HDL core and cholesterol is transformed in cholesteryl ester, decreased acceptance of both cholesterol from other lipoprotein particles may account for the smaller HDL particle diameter found in the HT patient group. These alterations in HDL metabolism can potentially destabilizing the plasma cholesterol pool and the reverse cholesterol transport. This finding can contribute for the accelerated atherosclerotic process that commonly occurs in those patients.

7-cetocoleterol (7KC) é um oxisterol conhecido por inibir a proliferação celular e por ser citotóxico. Desenvolvemos uma nanoemulsão contendo 7KC (LDE/7KC) que demonstrou efeito anti-proliferativo sobre as linhagens RPMI 8226 (mieloma) e melanoma (B16F10), in vitro, sendo preferencialmente captada via receptores de LDL. No presente trabalho avaliamos, in vivo, a cinética plasmática, biodistribuição, ação anti-tumoral e parâmetros tóxico-hematológicos em camundongos portadores de melanoma. A cinética plasmática apresentou um decaimento estatisticamente igual entre os animais portadores de melanoma e não portadores. Em relação à biodistribuição da nanoemulsão, houve um acúmulo de seus componentes radioativamente marcados, principalmente no fígado e no tumor, sugerindo sua captação via receptores de LDL. LDE/7KC promoveu uma redução superior a cinqüenta por cento do tamanho do tumor, que apresentou maior área de necrose e menor quantidade de vasos. Nos camundongos tratados com LDE/7KC houve um aumento da sobrevida. As análises toxico-hematológicas demonstraram que a nanoemulsão apresentou pouca ou nenhuma toxicidade. Os resultados demonstram a possibilidade da utilização da nanoemulsão LDE/7KC como um agente no tratamento do câncer, com poucos efeitos colaterais, devido a sua seletividade aos receptores da LDL. / 7-ketocholesterol (7KC) is an oxysterol known to inhibit cell proliferation and to be cytotoxic. A nanoemulsion containing-7KC (LDE/7KC) was shown to have antiproliferative effects on RPMI 8226 myeloma cell line and melanoma (B16F10), in vitro. This particle is taken up mainly by LDL receptors. Here we have evaluated the plasma kinetic, biodistribution, anti-tumoral action and hematologic toxicity of LDE/7KC in melanoma bearing mice. The nanoemulsion accumulated in the liver and tumor, tissues with a high expression of LDL receptors. LDE/7KC promoted a tumor size reduction over fifty percent. An increased necrosis area and a decreased amount of blood vessels were found. An increased survival rate was observed. The hematolgic analyses demonstrated a lack of toxicicity. The results shows the possibility to use the LDE/7KC nanoemulsion as an agent for cancer treatment, with few collateral effects probably due to its internalization by LDL receptors.

Bien que les matériaux poreux soient nombreux dans la nature, la synthèse en laboratoirede matériaux présentant une porosité multi-échelle ou hiérarchisée est toujours délicate. Enutilisant la matière molle (émulsions concentrées, auto-assemblages, mésophases lyotropes, etc)et le procédé sol-gel, il est possible d’obtenir une grande variété de matériaux monolithiques, àporosité hiérarchisée, composés d’un squelette silicique. La porosité de ces matériaux peut êtreoptimisée en jouant avec la nature de l’émulsion, le tensioactif utilisé, ou avec l’ajout d’agentd’extérieur comme le sel. En combinant ces méthodes, des matériaux possédant une mésoporositéhexagonale ont été obtenus. Grâce à leur surface riche en silanols, ces matériaux poreux ont étéfonctionnalisés par greffage post-synthèse de molécules organiques. Dès lors, l’immobilisationd’entités biologiques comme les enzymes au sein de la structure poreuse a permis d’utiliser cesmatériaux pour des réactions d’hydrolyse, de synthèse ou de décoloration en milieu aqueux dansune approche de « chimie verte ». Enfin, des micro-organismes ont été piégés dans ces matériauxporeux qui ont été recouverts d’une coque en silice. Les micro-organismes peuvent s’y développersans restriction et leur croissance est très différente de celle observée dans les cultures classiques.La coque en silice, formée en surface, est donc imperméable au passage des bactéries (taillemicrométrique) mais perméable à la diffusion des substrats et des réactifs. Cette diffusion a étémise à profit pour réaliser des réactions enzymatiques en cascade. Ces matériaux se positionnentcomme des biocatalyseurs très prometteurs pour de nombreuses applications. / Although porous materials are numerous in nature, the laboratory synthesis of materials withmulti-scale or hierarchical porosity is always difficult. By using soft matter (concentrated emulsions,self-assemblies, lyotropic mesophases, etc.) and the sol-gel process, it is possible to obtaina wide variety of monolithic materials with hierarchical porosity composed of a silicic skeleton.The porosity of these materials can be optimized by playing with the nature of the emulsion,the surfactant used, or with the addition of external agents such as salt. By combining these methods,materials with hexagonal mesoporosity have been obtained. Thanks to their silanol-richsurface, these porous materials have been functionalized by post-synthesis grafting of organicmolecules. Therefore, the immobilization of biological entities such as enzymes within the porousstructure has made it possible to use these materials for hydrolysis, synthesis or discolorationreactions in aqueous media in a "green chemistry" approach. Finally, microorganisms were trappedin these porous materials which were covered with a silica shell. Microorganisms can growthere without restriction and their growth is very different from that observed in conventionalcultures. The silica shell formed on the surface is therefore impermeable to the passage of bacteria(micrometric size) but permeable to diffusion of substrates and reagents. This diffusion wasused to carry out cascade enzymatic reactions. These materials are positioned as very promisingbiocatalysts for many applications.

