Le développement de la thérapie génique dépend des systèmes utilisés pour le transport de gènes vers les cellules eucaryotes. Les systèmes à base de virus sont les plus efficaces. Cependant, il est urgent de trouver une alternative à de tels systèmes viraux pathogènes et oncogènes. Les polymères cationiques sont des vecteurs synthétiques prometteurs ; toutefois, une question cruciale reste en suspens : quelle structure de polymère cationique visée pour une efficacité de transfection élevée et une faible cytotoxicité ? Face à ce questionnement scientifique, de nouveaux polymères cationiques offrant une grande flexibilité en termes de structure et de fonctionnalité sont développés dans cette thèse. Les différents paramètres structuraux pertinents étudiés sont : (i) des entités amines primaire et tertiaire pH-sensibles pour la complexation de l'ADN et pour la libération des polyplexes ADN/polymère, (ii) un groupe alcyne destiné à l’ancragepar chimie click de ligands capables de viser des récepteurs spécifiques de membrane cellulaire pour une reconnaissance efficace des cellules, (iii) des entités polyacrylates à « charge modulable » pour libérer l'ADN et diminuer la cytotoxicité du polymère et (iv) un poly (oxyde d'éthylène) (PEGylation) pour une meilleure stabilité en milieu physiologique et une meilleure biocompatibilté. / The clinical success of gene therapy is really dependent on the development of new efficient gene transfer systems. Viral-based gene transfer systems are remarkably efficient in transfecting body cells. However, viral-based systems raised some concerns in terms of immunogenicity, pathogenicity, and oncogenicity. Cationic polymers are promising candidates as they show low host immunogenicity, are cheaper and easier to produce in a large scale than viral ones. However, a crucial question is still pending: which cationic polymer structures and functionalities give the highest transfection efficiency and the lowest cytotoxicity? In dealing with this scientific issue, new cationic polymers with key structural parameters and functionalities were developped during this PhD thesis. The key structural features studied are : (i) pH sensitive primary and tertiary amine entities for DNA complexation and to ensure the endosomal escape, (ii) an alkyne group to attach ligands capable to target specific cell membrane receptors for an efficient cell recognition and receptor-mediated cellularuptake, (iii) “charge-shifting” amino-based polyacrylates for DNA release and to decrease cytotoxicity and (iv) PEG chains (PEGylation) to achieve high stability, longer circulation in physiological conditions and a better biocompatibility. The synthesis of such multi-structural cationic polymers has been achieved through the combination of RAFT polymerization and thiol-yne click coupling reaction. The structure/complexation and the structure/cells viability relationships have been investigated during this work.

Protein adsorption on solid surfaces is a common yet complicated phenomenon that is not fully understood. Self-assembled monolayers have been utilized in many studies, as well-defined model systems for studying protein-surface interactions in the atomic level. Various strategies, including the use of single component SAMs[1, 2], combinations of long and short alkanethiolates with methyl- and hydroxyl- terminal groups[3, 4], and using mixtures of alkanethiolates with similar chain length and varying terminal functional group [5] have been used to effectively control the surface wettability and determine the effect of surface composition and wettability on protein adsorption. In this dissertation we report key new findings on the effect of surface density of functional groups on protein adsorption phenomenon. In The first phase of this research, we developed a novel approach for preparation of low-density self-assembled monolayers(LD-SAMs) on gold surfaces, based on radical-initiated thiol-yne click chemistry. This approach provides exceptional adsorbate stability and conformational freedom of interfacial functional groups, and is readily adapted for low-density monolayers of varied functionality. The resulting monolayers have two distinct phases: a highly crystalline head phase adjacent to the gold substrate, and a reduced density tail phase, which is in contact with the environment. First, we investigated the feasibility of the proposed chemistry in solution-phase. In this approach, we synthesized “Y” shaped carboxylate-terminated thiol adsorbates via radical-initiated thiol-yne reaction. The LD-SAMs were then prepared through immersion of gold substrates into the solution of synthesized adsorbate molecules in hexane. The chemical structuring and electrochemical properties of resultant LD-SAMs were analyzed and compared with those of analogous traditional well-packed monolayers, using techniques such as Fourier transform infrared spectroscopy, ellipsometry, electrochemical impedance spectroscopy, reductive desorption, and contact angle goniometry. Characterization results indicated that resulting LD-SAMs have a lower average crystallinity, and higher electrochemical stability compared to well-packed monolayers. In addition, using a three-electrode system, we were able to show a reversible change in LD-SAM surface wettability, in response to an applied voltage. This remodeling capacity confirms the low density of the surface region of LD-SAM coatings. The second area of work was focused on using the developed chemistry in solid-phase. The solid-phase approach minimized the required synthesis steps in solution-phase method, and used the photo-initiated thiol-yne click-reaction for grafting of acid-terminated alkynes to thiol-terminated monolayers on a gold substrate to create similar LD-SAMs as what were prepared through solution-phase process. We characterized the resulting monolayers and compared them to analogous well-packed SAMs and the also low-density monolayers prepared through the solution phase approach. The results confirmed the proposed two-phase structure, with a well-packed phase head phase and a loosely-packed tail phase. In addition, the electrochemical studies, indicated that the resultant monolayers were less stable than the monolayers prepared via solution-phase, but they are yet significantly more stable than typical well-packed monolayers. The less stability of these monolayers were attributed to the partial desorption of adsorbates from the gold substrate due to UV irradiation during the grafting process. Building on the established chemistry, we studied the effect of lateral packing density of functional groups in a monolayer on the adsorption of Bovine serum albumin protein. we used surface plasmon resonance spectroscopy (SPR) and spectroscopic ellipsometry, to evaluate BSA adsorption on carboxylate‑, hydroxyl-, or alkyl- terminated LD-SAMs. It was found that for the LD-SAMs, the magnitude of protein adsorption is consistently higher than that of a pure component, well-packed SAM for all functionalities studied. In addition, it was seen that the magnitude of BSA adsorption the LD-SAMs, was consistently higher than that of a pure component, well-packed SAM for all functionalities studied. The difference of protein adsorption on LD-SAMs and SAMs can not be associated to difference in lateral packing density, unless we eliminate the impact of other contributing factors in protein adsorption such as surface energy. In order to better understand the impact of packing density on protein-surface interactions, we prepared the mixed SAMs of (carboxylate/alkyl) and (hydroxyl/alkyl) with matching surface energy as the carboxylate and hydroxyl terminated LD-SAMs. It was found that the energy-matched mixed SAMs of carboxylate and hydroxyl functionality adsorbed more protein than the LD-SAMs. However, an opposite trend was seen for the alkyl surfaces, where surface energies are comparable for LD-SAMs and pure component SAMs, indicating that BSA proteins have higher affinity for methyl- terminated LD-SAMs than well-packed SAMs.

