Academic literature on the topic 'Série Hofmeister'

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Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco
O biossensor baseado no nanoporo unitário formado pela -hemolisina (-HL) do Staphylococcus aureus incorporada em bicamada lipídica plana permite a detecção, identificação e quantificação de diferentes compostos em meio aquoso. Os íons em meio aquoso podem causar efeitos específicos conhecidos como efeitos de Hofmeister. De acordo com a sua atuação na estrutura da água, os íons podem ser classificados como cosmotrópicos e caotrópicos. A mudança da estrutura da água por sua vez é capaz de influenciar na solubilidade e estrutura dos co-solutos. Então, a composição iônica da solução pode alterar a interação das moléculas solubilizadas. Este trabalho teve como objetivo investigar a influência de íons monovalentes na interação de moléculas unitárias orgânicas com nanoporos protéicos visando o entendimento dos mecanismos moleculares do processo e o aumento da sensibilidade do sensor. A confecção da bicamada lipídica plana e a inserção do nanoporo unitário na membrana, bem como os registros de correntes iônicas através dos poros foram realizados em condições de fixação de voltagem. No estudo da influência da concentração do eletrólito utilizamos as soluções de KCl em concentrações de 1M à 4M. A comparação dos efeitos dos ânions da família VIIA foi feita com sais de potássio em concentração de 4M e os efeitos dos cátions da família IA mais o NH4 + foram estudados utilizando sais de cloreto (4M). A ligação da molécula unitária (analito) ao nanoporo causa um bloqueio característico na corrente iônica que passa através do poro protéico. A análise desses eventos moleculares (bloqueios) permite determinar as constantes cinéticas da interação analito-nanoporo. Estabelecemos que aumentando a concentração do KCl na solução banhante de 1M para 4M ocorre um aumento na frequência, profundidade de bloqueio e tempo de residência do analito (polietilenoglicol 1294; PEG 1294). Analisando a mudança da frequência dos bloqueios com relação à concentração de KCl, estabelecemos que a concentração do analito detectável pelo sensor diminui com o aumento da concentração do sal de 1M para 4M cerca de cem vezes, indicando maior sensibilidade do sensor quando banhado por uma solução de KCl 4M. O forte aumento no tempo de residência do analito dentro do nanoporo ocorre devido ao aumento da energia de interação do complexo analito/nanoporo. A constante de associação do complexo PEG/nanoporo é cerca de cem vezes maior e a constante de dissociação é cerca de cem vezes menor em KCl 4M do que em KCl 1M. Essas mudanças melhoram a detecção e tornam viável a detecção da molécula unitária. Encontramos que a interação PEG/nanoporo é dependente de voltagem transmembrana indicando que o polímero nãoiônico (PEG) atua como uma molécula com carga elétrica em meio aquoso. Foi visto que a solubilidade do PEG é uma função da concentração do sal também. Uma forte correlação entre as mudanças das constantes e a solubilidade do PEG foi estabelecida. Provavelmente, o efeito salting-out é o responsável por mudanças estabelecidas na interação do analito com o nanoporo. Avaliando a influência dos íons da família IA e VIIA na interação do complexo PEG/nanoporo observamos que esta é muito dependente do tipo do sal. A sensibilidade do sensor depende fortemente do tipo de ânion da solução banhante e na solução de KF 4M é cerca de dez vezes maior e na solução de KI 4M é cerca de dez vezes menor quando comparada com a solução de KCl 4M. Estabelecemos que os valores das constantes de formação do complexo PEG/nanoporo diferem dependendo do tipo do cátion. A solução de KCl teve a maior constante de formação, enquanto que, as soluções de NH4Cl e LiCl tiveram as menores constantes, portanto, evidencia-se que o tipo de eletrólito influencia em todos os parâmetros da interação do analito com o nanoporo. Por isso, a escolha do eletrólito ótimo é uma etapa importante para sensores estocásticos baseados em um único nanoporo

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FACEPE
A interação de moléculas unitárias com nanoporos individuais é relevante em diversos processos biológicos, químicos e físicos, uma vez que pode proporcionar o desenvolvimento de dispositivos analíticos, dentre os quais, podemos destacar: sensores, biossensores, espectrômetros de massa e sequenciadores moleculares. Nesse contexto, o nanoporo formado pela α-hemolisina (α-HL) de Staphylococcus aureus é de especial interesse no desenvolvimento de dispositivos sensores devido às suas características estruturais e funcionais. Várias estratégias são utilizadas para melhorar a sua capacidade de detecção pelo uso de adaptadores moleculares ou pela modificação química do nanoporo. O diferencial deste trabalho deve-se a modificação das condições físicos-químicas da solução banhante do elemento de reconhecimento molecular ou seja, o nanoporo unitário. Os íons em meio aquoso podem causar efeitos específicos conhecidos como efeitos de Hofmeister. De acordo com a sua atuação na estrutura da água, os íons podem ser classificados como cosmotrópicos ou caotrópicos. A mudança da estrutura da água por sua vez é capaz de influenciar na solubilidade e estrutura dos co-solutos. Igualmente a composição iônica da solução pode alterar a interação das moléculas solubilizadas. Deste modo neste estudo investigamos os efeitos específicos