Layer-by-Layer coated microparticle templates for biomedical applications

• Autor(a) principal: Ribeiro, Carla Madalena Moreira
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10348/9203
• topic: biocompatible polymers; layer-by-layer assembly; microparticles; hollow multilayered microcapsules; drug delivery; cellular internalization

Over the last decades there has been a great interest in the design and development of nanoand microscale drug delivery systems for the encapsulation, protection, and sustained and targeted delivery of therapeutics at injured sites, as well as for triggering the regeneration of specific tissues and/or organs. Among them, polymeric microparticles and microcapsules produced by using natural and/or synthetic polymers, as well as surface engineering approaches have emerged owing to their intriguing features, including large surface area, easy and versatile surface functionalization, and tunable physicochemical properties. In particular, particles and capsules developed by resorting to natural-origin polymers have attracted massive attention in the biomedical field due to their biocompatibility, biodegradability and wide bioavailability. Nevertheless, some synthetic polymers have been also used in the biomedical arena owing to their promising features. For instance, poly(lactic-co-glycolic) acid (PLGA) is one of the most attractive synthetic polymers due to its biocompatibility, biodegradability, and easily tunability, being already approved by the regulatory authorities to be used in the clinics. Concomitantly, PLGA-based drug carriers have shown to not elicit biological risk upon cellular uptake. In this work, two distinct microparticle templates were produced and surface functionalized with polymeric materials via the bottom-up Layer-by-Layer (LbL) assembly technology to assess the sustained released of model compounds or their cellular uptake. As such, polymeric PLGAbased microparticles were produced, loaded with a model hydrophobic compound with fluorescent features, namely coumarin 6 (C6), and further surface-functionalized via the Layerby-Layer (LbL) assembly of oppositely charged poly-L-lysine (PLL) and alginate (ALG) polymers, to assess the influence of the number of layers on the sustained release of C6. The encapsulation efficiency and the in vitro release profile were assessed and quantified by fluorescence spectroscopy, confirming the sustained release upon 21 days. The role of some of the most relevant physicochemical properties of the particles, known to have a significant impact on the interaction with biological systems, including the mean particle size and surface charge was evaluated. Following this study, hollow polysaccharide-based microcapsules were produced by alternate deposition of chitosan (CHT) and ALG multilayers onto calcium carbonate (CaCO3) microparticles surface, followed by core template dissolution. The mean particle size, surface charge, and aggregation tendency were evaluated aiming to produce welldispersed microcapsules. The in vitro cellular uptake of aggregated and well-dispersed microcapsules was assessed by confocal laser scanning microscopy using mouse lung fibroblast cell line (L929), proving that, in opposition to the aggregated microcapsules, the well-dispersed microcapsules were successfully internalized by cells and, very importantly, the cells remained viable. In both systems, the morphological properties of the particles/capsules were assessed by advanced microscopy techniques, including scanning and transmission electron microscopy, as well as widefield fluorescence microscopy.