Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Dans le lait on peut distinguer les protéines sériques et les caséines. Les protéines sériques sont des protéines globulaires qui se trouvent dans le sérum du lait et elles sont connues pour leurs propriétés fonctionnelles exceptionnelles. Quand une solution de protéines sériques est chauffée, elles perdent leur structure native et peuvent s'agréger. Elles forment des agrégats de différentes formes, tailles et densités : des cylindres, des agrégats fractals, des microgels et des agrégats fibrillaires. De l'autre côté, les caséines sont organisées dans des micelles de caséine d'un rayon environ 100-200 nm stabilisées par du phosphate de calcium colloïdal.Au cours de ce travail, nous avons cherché à comprendre comment les agrégats de protéines sériques pouvaient être utilisés en mélange avec les micelles de caséine pour obtenir et contrôler la texture de produits laitiers. Dans un premier temps, nous avons étudié le processus de « cold gelation » induit par ajout de calcium et/ou acidification d'agrégats et de microgels de protéines sériques seuls. Dans une deuxième partie, nous nous sommes intéressés à la fonctionnalité des agrégats dans les mélanges plus complexes avec les autres protéines laitières et en présence de minéraux. L'addition de petites quantités d'agrégats fractals dans des suspensions de micelles diminuait leur température critique de gélification, augmentait le module élastique et diminuait la synérèse des gels.Les agrégats de protéines sériques peuvent être utilisés pour modifier la viscosité des mélanges, comme gélifiant ou pour enrichir la teneur en protéine du milieu sans en augmenter la viscosité. / The proteins of milk can be divided into whey proteins and caseins. Whey proteins are compact globular proteins that are found in the aqueous phase of milk. They are well-known for their exceptional functional properties. Upon heating, individual whey proteins denature and aggregate, forming aggregates of different morphologies and sizes, such as strands, fractal aggregates, microgels and fibrillar aggregates, depending on the heating conditions. On the other hand, the caseins in milk are organized in complex protein units with a diameter of 100-200 nm called casein micelles stabilized by colloidal calcium phosphate (CCP).The current work is an endeavor to understand how whey protein aggregates might be used in mixtures with other dairy proteins, such as casein micelles, in order to get a particular texture in a dairy product. We first extended the understanding of so-called “cold gelation” of pure WPI aggregates induced by calcium and acidification and then studied how the aggregates work in more complex mixtures of proteins and minerals. Interestingly, addition of small amounts of fractal aggregates to suspensions of casein micelles has been demonstrated to decrease the critical gelation temperature, increase the elastic modulus and decrease the syneresis of the gels.The aggregates are to be used to modify the viscosity of dairy products, as a gelling agent and for protein enrichment. The properties of strands, fractal aggregates and microgels have been studied and compared. WPI aggregates might be considered as “clean label” texturizing ingredients that do not require approval from the European Food Safety Authority (EFSA).

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Ce travail décrit une nouvelle route synthétique qui a pour objectif l'obtention de diblocs amphiphiles constitués uniquement d'oligosaccharides issus de xyloglucanes des graines de Tamarin. Les xylogluco-oligosaccharides (XGOs, DP7, 8, 9) de tailles parfaitement définies ont été obtenus par une digestion enzymatique contrôlée (cellulase) de xyloglucanes. Dans la perspective de lier les deux blocs par cycloaddition 1,3-dipolaire de Huisgen catalysée par le Cuivre I, dite aussi chimie « click », les XGOs ont subit une réaction d'amination réductrice assistée par micro-ondes. L'action de la propargylamine a permis d'intégrer en position réductrice du XGO la fonction alcyne et une peracétylation des focntions hydroxyles du sucre ont rendu ce bloc hydrophobe. D'un autre côté, l'azidoethylamine a permis d'insérer la fonction azoture et constitue le bloc hydrophile. Cette stratégie de synthèse a également été transposée à un oligosaccharide monodisperse (XGO, DP7) provenant de la