induzidos pelos cátions e ânions da Série de Hofmeister na interação de moléculas unitárias orgânicas com nanoporos proteicos individuais. A confecção da bicamada lipídica plana e a inserção do nanoporo unitário na membrana, bem como os registros de correntes iônicas através dos poros foram obtidos em condições de fixação de voltagem. Na solução banhante do nanoporo utilizou-se os ânions da família VIIA, formando sais com o K⁺, ou, os cátions da família IA e o íon amônio, formando sais com o Cl⁻, todos na concentração de 4M. A interação da molécula unitária (analito) com o nanoporo causa um bloqueio característico na corrente iônica que passa através dele. A análise desses eventos permite determinar as constantes cinéticas da interação analito-nanoporo. Avaliando a influência do íon amônio e dos íons da família IA e VIIA na interação do analito (polietilenoglicol 1294; PEG 1294) com o nanoporo observamos que esta é muito dependente do tipo do sal. Todos os íons utilizados nesse trabalho induziram efeitos específicos em sistema confinado. Com relação à influência na constante de associação, todos os ânions seguiram a típica série de Hofmeister: F⁻ > Cl⁻ > Br⁻ > I⁻. Já para a constante de dissociação e a solubilidade do PEG, encontramos uma sequência de Hofmeister inversa: F⁻ < Cl⁻ < B⁻ < I⁻. Ao contrário do observado com os ânions, a influência dos cátions sobre as constantes de interação não seguiu a série de Hofmeister. Para a constante de associação, obtivemos a seguinte sequência: Cs⁺ > K⁺ ≥ Rb⁺> Na⁺ > NH⁺ > Li⁺. Para a constante de dissociação obtivemos: K⁺ < Rb⁺ < Cs⁺ < Na⁺ < NH₄⁺ < Li⁺. Uma forte correlação entre as mudanças das constantes cinéticas e a solubilidade do PEG também foi estabelecida. Demonstramos que o efeito salting-out é o responsável por mudanças estabelecidas na interação do analito com o nanoporo. Adicionalmente as constantes de interação PEG/nanoporo são dependentes do potencial transmembrana indicando que o polímero não iônico (PEG) atua como uma molécula com carga elétrica em meio aquoso iônico. Estabelecemos também que a sensibilidade do sensor ao PEG depende fortemente do tipo de íon presente na solução banhante do nanoporo.
The interaction of single molecules with single nanopores is important in several biological, chemical and physical processes because it can provide the development of analytical devices, such as sensors, biosensors, mass spectrometers and molecular sequencers. In this context, the nanopore formed by α-hemolysin (α-HL) of Staphylococcus aureus is very studied for the development of sensor devices due to their structural and functional characteristics. Several strategies are adopted to improve its detection ability, such as the use of molecular adapters and chemical modification of the nanopore. In this work, our approach is different, we modify the ionic composition of the bath solution of the nanopore protein. Ions in aqueous environment can cause specific effects known as Hofmeister effects. According to their influence on the structure of water, the ions can be classified as kosmotropic and chaotropic. The change in the structure of water in turn can influence the structure and solubility of the co- solutes. Then the ionic composition of the solution may change the interaction of solubilized molecules. The goal of this study was to investigate the specific effects induced by cations and anions from Hofmeister series on the interaction of single molecules with nanopores. The preparation of planar lipid bilayer, and single nanopore insertion into membrane, and records of ionic currents were conducted in conditions of voltage clamp. In the bath solution, we use the anions from group VIIA, forming salts with K⁺, and cations from group IA plus ammonium ion, forming salts with Cl⁻ at 4M concentration. The interaction of the analyte with the nanopore causes a blocking characteristic in ionic current through the pore protein. The analysis of these molecular events permit to determine the kinetic constants of the analyte-nanopore interaction. The influence of the anions and cations here investigated in interaction of the analyte (polyethylene glycol 1294, PEG 1294 ) with the nanopore is very dependent on the type of salt. All ions used in this study induced specific effects in confined spaces. With regard to the influence on the on-rate constant, all anions followed the typical Hofmeister series: F⁻ > Cl⁻ > Br⁻ > I⁻. For the off-rate constant and solubility of PEG, we found an inverse Hofmeister sequence: F⁻ < Cl⁻ < Br⁻ < I⁻. However, the influence of the cations on the rate constants didn’t follow the Hofmeister series. For the on-rate constant, we obtained the following sequence: Cs⁺ > K⁺ ≥ Rb⁺ > Na⁺ > NH⁺ > L⁺. For the off-rate constant, we obtained : K⁺ < Rb⁺ < Cs⁺ < Na⁺ < NH₄⁺ < Li⁺. Strong correlation between the changes of the rate constants and the PEG solubility was established. We suggest that the salting-out effect is responsible for the changes on the interaction analyte/ nanopore. Additionally, we found that the rate constants are dependent on voltage transmembrane indicating that the non-ionic polymer (PEG) acts as a molecule with electric charge in an aqueous environment. We also established that the sensitivity of the nanopore it was strongly dependent on the type of ion present in the bath solution. So, the choice of the optimal electrolyte is an important step to stochastic sensors based on a single nanopore.

