Layde Teixeira Carvalho

Développement de systèmes de délivrance de médicament à base de pullulane pour le traitement du cancer: Le pullulane (PULL) est un polysaccharide produit par le champignon Aureobasidium Pullulans, largement exploité comme support polymérique pour le développement de systèmes d'administration de médicaments. Le grand nombre de groupes hydroxyles dans la chaîne du pullulane le rend facilement modifiable, permettant ainsi d'obtenir un polymère aux propriétés intéressantes pour les applications pharmaceutiques. Les dernières décennies, de nombreux nouveaux agents thérapeutiques sont apparus pour le traitement du cancer, notamment les petites molécules inhibitrices de tyrosine kinase (smTKI). L'erlotinib (ERL), un membre de la famille des smTKI, a été proposé pour la chimiothérapie orale comme alternative à la thérapie parentérale plus invasive. En raison de la faible solubilité aqueuse et de la mauvaise biodisponibilité de l'ERL, les systèmes d'administration de médicaments est nécessaire pour améliorer l'efficacité de la chimiothérapie orale avec l'ERL. Cette thèse porte sur la préparation de pullulane cationique et amphiphile cationique, et son utilisation pour le développement de systèmes d'administration d'ERL destinés à l'administration orale et à la libération contrôlée de médicaments dans le tractus gastro-intestinal. Deux réactions ont été effectuées pour modifier chimiquement le pullulane, d'abord avec la DEAE, pour la préparation du polysaccharide hydrophile cationique PULL-DEAE, puis par copolymérisation avec poly(Z-L-lysine), en utilisant différentes proportions du monomère, ce qui a permis d'obtenir trois pullulanes amphiphiles cationiques, PULL-DEAE-g-PZLL 25, 40 et 55%. La modification chimique a été confirmée par RMN et FTIR. Le potentiel zêta a démontré le caractère cationique du polysaccharide modifié, en même temps que la concentration critique d'agrégation a montré la capacité d'auto-agrégation du copolymère. Après la synthèse, les polysaccharides ont été utilisés pour la préparation de différents systèmes d'administration de médicaments basés sur les particules solides : dispersions solides par séchage par atomisation (microparticules de PULL et PULL-DEAE), dispersions solides amorphes par extrusion à chaud (microparticules de PULL, PULL-DEAE et PULL-DEAE-g-PZLL ASD) et dispersions solides par nanoprécipitation par dialyse (nanoparticules PULL-DEAE-g-PZLL). Chaque formulation a été évaluée en termes de profil de libération du médicament, en utilisant deux milieux différents pour simuler l'administration orale de l'ERL. Tout d'abord, la dissolution a été réalisée dans un pH acide, simulant les conditions de l'estomac, puis en changeant le pH à des conditions neutres après deux heures pour simuler le passage gastrique-intestinal. Les résultats ont démontré une libération contrôlée des microparticules PULL :ERL et PULL-DEAE :ERL par rapport à l'ERL libre dans des conditions acides. Pour les microparticules PULL, PULL-DEAE et PULL-DEAE-g-PZLL ASD, contenant 30% d'ERL, en plus d'une libération contrôlée, les formulations ont également montré un retard initial de la recristallisation de l'ERL en milieu basique. Les nanoparticules PULL-DEAE-g-PZLL ont montré un comportement similaire à celui des microparticules préparées par extrusion à chaud. Le pullulane chimiquement modifié a démontré un potentiel d'encapsulation de l'ERL, avec la modification de la libération du médicament dans l'environnement gastro-intestinal simulé.

The complete use of all fractions of agro-industrial by-products is essential to promote sustainability and consolidated bioprocesses in biorefineries. Among the biomass fractions, hemicellulose is still underutilized and could be used to produce high value bioproducts, as fungal biopigments, emerging biomolecules with potential applications in different industrial sectors. Besides raw material, cultivation strategies such as the use of immobilized cells can be interesting for industrial applications, presenting advantages by favoring downstream steps and reuse of cells in repeated or continuous bioprocesses. In this study, the production of biopigments by Monascus ruber immobilized in polyurethane foam was evaluated as a strategy to valorize a xylose-rich sugarcane bagasse hemicellulosic hydrolysate. An experimental design was carried out and showed the optimum xylose/glucose ratio obtained was similar to the values usually found in sugarcane bagasse hemicellulosic hydrolysates. Then, the kinetic profile of the in situ immobilization of the fungus (simultaneous cell growth and adsorption) in polyurethane indicated an inoculum preparation time of 8 days of growth/immobilization before the process conducted in hydrolysate-based medium. The use of immobilized cells resulted in the production of biopigments with maximum values of 13.1 AU, 11.87 AU, and 11.32 AU of yellow, orange and red biopigments, respectively, in medium based on detoxified hydrolysate. The obtained results can contribute to the valorization of agro-industrial by-products as an alternative source of substrates, as well as to future research to explore the potential of immobilizing filamentous fungi in bioprocesses, such as the reuse of cells and continuous systems for production of biopigments. Graphical abstract

