El CMC, tamaño y forma de micelas son características importantes en la determinación de sus principales propiedades y campos de aplicación. Esta tesis tiene dos partes, las transiciones de forma de las micelas que se trata con "Single chain Field Theory, /SCMFT)" y simulaciones de Monte Carlo. El SCMFT reveló todas las características esenciales de las transiciones de forma esférica a cilíndrica y esférica a disco de las micelas. MC muestra que las transiciones esfera a cilindro se produce a través de una región en que esferas y cilindros coexisten junto con otras formas intermedias.

Structure function changes of casein micelles were studied as a function of concentration using a non invasive concentration method, osmotic stressing. A combination of serum analysis, light scattering and rheological measurements were used to characterize the physico-chemical properties of casein micelles. In heated and unheated milk, rheological studies indicated that casein micelles behave as hard spheres of similar volume fractions, if the viscosity changes in the serum phase and the particle particle interactions are taken into account. The differences in the distribution of the heat induced complexes between colloidal and soluble phase affected the colloidal properties of casein micelles. Above 70 g L-1 protein, the protein particles were no longer free diffusing. Re-dilution of the suspensions showed no irreversible aggregation. The data suggested that in the range of concentration studied casein micelles behave as hard spheres. Age gelation was also investigated on heated and unheated concentrated milk. In unheated concentrated milk proteolysis played an important role in imparting an increase in viscosity by causing aggregation of the casein micelles. On the other hand, in heated milk, there was a significant effect of the whey protein aggregates, which increased their interaction with the casein micelles over time. This effect, together with proteolysis caused age gelation in heated concentrated milk. The method of concentration used in this research, osmotic stressing, was then compared to ultrafiltration. It was demostrated that these two methods are not equivalent, as shear and mixing during ultrafiltration cause rearrangements to the casein micells. The differences were clearly demonstrated by adding soluble caseins to the milk before or after concentration. This project brings a better understanding on the effects of concentration on the structure-function of casein micelles and the interactions occurring in milk proteins during concentration.