dégalactosylation enzymatique du xyloglucane par l'action supplémentaire de la galactosidase d'Aspergillus Niger. Finalement, les diblocs amphiphilies ont été synthétisé aussi bien à partir des XGOs de DP7, 8, 9 (XGO-b-XGO,Ac), que du XGO DP7 (DP7-b-DP7,Ac). Leurs propriétés d'auto-assemblages dans l'eau ont été réalisées ainsi que leur caractérisation physico-chimique. Suite à des mesures de concentration micellaire critique (CMC) obtenus par spectroscopie de fluorescence du pyrène, nous avons observé que l'élimination des unités de galactose provoque une augmentation de la CMC. La détermination du diamètre des micelles en solution aqueuse a été réalisée grâce à la technique de diffusion de la lumière (DLS) et a été confirmée par microscopie électronique à transmission (MET). Des micelles sphériques d'une taille moyenne de 25 nm (XGO-b-XGO,Ac) et de 6 nm (DP7-b-DP7,Ac) ont été observées au MET. La digestion enzymatique partielle des micelles formés à partir du dibloc XGO-b-XGO,Ac dans l'eau, conduisant à la formation des micelles DP7-b-XGO,Ac a conduit à un système moins polydisperse et à une diminution de la taille moyenne du diamètre micellaire de l'ordre de 50% (déterminée par DLS). Des nanoparticules de gliadine et de zéine ont été préparées par désolvatation en utilisant le dibloc XGO-b-XGO,Ac comme surfactant en comparaison au surfactant commercial non-ionique, le Pluronic F68. Les résultats suggèrent la capacité du dibloc à stabiliser la protéine de zéine sous forme de nanoparticules sphériques et de façon relativement monodisperses. Les particules formées et stabilisées grâce à l'association de protéines d'origine végétale et d'un surfactant « biopolymérique » synthétisé uniquement par des oligosaccharides, apparaissent comme des systèmes idéaux, associant biocompatibilité, biodégradabilité et des origines naturelles et renouvelables. Ces systèmes peuvent tout à fait être valorisés pour la libération contrôlée de substances actives. / This work describes a new synthetic route to obtain fully oligosaccharides-based amphiphilic diblock copolymers, made from tamarind seeds xyloglucan. A mixture of well size-defined xyloglucooligosaccharides (XGO of 7, 8 and 9 carbohydrate units) were obtained from the cellulose-mediated enzymatic digestion of xyloglucanes. To perform the Huisgen click reaction the oligosaccharides were reducing end functionalized by azide and propargyl functions via microwave-catalyzed reductive amination. The hydrophobic block was obtained after peracetylation of alkyne-containing XGO. The amphiphilic co-oligomers were synthesized either from the mixture of xyloglucan oligosaccharides to give XGO-b-XGO,Ac, either from the monodisperse XGO of 7 carbohydrate units (DP7), obtained by a degalactosylation process involving another specific enzymatic hydrolysis (beta-galactosidase from Aspergillus Niger), to give DP7-b-DP7,Ac. The XGO-based diblocks were characterized according to the state-of-the-art in structural characterization (NMR, MS, FT-IR) and Soft Matter physico-chemistry (SLS, DLS, CMC, TEM) techniques. The removal of galactose units (DP7-b-DP7,Ac) conferred an increase in the critical micellar concentration value compared to XGO-b-XGO,Ac, which were determined by fluorescence spectroscopy. The size diameter of the micelles were carried out by dynamic light scattering (DLS) and confirmed by transmission electron microscopy (TEM). Spherical micelles with an average size of 25 nm for XGO-b-XGO,Ac and 6 nm DP7-b-DP7,Ac nanoparticles were observed by TEM. The partial enzymatic digestion of the shell constituting XGO-b-XGO,Ac micelles in water led to formation of DP7-b-XGO,Ac micelles with a lowest polydispersity and a decrease in the average size diameter by 50 %, as determined by DLS. XGO-b-XGO,Ac was tested as a nonionic block copolymer surfactant to stabilize zein and gliadin nanoparticles, which come from gluten of wheat and maize and were prepared by the method of desolvation. Its stabilizing properties were compared to Pluronic F68 surfactant belonging to poloxamers' family. The results suggest the suitability of the XGO-based diblock to stabilize zein aggregates, resulting in stable, monodisperse and spherical nanoparticles. Finally, this work proposed a system consisting in potential nanocarriers prepared from vegetable proteins stabilized by biosourced oligosaccharide surfactants.