Les catasurfs sont des tensioactifs cationiques à contre-ion catalytiques qui ont été conçus pour la formulation de systèmes de microémulsion oxydante triphasiques utilisés comme milieux réactionnels pour l’oxydation de substrats organiques par H2O2. Les propriétés physicochimiques en solution aqueuse (solubilité, température de Krafft, cmc) d’ammonium quaternaires amphiphiles ont été déterminées pour une série de contre-ion, mettant en évidence l’importance de la polarisabilité et de l’hydratation de l’anion sur le caractère amphiphile du tensioactif. Le comportement de phase des systèmes ternaires eau/solvant/tensioactif a été étudié en fonction de divers paramètres (contre-ion, solvant, structure de l’ammonium quaternaire, addition de tensioactif non ionique) et notamment le comportement des tensioactifs catalytiques à base de molybdate et tungstate en présence de H2O2. La peroxydation de l’anion, en modifiant la polarisabilité de celui-ci, modifie radicalement le caractère hydrophile/hydrophobe du tensioactif et son comportement de phase. Les diverses considérations ont conduit à la conception de milieux réactionnels triphasiques à base de molybdate ou tungstate d’ammonium quaternaires, avec divers solvants (aromatiques, acétates d’alkyles) et contrôle du pH. Ce type de milieu présente plusieurs avantages majeurs en termes d’application : large interface eau/solvant dans la phase microémulsion, simplicité de mise en œuvre avec seulement trois constituants, facilité de traitement du milieu après réaction avec le catalyseur localisé en phase microémulsion et le(s) produit(s) en phase organique, séparation instantanée des phases grâce aux tensions de surface ultra-basses. L’efficacité de ces systèmes a été évaluée et validée dans le cas de l’oxydation des sulfures par le système catalytique H2O2/MoO42-, et dans le cas de l’époxydation d’alcènes par H2O2/WO42- en milieu acide
Catasurfs are cationic surfactant bearing a catalytic counterion and have been designed for the formulation of three-phase oxidative microemulsion systems whose purpose is the H2O2 oxidation of organic substrates. Physicochemical properties of amphiphilic quaternary ammonium in aqueous solution have been investigated with various counterions, showing the dependence of anion polarisability and hydration on the amphiphilic properties of the surfactant. The phase behavior of water/solvent/surfactant ternary mixtures has been examined according to various parameters (counterion, solvent, quaternary ammonium structure, addition of non ionic surfactant), and particularly the behavior of catalytic surfactants with H2O2. Anion peroxydation, by a variation of its polarisability, radically changes its water and oil affinities, and its phase behavior. The various observations led us to elaborate three-liquid-phase reaction media based on quaternary ammonium molybdate or tungstate, with various solvents (aromatic and alkyl acetates) and under pH control. This type of medium has several practical major advantages: large water/oil interface in the microemulsion phase, simplicity of implementation with only three components, ease of reaction medium treatment with the catalyst lying in the middle phase and the product(s) in the organic phase, instantaneous phase separation thanks to ultra-low interfacial tensions. The efficiency of these three-phase microemulsion systems has been evaluated and validated for the oxidation of sulfides by the H2O2/MoO42- catalytic system, and for the epoxidation of alkenes with H2O2/WO42- in acidic media

Une étude de la structure d'interfaces liquide-vapeur est détaillée dans cette thèse. Les surfaces étudiées sont étroitement liées, afin de pouvoir déterminer l'influence des différents types d'interactions moléculaires, et de cerner les mécanismes responsables des propriétés physiques de ces surfaces. La diffusion diffuse de rayons x a permis de mesurer, pour différents liquides, le spectre des fluctuations de hauteur d'une surface nue. Ces mesures ne concordent plus avec le modèle des ondes capillaires pour des vecteurs d'onde supérieurs à 10^8 m^(-1) : la notion de tension de surface n'est plus valable à ces échelles et doit être remplacée par l'énergie de surface effective. Il est montré que cette dernière décroît lorsque la longueur d'onde associée à la fluctuation est de l'ordre de quelques dizaines de distances moléculaires. Elle augmente pour les plus petites longueurs d'onde envisageables. L'accord remarquable avec la théorie proposée par K. Mecke et S. Dietrich. Ces mesures ont été étendues au cas d'interfaces décorées par un film moléculaire: l'énergie de surface effective est alors correctement décrite par une rigidité de courbure seule, qui est mesurée pour des films dans différentes phases. En particulier, l'effet de la renormalisation de la rigidité de courbure par l'élasticité lorsque le film s'apparente à un réseau bidimensionnel connecté à été mis en évidence. En complément de mesures de fluctuations de surfaces de solutions ioniques, nous avons montré que l'excès de concentration en ions au voisinage de la surface peut être mesuré par des expériences de fluorescence de rayons x et d'ellipsométrie. Cette mesure est essentielle pour comprendre les origines de la variation de la tension de surface, et plus généralement pour expliquer la spécificité des ions de la série de Hofmeister. Ces expériences ouvrent ainsi une voie pour comprendre un phénomène inexpliqué depuis plus d'un siècle
