No description available.

2-Methacryloyloxyethyl Phosphorylcholine is an interesting biocompatible monomer. An improved method for the synthesis of poly(MPC) and its copolymers using Reversible Addition-Fragmentation chain Transfer (RAFT) has been discussed in the first part of the thesis. Previous reports related to the synthesis of MPC homopolymers and copolymers in aqueous medium are found to be less effective because of the hydrolysis of chain transfer agent in water. Hydrolysis of chain transfer agent results in the loss of active chain ends thereby, reducing control over polymerization and increasing the polydispersity of resulting polymers. Therefore, in this work MPC polymers were synthesized by RAFT using methanol as solvent. This method of synthesis produced polymers having controlled molecular weights as well as narrow polydispersities. In the second part of the work, methoxydiethylene glycol methacrylate (MeODEGM)-MPC based thermo-responsive core-shell nanogels were synthesized for use in protein encapsulation and release. The size of the nanogels was controlled by varying the concentration of cross-linker. The nanogels were synthesized using an acid degradable crosslinker which helped in the release of encapsulated protein at acidic pH. The effect of various parameters on encapsulation efficiency of proteins was studied and it was found that apart from the size of protein, the cross-linker concentration of nanogel also affected the amount of protein encapsulated. / Chemical Engineering

In recent decades, a variety of nanoparticle drug delivery systems (NP DDS) – nanometer-scaled materials physically or covalently interacting with therapeutics – has been developed to overcome biological barriers, improve the half-life, reduce toxicity, and improve the efficacy of conventional drug delivery. However, many NP DDS fail to translate to the clinic. While this is in part due to immense heterogeneity within many disease types across individuals, the conflicting size and surface chemistries required in the “drug delivery pathway” (i.e. to avoid the clearance mechanisms and unintended tissues in the body, then to reach and specifically enter target tissues) also pose a significant challenge. Recent advances in the field of drug delivery have created size- and surface-switching nanoparticles that overcome biological barriers. For example, large (100 – 200 nm) NPs are adequate at evading corporeal defense mechanisms, while small (< 50 nm) NPs can actively enter cancerous tissue. Further, release profiles of drug-loaded NP DDS must be tailored to stay within a narrow therapeutic window to prevent toxic effects. This thesis highlights the synthesis of “nanoassemblies”, an NP DDS that contains small, drug-loaded starch nanoparticles (SNPs) within a larger nanogel matrix. Nanoassemblies are chemically tuned to reach specific targets via different administration routes (notably, cancerous tissues via systemic administration and brain tissue via intranasal administration). Furthermore, therapeutic-loaded SNPs are released under endogenous (pH, redox) or exogenous (ultrasound) stimuli for disease-specific release kinetics, allowing for deeper penetration into tumor cores or through the nose-to-brain pathway as required. Both the physicochemical characterization of these nanoassemblies as well as in vitro and in vivo experiments have been performed to assess the efficacy of nanoassemblies in biological systems and how they may provide performance improvements over non-assembled SNPs. As such, nanoassemblies show great promise in overcoming complex biological barriers to ultimately improve drug delivery in clinical applications. / Thesis / Doctor of Philosophy (PhD) / Using drugs to treat diseases is not always effective: the drug often does not work or comes with many side effects. A combination of factors prevents promising drugs from working. Most often the drug is either (partially or fully) removed from the body before it reaches the disease, or it improperly enters healthy tissue to cause undesirable responses. Previous research has shown that if drugs are put into nanoparticles, the nanoparticles can better deliver the drug to the correct target. However, conflicting sizes are needed to travel through different parts of the body, making nanoparticle-based drug delivery only of limited effectiveness in humans. This thesis aims to address these issues by creating “nanoassemblies” – nanoparticles with smaller, drug-containing nanoparticles inside of them – that overcome the typical issues with drug delivery. Nanoassemblies are able to switch their size to better reach the target tissue, ultimately leading to more effective and safe treatments.