Les sphéroïdes multicellulaires tumoraux (SMT) constituent un outil prometteur dans le domaine de l’étude biologique des tumeurs. Le but de la thèse était de développer une technique de la formation de SMT et de démontrer la disponibilité de ces sphéroïdes comme modèle in vitro 3D pour tester l’efficacité de principes actifs anticancéreux ainsi que celle de formulations de délivrance de médicaments. L'effet d’auto-assemblage de cellules induit par une addition des peptides RGD cycliques a été étudié pour 16 lignées cellulaires de différentes origines. Le peptide cyclique RGDfK et sa modification avec le cation triphenylphosphonium (TPP) ont permis de mettre en évidence l’induction de formation de sphéroïdes. Les sphéroïdes ont été employés comme modèles pour évaluer la cytotoxicité de principes actifs antitumoraux (doxorubicine, curcumine, temozolomide) et un certain nombre de formulations nano- et micrométriques (microréservoirs, nano-émulsions et micelles). / Multicellular tumor spheroids (MTS) are a promising tool in tumor biology. The aim of the Thesis was to develop a novel highly reproducible technique for MTS formation, and to demonstrate the availability of these spheroids as 3D in vitro model to test anticancer drugs and drug delivery vehicles. Cell self-assembly effect induced by an addition of cyclic RGD-peptides directly to monolayer cultures was studied for 16 cell lines of various origin. Cyclo-RGDfK peptide and its modification with triphenylphosphonium cation (TPP) were found to induce spheroid formation. The spheroids were used as a model to evaluate the cytotoxicity of antitumor drugs (doxorubicin, curcumin, temozolomide) and a number of nano- and micro- formulations (microcontainers, nano-emulsions and micelles).

L'objectif de cette thèse repose sur le développement de micelles de polymères polyioniques, vecteurs de molécules thérapeutiques en immunothérapie avec des cellules dendritiques (DCs). Elles sont préparées à partir d'un copolymère à blocs double-hydrophiles, l'acide polyméthacrylique-b-polyoxyde d'éthylène (PMAA-b-POE) et d'un contre ion de charge opposée. De taille nanométrique, elles sont capables d'encapsuler des molécules thérapeutiques selon une association tripartite originale et de se désassembler à pH acide pour permettre leur libération dans le milieu endosomal.Le premier axe de travail a porté sur l'évaluation de la propriété des copolymères à induire un échappement endosomal en fonction de leur masse molaire en utilisant deux modèles membranaires (liposomes et globules rouges). La complexation des copolymères de masses molaires différentes avec la poly-L-lysine comme contre-ion a permis l'obtention de micelles avec des propriétés d'échappement endosomal variables. Cette propriété est intéressante car en fonction de la stratégie thérapeutique adoptée, elle orientera le choix de la masse molaire du copolymère pour la formulation des micelles.Le second axe a consisté en l'application de ces micelles pour la vectorisation d'un peptide modèle (peptide OVA) dans les DCs. La capacité des micelles à encapsuler le peptide et à le libérer au niveau des compartiments endosomaux a été évaluée par des techniques de spectrofluorimétrie et de microscopie confocale. Enfin, l'efficacité de présentation du peptide formulé dans les différentes micelles a été mise en évidence et a montré l'amélioration de la présentation par les DCs du peptide formulé dans les micelles comparé au peptide non formulé. Cette présentation est nettement supérieure en utilisant les micelles composées de copolymères de masse molaire élevée qui n'entraînent pas d'échappement endosomal.Le troisième axe de recherche a reposé sur la transfection des DCs avec des micelles de siRNA dirigés contre la protéine de surface CD86. Seules les micelles composées de copolymères de faible masse molaire ont permis l'encapsulation du siRNA et la baisse de l'expression de la protéine CD86 à la surface des DCs. Afin d'optimiser la capacité des micelles à encapsuler et transfecter les DCs, la formulation des micelles a été optimisée en remplaçant la PLL par un autre polycation la polyethylene imine PEI. Ces micelles polyioniques à base de copolymère PMAA-b-POE apparaissent donc comme des vecteurs de molécules d'intérêt thérapeutique prometteurs pour les cellules dendritiques en immunothérapie ou en thérapie génique. / The aim of the thesis work is based on the development of polymeric micelles vectors of therapeutic molecules in immunotherapy with dendritic cells (DCs). They are composed of a