Le cancer est la principale cause de mortalité au Canada. Les taxanes (e.g. le paclitaxel et le docétaxel (DCTX)) constituent des remèdes efficaces contre une série de tumeurs solides telles que les cancers du sein, du poumon et de l’ovaire. Par ailleurs, des acides nucléiques (e.g. les oligonucléotides antisens (AON) ou les petits ARN interférents (siRNAs)), capables de supprimer sélectivement certains oncogènes impliqués dans la carcinogénèse, sont actuellement étudiés pour traiter une large gamme de cancers. Bien que l’activité des taxanes et des acides nucléiques soit bien établie sur des modèles humains et/ou animaux, plusieurs aspects physico-chimiques et cliniques restent encore à améliorer. Leur solubilité limitée (pour les taxanes), leur dégradation rapide dans le sang (pour les acides nucléiques), leur élimination précoce, leur absence de sélectivité et leur toxicité envers les tissus sains sont les principaux facteurs limitant leur efficacité. C’est pourquoi de nombreux efforts ont porté sur l’élaboration de systèmes de vectorisation ciblés à base de polymères, dans le but de surmonter les problèmes associés aux thérapies actuelles. Dans cette thèse, deux types de micelles polymères ont été développés pour la vectorisation de DCTX et d’acides nucléiques. D’une part, des micelles de poly(oxyde d’éthylène)-bloc-poly(oxyde de butylène/styrène) ont été étudiées pour la première fois pour solubiliser le DCTX et le protéger de l’hydrolyse. Ces polymères se sont révélés moins toxiques que le surfactant utilisé commercialement pour solubiliser le DCTX (i.e. polysorbate 80) et ont permis une libération prolongée du principe actif. D’autre part, deux systèmes différents de micelles polyioniques (PICM) ont été mis au point pour la vectorisation d’acides nucléiques. De nouveaux conjugués de poly(éthylène glycol) (PEG)-oligonucléotide ont été proposés pour la protection et la libération contrôlée d’AON. Lorsque ces conjugués ont été formulés avec des dendrimères de poly(amidoamine) (PAMAM), des complexes de taille homogène ont été obtenus. Ces PICM ont permis de prolonger la libération de l’AON et de le protéger efficacement contre la dégradation enzymatique. De plus, des polymères de poly(oxyde d’éthylène)-bloc-poly(méthacrylate de propyle-co-acide méthacrylique) ont été incorporés afin de conférer des propriétés acido-sensibles aux PICM. Dans ces micelles, formées de ce dernier polymère formulé avec le dendrimère PAMAM, des oligonucléotides (AON et siRNA) ciblant l’oncogène Bcl-2 ont été encapsulés. L’internalisation cellulaire fut assurée par un fragment d’anticorps monoclonal (Fab’) situé à l’extrémité de la couronne de PEG. Après l’internalisation cellulaire et la protonation des unités d’acide méthacrylique sous l’effet de l’acidification des endosomes, les micelles se sont affranchies de leur couronne. Elles ont ainsi exposé leur cœur composé d’acide nucléique et de dendrimère PAMAM, qui possède une charge positive et des propriétés endosomolytiques. En effet, ces PICM acido-sensibles ciblées ont permis d’augmenter la biodisponibilité des acides nucléiques vectorisés et se sont avérées plus efficaces pour silencer l’oncoprotéine Bcl-2 que les micelles non ciblées ou que le dendrimère de PAMAM commercial seul. Finalement, les nanovecteurs polymères présentés dans cette thèse se révèlent être des systèmes prometteurs pour la vectorisation des anticancéreux et des acides nucléiques. / Cancer is considered as the leading cause of premature death in Canada. Taxanes (e.g. paclitaxel and docetaxel (DCTX)) are effective against a range of solid tumors including breast, lung, and ovarian malignancies. In addition, nucleic acids (e.g. antisense oligonucleotides (AON) and short interfering RNA (siRNA)) which are capable of selectively suppressing oncogenes involved in carcinogenesis are currently being investigated for the treatment of a wide variety of cancers. Although the activity of taxanes and nucleic acid drugs is well-established in human and/or animal models, several physicochemical and clinical issues still need to be addressed. Low aqueous solubility (i.e. taxanes), rapid degradation in the blood (i.e. nucleic acids), fast clearance, non-selectivity and toxicity to normal tissues are limiting factors to their effectiveness. Hence, many efforts have been focused on developing targeted polymeric delivery systems to overcome the problems associated with the current therapies. In this thesis, two types of polymeric micelles have been developed for the delivery of DCTX and nucleic acids. On the one hand, poly(ethylene oxide)-block-poly(butylene oxide/styrene oxide) micelles were tested for the first time to solubilize and protect DCTX from hydrolytic degradation. The polymers showed less toxicity than the surfactant used commercially to dissolve DCTX (i.e. polysorbate 80) and released the drug in a sustained fashion. On the other hand, two different systems of polyion complex micelles (PICM) were developed for the sustained release and intracellular delivery of nucleic acids. Novel poly(ethylene glycol) (PEG)-oligonucleotide conjugates were assessed to protect AON against degradation and release them in a sustained manner. When these conjugates were mixed with poly(amidoamine) (PAMAM) dendrimers, monodisperse PICM were formed. These PICM further slowed down AON release and significantly protected it against enzymatic degradation. In addition, the incorporation of poly(ethylene oxide)-block-poly(propyl methacrylate-co-methacrylic acid) was exploited to impart pH-sensitivity to PAMAM-based PICM. This system was composed of the previous copolymer mixed with PAMAM dendrimer. Such PICM were loaded with AON or siRNA targeting the Bcl-2 oncogene. Micelles uptake by the cancer cells was mediated by a monoclonal antibody fragment (i.e. Fab') positioned at the extremity of the PEG corona. Upon cellular uptake and protonation of the methacrylic acid units in the acidic endosomal environment, the micelles lost their corona, thereby exposing their positively-charged endosomolytic PAMAM/nucleic acid core. The targeted, pH-sensitive PICM were found to increase the intracellular bioavailability of the entrapped nucleic acids and knock down the Bcl-2 oncoprotein more than either non-targeted micelles or commercial PAMAM dendrimers. The polymeric nanocarriers reported in this thesis appear to be promising vehicles for the delivery of anticancer drugs and nucleic acids.

No description available.