The structure of liquid-vapor interfaces is investigated in this thesis. Different kinds of surfaces have been examined in order to determine the influence of each component of molecular interactions on the physical properties of these surfaces. The height-height fluctuation spectrum of different bare liquid-vapor surfaces has been determined by x ray diffuse scattering. These measurements show that the cappilary-wave model fails at small length scales (wave-vector > 10^8 m^(-1)). The problem of the small scale structure can be addressed by considering corrections to the surface energy through an effective momentum-dependent surface energy. We show that the momentum-dependent surface energy first decrease from its macroscopic value and then increases with increasing wave vector. The agreement with a theory proposed by K. Mecke and S. Dietrich is excellent. We then turned to fatty acid films at the water-air interface: a bending energy is sufficient to describe the whole momentum-dependent surface energy. It has been measured for films in various phases. The particular case of a polimerized monolayer has been specially investigated, and a coupling between height fluctuations and in-plane phonons has been demonstrated. Surface of ionic solutions have also been investigated: height fluctuations spectrum has been measured. In addidition, x ray grazing incidence fluorescence and ellipsometry experiment have been performed in order to measure the adsorption excess of ions. Knowing this excess is essential to understand the origins of surface tension's variation when salts are added, and so to explain ion specificity and the Hofmeister effect. Then, these experiments are fundamental to account for a long time unexplained phenomenon

La peau constitue une interface unique entre l’organisme et son environnement extérieur. Son rôle principal est de protéger les organes internes contre les facteurs externes. Le stratum corneum, est la couche supérieure et très hydrophobe de la peau. Elle était considérée peu perméable pour les molécules hydrophiles chargées tels que les ions inorganiques. Plusieurs études ont démontré le contraire et l’étude récente par Paweloszek et al. a indiqué l’importance du transport actif dans le passage cutanée des ions halogénures. L’absorption cutanée des ions classés selon la série de Hofmeister (F-, Br-, I-, SCN, ClO4-) seuls et en mélanges bi- et ternaires a été évaluée dans deux séries d’expériences in vitro. Tous les ions ont pénétré dans la peau viable en 24h. Parmi les halogénures, la presence de F- a diminué l’absorption de Br- et de I- en mélanges, tandis qu’une synergie d’absorption entre Br- et I- a été observée. Dans le second groupe (I-, SCN-, ClO4-), la pénétration cutanée du ClO4- a été inhibé par la présence des autres ions. L’impact de la formulation sur l’absorption cutanée de Ca2+ et Mg2+ présents dans des eaux thermales (TSW) a été évaluée. Différentes formes galéniques telles que des émulsions (TSW/O, O/TSW, TSW/O/W) et des liposomes ont été étudiées. Les liposomes et les émulsions ont favorisé la rétention de ces ions d’intérêt dans les couches cutanées en comparaison à l’eau themale pure. Nos résultats ont démontré que les effets bénéfiques associés aux traitements à base de TSW ne sont pas seulement dus à une action superficielle mais à la pénétration des ions dans la peau. Dans cette thèse nous démontrons la capacité des anions et cations à pénétrer la peau viable in vitro et nous mettons en évidence les effets de mélange et de la formulation sur la pénétration cutanée
