Très récemment, notre équipe a mis en évidence une réaction dite de ligation et coupure entre une famille de composés mésoioniques, les sydnone-imines, et les cyclooctynes. Cette réaction bioorthogonale agit selon un processus en deux étapes, une cycloaddition [3+2] suivie d’une rétro Diels-Alder, qui génère deux nouveaux composés : un produit de ligation et un produit de coupure. L’objectif de cette thèse consiste à améliorer la cinétique de réaction entre ces deux partenaires afin de pouvoir l’utiliser en tant qu’outil pour la libération contrôlée de principes actifs in vivo.Trois stratégies ont été développées lors de cette thèse afin d’optimiser ce système réactionnel : l’étude d’une relation structure/réactivité du partenaire sydnone-imine vis-à-vis de la réaction bioorthogonale; l’utilisation de micelles constituées d’amphiphiles possédant un motif sydnone-imine en tant que lien clivable entre la partie hydrophobe et la partie hydrophile de la molécule; et enfin, l’étude de l’utilisation de la reconnaissance moléculaire entre deux brins d’acides nucléiques peptidiques (ANP) complémentaires. / Recently, our laboratory has discovered a click and release reaction involving iminosydnones, a family of mesoionic compounds, and cyclooctynes. This bioorthogonal reaction occurs via a two step process: a [3+2] cycloaddition followed by a retro Diels-Alder, to give two new compounds: a click product and a release product.The main goal of this work is to improve the kinetic of the reaction between these two partners in order to use it as a powerful tool for in vivo drug delivery. Three strategies were developed during this thesis to optimize this reaction system: the study of a structure/reactivity relationship of the iminosydnone partner regarding the bioorthogonal reaction; the development of micelles built by amphiphiles containing an iminosydnone moiety as a cleavable linker, strategically located between the hydrophobic and the hydrophilic part of the compound and finally, the use of molecular recognition between two peptide nucleic acids (PNA) complementary strands.

No description available.

Les micelles polyioniques ont émergé comme des systèmes prometteurs de relargage de médicaments hydrophiles ioniques. Le but de cette étude était le développement des micelles polyioniques à base de dextrane pour la relargage de médicaments hydrophiles cationiques utilisant une nouvelle famille de copolymères bloc carboxymethyldextran-poly(éthylène glycol) (CMD-PEG). Quatre copolymères CMD-PEG ont été préparés dont deux copolymères identiques en termes de longueurs des blocs de CMD et de PEG mais différent en termes de densité de charges du bloc CMD; et deux autres copolymères dans lesquels les blocs chargés sont les mêmes mais dont les blocs de PEG sont différents. Les propriétés d’encapsulation des micelles CMD-PEG ont été évaluées avec différentes molécules cationiques: le diminazène (DIM), un médicament cationique modèle, le chlorhydrate de minocycline (MH), un analogue semi-synthétique de la tétracycline avec des propriétés neuro-protectives prometteuses et différents antibiotiques aminoglycosidiques. La cytotoxicité des copolymères CMD-PEG a été évaluée sur différentes lignées cellulaires en utilisant le test MTT et le test du Bleu Alamar. La formation de micelles des copolymères de CMD-PEG a été caractérisée par différentes techniques telles que la spectroscopie RMN 1H, la diffusion de la lumière dynamique (DLS) et la titration calorimétrique isotherme (ITC). Le taux de relargage des médicaments et l’activité pharmacologique des micelles contenant des médicaments ont aussi été évalués. Les copolymères CMD-PEG n'ont induit aucune cytotoxicité dans les hépatocytes humains et dans les cellules microgliales murines (N9) après 24 h incubation pour des concentrations allant jusqu’à 15 mg/mL. Les interactions électrostatiques entre les copolymères de CMD-PEG et les différentes drogues cationiques ont amorcé la formation de micelles polyioniques avec un coeur composé du complexe CMD-médicaments cationiques et une couronne composée de PEG. Les propriétés des micelles DIM/CMDPEG ont été fortement dépendantes du degré de carboxyméthylation