1,3-β-glucans are a class of natural polysaccharides with unique pharmacological properties and the ability to form triple helical structures and resilient gels. Curdlan and other 1,3-β-glucans have found application pharmacologically in the treatment of cancers and acceleration of wound healing in humans and in the impartation of infection resistance in animal husbandry. Structurally, these polysaccharides have found application in food science as thermal gels, in nanostructure formation as helical scaffolds, and in drug delivery as nanocarriers for drugs and as inclusion complexes with polynucleotides. A literature review of the important work on Curdlan research reveals two streams of research: investigation of the pharmacological significance of these polymers and their application in increasing host immunocompetency and investigation of the nature of the triple helix and its application in a variety of fields from food gels to drug delivery. Two significant contributions to the field of Curdlan research have been completed including 1) The development of a Curdlan nanoparticle drug delivery platform and 2) A new multi-component liquid crystalline hydrogel providing a new route to form polynucleotide inclusion complexes with Curdlan for gene delivery. The developed nanoparticle platform exhibited high encapsulation of chemotherapeutic drugs and a 24-hour controlled release with a particle size of 109.9 nm. The liquid crystalline hydrogel exhibited homogeneous inclusion of DNA into amorphous and crystalline phases of Curdlan and delayed and triggered release of polynucleotide content. This work has been a significant demonstration of the potential of Curdlan as a new polymer for multi-functional drug delivery.

1,3-β-glucans are a class of natural polysaccharides with unique pharmacological properties and the ability to form triple helical structures and resilient gels. Curdlan and other 1,3-β-glucans have found application pharmacologically in the treatment of cancers and acceleration of wound healing in humans and in the impartation of infection resistance in animal husbandry. Structurally, these polysaccharides have found application in food science as thermal gels, in nanostructure formation as helical scaffolds, and in drug delivery as nanocarriers for drugs and as inclusion complexes with polynucleotides. A literature review of the important work on Curdlan research reveals two streams of research: investigation of the pharmacological significance of these polymers and their application in increasing host immunocompetency and investigation of the nature of the triple helix and its application in a variety of fields from food gels to drug delivery. Two significant contributions to the field of Curdlan research have been completed including 1) The development of a Curdlan nanoparticle drug delivery platform and 2) A new multi-component liquid crystalline hydrogel providing a new route to form polynucleotide inclusion complexes with Curdlan for gene delivery. The developed nanoparticle platform exhibited high encapsulation of chemotherapeutic drugs and a 24-hour controlled release with a particle size of 109.9 nm. The liquid crystalline hydrogel exhibited homogeneous inclusion of DNA into amorphous and crystalline phases of Curdlan and delayed and triggered release of polynucleotide content. This work has been a significant demonstration of the potential of Curdlan as a new polymer for multi-functional drug delivery.

Curdlan, a (1,3)-linked linear homopolysaccharide composed of beta-D-glucan, is produced by the bacterium Alcaligenes faecalis var. myxogenes. Several strategies to synthesize chemically modified curdlan derivatives have been reported, but there have been few reports of regioselective functionalization at specific positions of the curdlan backbone, especially of aminated curdlan derivatives which have remarkable potential in biomedical and pharmaceutical applications. We demonstrate herein the design, synthesis and characterization of a family of regioselectively aminated curdlan derivatives including 6-deoxy-6-(bromo/azido/amino/amido/ammonium) curdlans starting from 6-bromo/azido-6-deoxycurdlan. A key reaction that enabled the whole synthesis of new curdlan derivatives at C-6 described in this dissertation was the highly selective bromination of curdlan. The resultant 6-bromo-6-deoxycurdlan, prepared with high regioselectivity, was treated with trialkylamines or heterocyclic amines to produce a range of water-soluble curdlan ammonium salts. The bromide was then nucleophilically displaced by sodium azide to produce the versatile precursor 6-azido-6-deoxycurdlan. Its water solubility was enhanced either by the incorporation of hydrophilic trioxadecanoate esters into O-2/4 positions or by the borohydride reduction to afford 6-amino-6-deoxycurdlan. The iminophosphorane intermediate generated during Staudinger reactions was further investigated for subsequent syntheses: i) 6-amino or 6-amido-6-deoxycurdlan by in situ reaction with water or excess carboxylic anhydride, ii) 6-monoalkylamino curdlan by reductive amination using aldehydes and sodium cyanoborohydride, and iii) 6-dialkylamino-/tri-alkylammoniocurdlans by reacting with methyl iodide. Such derivatives could have properties useful for a range of biomedical applications, including interactions with proteins, encapsulation of drugs, and formulation with genes or other biological compounds. / Ph. D.