double hydrophilic blocks copolymers, poly(methacrylic acid)-b-poly(ethylene oxide) (PMAA-b-PEO) and an oppositely charged polyion. They are caracterized by a nanometric size, a capacity to encapsulate therapeutic molecules according to a tripartite association and are able to disassemble at acidic pH allowing the release of their cargo.The first part of this work has focused on the evaluation of the endosomal escape property of copolymers based on their molecular weight by using two membrane models (liposomes and red blood cells). Complexation of different molecular weight copolymers with poly- L- lysine as counter ion allowed the formation of micelles with variable endosomal escape properties. This property is interesting because according to the adopted therapeutic strategy, it will guide the choice of the copolymer micelles for formulation.The second part consisted of the application of these micelles for the vectorization of a model peptide (OVA peptide) in DCs. The ability of micelles to encapsulate and release this peptide in the endosomal compartments was assessed by fluorescence spectroscopy and confocal microscopy techniques. Finally, the effectiveness of the OVA presentation formulated in the different type of micelles has been demonstrated and shown that the peptide presentation by DCs was improved when it was formulated in micelles compared to unformulated peptide. This presentation was much higher using micelles composed of high molecular weight copolymers that do not involve endosomal escape.The third part of the research was based on the transfection of DCs with siRNA directed against CD86 protein surface. Only micelles composed of low molecular weight copolymers allowed the encapsulation of siRNA molecules and decreased the expression of CD86 protein on DCs surface. To increase the ability of micelles to encapsulate and transfect DCs, the micelle formulation was optimized by changing the PLL with another polycation PEI.These polyion micelles based PMAA-b-PEO copolymers appear as vectors of therapeutic molecules for promising strategies with dendritic cells such as vaccination and gene therapy.

In this thesis, we have tried to explain the regular and irregular(chaotic) dynamics of worm like micellar solutions on applying shear, through a detailed study of the equation of motion of a nematic order parameter tensor coupled to a hydrodynamic velocity field. We have assumed spatial variations only along one direction i.e. the gradient direction(1D model). The resulting phase diagram shows various interesting steady states or phases such as spatiotemporal chaos, temporal and spatiotemporal periodicities, and alignment of the director axis along the imposed flow field. The coupling of the orientational degrees of freedom of the order parameter with the hydrodynamic flow field holds the key to the appearance of dynamic shear bands in the system. We have solved numerically a set of coupled nonlinear equations to obtain the order parameter stress developed in the system; the magnitude of the order parameter tensor, the biaxiality parameter and the orientation of the director axis of the nemato gens under shear have also been studied in detail. To study the phase diagram obtained by time integration of the equation of motion mathematically, a stability analysis of the fixed point of motion for various parameter values has been performed so that the location of the chaotic-to-aligned phase boundary is verified. Also in the periodic region of the phase diagram, the stability of limit cycles is tested by analysing the fixed point of the corresponding Poincare map. Stability analysis of the periodic orbits leads to the observation that in the parameter space, there are regions of phase coexistence where chaotic or spatiotemporally intermittent behaviour coexists with periodic behaviour. When corrections in the imposed velocity field due to the order parameter stress were taken into account and the order parameter response was looked into at several points in the parameter space, the modified equations of motion were found to reproduce the earlier behaviour in all the different regimes if the value of a dimensionless viscosity parameter is taken to be such that the bare viscous stress overrides the order parameter stress. The phase boundaries are however different from the ones seen in the earlier model. However, for a choice of the viscosity parameter such that the order parameter stress and the bare viscous stress are comparable, we see two distinctly different attractors: a banded, periodic one that is common to both α1equalto 0, and not equal to 0 and a banded chaotic one for α1not equal to 0. Here, α1is a parameter that governs the nonlinearity in the stretching of the order parameter tensor along the direction of the applied shear. Quantitative analysis of the various chaotic attractors throws up not only positive Lyapunov exponents but also that the banded chaos is a “flip-flop” kind of chaos where the switching between two long-lived states of high and lows hear stress is chaotic, where as the behaviour in either of the two states is periodic, with either a single, isolated frequency or a bunch of harmonics. Also, the spatial correlation of the shear stress in the chaotic attractors is of much larger range than the temporal correlation, the latter being almost delta-function-like. On increasing the temperature of the system till it is above the isotropic–nematic transition temperature in the absence of shear, we find that under shear, similar attractors as those in the nematic case are observed, both for passive advection and for the full 1D hydrodynamics. This is an encouraging result since actual experiments are performed at a temperature for which the system is in the isotropic phase in the absence of shear. Thus for the 1D system, the parameter space has been explored quite extensively. Considering spatial variations only along the gradient axis of the system under shear is not enough since experiments have observed interesting behaviour in the vorticity plane in which Taylor velocity rolls were noted. Hence taking the system to 2D was necessary. Our numerical study of the 2D system under shear is incomplete because we came across computational difficulties. However, on shorter time scales we have seen a two-banded state with an oscillating interface and Taylor velocity rolls as well. The methodology used for the 2D study can also be used to reproduce the 1D results by the simple step of taking initial condition with no variation in the vorticity direction. This automatically ensures that no variation in the vorticity direction ever builds up because the equations of motion ensure that these variations in the system do not grow by themselves unless fed in at the start. Using this method, we were able to reproduce all the attractors found in the 1D calculation. Thus the 1D attractors have been observed using two different methods of calculation. Further work on the full 2D numerics needs to be done because we believe that spatiotemporally complex steady-state attractor s exist in the 2D system also for appropriate values of the parameters.

L’objet de cette étude est d’utiliser la technique des micelles inverses pour synthétiser des nanoparticules à transition de spin, de taille et de forme contrôlées afin d’en permettre l’utilisation en électronique moléculaire. Dans la première partie, nous avons déterminé les paramètres de synthèse influençant la taille et la forme des particules d’un complexe à transition de spin à fort potentiel d’application. Dans un deuxième temps, nous avons utilisé ces paramètres sur trois autres complexes afin de comprendre la relation entre les paramètres de la synthèse et la morphologie des particules. Les nanoparticules ainsi synthétisées constituent la base d’une discussion sur l’existence d’un lien entre la taille/forme des particules et les propriétés de transition de spin. Enfin, la dernière partie de ce travail est consacrée à l’utilisation de ces matériaux en électronique moléculaire, et l’observation des propriétés de photoconductivité et photovoltaïque à l’échelle des nanoparticules. / The aim of this project is to use the reverse micelles technique to synthesize spin crossover (SCO) nanoparticles with controlled size and shape in order to use them in molecular electronic applications. In the first part, we have determined the synthesis parameters that influence the particles size and shape of an attractive spin crossover complex, due to his potential application. In a second time, we used the determined parameters on three other SCO complexes to generalize the relationship between the synthesis parameters and the particles morphology. All the as-prepared nanoparticles are the basis of a discussion about the existence of a link between the size and/or shape of the particles and the SCO properties. The last part of this work is dedicated to the utilization of this materials in molecular electronic, and the observation of photovoltaic and photoconductive properties at the nanoparticles scale.