A novel methacrylate based nanogel system has been designed and developed for drug delivery applications. Methacrylates are optimal tuneable materials in terms of polarity, with combination of hydrophobic and hydrophilic moieties. Synthesis of these nanogels (NGs) was achieved via high dilution radical polymerisation using 2-(tert-butylamino)ethyl methacrylate (tBAEMA) as functional monomer, methacrylic acid (MAA) or ethylene glycol methyl ether methacrylate (EGMMA) as co-monomer and N,N'-methylenebis(acrylamide) (MBA) as cross-linker. Fabricated nanoparticles (NPs) were shown to possess water solubility higher than 2 mg/mL and diameter ranging from 5 to 20 nm (depending on nanogels' composition) as confirmed by either dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, nanogels produced have shown the ability to be employed as Pickering-Ramsden emulsion stabiliser. Their reduced size together with their emulsion capabilities make these nanoparticles a promising system for drug delivery, in particular taking into account skin as administration route. The size is in fact small enough to favour their penetration through the stratum corneum. Furthermore, in the view of their ability to form emulsions, nanogels could be used both as drug carrier and emulsifier in a final pharmaceutical formulation. NGs proved to be able to incorporate both small molecule such as fenoprofen (an anti-inflammatory non-steroidal drug) and big macromolecule such as siRNA. Cytotoxicity and cell metabolism were also evaluated by transfecting normal human dermal fibroblasts (NHDF), keratinocytes (HaCaT) and HeLa cells with nanogels. Data showed that nanoparticles did not affect viability, cells' morphology and adenosine triphosphate (ATP) levels up to high concentration of 100 μg/mL. In addition, preliminary studies indicated the ability of the nanogels to internalise and release their payload inside cells. In conclusion, the results confirmed that this novel system possesses all the desired characteristics to be used as a promising platform for drug delivery.

Intelligent and more advanced therapeutic agents, capable of sensing and responding to their environment, are required to treat more complicated and complex diseases. Among all recently developed therapeutic agents, hydrogels are not only intelligent to sense and respond to external stimulus, but also they can be synthesized and designed in the cellular and sub-cellular size scale, which enhance their therapeutic ability. Most body physiological processes are regulated as a consequence of pH gradient in different compartments of the body; besides, changes in pH are also associated with disease or damaged sites within the body. A unique feature of hydrogels is that they can provide a network for loading and release of drugs. Therefore, the drug loaded within pH-responsive nanogels are able to locally release onto the target sites because of their small size, and capability to sense and respond to environmental changes. The goal of this research is to design and implement novel pH-responsive magnetic nanogels for drug delivery that respond to changes in pH. Semi-continuous emulsion polymerization was conducted to synthesize polyampholyte nanogels comprising of methacrylic acid (MAA) and 2-(diethylamino) ethyl methacrylate (DEAEMA) in the presence and absence of steric stabilizer poly (ethylene glycol) methacrylate (PEGMA). The synthesized nanogels demonstrated swelling behavior at both acidic and basic pHs. Herein, procaine hydro chloride (PrHy) was utilized as cationic drug to investigate the release behavior from synthesized nanogels under different conditions. PrHy was loaded within nanogels through hydrophobic interaction and hydrogen bonding, as confirmed by isothermal titration calorimetry. The release study of PrHy molecules from nanogels was conducted by applying the versatile and easy technique of drug selective electrode, in which the concentration of released drug was measured as a function of time. In order to facilitate the purification and enhance the detection of nanogels, iron oxide particles (Fe3O4) were co-precipitated within nanogels to form magnetic nanogels. Subsequently, layer-by-layer coating of polyelectrolytes were performed to control and eliminate the initial burst release of PrHy from nanogel by increasing the diffusion barrier and manipulating the permeability of nanogels. For the purpose of this research low molecular weight chitosan (CS) was used as polycation and poly (sodium 4-styrenesulfonate) (PSS) was acted as polyanion to coat magnetic nanogels. The more layers was applied, the more reduction in burst release was observed, which was revealed by using drug selective electrode to measure the concentration of the released drug from coated nanogels. Besides, layer-by-layer coating prolonged the time require to reach the steady state drug release. Therefore, this synthesized polyampholyte coated iron-oxide nanogels demonstrate great potential for use in controlled drug delivery systems.