β-Glucans have beneficial health effects due to their immune modulatory properties. Oral administration of β-glucans affects tumour growth, microbial infection, sepsis, and wound healing. We hypothesized that pre-treatment with orally delivered soluble and particulate β-glucans could ameliorate the development of aggravate dextran sulfate sodium (DSS) induced intestinal inflammation. To study this, mice were orally pre-treated with β-glucans for 14 days. We tested curdlan (a particulate β-(1,3)-glucan), glucan phosphate (a soluble β-(1,3)-glucan), and zymosan (a particle made from Saccharomyces cerevisiae, which contains around 55% β-glucans). Weight loss, colon weight, and feces score did not differ between β-glucan and vehicle treated groups. However, histology scores indicated that β-glucan-treated mice had increased inflammation at a microscopic level suggesting that β-glucan treatment worsened intestinal inflammation. Furthermore, curdlan and zymosan treatment led to increased colonic levels of inflammatory cytokines and chemokines, compared to vehicle. Glucan phosphate treatment did not significantly affect cytokine and chemokine levels. These data suggest that particulate and soluble β-glucans differentially affect the intestinal immune responses. However, no significant differences in other clinical colitis scores between soluble and particulate β-glucans were found in this study. In summary, β-glucans aggravate the course of dextran sulfate sodium (DSS)-induced intestinal inflammation at the level of the mucosa.

β-Glucans are components of fungal cell walls and potent stimulants of innate immunity. The majority of research on biological activities of glucans has focused on β-(1→3)-glucans, which have been implicated in relation to fungal exposure-associated respiratory symptoms and as important stimulatory agents in anti-fungal immune responses. Fungi - and bacteria and plants - produce a wide variety of glucans with vast differences in the proportion and arrangement of their β-(1→3)-, -(1→4)- and -(1→6)-glycosidic linkages. Thus far, the pro-inflammatory potential of different β-glucans has not been studied within the same experimental model. Therefore, we compared the potency of 13 different glucan preparations to induce in vitro production of IL-1β, IL-6, IL-8 and TNF-α in human, whole blood cultures. The strongest inducers of all cytokines were pustulan [β-(1→6)-glucan], lichenan [β-(1→3)-(1→4)-glucan], xyloglucan [β-(1→4)- glucan] and pullulan [α-(1→4)-(1→6)-glucan]. Moderate-to-strong cytokine production was observed for curdlan [β-(1→3)-glucan], baker's yeast glucan [β-(1→3)-(1→6)-glucan] and barley glucan [β-(1→3)-(1→4)-glucan], while all other glucan preparations induced very low, or no, detectable levels of cytokines. We therefore conclude that innate immunity reactions are not exclusively induced by β-(1→3)-glucans, but also by β-(1→6)- and β-(1→4)-structures. Thus, not only β-(1→3)-glucan, but also other β-glucans and particularly β-(1→6)-glucans should be considered in future research.