Human skin forms a unique interface between the body and the external environment. Its main role is to protect the internal organs from external factors. Its highly hydrophobic outermost layer, stratum corneum, has long been believed impermeable for highly hydrophilic compounds, including ions. Several studies proved this concept wrong, and recent research by Paweloszek et al. demonstrated the important contribution of facilitated transport in permeation of halide anions. Skin penetration of anions classified in Hofmeister series (of F-, Br-, I-, SCN, ClO4-) alone and in bi- and ternary mixtures in two experimental series was studied in vitro. All tested ions permeated viable skin within 24h. Among halides, the presence of F- reduced the penetration of Br- and I- in mixtures, and synergy between Br- and I- was observed. Within the second group (I-, SCN-, ClO4-) the inhibition of ClO4- penetration in the presence of other ions was observed. Finally, the impact of formulation of marketed thermal spring water (TSW) into emulsions (TSW/O, O/TSW, TSW/O/W) and liposomes on skin absorption of Ca2+ and Mg2+ was evaluated. Liposomes and emulsions promoted retention of Ca2+ and Mg2+ in skin layers as compared to TSW. Our results prove that the beneficial effects observed during treatment with TSW are associated with penetration of the minerals into and through the skin and are not only a surface action. In this thesis, we demonstrate the possibility of both anions and cations to penetrate viable skin in vitro, and we disclose the effects of mixing and formulating on skin penetration profiles

La poly(2-isopropyl-2-oxazoline) (PIPOZ) est un polymère thermosensible qui possède une température de solution critique inférieure (LCST) autour de 40 °C en solution aqueuse. Les travaux présentés s’intéressent aux propriétés en solution aqueuse et aux interfaces, de l’homopolymère PIPOZ, d’une PIPOZ fonctionnalisée avec un groupement lipidique (lipo-PIPOZ) et de copolymères à blocs à base de poly(éthylène glycol) et de PIPOZ. Si elle est régulièrement comparée à son isomère structurel le poly(N-isopropylacrylamide) (PNIPAM), les études sur les propriétés en solution de la PIPOZ sont cependant moins complètes que celles sur le PNIPAM. Le premier objectif des travaux présentés ici est de parfaire la connaissance du comportement en solution de la PIPOZ en présence d’additifs. Les effets de sels et de solvants hydromiscibles sur la solubilité de la PIPOZ ont été investigués par turbidimétrie et microcalorimétrie sur trois homopolymères de masses moléculaires différentes. Contrairement aux solutions de PNIPAM, l’ajout de méthanol à la solution de PIPOZ ne conduit pas au phénomène de cononsolvency où la solubilité du polymère diminue pour une certaine gamme de fractions volumiques de cosolvant. L’effet a néanmoins été observé dans le cas de système PIPOZ/Eau/THF. L’effet de sels sur la solubilité de la PIPOZ suit la série Hofmeister. La présence de sels chaotropes (NaI et NaSCN) en solution ont révélé un effet bien plus important sur la solubilité de la PIPOZ que pour son isomère. Les valeurs de point troubles de la solution de PIPOZ augmentent de plus de 30 °C pour une concentration en sel supérieure à 1 M. L’autre objectif de cette thèse est de synthétiser un système à base de PIPOZ capable de s’auto-assembler à l’interface air-eau afin de former des films interfaciaux par la technique Langmuir-Blodgett. A cette fin, un amorceur contenant un groupement lipidique (2 chaînes alkyles et un groupement phosphate) a été synthétisé et utilisé pour la polymérisation cationique par ouverture de cycle (CROP) du monomère 2-isopropyl-2-oxazoline conduisant à l’obtention d’un lipo-PIPOZ (Mn = 10 kg.mol-1). L’effet de deux sels (NaSCN et NaCl) sur les films interfaciaux a été étudié. Malgré leur effet opposé sur la solubilité de la PIPOZ en solution, ils conduisent tous les deux à l’expansion de la monocouche de lipo-PIPOZ. Transférés sur des substrats de mica, ces films ont été visualisés par microscopie à force atomique (AFM). La iv présence de sels dans la sous-phase lors de la formation de monocouches conduit à la formation d’agrégats d’épaisseur ~ 10 nm dont le diamètre augmente avec la concentration en sel. Enfin, le dernier objectif est de caractériser les propriétés en solutions de copolymères à blocs PIPOZ-b-PEG-b-PIPOZ. La polymérisation par CROP de la 2-isopropyl-2-oxazoline a été amorcée à partir d’un PEG (Mn = 2 kg.mol-1) bifonctionnel, Le polymère synthétisé (TrOH, Mn = 11 kg.mol-1) a ensuite subit une fonctionnalisation des extrémités de chaînes par des groupements octadécyles conduisant à l’obtention d’un copolymère à blocs téléchélique amphiphile et thermosensible (TrC18). Les propriétés des copolymères en solution aqueuse ont été étudiées par turbidimétrie, diffusion dynamique de la lumière (DLS), microcalorimétrie (DSC), microscopie électronique à transmission et spectroscopie à sonde fluorescente, FT-IR et AFM. Les deux copolymères sont thermosensibles et présentent des valeurs de points troubles de ~ 48 °C pour le copolymère TrOH et de ~ 38 °C pour le copolymère amphiphile. Ce dernier s’auto-assemble à température ambiante et forme, en solution aqueuse, des micelles de type fleurs de rayon hydrodynamique RH ~ 8 nm. L’effet prolongé de la température sur la cristallisation des blocs de PIPOZ a aussi été examinée. Les deux polymères cristallisent en solution aqueuse conduisant à la formation de fibres insolubles dans l’eau. Mots-