O monitoramento de emulsões utilizadas na indústria metalmecânica compõe uma importante atividade para o controle da qualidade das peças trabalhadas, proporcionando também o aumento da vida útil de ferramentas e maquinários utilizados neste setor através da lubrificação e refrigeração da região de corte. Em grande parte dos casos, estas emulsões são preparadas pela diluição de um fluido de corte em meio aquoso, constituindo assim um conjunto de gotículas estabilizadas em um meio contínuo devido à presença de compostos emulsificantes, estando constantemente sujeitas a ciclos de aquecimento e resfriamento durante os processos de usinagem. Apesar do acompanhamento deste material ser realizado através de análises periódicas usuais, não há um método eficiente estabelecido para verificar sua qualidade em tempo real e em linha de processo. Neste contexto, torna-se possível aplicar técnicas relacionadas à espectroscopia UV-Vis para se obterem informações sobre a estabilidade destes sistemas, correlacionando intensidades de espalhamento de luz com as dimensões das gotas presentes no meio. Dessa forma, tornou-se possível o estudo da desestabilização térmica de emulsões de um fluido de corte comercial, a qual mostrou-se, através do acompanhamento do cálculo do expoente do comprimento de onda, dependente do tempo de exposição ao aquecimento e de sua temperatura média temporal, não sendo influenciada pela perda de meio contínuo por processos evaporativos ou sua posterior reposição. Também se verificou que parâmetros típicos do processo de preparo de emulsões, como a temperatura do meio dispersante e o tempo de repouso do fluido de corte sobre a superfície do mesmo, apresentam fundamental importância para a definição do tamanho médio de gota inicial destes sistemas, o que forneceu evidência da possibilidade de se relacionar a área sob espectros de extinção de luz com tamanhos médios de gota. / The monitoring of emulsions used in the metal-mechanical industry comprise an important activity to the quality control of the products manufectured, also providing an increase in the working life of the tools and machinery employed in this sector through the lubrication and refrigeration of the cutting zone. In the majority of cases, these emulsions are prepared diluting a metalworking fluid in an aqueous media, constituting a collection of particles stabilized by emulsifiers and undergoing heating and cooling cycles during metalworking processes. Currently, monitoring routines are based on regular analyses of samples taken from the process fluid, and an effective in-line method is not available to monitor emulsion quality in real time. In this context, it is possible to apply techniques related to UV-Vis spectrocopy in order to obtain information concerning the stability of those systems, correlating light scattering intensities to the droplet dimensions. In this study, it was possible to investigate the thermal destabilisation of a commercial metalworking fluid emulsion, which showed, through the evaluation of the wavelength exponent, to be dependant on the exposure time to heating and its time-averaged temperature. It was also noted that the loss of continuous phase by evaporation and its reposition do not affect the emulsion stability. Moreover, it was observed that important emulsion preparation parameters, such as continuous phase temperature and the time span between the addition of the metalworking fluid on the water surface and the stirring, have fundamental roles in defining the initial average droplet size, which made possible to correlate the area under the light extinction spectra with average droplet sizes.