β-Glucans are components of fungal cell walls and potent stimulants of innate immunity. The majority of research on biological activities of glucans has focused on β-(1→3)-glucans, which have been implicated in relation to fungal exposure-associated respiratory symptoms and as important stimulatory agents in anti-fungal immune responses. Fungi - and bacteria and plants - produce a wide variety of glucans with vast differences in the proportion and arrangement of their β-(1→3)-, -(1→4)- and -(1→6)-glycosidic linkages. Thus far, the pro-inflammatory potential of different β-glucans has not been studied within the same experimental model. Therefore, we compared the potency of 13 different glucan preparations to induce in vitro production of IL-1β, IL-6, IL-8 and TNF-α in human, whole blood cultures. The strongest inducers of all cytokines were pustulan [β-(1→6)-glucan], lichenan [β-(1→3)-(1→4)-glucan], xyloglucan [β-(1→4)- glucan] and pullulan [α-(1→4)-(1→6)-glucan]. Moderate-to-strong cytokine production was observed for curdlan [β-(1→3)-glucan], baker's yeast glucan [β-(1→3)-(1→6)-glucan] and barley glucan [β-(1→3)-(1→4)-glucan], while all other glucan preparations induced very low, or no, detectable levels of cytokines. We therefore conclude that innate immunity reactions are not exclusively induced by β-(1→3)-glucans, but also by β-(1→6)- and β-(1→4)-structures. Thus, not only β-(1→3)-glucan, but also other β-glucans and particularly β-(1→6)-glucans should be considered in future research.

Les hydrogels de polysaccharide sont des biomatériaux utilisés comme matrices à libération contrôlée de médicaments et comme structures modèles pour l’étude de nombreux systèmes biologiques dont les biofilms bactériens et les mucus. Dans tous les cas, le transport de médicaments ou de nutriments à l’intérieur d’une matrice d’hydrogel joue un rôle de premier plan. Ainsi, l’étude des propriétés de transport dans les hydrogels s’avère un enjeu très important au niveau de plusieurs applications. Dans cet ouvrage, le curdlan, un polysaccharide neutre d’origine bactérienne et formé d’unités répétitives β-D-(1→3) glucose, est utilisé comme hydrogel modèle. Le curdlan a la propriété de former des thermogels de différentes conformations selon la température à laquelle une suspension aqueuse est incubée. La caractérisation in situ de la formation des hydrogels de curdlan thermoréversibles et thermo-irréversibles a tout d’abord été réalisée par spectroscopie infrarouge à transformée de Fourier (FT-IR) en mode réflexion totale atténuée à température variable. Les résultats ont permis d’optimiser les conditions de gélation, menant ainsi à la formation reproductible des hydrogels. Les caractérisations structurales des hydrogels hydratés, réalisées par imagerie FT-IR, par microscopie électronique à balayage en mode environnemental (eSEM) et par microscopie à force atomique (AFM), ont permis de visualiser les différentes morphologies susceptibles d’influencer la diffusion d’analytes dans les gels. Nos résultats montrent que les deux types d’hydrogels de curdlan ont des architectures distinctes à l’échelle microscopique. La combinaison de la spectroscopie de résonance magnétique nucléaire (RMN) à gradients pulsés et de l’imagerie RMN a permis d’étudier l’autodiffusion et la diffusion mutuelle sur un même système dans des conditions expérimentales similaires. Nous avons observé que la diffusion des molécules dans les gels est ralentie par rapport à celle mesurée en solution aqueuse. Les mesures d’autodiffusion, effectuées sur une série d’analytes de diverses tailles dans les deux types d’hydrogels de curdlan, montrent que le coefficient d’autodiffusion relatif décroit en fonction de la taille de l’analyte. De plus, nos résultats suggèrent que l’équivalence entre les coefficients d’autodiffusion et de diffusion mutuelle dans les hydrogels de curdlan thermo-irréversibles est principalement due au fait que l’environnement sondé par les analytes durant une expérience d’autodiffusion est représentatif de celui exploré durant une expérience de diffusion mutuelle. Dans de telles conditions, nos résultats montrent que la RMN à gradients pulsés peut s’avérer une approche très avantageuse afin de caractériser des systèmes à libération contrôlée de médicaments. D’autres expériences de diffusion mutuelle, menées sur une macromolécule de dextran, montrent un coefficient de diffusion mutuelle inférieur au coefficient d’autodiffusion sur un même gel de curdlan. L’écart mesuré entre les deux modes de transport est attribué au volume différent de l’environnement sondé durant les deux mesures. Les coefficients d’autodiffusion et de diffusion mutuelle similaires, mesurés dans les deux types de gels de curdlan pour les différents analytes étudiés, suggèrent une influence limitée de l’architecture microscopique de ces gels sur leurs propriétés de transport. Il est conclu que les