du bloc CMD. Les micelles de CMD-PEG de degré de carboxyméthylation du bloc CMD ≥ 60 %, ont incorporé jusqu'à 64 % en poids de DIM et ont résisté à la désintégration induite par les sels et ceci jusqu'à 400 mM NaCl. Par contre, les micelles de CMD-PEG de degré de carboxyméthylation ~ 30% avaient une plus faible teneur en médicament (~ 40 % en poids de DIM) et se désagrégeaient à des concentrations en sel inférieures (∼ 100 mM NaCl). Le copolymère de CMD-PEG qui a montré les propriétés micellaires les plus satisfaisantes a été sélectionné comme système de livraison potentiel de chlorhydrate de minocycline (MH) et d’antibiotiques aminoglycosidiques. Les micelles CMD-PEG encapsulantes de MH ou d’aminoglycosides ont une petite taille (< 200 nm de diamètre), une forte capacité de chargement (≥ 50% en poids de médicaments) et une plus longue période de relargage de médicament. Ces micelles furent stables en solution aqueuse pendant un mois; après lyophilisation et en présence d'albumine sérique bovine. De plus, les micelles ont protégé MH contre sa dégradation en solutions aqueuses. Les micelles encapsulant les drogues ont maintenu les activités pharmacologiques de ces dernières. En outre, les micelles MH réduisent l’inflammation induite par les lipopolysaccharides dans les cellules microgliales murines (N9). Les micelles aminoglycosides ont été quant à elles capable de tuer une culture bactérienne test. Toutefois les micelles aminoglycosides/CMDPEG furent instables dans les conditions physiologiques. Les propriétés des micelles ont été considérablement améliorées par des modifications hydrophobiques de CMD-PEG. Ainsi, les micelles aminoglycosides/dodecyl-CMD-PEG ont montré une taille plus petite et une meilleure stabilité aux conditions physiologiques. Les résultats obtenus dans le cadre de cette étude montrent que CMD-PEG copolymères sont des systèmes prometteurs de relargage de médicaments cationiques. / Polyion complex (PIC) micelles have emerged as promising delivery systems of ionic hydrophilic drugs. It was the aim of this study to develop dextran-based PIC micelles for the delivery of hydrophilic cationic drugs using a new family of carboxymethyldextranblock- poly(ethylene glycol) (CMD-PEG) copolymers. Four CMD-PEG copolymers were prepared: (i) two copolymers identical in terms of the length of CMD and PEG blocks, but different in terms of the charge density of the CMD block; and (ii) two copolymers in which the charged block is the same, but the PEG block is of different molecular weight. The micellization of CMD-PEG copolymers and drug delivery aspects of the resulting micelles were evaluated using different cationic drugs: diminazene (DIM), a model cationic drug, minocycline hydrochloride (MH), a semisynthetic tetracycline antibiotic with promising neuroprotective properties and different aminoglycoside antibiotics. The cytotoxicity of CMD-PEG copolymers was evaluated in different cell lines using MTT and Alamar blue assays. CMD-PEG micelles encapsulating different drugs were characterized using different techniques, such as 1H NMR spectroscopy, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). The pattern of drug release and pharmacological activity of micelles-encapsulated drugs were also evaluated. The CMD-PEG copolymers did not induce cytotoxicity in human hepatocytes and murine microglia (N9) in concentrations as high as 15 mg/mL after incubation for 24 h. Electrostatic interactions between CMD-PEG copolymers and different cationic drugs triggered the formation of PIC micelles with a CMD/drug core and a PEG corona. The properties of DIM/CMD-PEG micelles were strongly dependent on the degree of carboxymethylation of the CMD block. Micelles of CMD-PEG copolymers having degree of carboxymethylation ≥ 60%, incorporated up to 64 wt% DIM, resisted salt-induced disintegration in solutions up to 400 mM NaCl and sustained DIM release under physiological conditions (pH 7.4, 150 mM NaCl). In contrast, micelles of CMD-PEG of degree of carboxymethylation ~ 30% had lower drug content (~ 40 wt% DIM) and disintegrated at lower salt concentration (∼ 100 mM NaCl). The CMD-PEG copolymer that showed the most satisfactory micellar