Intelligent and more advanced therapeutic agents, capable of sensing and responding to their environment, are required to treat more complicated and complex diseases. Among all recently developed therapeutic agents, hydrogels are not only intelligent to sense and respond to external stimulus, but also they can be synthesized and designed in the cellular and sub-cellular size scale, which enhance their therapeutic ability. Most body physiological processes are regulated as a consequence of pH gradient in different compartments of the body; besides, changes in pH are also associated with disease or damaged sites within the body. A unique feature of hydrogels is that they can provide a network for loading and release of drugs. Therefore, the drug loaded within pH-responsive nanogels are able to locally release onto the target sites because of their small size, and capability to sense and respond to environmental changes. The goal of this research is to design and implement novel pH-responsive magnetic nanogels for drug delivery that respond to changes in pH. Semi-continuous emulsion polymerization was conducted to synthesize polyampholyte nanogels comprising of methacrylic acid (MAA) and 2-(diethylamino) ethyl methacrylate (DEAEMA) in the presence and absence of steric stabilizer poly (ethylene glycol) methacrylate (PEGMA). The synthesized nanogels demonstrated swelling behavior at both acidic and basic pHs. Herein, procaine hydro chloride (PrHy) was utilized as cationic drug to investigate the release behavior from synthesized nanogels under different conditions. PrHy was loaded within nanogels through hydrophobic interaction and hydrogen bonding, as confirmed by isothermal titration calorimetry. The release study of PrHy molecules from nanogels was conducted by applying the versatile and easy technique of drug selective electrode, in which the concentration of released drug was measured as a function of time. In order to facilitate the purification and enhance the detection of nanogels, iron oxide particles (Fe3O4) were co-precipitated within nanogels to form magnetic nanogels. Subsequently, layer-by-layer coating of polyelectrolytes were performed to control and eliminate the initial burst release of PrHy from nanogel by increasing the diffusion barrier and manipulating the permeability of nanogels. For the purpose of this research low molecular weight chitosan (CS) was used as polycation and poly (sodium 4-styrenesulfonate) (PSS) was acted as polyanion to coat magnetic nanogels. The more layers was applied, the more reduction in burst release was observed, which was revealed by using drug selective electrode to measure the concentration of the released drug from coated nanogels. Besides, layer-by-layer coating prolonged the time require to reach the steady state drug release. Therefore, this synthesized polyampholyte coated iron-oxide nanogels demonstrate great potential for use in controlled drug delivery systems.

Ce travail de thèse s'inscrit dans un domaine de recherche actuellement en pleine expansion, celui des nanomatériaux stimulables. Il vise à concevoir de nouveaux matériaux biocompatibles et biodégradables par modification chimique contrôlée de polysaccharides pour le traitement de patients diabétiques. Le diabète est un problème de santé publique majeur qui affecte environ 250 millions de personnes dans le monde actuellement contre 30 millions il y a 20 ans. Cette maladie se traduit par un taux de glucose anormalement élevé dans le sang dû à un manque d'insuline. Cette protéine est habituellement injectée de manière sous-cutanée, 2 à 4 fois par jour. Les hydrogels/nanogels visés dans ce travail doivent donc être capables de libérer l'insuline en fonction du taux de glucose dans le sang. Ce projet comporte plusieurs volets : (i) la synthèse contrôlée de polysaccharides porteurs de groupements permettant la réticulation des polymères ainsi que des molécules sensibles au glucose , (ii) la synthèse et la caractérisation d'hydrogels et nanogels (en utilisant des liposomes comme nanoréacteurs). / This PhD thesis belongs to the area of stimuli-responsive materials, which have attracted a growing interest since several years. Its aim is to design biocompatible and biodegradable stimuli-responsive nanogels obtained from chemically modified polysaccharides to treat diabetic patients. These systems may be used to release insulin in a self-regulated manner. This common disorder of blood glucose regulation due to a lack of insulin is a major public health problem affecting about 250 millions of people in the world today, as compared to 30 millions twenty years ago. Patients diagnosed with insulin-dependent diabetes must take insulin by injecting themselves with a needle at least twice a day. The nanogels targeted in this work are thus expected to release insulin as a function of blood glucose concentration.This project will thus consist in the controlled synthesis of polysaccharides bearing cross-linkable groups and a sugar sensor. These biopolymers will be then used to prepare hydrogels and nanogels (using liposomes as nanoreactors).