No description available.

No description available.

La première partie de ce travail traite de la macrocyclisation photochimique. Les macrocycles nécessitent de conditions de dilution élevées, avec de grandes quantités de solvant, généralement incompatibles avec les conditions photocatalytiques en raison de l'absorption de la lumière par le solvant. Pour remédier à ce problème, notre groupe a développé un réacteur hybride pour l'oxydation aérobique photocatalytique des thiols en disulfures dans des conditions de flux continu. Les travaux antérieurs comprenaient une etendue de réaction contenant plusieurs exemples utilisant des molécules de liaison “linker” octanediol, PEG et haloaromatiques, ainsi que des peptides macrocycliques contenant jusqu'à quatre acides aminés. L’étendue ne comprenait toutefois pas les linkers dérivés de molécules atropisomères, comme le BINOL, ni de peptides macrocycliques plus grands dérivés de chaînes d'acides aminés plus longues. Le chapitre 1 présentera les concepts de macrocycles et de photochimie, tandis que le chapitre 2 décrira la chimie de flux et les recherches du Dr Émilie Morin sur la macrocyclisation à l'aide du réacteur hybride. Le chapitre 3 traite de la tentative de synthèse, finalement réussie, d'un macrocycle destiné à élargir le champ des macrocycles pouvant être préparés à l'aide du réacteur hybride. La deuxième partie de ce travail traite des réactions thiol-yne des sulfures d'alcynyle. Les réactions thiol-yne ont de nombreuses applications, notamment dans la chimie des polymères et la macrocyclisation. Les réactions thiol-yne peuvent se dérouler par des voies radicalaires rendues possibles par la photocatalyse à la lumière visible. Cependant, les réactions thiol-yne sont généralement réalisées avec des thiols et des alcynes terminaux. Les alcynes internes représentent un plus grand défi en raison de l'absence de régiocontrôle, mais les sulfures d'alcynyle constituent une solution viable au problème en polarisant la triple liaison de l'alcyne et en offrant une réactivité et une régiosélectivité améliorées par rapport à leurs homologues "tout carbone". Le chapitre 4 présentera les réactions thiol-yne et les différents mécanismes qui y sont associés, ainsi que les sulfures d'alkyles et les méthodes de leur synthèse. Le chapitre 5 présentera les recherches effectuées sur les réactions thiol-yne photocatalytiques des sulfures d'alcynyle. / The first section of the present work deals with photochemical macrocyclization. Macrocyclic peptides are important molecules in the pharmaceutical domain for numerous reasons. Macrocyclizations require high dilution conditions, i.e., large amounts of solvent, typically incompatible with photocatalytic conditions due to the absorption of light by the solvent. To remedy the problem, our group developed a hybrid reactor for the photocatalytic aerobic oxidation of thiols into disulfides in flow conditions. Prior work included a scope containing several examples using octanediol, PEG, and haloaromatic linker molecules, and of macrocyclic peptides containing up to four amino acids. Lacking in the scope, however, were linkers derived from atropisomeric molecules like BINOL and larger macrocyclic peptides derived from longer amino acid chains. Chapter 1 will introduce the concepts of macrocycles and photochemistry, while Chapter 2 will describe flow chemistry and the research of Dr. Émilie Morin on macrocyclization using the hybrid reactor. Chapter 3 will discuss the attempted, and ultimately successful, synthesis of a macrocycle intended to further the scope of macrocycles that can be prepared using the hybrid reactor. The second section of the present work deals with thiol-yne reactions of alkynyl sulfides. Thiol-yne reactions have many applications including use in polymer chemistry and in macrocyclization. Thiol-yne reactions can proceed via radical-mediated pathways made possible with visible light photocatalysis. However, thiol-yne reactions are typically accomplished with thiols and terminal alkynes. Internal alkynes would offer a greater challenge due to the lack of regiocontrol, but alkynyl sulfides present a viable solution to the problem by polarizing the triple bond of the alkyne and offering improved reactivity and regioselectivity over “all-carbon” counterparts. Chapter 4 will introduce thiol-yne reactions and different mechanisms associated with them, as well as alkynyl sulfides and methods for their synthesis. Chapter 5 will present the research done on photocatalytic thiol-yne reactions of alkynyl sulfides.