L'objectif de ce travail est de développer des vecteurs pharmaceutiques, encapsulant la vitamine E, adaptés à l'administration pulmonaire par aérosolisation. La vitamine E, antioxydant physiologique, peut être utilisée pour lutter contre les phénomènes du stress oxydatif en particulier ceux observés au niveau pulmonaire. L'encapsulation de la vitamine E dans des vecteurs inhalables a été envisagée afin d'optimiser son efficacité thérapeutique en améliorant la concentration du principe actif pouvant atteindre son site d'action, les alvéoles pulmonaires. Les différents systèmes d'encapsulation de la vitamine E ont été préparés par des méthodes utilisant des contacteurs à membrane. Le principe de préparation se résume au passage de la phase dispersée, à travers les pores d'une membrane microporeuse, au sein de la phase continue. Les avantages de cette technique sont en particulier une bonne reproductibilité et un faible apport d'énergie et par conséquent un coût d'exploitation modéré. De plus, les procédés à base de contacteurs à membrane se prêtent aisément au passage à l'échelle de production industrielle. Au cours de ce travail, les paramètres influençant le procédé de fabrication par contacteur à membrane ont été étudiés ; principalement la pression transmembranaire de passage de la phase discontinue, la force de cisaillement de la phase continue et la microstructure de la membrane utilisée. Différentes configurations membranaires ont été testées telles que (i) les modules membranaires tubulaires avec écoulement tangentiel de la phase continue, (ii) les membranes planes montées dans des cellules d'agitation et (iii) les membranes dotées d'un mouvement d'oscillation à l'intérieur de la phase continue. En cas d'émulsification directe, diverses membranes ont été utilisées : des membranes SPG, des membranes microsieves et des membranes en céramique. Pour la « premix emulsification » des membranes dites dynamiques, constituées par un lit de billes en verre, ont été étudiées / The present study investigated the preparation of pharmaceutical drug carriers encapsulating the vitamin E and intended for pulmonary administration after nebulisation. Vitamin E, a physiological antioxidant, could be used to prevent cigarette smoke toxicity since several pulmonary disorders are mainly caused by oxidative stress phenomena. The methods used for the drug carriers’ preparation were based on the membrane emulsification principle. In these methods, the to-be-dispersed phase was injected in the continuous phase through the pores of a microporous membrane. The advantages of this method are: a better control over the diffusive mixing at the liquid / membrane interface and thus a fine control of droplets size distribution, a less energy consumption and an easy extrapolation of the obtained results for an industrial large scale-up. In order to investigate the preparation processes, key parameters influence on particles characteristics was investigated. Different experimental set-ups were used: (i) tubular membranes with a cross flow circulation of the continuous phase, (ii) stirred cell device with a flat micro-engineered membrane, (iii) oscillating membrane module in a stationary continuous phase. For direct emulsification, various membranes were used such as : SPG membranes, micro-engineered membranes and ceramic membranes. For premix emulsification, a packed bed of glass beads, called dynamic membrane, was studied. Four different drug carriers were developed during this study: liposomes, micelles, nano-emulsion and solid-lipid particles. The different encapsulating systems were characterized in terms of size distribution, zeta potential, microscopic morphology, encapsulation efficiency and stability. Results showed that the obtained drug carriers presented convenient properties. After nebulization of vitamin E encapsulating systems, the obtained aerosols presented satisfying aerodynamic characteristics which allowed the prediction (using a mathematical model) of a high level of vitamin E deposit on its action site

Membranas e organelas constituem estruturas presentes nas células dos organismos. Estas estruturas representam interfaces entre eletrólitos. Uma tentativa de descrever, interpretar e compreender a distribuição iônica nas vizinhanças destas estruturas é feita neste trabalho com a análise de resultados de experimentos obtidos na investigação de alguns sistemas: 1) Sistemas constituídos por micelas de SDS. Medidas do pH nas vizinhanças de superfícies das micelas por sondas derivadas do ácido salicílico mostra variações do pH em termos da concentração de SDS e da concentração de sal adicionado. O objetivo dos experimentos é inferir o comportamento do pH nas vizinhanças de membranas biológicas que, por dissociação de alguns fosfolipídios, podem apresentar segmentos da membrana com carga na superfície. 