Development of Chitosan and Poly (Vinyl Alcohol) Blended scaffolds for cell culture using supercritical fluids technology

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Mestrado Integrado em Engenharia Química e Bioquímica

In this work new porous materials for biomedical applications were developed using supercritical fluids (SCF) technology. In this context, two types of porous structures constituted by blends of chitosan and poly (vinyl alcohol) (PVA) using different ratios were prepared: membranes and three dimensional (3D) scaffolds. Phase inversion method using supercritical carbon dioxide (scCO2) as non-solvent was used to prepare porous membranes. The characterization of these materials showed that the presence of PVA in the membranes composition causes a decrease in porosity values and contact angle and an increase on pores interconnectivity and swelling degree. The mechanical properties were also modified by the existence of PVA in the membranes composition, increasing the elongation capacity of these structures and decreasing the supported break stresses. The 3D-scaffolds were prepared using freeze-drying technique and were treated with glutaraldehyde using a CO2-assisted crosslinking process. The optimization of the crosslinking process comprised the study of different glutaraldehyde concentrations and operation time. Morphological characterization showed that the casting solution concentration was a parameter with no influence in the 3Dscaffolds porosity neither on the pores interconnectivity. However, the PVA content in these matrices and the temperature used in the freeze-drying process determined their morphology. These highly porous structures were also submitted to dynamic swelling tests proving to be pH-sensitive with the capacity of swelling and deswelling when submitted to pH variations. The best response was obtained for scaffolds crosslinked with 1% (v/v) of glutaraldehyde during 10 minutes. Membranes and 3D-scaffolds were also tested for in vitro biodegradation using lysozyme and for cytotoxicity, proving to have potential applications in tissue engineering and regenerative medicine.