Les écoulements de trains périodiques de gouttes monodisperses confinées dans des microcanaux sont largement utilisés pour diverses applications haut-débits en microfluidique digitale. Pour cela, il est nécessaire de réaliser différentes opérations sur ces gouttes comme les fragmenter, les fusionner ou les trier. Dans ce manuscrit, nous discutons de trois de ces opérations expérimentalement et théoriquement. La première concerne l’encapsulation d’un train de gouttelettes dans des gouttes. Nous étudions la dynamique d’encapsulation et nous présentons une nouvelle méthode d’encapsulation. Par suite, nous investiguons deux modes de fragmentation de gouttes, tous deux influencés par des interactions hydrodynamiques entre gouttes consécutives dans un train. Enfin, nous cherchons à comprendre la sélection du chemin suivi par des gouttes à des bifurcations successives. / Flows of periodic trains of monodisperse drops confined in microchannels are widely used for numerous high-throughput applications in digital microfluidics. The development of such applications requires performing and combining various operations on these drops like breakup, fusion or sorting. In this manuscript, we study experimentally and theoretically three of these operations. We first discuss the encapsulation of a train of droplets inside drops, focusing on the encapsulation dynamics. Also, we present a new way to encapsulate drops to produce double emulsions. We then investigate two ways to break drops against micro-obstacles, both being influenced by hydrodynamics interactions between two consecutives drops in a train. Lastly, we report the investigation of the path selection of drops at successive bifurcations.

La spécificité des émulsions de Pickering repose sur la présence de particules stabilisantes, substituant l'utilisation de tensio-actifs. Les particules s'adsorbent de manière irréversible aux interfaces des gouttes d'émulsions, leur conférant une stabilité à long terme.
L'objectif de cette thèse a été de comprendre, développer et optimiser des procédés permettant la fabrication de différents types d'émulsions de Pickering grâce à des nanoparticules de silice. Trois projets ont vu le jour dans ce travail : (i) Tout d'abord une approche théorique concernant l'étude physico-chimique des interfaces d'émulsions de Pickering stabilisées par des nanoparticules de silice individuelles non- agrégées. L'adsorption de ces nanoparticules sous forme de mono- ou multi- couches aux interfaces des gouttes d'émulsion a pu être mise en évidence en fonction du ratio Huile/Silice intégré au milieu. A haut ratio, le diamètre des gouttes d'émulsion dépend des paramètres de formulation. Des monocouches de nanoparticules peuvent s'adsorber aux interfaces avec un taux de couverture maximal de 54% à la surface des gouttes d'huile. Tandis qu'à bas ratio, le diamètre des gouttes dépend du procédé de fabrication de l'émulsion. Des multicouches de nanoparticules s'adsorbent aux interfaces. (ii) La taille des gouttes d'émulsion a ensuite été réduite par divers procédés afin d'obtenir des nanoémulsions de Pickering, également appelées NanoPickering. La première étape consistait à tester la viabilité de telles émulsions en les fabriquant par un procédé fort en énergie, i.e. la sonication. Dans un second temps un procédé faible en énergie a été utilisé : la nanoprécipitation. Il a ainsi été possible d'obtenir des nanoémulsions de Pickering stables sur plus d'un mois. Cependant, la quantité d'huile maximale incorporable au système final reste faible (environ inférieure à 1wt%). (iii) Une nouvelle application a été développée en parallèle permettant de formuler des émulsions foisonnées de Pickering, intégralement stabilisées par des nanoparticules. Il est possible d'obtenir deux types d'émulsions foisonnées de Pickering : les premières ont une très forte teneur en air ; les secondes sont stables en termes de hauteur grâce à un phénomène de gélification qui a lieu après un changement d'état macroscopique.