Poly(2-isopropyl-2-oxazoline) (PIPOZ) is a thermosensitive polymer whose lower critical solution temperature (LCST) in water is ~ 40 °C. This thesis focuses on the properties in aqueous solution and on interfaces of new poly(2-isopropyl-2-oxazoline) systems. PIPOZ is often compared to its structural isomer, the renowned poly(N-isopropylacrylamide) (PNIPAM). If PNIPAM has been the center of thermosensitive polymer research for the last three decades, it is PIPOZ which has recently been gaining interest. The first aim of the thesis is to improve on the knowledge on PIPOZ properties in aqueous solution in the presence of water-soluble additives. Effect of salts and cosolvents were investigated by turbidimetry and microcalorimetry (DSC) on PIPOZ homopolymers of different molecular weights. Effect of salts on PIPOZ solubility follows the Hofmeister series. Chaotropic anions (SCN-, I-) induce a large increase (up to 30 °C) of the cloud point temperature of PIPOZ solution which is 10 times larger than for PNIPAM. Adding methanol into PNIPAM aqueous solution leads to a decrease in solubility of the polymer. This phenomena is called cononsolvency. Unlike PNIPAM solutions, the addition of methanol in PIPOZ solution does not lead to a cononsolvency effect. Nevertheless, cononsolvency has been observed in the case of THF addition into PIPOZ aqueous solutions. The second aim of this work was to design and synthesize an amphiphilic PIPOZ able to anchor itself at the air-water interface and to form stable monolayer via the Langmuir-Blodgett technique. For that purpose, a lipidic initiator containing two alkyl chains and a phosphate group, was synthesized and used to initiate the cationic ring opening polymerization (CROP) of 2-isopropyl-2-oxazoline. The obtained amphiphilic (lipo-PIPOZ, Mn = 10 kg.mol-1) forms stable monolayers at the air-water interface. The presence of salt (NaCl or NaSCN) in the sub-phase during the compression of the films leads to expansion of the monolayer even if the salts have opposite effect on PIPOZ solubility in solution. The interfacial films were then transferred onto mica substrates and captured by atomic force microscopy (AFM). The salts induced the formation of aggregates (height ~ 10 nm) whose diameter depends on the salt and its concentration. At last, a block copolymer, TrOH, containing a central poly(ethylene glycol) (PEG) (Mn = 2 kg.mol-1) and two PIPOZ blocks was obtained by CROP of 2-isopropyl-2-oxazoline initiated vi by a bi-functionnal PEG. The total molecular weight was Mn ~ 11 kg.mol-1. Hydrophobic chain ends modification has been performed onto TrOH to bring amphiphilicity and to get a telechelic octadecyl-end capped block copolymer TrC18. The properties of these two block copolymers in water were characterized by dynamic light scattering (DLS), microcalorimetry (DSC), electronic transmission microscopy (TEM) and fluorescence spectroscopy, FT-IR and AFM. Cloud point temperature of copolymer solutions was found to be around 48 °C for TrOH and around 38°C for the amphiphilic analogue TrC18. The latter self-assembles at room temperature into flower micelles whose hydrodynamic radius is RH ~ 8 nm. Extended heating of both copolymer solutions leads to crystallization of PIPOZ block and insoluble fibers form in solution.

Les stérosomes, des vésicules artificielles composées d’amphiphiles monoalkylés et d’un grand pourcentage de stérols, sont prometteurs dans plusieurs domaines comme les industries pharmaceutiques et alimentaires. Il existe des stérosomes chargés négativement, positivement et neutres. Dans ce mémoire, nous avons approfondi nos connaissances sur les propriétés physico-chimiques des stérosomes chargés : acide palmitique (PA)/stérol et stéarylamine (SA)/cholestérol (Chol). Premièrement, afin de mesurer la diffusion latérale de PA dans les membranes PA/stérol (30/70 mol/mol) par RMN à gradients pulsés, nous avons tenté de former des bicouches liquide-ordonnées (lo) orientées magnétiquement avec ce mélange. En s'inspirant de l’idée que l’ajout de 1,2-dihexanoyl-sn-glycéro-3-phosphocholine (DHPC), un lipide à courtes chaînes, dans le système 1,2-dimyristoyl-sn-glycéro-3-phosphocholine (DMPC) mène à la formation de bicouches orientées, nous avons étudié la formulation PA perdeutéré/acide hexanoïque (HA)/Chol avec une proportion molaire de 25/18/57 à plusieurs températures; aucune formation de bicouches orientées n’a été observée. Ce résultat pourrait être expliqué par la solubilisation partielle de HA en milieu aqueux. Alors, une quantité insuffisante