properties, in terms of high drug loading capacity, sustained drug release and micelles stability was selected as a potential delivery system of minocycline hydrochloride (MH) and different aminoglycosides. CMD-PEG micelles encapsulating either MH or aminoglycosides had small size (< 200 nm in diameter), high drug loading capacity (≥ 50 wt% drug) and sustained drug release. These micelles were stable in aqueous solution for up to one month, after freeze drying and in the presence of bovine serum albumin. Furthermore, the micelles protected MH against degradation in aqueous solutions. Micelles-encapsulated drugs maintained their pharmacological activity where MH micelles reduced lipopolysaccharides-induced inflammation in murine microglia (N9) cells. And aminoglycosides micelles were able to kill a test micro-organism (E. coli X-1 blue strain) in culture. Aminoglycosides/CMD-PEG micelles were unstable under physiological conditions. Micelle properties were greatly enhanced by hydrophobic modification of CMD-PEG. Thus, aminoglycosides/dodecyl-CMD-PEG micelles showed smaller size and better stability under physiological conditions. The results obtained in this study show that CMD-PEG copolymers are promising delivery systems for cationic hydrophilic drugs.

Consideramos um modelo de interações quadrupolares entre micelas capaz de explicar a ocorrência de fases nemáticas biaxiais. Micelas uniaxiais de formatos variáveis, representando a polidispersividade do sistema, são incluídas. O modelo apresenta uma fase nemática calamítica separada de uma fase discótica por uma fase biaxial, segundo resultados de campo médio e de simulações de Monte Carlo. / We consider a model of quadrupole interactions between micelles which is able to explain the occurrence of biaxial phases. Uniaxial micelles of variable shape, representing system polydispersity, are included. The model displays a calamitic nematic phase separated from a discotic phase by a biaxial phase, according to mean-field and Monte Carlo simulation results.

O interesse por sistemas formados por misturas de surfatantes se deve ao fato destas misturas apresentarem propriedades diferentes, e algumas vezes superiores, às dos surfatantes puros. Neste trabalho foram realizadas, em água e em soluções aquosas de sal, medidas de CMC, constantes de dissociação iônica, concentrações superficiais de contra-íons e entalpias de micelização para misturas de surfatantes zwiteriônicos e catiônicos. Os surfactantes catiônicos utilizados foram: brometo e cloreto de N- hexadecil - N,N,N - trimetil amônio, CTAB(C), e brometo de N- dodecil N,N,N - trimetil amônio, DTAB. Os zwiteriônicos foram: N-hexadecil- N,N-dimetil-3-amônio-1-propanosulfonato, HPS, e N-dodecil- N,N-dimetil-3amônio-1-propanosulfonato, DPS, e n-hexadecil- fosforil colina, HFC. Medidas de tensão superficial, condutividade e entalpia molar de diluição em função da concentração da mistura mostraram que, em água, ocorre primeiro a formação de micelas zwiteriônicas, seguida, com o aumento da concentração total de detergente, da incorporação do surfatante catiônico na fase micelar. A adição de sal facilita a formação de micelas mistas, principalmente nas misturas formadas por surfatantes de maior cadeia hidrocarbônica. Em micelas mistas medidas da concentração superficial de contra-íons por captura química mostraram que a concentração superficial de contra-íons aumenta com a fração molar do detergente catiônico. A concentração superficial de ânions é maior para misturas HPS/CT AB do que para misturas H FC/CTAB, quando a fração molar do detergente zwiteriônico é alta, denotando importância da composição da mistura e do sentido do momento de dipolo da cabeça polar do surfatante zwiteriônico, na capacidade da interface micelar em ligar ânions. Com o objetivo de verificar a extensão na qual a catálise de uma reação unimolecular pode ser controlada por propriedades interfaciais de micelas, foi estudada a reação de descarboxilação do íon 6-nitro benzisoxazol-3- carboxilato que é favorecida em micro-ambientes menos hidratados. Os resultados obtidos nos diferentes sistemas mostraram que misturas HFC/CTAB favorecem mais a reação do que micelas constituídas