L'ensemble de ces résultats confirme que les émulsions de Pickering offrent encore à ce jour la possibilité de découvrir de toutes nouvelles applications fabriquées par des procédés innovants. Par exemple, les nanoémulsions sans émulsifiant émulsifiées de manière spontanée, ou encore les émulsions foisonnées intégralement stabilisées sans émulsifiant. De plus, les approches théoriques restent également nombreuses, et les études des phénomènes interfaciaux sont encore des questions scientifiques très actuelles / Pickering emulsions are emulsions stabilized by solid particles in opposition to emulsifiers-stabilized emulsions. The stabilization of Pickering emulsions comes from a strong adsorption of solid particles at the oil-water interface that builds a rigid barrier against coalescence. The aim of this work was to understand, develop and optimize methods for the fabrication of different types of Pickering emulsions stabilized by silica nanoparticles. Three mains axes can be exposed: (i) Firstly, a theoretical approach on the physico-chemical interfacial phenomena of Pickering emulsions stabilized by non-aggregated individual silica nanoparticles. Adsorption as mono- or multi-layers can be reached depending the Oil/Silica ratio. Two behaviors were observed: At high oil/silica mass ratio, the oil/water interface was covered by a monolayer of nonaggregated silica particles. Stable emulsions were stabilized by a monolayer of silica particles at 54% coverage of the oil droplets surface. Oil droplet diameter depends on formulation parameters. Adsorption as multilayers was reached at lower oil/silica mass ratio and oil droplet diameter depends on fabrication process. (ii) Droplets diameters could be reduced thanks to various processes in order to obtain Pickering nanoemulsions, also called NanoPickering. The first step was to test the viability of such emulsions using a high energy process (sonication). Then, a low energy process (nanoprecipitation) was used. Stable Pickering nanoemulsions can be made on more than one month. However, the oil quantity obtained in the final media is low (less than 1wt%). (iii) In parallel, a new application was developed allowing the formulation of Pickering aerated emulsions, totally stabilized by nanoparticles. Two types of Pickering whipped emulsions can be made. One which has high air content or one which has a stable height, thanks to a gelification phenomenon. This occurs after a macroscopic change of state. All of these results confirm that Pickering emulsions offer the opportunity to discover new applications made by innovative processes. For instance, NanoPickering made by spontaneous emulsification, or Pickering whipped emulsion fully stabilized without emulsifiers. Moreover, theoretical approaches and interfacial phenomena studies are still current scientific questions

Polímeros e copolímeros hidrossolúveis a base de acrilamida e seus derivados são sintetizados e aplicados principalmente como floculantes, auxiliando na remoção de sólidos finos presentes em águas residuais e industriais. As poliacrilamidas, como são assim chamadas, podem se apresentar em sua forma neutra ou contendo diferentes cargas iônicas (positivas ou negativas) em sua composição em função do tipo de aplicação específica. As poliacrilamidas são sintetizadas, em sua grande maioria, através de emulsões inversas via polimerização radicalar, visando à elevada massa molar do polímero formado. A formulação da poliacrilamida catiônica com fração molar de 0,6 do comonômero iônico foi otimizada através de planejamento fatorial experimental, variando-se os principais fatores de processo: concentração do pacote de surfactante para formação da emulsão inversa, tempo de micronização, concentração de VISCOPLEX® e concentração de ácido graxo. Com base nos resultados obtidos a partir do primeiro planejamento, foram estudadas as seguintes variáveis: HLB do sistema de surfactantes e a troca dos surfactantes monoméricos por surfactantes poliméricos. A otimização da formulação levou em conta principalmente o custo-benefício para produção e comercialização em escala industrial. O fator micronização foi elevado em seu máximo e os fatores VISCOPLEX® e ácido graxo foram excluídos da formulação, após conclusão dos estudos. A troca dos surfactantes monoméricos por poliméricos foi vantajosa devido ao ganho de qualidade do produto final, mesmo com maior custo de implementação. Para minimizar os custos de formulação o fator HLB foi utilizado em seu máximo, onde houve incremento do ALKONAT® L 50 para formação da emulsão inversa. / Acrylamide based hydrosoluble polymers and copolymers and their derivatives are synthesized and mainly applied as flocculants, assisting removal of fine solids present in wastewater and industrial wastewater. Polyacrylamides may be present in their neutral form or with different ionic charges (positive or negative) in their composition depending on the type of specific application. Polyacrylamides are synthesized, mostly by inverse emulsions using radical polymerization, aiming polymers with high molecular weight. Cationic polyacrylamide formulation with 0.6 mole fraction of the ionic comonomer was optimized through design of experiments (DOE), varying the major process factors: surfactant package concentration to form inverse emulsion, micronization time, VISCOPLEX® concentration and fatty acid concentration. Based on the responses from the first DOE, a second DOE was performed, where the variables surfactant system HLB and the exchange of monomeric surfactant by polymeric surfactants were investigated. The formulation optimization considered mainly cost-effective production and industrial scale. The micronization factor was set at its maximum and VISCOPLEX® and fatty acid factors were excluded from the formulation, after conclusion of studies. Exchanging monomeric surfactants by polymeric surfactants led to a final product with higher quality, even considering a higher implementation cost. In order to minimize formulation costs HLB factor was used at its maximum, increasing the content of ALKONAT® L50 to form the inverse emulsion.