La synthèse de nanogels par voie directe est étudiée par la copolymérisationradicalaire réticulante contrôlée par le cobalt (CMRCcP) d’un monomère monovinylique et d’unréticulant divinylique. La synthèse de nanogels globulaires a été réalisée en utilisant unsystème de co-monomères soit neutres (acétate de vinyle et adiapte de divinyle) soit liquidesioniques. Le contrôle de la polymérisation est vérifié dans tous les cas, les liaisons C-Cosituées aux extrémités des chaînes polymères ont été réactivées, afin de former des nanogelsde « seconde-génération ». Dans le cas de monomères liquides ioniques, différents contreanionsont été utilisés afin de jouer sur l’hydrophilie des co-monomères : la CMRCcP dubromure de N-vinyl-3-ethyl imidazolium (VEtImBr) et du bromure de 1,13-divinyl-3-decyldiimidazolium (DVImBr) a été réalisée dans l’eau, à 30 °C, pour former des nanogelspoly(VEtImbr-co-DVImBr) hydrophiles. Les propriétés antibactériennes de ces nanogels ontété étudiées.Les pendants hydrophobes de ces nanogels à base de PILs ont été synthétisés via laCMRCcP directe, dans l’acétate d’éthyle, de co-monomères contenant des contre-anionsbis(trifluromethanesulfonyl)imide (NTf2-). La capacité à former des surfaces poreusesordonnées de ces nanogels hydrophobes poly(VEtImNTf2-co-DVImNTf2) a été examinée, ainsique leur conductivité ioniques en films minces.Des copolymérisations ‘mixtes’ ont également été étudiées, dans l’optique de formerdifférentes architectures nanogels en utilisant des co-monomères ayant des réactivités trèsdifférentes. / The syntheses of globular nanogels were first investigated under mild conditions,using a mono- and a divinyl co-monomer with similar reactivities. CMRCcP was implementedon either neutral (vinyl acetate (VAc) and divinyl adipate (DVA)) co-monomers, or ionic liquidco-monomers. Control over each polymerization was ascertained, and dormant cobaltcarbonchain-ends could be re-activated to form “second-generation” nanogels. CMRCcP ofN-vinyl-3-ethyl imidazolium bromide (VEtImBr) and 1,13-divinyl-3-decyl diimidazoliumbromide (DVImBr) was achieved in water at 30 °C, leading to hydrophilic poly(VEtImBr-co-DVImBr) nanogels. The antibacterial activity of these cross-linked structures wasinvestigated. The hydrophobic pendants of these PIL-based nanogels were synthesized viadirect CMRCcP in ethyl acetate, using bis(trifluromethanesulfonyl)imide (NTf2-) counteranions. An array of these poly(VEtImNTf2-co-DVImNTf2) nanogels was then investigated aspossible coatings for porous patterned surfaces, and their ionic conductivity assessed.Different cross-linked architecture were approached, using a mono- and a divinyl comonomersof completely different reactivities.