pelos anfifílicos puros, enquanto que nas misturas HPS/CTAB e DPS/DTAB, a velocidade de descarboxilação aumenta linearmente com a fração molar do surfatante zwiteriônico. A variação das constantes de velocidade com a concentração de detergente para misturas com menos de 30% de surfatante catiônico foi analisada usando o formalismo da pseudo fase, enquanto que as demais foram analisadas usando o formalismo da troca-iônica, levando em conta a dependência de a com a concentração. Este estudo representa a primeira análise integrada de propriedades físico-químicas e cinéticas para um sistema de misturas de detergentes zwiteriônicos e catiônicos. Os dados estruturais, junto com os efeitos cinéticos, fornecem uma descrição detalhada tanto do efeito de interfaces sobre reatividade como da estrutura das micelas mistas. / The interest for systems formed by surfactant mixtures is related to the fact that these mixtures exhibit properties that are more interesting, or useful, than those of the isolated components. Some mixtures can, for example, have a lower critical micelle concentration (CMC) or a higher efficiency on the reduction of the surface tension than the components. In this work we determined CMC\'s, ionic dissociation constants, surface counter-ion concentrations and micellization enthalpies for pure zwiterionic and cationic surfactants and their mixtures, in water and in aqueous salt. For this purpose, we used different alkyl chain sizes and varying structures of the polar head groups of zwiterionic detergents thereby changing the dipole moment orientation. In addition the nature of the cationic surfactant counter-ion was varied. Ammonium quaternary detergents (cationic) and sulphobetaines and phosphocholines derivatives (zwiterionic) were used as surfactants. Surface tension, conductivity and isothermal titration calorimetry were used as the main analytical methods. The judicious use of these methods allowed a better understanding of mixed micelle formation. The formation of mixed micelles depended upon several conditions such as: salt concentration, molar fraction of the components and hydrocarbon chain length. Measurements of the surface counter-ion concentrations by chemical trapping demonstrated the importance of mixture composition and of dipole moment orientation on the ability of micellar interface to bind anions. In water, zwitterionic micelles form first and, as the total detergent concentration rises, the positively charged detergent increasingly incorporates into the micellar pseudophase. Salt addition assists mixed micelle formation, especially with longer chain surfactants. Determination of interfacial anion concentration by chemical capture showed that, as expected, the interfacial counterion concentration increases with the molar fraction of the positively charged detergent. Interfacial anion concentration was larger for mixtures of HPS/CTAB when compared with HFC/CTAB mixtures at high molar ratio of the zwitterionic detergent. These results evidence the importance of mixture composition and dipole orientation on the interfacial properties of mixed micelles. The kinetic study of the effects of surfactant mixtures on the rate of a unimolecular decarboxylation reaction using 6-nitro benzisoxazole-3-carboxylate (NBOC) also showed important features of the mixed micellar surface. The rate of the unimolecular NBOC decomposition is extremely sensitive to the hydrogen donating capacity of the solvent at the reaction site. HFC/CTAB mixtures increase the reaction rate more than the single detergent micelles. For HPS/CTAB and DPS/DTAB mixtures the reaction rate increases linearly with the mole fraction of the zwitterionic component. Quantitative kinetic analysis was done using the ion exchange formalism above 30 mole % CTAB and the simple pseudophase model at lower positively charged detergent. This study represents the first integrated analysis of both physicochemical and kinetic properties of zwitterionic/positively charged micelles. The structural data, together with the kinetic effects furnish a detailed description of both micellar interfacial effects on reactivity and mixed micelle formation and properties.