serait insérée dans la bicouche pour induire son orientation. La formulation PA perdeutéré/DHPC/Chol n’a pas conduit, elle non plus, à des bicouches orientées magnétiquement à des températures et concentrations lipidiques variées. En étudiant le mélange DMPC/DHPC/Chol (67/17/14), nous avons remarqué que la présence de Chol inhibait l'orientation magnétique des bicouches. Tandis que le mélange DMPC/DHPC/stigmastérol (SS) avec les proportions molaires 67/19/14 et 72/21/7 conduisait à des bicouches orientées avec leur normale (n) perpendiculaire au champ magnétique à 40 °C et 50 °C. Ces résultats suggèrent que le mélange PA/SS avec une proportion de lipide à courtes chaînes, HA et DHPC, pourrait mener à des bicouches orientées magnétiquement. Le mélange PA/Chol avec un lipide à courtes chaînes pourrait aussi être étudié en présence des lanthanides. Deuxièmement, nous avons examiné la possibilité de moduler la libération de matériel encapsulé dans des liposomes essentiellement composés de PA et d’un stérol. Il est connu que le mélange PA/Chol (30/70) à pH ≥ 7,5 forme des liposomes très peu perméables. Il est avantageux de pouvoir moduler la perméabilité pour avoir un contrôle sur le temps de libération de leur contenu, qui est un paramètre de grande importance pour les formulations liposomales de médicaments. D’abord, il a été montré que l’acide oléique (OA)/Chol (30/70) est capable de former des vésicules, ce qui n’avait jamais été prouvé auparavant. Par contre, les bicouches OA/Chol (30/70) ne sont pas plus perméables que les bicouches PA/Chol (30/70). L’ajout de 1-palmitoyl-2-oléoyl-sn-glycéro-3-phosphatidylcholine (POPC) dans le mélange PA/Chol n’augmente pas plus la perméabilité. En effet, les cinétiques de relargage de calcéine des vésicules PA/POPC/Chol (15/27.5/57.5), POPC/Chol (40/60) et POPC étaient très semblables à celle de PA/Chol (30/70). Il a été remarqué que les études littéraires se contredisent à propos de la perméabilité à la calcéine des bicouches de phosphatidylcholine (PC). L’explication de ces divergences est inconnue pour le moment. En remplaçant la moitié de la proportion molaire de Chol par le cholate de sodium (SC) dans le mélange PA/Chol (30/70), la membrane n’était pas plus apte à libérer son contenu. Il se pourrait que le SC se retrouvant dans la bicouche n’induit pas une diminution d’empilement. Il est aussi possible que le SC ne s'insère pas dans la membrane à cause de son hydrophilie considérable et il pourrait alors former seul des micelles. En remplaçant complètement le Chol par le sulfate de cholestérol (SChol), un stérol chargé négativement, et en préparant les vésicules à un bas pH, la formulation PA/SChol (30/70) mène à une très grande perméabilité à pH 7.5; le relargage est provoqué par un saut de pH. Nos travaux suggèrent qu'il serait possible de moduler la perméabilité des liposomes en les préparant avec le mélange PA/SChol/Chol en variant les proportions entre 30/63/7 à 30/70/0. Le diagramme pH-composition du mélange PA/SChol/Chol indique que ces proportions conduisent, à pH 7.4, à la coexistence de phases solide et lo en différentes proportions, ce qui pourrait moduler la perméabilité membranaire. Troisièmement, les résultats de perméabilité obtenus avec la calcéine et les difficultés survenues lors de l’extrusion des vésicules encapsulant cette sonde nous ont amené à nous demander si la calcéine interagit avec les bicouches chargées. L’impact de certains anions, dont la calcéine, a été examiné sur les bicouches chargées positivement SA/Chol (50/50). La calorimétrie différentielle à balayage (DSC, de l’anglais differential scanning calorimetry), indique qu’il n’y a aucune transition entre 25 et 90 °C pour les liposomes SA/Chol (50/50) à pH = 7.4. L’ajout de chlorure de sodim (375 mM) n’a pas mené à la formation d’agrégats et aucune transition n’a été observée sur le thermogramme. La formation d’agrégats macroscopiques instantanément après l’ajout d’hydrogénophosphate de sodium (125 mM), de sulfate de sodium (125 mM) et de calcéine (3 mM) a été observée. Une transition a été observée sur les thermogrammes en présence de ces sels. Les agrégats observés pourraient être associés à la transition de phase. L’effet des anions sur la température et l’enthalpie de transition suivent le même ordre que la série d’Hofmeister : sulfate > hydrogénophosphate > chlorure (pas de pic). La calcéine avait l’impact le plus prononcé sur l’agrégation; ceci illustre que la calcéine n’est pas une sonde fluorescente inerte avec le mélange SA/Chol. Elle pourrait être un chaotrope volumineux. De plus, les interactions SA-calcéine plus fortes, menant à l’agrégation des vésicules, que les interactions PC-calcéine pourraient s’expliquer par le fait que la SA est chargée positivement.