Polymeric nanoparticles have great potential for targeted and controlled delivery of drugs for several health treatments. In this work, pullulan‐graft‐poly(ε‐caprolactone) (Pull‐g‐PCL) nanoparticles were prepared and used to encapsulate indomethacin via dialysis. The nanoparticles were characterized with respect to size, size distribution, and morphology, using dynamic light scattering and transmission electron microscopy. The average diameter of nanoparticles was 220.0 and 273.7 nm, with and without indomethacin, respectively. Encapsulation of indomethacin and its release from the nanoparticles were studied, and the calculated value of indomethacin efficiency encapsulation was 35.05 wt%. The ensuing release kinetics were evaluated in vitro at 37°C and pH 7.4 and evidenced the efficiency of polymer nanoparticles in reducing the release rate of the ingredient. Pull‐g‐PCL nanoparticles represent, therefore, promising materials with potential for application in controlled release systems of hydrophobic substances.

Biodegradable and biocompatible copolymers have been often studied for the development of biomaterials for drug delivery systems. In this context, this work reports the synthesis and characterization of a novel pullulan-g-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (Pull-g-PHBHV) graft copolymer using click chemistry. Well-defined and functional pullulan backbones containing azide groups (PullN₃) previously prepared by our group were successfully used for this purpose and propargyl-terminated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was prepared via transesterification using propargyl alcohol as a chain transfer agent. By an alkyne-azide cycloaddition reaction catalyzed by copper (Cu (I)) (CuAAC), the graft copolymer Pull-g-PHBHV was obtained. The chemical structures of the polymers were accessed by ¹H NMR and ¹³C NMR FTIR. Disappearance of the bands referring to the main bonds evidenced success in the grafting reaction. Besides that, DRX, DSC and TGA were used in order to access the changes in crystallinity and thermal behavior of the material. The remaining crystallinity of the Pull-g-PHBHV structure evidences the presence of PHBHV. Pull-g-PHBHV presented lower degradation maximum temperature values than the starting materials, indicating its minor thermal stability. Finally, the synthesized material is an innovative biopolymer, which has never been reported in the previous literature. It is a bio-derived and biodegradable polymer, chemically modified, resulting in interesting properties which can be useful for their further applications as biomedical systems for controlled delivery, for example.

Well-defined amphiphilic, biocompatible and partially biodegradable, thermo-responsive poly(N-vinylcaprolactam)-b-poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by combining reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerizations (ROP). Poly(N-vinylcaprolactam) containing xanthate and hydroxyl end groups (X–PNVCL–OH) was first synthesized by RAFT/macromolecular design by the interchange of xanthates (RAFT/MADIX) polymerization of NVCL mediated by a chain transfer agent containing a hydroxyl function. The xanthate-end group was then removed from PNVCL by a radical-induced process. Finally, the hydroxyl end-capped PNVCL homopolymer was used as a macroinitiator in the ROP of ε-caprolactone (ε-CL) to obtain PNVCL-b-PCL block copolymers. These (co)polymers were characterized by Size Exclusion Chromatography (SEC), Fourier-Transform Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance spectroscopy (¹H NMR), UV–vis and Differential Scanning Calorimetry (DSC) measurements. The critical micelle concentration (CMC) of the block copolymers in aqueous solution measured by the fluorescence probe technique decreased with increasing the length of the hydrophobic block. However, dynamic light scattering (DLS) demonstrated that the size of the micelles increased with increasing the proportion of hydrophobic segments. The morphology observed by cryo-TEM demonstrated that the micelles have a pointed-oval-shape. UV–vis and DLS analyses showed that these block copolymers have a temperature-responsive behavior with a lower critical solution temperature (LCST) that could be tuned by varying the block copolymer composition.

Por tratar-se de um biopolímero de baixa toxicidade, alta biodegradabilidade e biocompatibilidade, a pululana, bem como seus copolímeros, vêm sendo aplicada ...