BIOCHEMICAL AND BIOLOGICAL ASPECTS OF BIOMATERIALS BIOCOMPATIBILITY

The biocompatibility of a medical implant is influenced by a number of factors, including the toxicity of the materials employed, the form and design of the implant, the skill of the surgeon inserting the device, the dynamics or movement of the device in situ, the resistance of the device to chemical or structural degradation (biostability), and the nature of the reactions that occur at the biological interface. The increasing use of biopolymers as scaffolds in tissue regeneration and matrices in drug delivery systems requires testing of their biodegradability and tissue compatibility. The aim of this project was to investigate the in vitro biocompatibility of polymers by monitoring biochemical and biological responses. The research carried out within this PhD project was focused on two main topics: the biological evaluation of a set of poly(amidoamine) (PAA) hydrogels modified with different amount of agmatine and the biological evaluation of poly(ɛ-caprolactone) (PCL) and three-arm branched poly(ɛ-caprolactone) (PCL*) electrospun meshes prepared in our laboratory. Agmatine has been shown to interfere with polyamine metabolism by decreasing ornithine decarboxylase (ODC) activity and cell growth in tumor and normal cells cultured in vitro, in particular on cells with hepatic phenotype. Attention was focused on the cell response in terms of phenotype, cell specific protein production, metabolic activity and inflammatory response to PAA-agmatine hydrogels. Results of this investigation showed that covalently linked agmatine promotes cellular attachment and guide cellular spreading by modifying the characteristic cell shape. This particular change in morphology does not seem to interfere with the production on albumin and the synthesis of ODC in hepatoblastoma cell lines. Electrospun fibers of PCL* were originally developed by our group within a research activity aimed at the development of micro/nano fibrous meshes in scaffold-guided tissue engineering applications. Cellular proliferation assay was performed by means of WST-1 and the morphology of cells was evaluated by means of confocal laser scanning microscopy. Results showed an alteration in cytoskeleton organization. In particular less actin microfilaments were present and a peculiar pattern of green fluorescence dots was recordered into the cytoplasms of the cells, thus suggesting a possible depolymerization of actin. BioPlex investigation has showed the presence of various cytokines both in samples and in control suggesting a minimum influence of the polymer in eliciting inflammatory response.