Foram estudadas fases micelares do sistema lauril (dodecil) sulfato de sodio (sls)/agua/decanol nos estados isotropico i e liquido-cristalino por espalhamento de raios-x com enfase nas transicoes de fase iSETAhexagonal hALFA e iSETAnematica nc. O estudo das posicoes do pico intermicelar no sistema binario sls/agua, indica que as micelas sao estaveis e levemente anisometricas nas fases i concentradas com empacotamento local de micelas esferoidais. Ocorre crescimento micelar na vizinhanca da transicao iSETAhALFA. A analise da curva de espalhamento i (q) em concentracoes menores (ate 9% em peso de sls) mostra ser possivel a determinacao da funcao distribuicao de distancias p (r), em casos especificos onde i (q) e dominada por um pico predominantemente relacionado a estrutura interna micelar. As anisometrias micelares NI sao deduzidas dos valores de dmax sendo p (r)=0 para r> OU =dmax obtemos NIAPROXIMADAMENTE IGUAL1.5. A analise das curvas de espalhamento de solucoes mais concentradas evidenciam que as micelas crescem mais por adicao de decanol ao longo da transicao de fase iSETAnc (NIAPROXIMADA MENTE IGUAL3) do que por aumento de concentracao de anfifilico no sistema binario ao longo de iSETAhALFA (NIAPROXIMADAMENTE IGUAL2,4). Estes resultados sao discutidos no ambito de previsoes teoricas recentes de transicoes de fase iSETAliquido-cristalinas / Micellar phases of the system sodium dodecyl sulfate (SLS)/water/decanol have been studied by X-ray scattering in isotropic I and liquid crystalline states, with emphasis on the 1-+hexagonal Ha and 1nematic Nc phase transitions. Study of the intermicellar peak position in the binary SIS/water system, taking into account relative volumes of amphiphile, shows that micelles are stable and slightly anisometric in concentrated I phases, with local close packing of spheroidal micelles. Micellar growth occurs only near the 1Ha transition. Analysis of the scattering curve I( q) for lower concentrations (up to 9 wt% SLS) shows that it is possible to obtain the distance distribution function p(r), in specific cases in which l(q) is dominated by a peak due to the inner micellar structure. Micellar anisometries v are deduced from Dmax values, with p(r)=O for r Dmax. It results v.: 1.5. The electron density distribution p(r) obtained from p(r) in these lower concentrations confirm the existence of micellar anisometry.

Foram estudadas fases micelares do sistema lauril (dodecil) sulfato de sodio (sls)/agua/decanol nos estados isotropico i e liquido-cristalino por espalhamento de raios-x com enfase nas transicoes de fase iSETAhexagonal hALFA e iSETAnematica nc. O estudo das posicoes do pico intermicelar no sistema binario sls/agua, indica que as micelas sao estaveis e levemente anisometricas nas fases i concentradas com empacotamento local de micelas esferoidais. Ocorre crescimento micelar na vizinhanca da transicao iSETAhALFA. A analise da curva de espalhamento i (q) em concentracoes menores (ate 9% em peso de sls) mostra ser possivel a determinacao da funcao distribuicao de distancias p (r), em casos especificos onde i (q) e dominada por um pico predominantemente relacionado a estrutura interna micelar. As anisometrias micelares NI sao deduzidas dos valores de dmax sendo p (r)=0 para r> OU =dmax obtemos NIAPROXIMADAMENTE IGUAL1.5. A analise das curvas de espalhamento de solucoes mais concentradas evidenciam que as micelas crescem mais por adicao de decanol ao longo da transicao de fase iSETAnc (NIAPROXIMADA MENTE IGUAL3) do que por aumento de concentracao de anfifilico no sistema binario ao longo de iSETAhALFA (NIAPROXIMADAMENTE IGUAL2,4). Estes resultados sao discutidos no ambito de previsoes teoricas recentes de transicoes de fase iSETAliquido-cristalinas / Micellar phases of the system sodium dodecyl sulfate (SLS)/water/decanol have been studied by X-ray scattering in isotropic I and liquid crystalline states, with emphasis on the 1-+hexagonal Ha and 1nematic Nc phase transitions. Study of the intermicellar peak position in the binary SIS/water system, taking into account relative volumes of amphiphile, shows that micelles are stable and slightly anisometric in concentrated I phases, with local close packing of spheroidal micelles. Micellar growth occurs only near the 1Ha transition. Analysis of the scattering curve I( q) for lower concentrations (up to 9 wt% SLS) shows that it is possible to obtain the distance distribution function p(r), in specific cases in which l(q) is dominated by a peak due to the inner micellar structure. Micellar anisometries v are deduced from Dmax values, with p(r)=O for r Dmax. It results v.: 1.5. The electron density distribution p(r) obtained from p(r) in these lower concentrations confirm the existence of micellar anisometry.