Cancer remains a leading cause of death in the United States. The most common treatment options include chemotherapy, but poor solubility, adverse side effects and differential drug sensitivity hamper clinical applications. Current chemotherapy generally aims to deliver drugs at the limit of toxicity, assuming that higher dosage increases efficacy, with little attention paid to potential benefits of tunable release. Growing evidence suggests that releasing drugs at a constant rate will be as effective as a single bolus dose. To test this hypothesis, it is critical to develop drug delivery systems that fine-tune drug release and elucidate the impact of tunable drug release rates on chemotherapeutic efficacy. Block copolymer micelles, spherical nanoassemblies with a core-shell structure, are widely used in recent research. Micelles for this study were engineered to release a model drug (doxorubicin: DOX) at differential rates under acidic conditions, corresponding to tumor tissue (pH < 7). Three specific aims were pursued: to develop drug carriers capable of tuning drug release rates; to determine activity of developed carriers in vitro; and to elucidate effects of tunable drug release rates in vivo. Block copolymers with covalently linked DOX were synthesized and self-associated, forming micelles. Drug binding linkers (glycine, aminobenzoate, or hydrazide) were used to tune release of DOX. Micelles were characterized to determine physicochemical properties such as particle size, drug entrapment yields, and drug release parameters. Characterization revealed that drug release profiles were modulated by interchanging drug binding linkers. Micelles were evaluated in vitro to elucidate the effect of tunable drug release. Micelles delivered drugs at a slower, prolonged rate compared to free DOX. Cytotoxicity and cellular internalization analysis revealed that by slowing release rates, micelles kill cells more efficiently. Biodistribution studies showed that micelles decrease DOX accumulation in peripheral tissue while increasing the maximum tolerated dose. Antitumor activity studies verified that micelles with slower release rates better suppressed tumor growth. This further confirms that release rates play a key role in chemotherapeutic efficacy. Therefore, this thesis provides better insights into the effects of tunable drug release in tumors, leading the way for improved chemotherapy treatments in the future.

Notre équipe a récemment développé une méthode polyvalente permettant de préparer des dérivés complexes de C60 hexa-adduits fonctionnalisés. Cette méthodologie permet d'obtenir des produits aux caractéristiques originales. Le C60 central agit comme un support central peu réactif, autour duquel des fonctionnalités sont réparties dans un espace octaédrique parfaitement défini. La première partie de ce travail de thèse a consisté à exploiter cette méthodologie pour créer des C60 hexa-adduits polycationiques aux propriétés de transfection remarquables. Dans un second temps, les dendrons polyamines synthétisés ont été mis à profit pour créer des structures supramoléculaires de C60 hexa-adduits, sous forme micellaire. Par la suite, l'étude de ces assemblages a orienté nos investigations vers l'élaboration de dérivés de C60 hexa-adduits mannosylés multivalents résultant d'un assemblage supramoléculaire, dont leurs possibles applications biologiques sont actuellement à l'étude. En parallèle une synthèse covalente a permis d'obtenir un "équivalent dendritique" de C60 hexa-adduit multimannosylé. Partant du constat que notre méthodologie est efficace principalement pour des dérivés de C60 hexa-adduits qui ont une régio-sélectivité particulière, la dernière partie a été consacrée au développement de nouvelles voies de synthèses qui pourront permettre de créer des dérivés de C60 avec un contrôle régio-sélectif original.

La dualité hydrophobe/hydrophile des molécules amphiphiles est à l'origine de leur autoassemblage en solution, sous forme de nombreuses structures supramoléculaires, telles que les micelles. Ce travail de thèse présente la formation, la caractérisation et l'étude de nouvelles micelles diacétylèniques photopolymérisables. Une première partie décrit ainsi lasynthèse de nouvelles micelles cationiques et l'étude de leur utilisation en tant qu'agent de transfert de gènes. Dans une seconde partie, nos travaux présentent l'étude de micelles polydiacétylèniques, porteuses de têtes polaires octaéthylèneglycol, comme potentiel système de délivrance de médicament. Les propriétés d'encapsulation de ces micelles ont été évaluées en présence d'un dérivé fullerène fluorescent. Puis, l'incorporation d'une sonde membranaire dans leur couronne lipophile a permis de réaliser une étude de leurs propriétés de délivrance in vitro. Une étude préliminaire de leur biodistribution in vivo a également été réalisée par tomographie à émission monophotonique grâce à la chélation d'un isotoperadioactif sur la surface des micelles. Enfin une dernière partie présente l'analyse de deux nouveaux auto-assemblages tubulaires obtenus au cours de nos travaux.