Atualmente, decorrente da cultura estética onde há o culto aos corpos esbeltos com aparência saudável e pele lisa, macia e viçosa, a hidrolipodistrofia ginóide, conhecida como celulite, tem sido um dos desafios para os dermatologistas e cirurgiões plásticos. Assim, temse testado diferentes formas de tratamentos entre as quais estão aplicações de cremes à base de xantinas visando a atenuação dos sintomas. O conhecimento das propriedades físicoquímicas de tais formulações é essencial para otimizar as condições de produção e liberação do ativo na pele, além de prover elegância cosmética do produto desenvolvido. Os objetivos desse trabalho foram obter e avaliar a estabilidade de emulsões O/A contendo fase líquida cristalina, adicionada de cafeína, para aplicação no tratamento da hidrolipodistrofia ginóide, bem como avaliar o perfil de liberação da substância ativa in vitro com intuito de determinar sua disponibilidade. A emulsão O/A contendo como fase oleosa, óleos vegetais naturais (óleo de urucum, de café e de melaleuca) foi desenvolvida através da utilização do Sistema Equilíbrio Hidrófilo- Lipófilo (EHL). Utilizando os tensoativos não-iônicos Ceteareth 5 e Steareth 2 nas concentrações de 10,0 e 15,0% foi possível obter fases líquidas cristalinas lamelares. A adição de cafeína a 1,0% foi conseguida em emulsão contendo 15,0% da mistura de tensoativos e com auxílio na solubilização através do uso de benzoato de sódio na mesma concentração (1,0%). As emulsões foram consideradas estáveis segundo as condições experimentais e parâmetros analisados. O perfil de liberação da substância ativa apresentou fase inicial de liberação mais rápida seguida de outra mais lenta. A eletroforese capilar mostrou-se ferramenta mais adequada para quantificação do ativo. Os resultados sugerem que os cristais líquidos lamelares estejam atuando provavelmente como veículo de liberação lenta. / Nowadays, due to aesthetic culture that there is the cult to slim body with health appearance and smooth, vigorous skin, the gynoid hydrolipodystrophy, known as cellulite, has been one of the challenges for dermatologists and plastic surgeons. Thus, different kinds of treatments have been tested, and among them, the application of xantines-based creams in order to attenuate the symptoms. The knowledge of the physicochemical properties of such formulations is essential to optimize the production conditions and active skin delivery, besides promoting cosmetic elegance of the developed product. The aims of this research were to attain and to evaluate the stability of O/W emulsions containing liquid crystalline phase, with the addition of caffeine, to be used on the gynoid hydrolipodystrophy treatment, as well as evaluate the release profile of the active in vitro in order to determine its availability. The O/W emulsion containing natural vegetable oils (annatto oil, coffee oil and tea tree oil) as oily phase was developed through the utilization of Hydrophilic Lipophilic Balance System (HLB). When using the non-ionic surfactants Ceteareth 5 and Steareth 2 in the 10.0 and 15.0% concentrations it was possible to obtain lamellar liquid crystalline phases. The addition of caffeine 1.0% was attained in emulsion containing 15.0% of the surfactant mixture and its solubility was improved through the sodium benzoate use in the same concentration. The emulsions were considered stable according to the experimental conditions and evaluated parameters. The release profile of the active agent presented a faster initial phase followed by a slower one. The capillary electrophoresis showed a more suitable tool to quantify the active. The results suggest that the lamellar liquid crystals are probably acting as slow delivery vehicle.