Consideramos um modelo de interações quadrupolares entre micelas capaz de explicar a ocorrência de fases nemáticas biaxiais. Micelas uniaxiais de formatos variáveis, representando a polidispersividade do sistema, são incluídas. O modelo apresenta uma fase nemática calamítica separada de uma fase discótica por uma fase biaxial, segundo resultados de campo médio e de simulações de Monte Carlo. / We consider a model of quadrupole interactions between micelles which is able to explain the occurrence of biaxial phases. Uniaxial micelles of variable shape, representing system polydispersity, are included. The model displays a calamitic nematic phase separated from a discotic phase by a biaxial phase, according to mean-field and Monte Carlo simulation results.

The behavior of surfactants in solution has been and still is of scientific, technological, and industrial interest. The micelle forming compounds sodium N( octyloxycarbonyl)sarcosinate (NaOcSarc), and sodium N-(decyloxycarbonyl)sarcosinate (NaDecSarc) show in aqueous solution two lH NMR N-methyl peaks arising from a possible cis- or trans-conformation. The relative population of the N-methyl peaks depends mostly on the concentration of surfactant indicating micelle formation. Upon heating the two peaks start to coalesce and finally appear as one single peak . The temperature range in which this phenomenon occurs is from 25°C to 65°C. The primary interest of this study was to determine the activation parameters of rotation about the carbonyl-nitrogen (C-N) bond. Dynamic nuclear magnetic resonance spectroscopy was employed to approach this problem. A complete bandshape analysis was performed in order to calculate the free energy (G++), enthalpy (H++), and entropy (S++) of activation. The effect of a different counter ion (Li+) and sodium chloride salt addition were tested for possible changes of the activation parameters. Studies in nonaqeous solvents were conducted with the free acid form of the mentioned carbarnates. Dimethylsulfoxide and chloroform were chosen as organic solvents for these particular experiments. The critical micellar concentrations of all surfactants were determined, and the assignment of the individual N-methyl peaks to the correspondend conformation could be unambiguously shown by a two dimensional NMR experiment. The cmc's show strong salt dependence. The effect of a lithium as an alternative counter ion has a less drastic effect. Micellization seems not to occur in the free acid cases. Interestingly, the surfactants show stronger salt dependence than micellization dependence upon the activation parameters, indicating that solvent exposure occurs at the C-N partial double bond and considerable deformation of the ideal spherical shape.

Pasteurized skim milk was acidified using glucono-δ-lactone (GDL) at 10, 20, 30, and 40°C or with 1.2% freeze-dried yogurt starter culture at 40°C. Milk coagulation was followed by measuring turbidity, curd firmness, particle size, and casein micelle microstructural changes using transmission electron microscopy . The pH of milk was gradually lowered during acidification with GDL or starter culture. Acidification rate showed greater influence on turbidity change at 10°C than at 20, 30, or 40°C. Average casein micelle size increased with decreasing temperature. The patterns of average micelle size versus pH were not affected by temperature. No great variation of average micelle size was observed above pH 5.2. Below pH 5.0 the size increased exponentially as the milk gelled. Acidification rate did not influence average micelle size at 10°C. Acidification rate, types of acidifying agents, and temperature had no effect on the Formagraph gelation pH and the rate at which curd firmness developed. Casein micelles became less compact and less distinct with decreasing temperature before acidification. As pH was lowered, protein was dissociated from and then reassociated with casein micelles. Acidification rate had no effect on microstructure change of casein micelles at 10°C.