interactions affectant la diffusion des analytes étudiés dans les hydrogels de curdlan se situent à l’échelle moléculaire. / Polysaccharide hydrogels are biomaterials used as controlled drug delivery matrices and serve as model scaffolds for the study of many biological systems like bacterial biofilms and mucus. In every case, the transport of drugs or nutriments across a hydrogel matrix is of prime importance. Therefore, the study of transport properties in hydrogels is an important issue for many fields of application. In this work, curdlan, a neutral bacterial polysaccharide made of β-D-(1→3) glucose repeating units, is used as a model hydrogel. Aqueous suspensions of curdlan can form thermogels of different conformations depending on the incubation temperature. In situ characterization of the preparation of thermo-reversible (low-set) and thermo-irreversible (high-set) curdlan hydrogels was first carried out using variable temperature attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FT-IR). The results allowed optimization of the gelling conditions leading to reproducible gel samples. Structural characterization of fully hydrated hydrogels, carried out by FT-IR imaging, environmental scanning electron microscopy (eSEM) and atomic force microscopy (AFM), allowed visualization of the different gel morphologies susceptible of influencing the diffusion of analytes in hydrogels. Our results show that both types of curdlan hydrogels have distinct microscopic architectures. The combination of pulsed field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy and NMR profiling allowed the study of self-diffusion and mutual diffusion on the same hydrogel system in similar experimental conditions. We showed that the diffusion of analytes in the gels is slower than in the aqueous solution. The diffusion experiments, carried out on a series of analytes of various sizes in both types of curdlan gels, show a decrease of the relative self-diffusion coefficient as a function of the analyte size. In addition, our results suggest that the equivalence between the self-diffusion and mutual-diffusion coefficients measured in the high-set curdlan gels is mainly due to the fact that the environment probed by the analytes during a self-diffusion experiment is representative of the one probed during a mutual-diffusion experiment. In such conditions, our results show that PFG NMR may present a valuable approach for the characterization of controlled drug release systems. Additional experiments show that the mutual-diffusion coefficient of dextran macromolecules is smaller than its self-diffusion coefficient in the same curdlan hydrogel. The difference between both transport rates is attributed to the different environment volumes probed by the analytes during the measurements. The similarities observed between the self-diffusion and mutual-diffusion coefficients, measured in both types of curdlan gels for all investigated analytes, suggest a limited influence of the microscopic gel architecture on its transport properties. It is therefore concluded that the interactions affecting the diffusion of the investigated analytes in the curdlan hydrogels lie at the molecular scale.

Les hydrogels de polysaccharide sont des biomatériaux utilisés comme matrices à libération contrôlée de médicaments et comme structures modèles pour l’étude de nombreux systèmes biologiques dont les biofilms bactériens et les mucus. Dans tous les cas, le transport de médicaments ou de nutriments à l’intérieur d’une matrice d’hydrogel joue un rôle de premier plan. Ainsi, l’étude des propriétés de transport dans les hydrogels s’avère un enjeu très important au niveau de plusieurs applications. Dans cet ouvrage, le curdlan, un polysaccharide neutre d’origine bactérienne et formé d’unités répétitives β-D-(1→3) glucose, est utilisé comme hydrogel modèle. Le curdlan a la propriété de former des thermogels de différentes conformations selon la température à laquelle une suspension aqueuse est incubée. La caractérisation in situ de la formation des hydrogels de curdlan thermoréversibles et thermo-irréversibles a tout d’abord été réalisée par spectroscopie infrarouge à transformée de Fourier (FT-IR) en mode réflexion totale atténuée à température variable. Les résultats ont permis d’optimiser les conditions de gélation, menant ainsi à la formation reproductible des hydrogels. Les caractérisations structurales des hydrogels hydratés, réalisées par imagerie FT-IR, par microscopie électronique à balayage en mode environnemental (eSEM) et par microscopie à force atomique (AFM), ont permis de visualiser les différentes morphologies susceptibles d’influencer la diffusion d’analytes dans les gels. Nos résultats montrent que les deux types d’hydrogels de curdlan ont des architectures distinctes à l’échelle microscopique. La combinaison de la spectroscopie de résonance magnétique nucléaire (RMN) à gradients pulsés et de l’imagerie RMN a permis d’étudier l’autodiffusion et la diffusion mutuelle sur un même système dans des conditions expérimentales similaires. Nous avons observé que la diffusion des molécules dans les gels est ralentie par rapport à celle mesurée en solution aqueuse. Les mesures d’autodiffusion, effectuées sur une série d’analytes de diverses tailles dans les deux types d’hydrogels de curdlan, montrent que le coefficient d’autodiffusion relatif décroit en fonction de la taille de l’analyte. De plus, nos résultats suggèrent que l’équivalence entre les coefficients d’autodiffusion et de diffusion mutuelle dans les hydrogels de curdlan thermo-irréversibles est principalement due au fait que l’environnement sondé par les analytes durant une expérience d’autodiffusion est représentatif de celui exploré durant une expérience de diffusion mutuelle. Dans de telles conditions, nos résultats montrent que la RMN à gradients pulsés peut s’avérer une approche très avantageuse afin de caractériser des systèmes à libération contrôlée de médicaments. D’autres expériences de diffusion mutuelle, menées sur une macromolécule de dextran, montrent un coefficient de diffusion mutuelle inférieur au coefficient d’autodiffusion sur un même gel de curdlan. L’écart mesuré entre les deux modes de transport est attribué au volume différent de l’environnement sondé durant les deux mesures. Les coefficients d’autodiffusion et de diffusion mutuelle similaires, mesurés dans les deux types de gels de curdlan pour les différents analytes étudiés, suggèrent une influence limitée de l’architecture microscopique de ces gels sur leurs propriétés de transport. Il est conclu que les interactions affectant la diffusion des analytes étudiés dans les hydrogels de curdlan se situent à l’échelle moléculaire. / Polysaccharide hydrogels are biomaterials used as controlled drug delivery matrices and serve as model scaffolds for the study of many biological systems like bacterial biofilms and mucus. In every case, the transport of drugs or nutriments across a hydrogel matrix is of prime importance. Therefore, the study of transport properties in hydrogels is an important issue for many fields of application. In this work, curdlan, a neutral bacterial polysaccharide made of β-D-(1→3) glucose repeating units, is used as a model hydrogel. Aqueous suspensions of curdlan can form thermogels of different conformations depending on the incubation temperature. In situ characterization of the preparation of thermo-reversible (low-set) and thermo-irreversible (high-set) curdlan hydrogels was first carried out using variable temperature attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FT-IR). The results allowed optimization of the gelling conditions leading to reproducible gel samples. Structural characterization of fully hydrated hydrogels, carried out by FT-IR imaging, environmental scanning electron microscopy (eSEM) and atomic force microscopy (AFM), allowed visualization of the different gel morphologies susceptible of influencing the diffusion of analytes in hydrogels. Our results show that both types of curdlan hydrogels have distinct microscopic architectures. The combination of pulsed field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy and NMR profiling allowed the study of self-diffusion and mutual diffusion on the same hydrogel system in similar experimental conditions. We showed that the diffusion of analytes in the gels is slower than in the aqueous solution. The diffusion experiments, carried out on a series of analytes of various sizes in both types of curdlan gels, show a decrease of the relative self-diffusion coefficient as a function of the analyte size. In addition, our results suggest that the equivalence between the self-diffusion and mutual-diffusion coefficients measured in the high-set curdlan gels is mainly due to the fact that the environment probed by the analytes during a self-diffusion experiment is representative of the one probed during a mutual-diffusion experiment. In such conditions, our results show that PFG NMR may present a valuable approach for the characterization of controlled drug release systems. Additional experiments show that the mutual-diffusion coefficient of dextran macromolecules is smaller than its self-diffusion coefficient in the same curdlan hydrogel. The difference between both transport rates is attributed to the different environment volumes probed by the analytes during the measurements. The similarities observed between the self-diffusion and mutual-diffusion coefficients, measured in both types of curdlan gels for all investigated analytes, suggest a limited influence of the microscopic gel architecture on its transport properties. It is therefore concluded that the interactions affecting the diffusion of the investigated analytes in the curdlan hydrogels lie at the molecular scale.