Les écoulements biphasiques en milieux poreux sont généralement accompagnés par des phénomènes d'émulsification d'une phase dans l'autre. Les causes peuvent être nombreuses, de la digitation visqueuse aux instabilités purement capillaires. Cette thèse expérimentale a pour objet l'étude d'un mécanisme particulier d'émulsification de l'huile en milieu poreux, ainsi que le transport des gouttes produites dans des milieux confinés. Dans la première partie de cette thèse, l'instabilité gravito-capillaire de Rayleigh-Taylor est revisitée dans un coin formé entre deux plaques de verre centimétriques. La présence d'un gradient de confinement introduit une force capillaire supplémentaire à cette instabilité canonique, susceptible de stabiliser une couche de liquide suspendue au-dessus du vide. Le seuil de stabilité, les longueurs d'onde caractéristiques et les taux de croissance sont bien modélisés par une analyse de stabilité linéaire de l'interface. La caractérisation de cette force capillaire induite par le gradient de confinement nous amène par la suite à l'étude d'une instabilité purement capillaire se produisant lorsqu'un fluide en mouillage très favorable migre vers les régions les plus confinées d'un coin, occupées initialement par un fluide en mouillage moins favorable. Le gradient de confinement introduit alors une force déstabilisante, aboutissant à l'inversion de la position respective des deux phases. Le liquide le moins mouillant est complètement émulsifié et transporté vers les régions les moins confinées sous la forme de gouttelettes. Une analyse de stabilité linéaire de l'interface permet, là encore, de prédire cette sélection de taille. Les taux de croissance mesurés ne sont en revanche pas en accord avec la modélisation, basée sur la loi de Darcy. Leur valeur suggère une localisation de la dissipation visqueuse dans les lignes de contact déplacées durant le développement de l'instabilité, ainsi que dans les films de lubrification également déposés. Ces dynamiques "non-darciennes" nous ont amenés dans une seconde partie de la thèse à l'étude du transport de gouttes d'huile très visqueuses confinées dans de l'eau en mouillage total. Dans cette configuration, la présence de films de lubrification d'eau entre la goutte et le substrat assure la localisation de la dissipation dans les films peu visqueux, favorisant ainsi la mobilité des gouttes. Nous montrons également que la présence de rugosités sur les parois du confinement induit un ralentissement significatif de la vitesse des gouttes, lié à l'amincissement du film de lubrification par ces rugosités. L'interdépendance subtile entre friction visqueuse à l'avant de la goutte et dans son volume est notamment mise en lumière. Dans une dernière partie, nous étudions l'instabilité capillaire se produisant lorsqu'une goutte binaire d'eau et d'alcool est déposée à la surface d'un bain d'huile. L'évaporation majoritaire de l'alcool à la surface de la goutte induit des variations locales de la tension de surface. Des écoulements interfaciaux de Marangoni se produisent, et aboutissent à la déstabilisation spectaculaire de la goutte en étalement. / Biphasic flows in porous media generally lead to the emulsification of one phase into the other. This may be due to several phenomena, such as viscous fingering or pure capillary instabilities. In this experimental thesis, we study a particular emulsifying phenomenon of oil in a model porous medium, as well as the transport of the produced droplets in confined regions. In the first part of the manuscript, the Rayleigh-Taylor instability is revisited in a wedge formed between two centimetric glass plates. The gradient of confinement leads to a capillary force not present in the canonical Rayleigh-Taylor instability. This new force can stabilize liquid layer above air submitted to gravity. The threshold of the instability, the characteristic wavelength and the growth rate are captured by a linear stability analysis of the interface. This characterization of the confinement-induced capillary force drove us to the study of a pure capillary instability occurring when a wetting liquid migrates toward the most confined regions of a wedge, initially filled with a less wetting liquid. The gradient of confinement generates a destabilizing force, leading to the complete inversion of the position of both phases. The less wetting liquid is fully emulsified and the produced droplets are convected towards the less confined regions. A linear stability analysis of the interface here again predicts the characteristic size of the droplets. However, the measured growth rates are not in agreement with the model, based on the Darcy law. This suggests a localization of viscous dissipation in the contact lines displaced during the development of the instability. Another source of viscous dissipation can be in the deposited lubrication films. Those "non-Darcian" dynamics motivated the second part of this thesis, which focuses on the motion of very viscous and non-wetting droplets confined in water. In this configuration, the lubrication film of water between the drop and the substrate ensures the localization of viscous dissipation in those films of low viscosity. This favors the extremely high mobility of the droplets. We also show that wall roughness may induce a thinning of these lubrication films. We shed light on the intricate coupling between viscous friction at the front of the drop and in its bulk. In a last part of this work, we study the capillary instability occurring when a binary droplet of water and alcohol is deposited at the surface of a vegetable oil bath. The dominant evaporation of alcohol at the surface of the drop induces local variations of surface tension. Interfacial Marangoni flows are thus observed, leading to the spectacular destabilization of the spreading droplet