2) A natureza \"zwitteriônica\" das membranas biológicas motivou o estudo da \"ligação iônica\" em micelas \"zwitteriônicas\", imersas em soluções com eletrólito, em concentrações variadas de sais de Cl- e Br- com os cátions monovalentes, Li+, Na+, K+, Rb+, Cs+ e tetrametil amônio (TMA+) e bivalentes Mg2+ e Ca2+. Os experimentos consistiram em determinar a concentração de haletos próximos a micela. A técnica de captura química mostra que há um grau de seletividade que não é determinado apenas pela carga iônica. 3) Resultados preliminares do grau de dissociação no interior de vesiculas de, cloreto de dimetildioctadecil amônio, DODAC, indicam que 8% dos monômeros estão dissociados em vesículas com o diâmetro médio em torno de 150 e 300 nm. As leis fundamentais usadas para compreender os resultados estão aliadas a hipótese de que os sistemas estudados estão em equilibrio termodinâmico, que a interação eletrostática é predominante e ao potencial eletrostático é conferido o papel do potencial da força média que atua nos íons. A simplificação adicional consistindo em admitir que os íons se comportam como cargas puntiformes no que se refere à interação eletrostática conduz o modelo teórico à equação de Poisson-Boltzmann que, linearizada, resulta na equação de Debye-Hückel. Hipóteses adicionais se fazem necessárias para formular o modelo como um problema matemático com condições de contorno. Para cada situação as hipóteses adicionais são discutidas. Sistemas hipotéticos são analizados com o intuito de comparar os resultados provenientes da equação de Poisson-Boltzmann e da equação de Debye-Hückel. A análise teórica dos sistemas conduz a resultados em acordo com os valores medidos. Entre as conclusões obtidas, neste trabalho, são mencionados: 1- As sondas derivadas do ácido salicílico mantêm os grupos dissociáveis próximos a superfície, a distância é da ordem de 0,1 nm, mesmo para sondas que apresentam cadeia longa entre o grupo nitrogênio e o grupo dissociável. 2- A especificidade iônica é bem descrita utilizando, além da carga elétrica, a massa do íon. Os íons na superfície de uma micela zwitteriônica têm liberdade translacional e portanto superfícies zwitteriônicas em solução de eletrólito apresentam condutividade elétrica na superfície. 3- As concentrações iônicas no interior de vesículas são uniformes em praticamente toda a região interna, apresentando variações apenas nas vizinhanças da superfície interna carregada eletricamente. / Membranes and organelles are structures present in biological systems. Such structures are interfaces between electrolytes. Addressing to the description, interpretation and comprehension of the ionic distribution around the structures an attempt is done is this work analyzing experimental results from the investigation of the following systems: 1) SDS micelles. \"pH\" measurements in the micellar surface neighborhood using salicylic acid probes show the pH values dependence with the SDS and added salt concentrations. The experiments aimed to infer the pH behavior in biological membranes where same phospholipids may dissociate and portions of the surface can acquire electrical charges. 2) The zwitterionic nature of biological membranes leads to the investigation of ion binding in zwitterionic micelles in electrolyte solutions with varied concentrations of Cl- or Br<SUP- salts with the cations Li+, Na+, K+, Rb+, Cs+ e tetramethylammonium (TMA+) and the bivalent cations Mg2+ e Ca2+. Halide concentration in the micellar vicinity was measured. Chemical trapping method shows there is a selectivity degree that does not depend only on the ionic charge. 3) Preliminary results in the determination of the inner dissociation degree of dioctadecyldimethylammonium chloride vesicles, DODAC, show that about 8% of the vesicle constituent monomers are dissociated in vesicles with 150 and 300 nm mean diameter. The theoretical description is based upon the thermodynamics equilibrium hypothesis about the systems and that the electrostatic interaction is the stronger interaction and also it is attributed to the mean electrostatic potential the role of the mean force potential acting on the ionic species. A further simplification in considering the ions as point charges with respect to the electrostatic interactions leads the model to the Poisson-Boltzmann equation and under linearization results in the Debye-Hückel alternative description. Additional hypothesis are necessary in order to have the model as a mathematical problem with boundary conditions and are discussed for each system. Hypothetical systems are analysed aiming the comparison between Poisson-Boltzmann and Debye- Hückel descriptions. Some conclusions derived in the analysis are: 1- The salicylic acid probes have the dissociable groups always near (~0,1nm) the micellar surface, even to the probes that have a long chain between the nitrogen group and the dissociable group. 2- In a zwitterionic micelle the ions on the surface have translational freedom and this is way the zwitterionic membranes in electrolyte solutions are conducting surfaces. 3- The ionic concentrations in the vesicle interior have uniformly value almost everywhere showing variations only in the vicinity of the electrically charged interior surface. The theoretical study of the three systems considered gives results in accord with experimental data.