Dans le domaine des systèmes d’administration de principes actifs, les nanovecteurs formés par auto-association en milieu aqueux de polymères biocompatibles amphiphiles sont apparus comme l’un des systèmes transporteurs de principes actifs (PA) hydrophobes les plus prometteurs. Ces systèmes offrent plusieurs avantages tels qu'une meilleure solubilité du PA hydrophobe dans l'eau, une diminution des effets secondaires et une amélioration de la libération dans les tissus tumoraux grâce à l’effet de perméabilité et de rétention tissulaire (effet EPR). À cet égard, les nanogels sensibles aux stimuli sont des plateformes attrayantes pour l'administration de médicaments en raison de leur capacité à modifier leurs propriétés physiques et/ou chimiques en réponse à un stimulus externe tel que la lumière, l’application d’un champ magnétique, une variation de pH ou de température. Les polymères thermosensibles sont particulièrement intéressants en raison de leur capacité à subir une transition de phase réversible sans avoir besoin de réactifs supplémentaires. Dans ce contexte, nous avons développé et étudié une nouvelle classe de nanogels thermosensibles, biocompatibles et biodégradables à base de glycoaminoglycanes (GAGs) en modifiant le squelette polysaccharidique avec un copolymère thermoresensible de méthacrylate de di(éthylène glycol) et de n-butylméthacrylate. Celui-ci a été conçu pour obtenir des nanogels stables à température ambiante. La voie de synthèse polyvalente a également permis la réticulation de la couronne afin de figer leur structure. Le choix des GAGs, composant la couronne hydrophile peut être exploité pour contrôler leur comportement biologique. Dans l’objectif d’utiliser ces systèmes en tant que plate-forme polyvalente pour la délivrance de principes actifs et d’autres molécules d'intérêt, nous avons étudié la possibilité d’incorporer des nanoparticules d'oxyde de fer pour des applications de guidage magnétique, d’imagerie et de traitement par hyperthermie. Les synthèses du composant magnétique ainsi que la conception du nanovecteur sont des étapes clés pour réaliser un système de délivrance magnétique capable de réaliser un ciblage efficace. / In the field of drug delivery systems, polymeric nanogels obtained by the self-assembly of biocompatible amphiphilic polymers in water have emerged as one of the most promising nanocarriers for various hydrophobic drugs. These systems offer several advantages such as enhanced hydrophobic drug solubility in water, decreased side effects, and improved drug delivery to tumor tissues via the enhanced permeability and retention (EPR) effect. In this regard, stimuli-responsive polymeric nanogels are attractive platforms for drug delivery due to their ability to change their physical and/or chemical properties in response to an external stimulus such as light, magnetic field, pH or temperature. Thermoresponsive polymers are particularly interesting due to their ability to undergo a reversible thermally-induced phase transition without the need of additional reagents. In this context, our aim was to engineer and to study a new class of thermoresponsive, biocompatible and biodegradable nanogels based on glycoaminoglycans (GAGs) through the modification of the polysaccharide backbone with a thermoresponsive copolymer of di(ethylene glycol) methacrylate (DEGMA) and n-butylmethacrylate (BMA)). The latter was properly designed to obtain stable nanogels at room temperature. The versatile synthetic route to nanogels also allowed their further shell-crosslinking to capture the nanogel structure at low temperature. The choice of the GAGs forming the hydrophilic shell can be exploited to control their biological behavior. In order to use these systems as a versatile platform for delivery of active ingredients and other molecules of interest, we investigated the possibility of incorporating iron oxide nanoparticles for magnetic guidance, imaging and hyperthermia treatment. The syntheses of the magnetic component as well as the design of the nanocarrier are key steps to achieve a magnetically-responsive nanodelivery system capable of efficient targeting.

The design and engineering of nanoscopic drug delivery vehicles that stably encapsulate lipophilic drug molecules, transport their loaded cargo to specific target sites, and release their payload in a controlled manner are of great interest in therapeutic applications, especially for cancer chemotherapy. This dissertation focuses on chemically cross-linked, water-soluble polymer nanoparticles, termed nanogels, which constitute a promising scaffold and offer the potential to circumvent encapsulation stability issues. A facile synthetic method for a new class of self-cross-linked polymer nanogels, synthesized by an intra/intermolecular disulfide cross-linking reaction in aqueous media, is described here. This simple emulsion-free method affords noncovalent lipophilic guest encapsulation and surface functionalization that may allow for targeted delivery. The encapsulation stability of lipophilic molecules sequestered within these nanoscopic containers is evaluated by a fluorescent resonance energy transfer (FRET) based method developed by our research group. We demonstrate that the encapsulation stability of noncovalently encapsulated guest molecules in disulfide cross-linked polymer nanogels can be tuned and that guest release can be achieved in response to a biologically relevant stimulus (GSH). In addition, varied hydrophobicity in the self-cross-linked nanogels affects the lipophilic loading capacity and encapsulation stability. We reveal that optimal loading capacity is limited by encapsulation stability, where over-loading of lipophilic molecules in the nanoscopic containers may cause undersirable leakage and severely compromise the viability of such systems for drug delivery and other biological applications.