<p>Elastin-like polypeptides (ELPs) are thermally responsive polymers composed of the pentapeptide repeat Valine-Proline-Glycine-X-Glycine where X is any amino acid except proline. ELP diblocks have been engineered by creating two ELP blocks with hydrophilic and hydrophobic guest residues. The hydrophobic block desolvates at a lower temperature and forms the core of a micelle while the still hydrated hydrophilic block forms the corona. ELP micelles are promising drug delivery vehicles for cancer therapeutics. ELP diblocks offer a unique method to display targeting proteins multivalently on micelles to improve tumor cell uptake. As ELPs are genetically encoded, proteins can be seamlessly fused at the genetic level to the ELP diblock. The protein ELP diblock fusions can be synthesized as one polypeptide chain that is of precise molecular weight and highly monodisperse, and no post-synthesis modification is necessary. Self-assembly behavior of ELP diblocks is known to tolerate fusion to small peptides (< 10 amino acids) but their self-assembly behavior has not be examined when fused to proteins that are 100-200 amino acids. Here, we hypothesize that molecular weight of the protein and the surface properties of the protein will be factors in determining its effect on ELP diblock self-assembly. In addition, the ELP block lengths and composition are hypothesized to be factors in the self-assembly behavior of protein ELP diblock fusions. This hypothesis is tested by fusing four proteins with different properties to various ELP diblocks and characterizing their self-assembly behavior. The proteins were found to dominate the self-assembly behavior. Proteins that disrupted self-assembly did so for all ELP diblock lengths and compositions. Protein that did not disrupt self-assembly behavior affected the thermal behavior of the hydrophilic block. Hydrophilic proteins increased the micelle-to-aggregate transition temperature while hydrophobic proteins decreased it. We also sought to understand the self-assembly of ELP diblocks on a theoretical basis. A previously developed model for the self-assembly of synthetic polymers was applied to our polypeptide system. Two parameters, solvent quality of the corona and surface tension of the hydrophobic block, were experimentally measured and used to fit the model. Predictions of micelle radius and aggregation numbers were in good agreement with experimental data. However, the corona was found to be unstretched compared to its Gaussian size by this model. Therefore, a new model was developed describing what is termed as weak micelles in which the corona is not stretched but rather close to Gaussian size. The weak micelle model prediction were also in good agreement with experimental data suggesting that ELP micelles are in the crossover regime between the previous model and the new model.</p> / Dissertation

This thesis is devoted to the development of microfluidic processes for the controlled self-assembly of quantum dot compound micelles (QDCMs). Microfluidic processes are developed to combine the constituents (cadmium sulfide quantum dots, and block copolymer stabilizing chains) with water to facilitate self-assembly of the composite particles, QDCMs, through initial phase separation, subsequent growth, and eventual quenching. Two genres of microfluidic reactors are developed. The on-chip evolution of QDCM formation and growth is resolved through fluorescence microscopy; QDCM size distributions and associated statistics are determined through off-chip analysis by transmission electron microscopy (TEM). In a flow-focusing reactor, control over the mean size of QDCMs is demonstrated through both the water concentration and the growth time (or reactor channel length). Controlled QDCM self-assembly is also demonstrated in a multiphase gas-liquid reactor. In contrast to the flow-focusing reactor, increasing the multiphase reactor channel length results in a decrease in QDCM size and polydispersity.

Although the native environment of the vast majority of proteins is a complex aqueous solution, like the interior of a cell, many analysis methods for assessing chemical and physical properties of biomolecules require the sample to be aerosolized; that is, transferred to the gas-phase. An important example is electrospray-ionization mass spectrometry, which can provide a wide range of information about e.g. biomolecules. That includes structural features, charged sites, and gas-phase equilibrium constants of reactions. To date much of the microscopic detail about the aerosolization process remains beyond the limits of experimental observation. How is the gas-phase structure of a protein related to the solution-phase structure? How transferable are observations done in the gas phase to solution? On the basis of classical molecular-dynamics simulations this thesis reveals important features of gas-phase biomolecular structure near the end of the the aerosolization process, the relation between gas-phase structure and native structure, microscopic detail about the de-wetting of gas-phase biomolecules, and the impact of temperature and residual solvent on structure preservation. Residual solvent on proteins is shown to have a stabilizing effect on proteins, in part because it allows the scarcely hydrated protein to cool through solvent evaporation, but also because part of the solvent provides structural support by hydrogen bonding to the protein. The gas-phase structure of micellar aggregates is seen to depend on composition, where some types of lipids cause rapid micelle inversion, whereas others maintain much of their collective structure when transferred to the gas phase. The thesis also addresses proton-transfer reactions, which have an impact on the biophysical aspects of proteins, both in the gas phase and in solution. The thesis presents a computationally efficient method for including proton-transfer reactions in classical molecular-dynamics simulations, which expands the range of scientific problems that can be addressed with molecular dynamics.