Sterosomes are artificial vesicles that are composed of monoalkylated amphiphiles and a large percentage of sterols. They are promising in areas such as pharmaceutical and food industries. Sterosomes can be found in anionic, cationic and neutral form. The work of this master’s thesis focuses on gaining additional knowledge on the physicochemical properties of charged sterosomes such as palmitic acid (PA)/sterol and stearlyamine (SA)/cholesterol (Chol). Our first aim was to find an approach to form liquid-ordered (lo) bilayers that can orient in a magnetic field with the PA/sterol (30/70 mol/mol) mixture. This will allow us to study the lateral diffusion of PA. It has been demonstrated that mixing 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), a short chain lipid, with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) results in bilayers that orient with their normal (n) perpendicular to the magnetic field. Therefore, perdeuterated PA/hexanoic acid (HA)/Chol (25/18/57) mixture was studied at different temperatures; however, results showed no bilayer orientation. It was suggested that this could be due to the partial solubility of HA in aqueous phase. Consequently, an insufficient quantity of HA was available to induce bilayer orientation. Furthermore, perdeuterated PA/DHPC/Chol mixture was studied at different temperatures and lipid concentrations, which also led to no bilayer orientation. While studying DMPC/DHPC/Chol (67/17/14) formulation, it was understood that Chol inhibits bilayer orientation. On the other hand, two different molar proportions of DMPC/DHPC/stigmasterol (SS) (67/19/14 and 72/21/7) led to bilayers that orient with their n perpendicular to the magnetic field at 40 °C et 50 °C. These results suggest that by adding a short chain lipid such as HA and DHPC to PA/SS mixture could lead to oriented bilayers. Another interesting track would be to work with PA/short chain lipid/Chol mixture in the presence of lanthanides. Our second aim was to find different formulations of vesicles, containing at least PA and a sterol, with distinctive permeability. It has already been established that PA/Chol (30/70) bilayers are in lo phase as long as PA is deprotonated (pH ≥ 7,5) and have a very limited permeability. The ability to modulate permeability would allow control over the release time of an encapsulated product, which is an important parameter in the development of novel liposomal drug delivery systems. It was proven that oleic acid (OA)/Chol (30/70) mixture is able to form bilayers, which has not been shown previously. However, OA/Chol (30/70) bilayers were not much more permeable than PA/Chol (30/70) bilayers. Adding 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in PA/Chol system did not lead to higher permeability either. Results of calcein release kinetics from PA/POPC/Chol (15/27.5/57.5), POPC/Chol (40/60) and POPC vesicles were not very different from the one found for PA/Chol (30/70) vesicles. It was noted that contradictory results were found in the literature regarding calcein permeability from phosphatidylcholine (PC) membranes. For the moment, explanations related to these divergences have yet to be given. Furthermore, no increase in membrane permeability was found after substituting half of the molar proportion of Chol by sodium cholate (SC) in PA/Chol (30/70) mixture. One suggestion would be that SC insertion in the bilayer does not induce a reduction in the packing of lipids. Another suggestion would be that SC does not insert in PA/Chol bilayers due to its considerable hydrophilic character and forms micelles on its own. Highly permeable membrane was found when Chol was completely replaced by cholesterol sulfate (SChol), a negatively charged sterol, and vesicle preparation was done at low pH. The pH-triggered release method was used. Our work suggests that by varying the molar proportion of PA/SChol/Chol mixture between 30/63/7 and 30/70/0, it would be possible to obtain different vesicle formulations with distinctive permeability. In between these molar proportions, the pH-composition diagram of PA/SChol/Chol shows the coexistence of solid and lo phases in different proportions at pH 7.4, which could modulate the permeability. Some ambiguous calcein release results and struggles arising from the extrusion of calcein-encapsulated liposomes led us to wonder if this dye interacts with charged bilayers. The impact of some anions, including calcein, was examined on SA/Chol (50/50) charged bilayers. Thermodynamic studies were done by differential scanning calorimetry (DSC). SA/Chol (50/50) mixture showed no transition between 25 and 90 °C at pH 7.4. In the presence of sodium chloride (375 mM), there was no indication of aggregation or the appearance of a transition on the thermogram. Macroscopic aggregates were instantly observed after addition sodium hydrogenphosphate (125 mM), sodium sulphate (125 mM) and calcein (3 mM). Furthermore, a phase transition was also noticed on the thermograms in the presence of these salts. It is suggested that the appearance of the transition can be associated with the formation of aggregates. The effect of anions on the transition temperature and enthalpy follows the Hofmeister series: sulfate > hydrogenphosphate > chloride (no peak). Calcein had the highest impact on the formation of aggregates. This indicates that calcein is not a good candidate to be used as a fluorescent dye with SA/Chol mixture. It was suggested that calcein could be a large chaotrope anion. In contrast to PC-calcein interactions, SA-calcein interactions led to the aggregation of vesicles probably due to stronger interactions in the presence of positively charged SA.