Ce projet de recherche mené en collaboration avec le CTP (Centre Technique du papier) a eu comme objectif de mettre en place une stratégie de greffage de polymères sur des fibres de cellulose via « Chimie Click » dans l’eau et dans des conditions douces et respectueuses de l’environnement afin de conférer de nouvelles propriétés mécaniques aux papiers résultants. La première étape a été d’élaborer une fonctionnalisation alcyne des fibres dans des conditions douces – dans l’eau ou dans un mélange eau/isopropanol – permettant à la fois une fonctionnalisation conséquente tout en préservant la cristallinité de la cellulose, la structure fibre et les propriétés mécaniques. Différentes méthodes de microscopie ont été utilisées pour mieux comprendre l’impact de la fonctionnalisation sur les propriétés mécaniques. Afin d’améliorer les propriétés mécaniques du papier, le greffage sur les fibres de polyéthers d’alkyle fonctionnalisés azoture a été réalisé dans l’eau par cycloaddition de Huisgen d’azoture-alcyne catalysée par le cuivre (II) (CuAAC). Plusieurs polymères de natures différentes (poly(éthylène glycol) et poly[(éthylène glycol)-stat-(propylène glycol)]), de différentes masses molaires et fonctionnalités (mono- ou difonctionnels) ont été liés aux fibres de cellulose. L’ajout de chaînes de poly(éthylène glycol) s’est avéré avoir un effet lubrifiant entraînant une légère diminution de l’indice de traction mais une augmentation importante de la flexibilité du papier. De plus, le greffage de polymères difonctionnels a démontré des propriétés originales de résistance à l’eau sans changer la nature hydrophile des fibres de cellulose. Enfin, le couplage Thiol-Yne a permis de fixer de petites molécules hydrosolubles fonctionnalisées thiol sur des fibres modifiées alcyne en s’affranchissant du cuivre nécessaire à la réalisation de la réaction de CuAAC. / This research project, in collaboration with CTP (Centre Technique du Papier), aimed at developing chemical pathway in water to graft polymers on cellulose fibers via “Click Chemistry” in eco-friendly and non-degrading conditions conferring new mechanical properties upon the resulting paper sheets. A first step was to develop a “green” alkyne derivatization method in mild conditions – through pure water or water/isopropanol mixture – allowing for a substantial alkyne functionalization without jeopardizing the cellulose crystallinity, the fiber structure, and maintaining good mechanical properties of the cellulose fibers and resulting paper sheets. To better understand how the functionalization impacts the mechanical properties, several microscopy methods were employed. Then, aiming at improving mechanical properties of the resulting paper, grafting of azidefunctionalized polyoxyalkylenes on alkyne-modified fibers was achieved via Copper(II)-Catalyzed Alkyne-Azide Cycloaddition (CuAAC) in pure water. Water soluble polymers of different nature (poly(ethylene glycol) or poly[(ethylene glycol)-stat-(propylene glycol)]), with different molar mass and functionality (one or two azide groups per macromolecular chain) were successfully attached on cellulose fibers. Grafting of PEG chains involved a slight decrease of the tensile index but a drastic increase of the flexibility of the paper sheet. Interestingly, fibers grafted with difunctional polymers demonstrated an original water resistance maintaining the hydrophilic nature of fibers. Finally, Thiol-Yne reaction was successfully carried out to attach small water soluble thiol-bearing reagents on alkyne-functionalized fibers in water as a metal-free alternative to CuAAC reaction.