Development of new biomaterials based on liquid crystalline phases of cellulose derivatives

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Biomédica

In the present work, new biomaterials based on liquid crystalline phases of cellulose derivatives were prepared and characterized. The possibility to monitor growth and differentiation of stem cells could be an interesting use for the HPC films studied in this thesis. Additionally, the application of HPC films as an anti-adhesive substratum in biomedical applications could also be interesting. For that purpose, two solutions of hydroxypropylcellulose (HPC) in dimethylacetamide (DMAc) were prepared. An isotropic 30% solution (HPCi) and an anisotropic 60% chiral nematic solution (HPCa) were obtained and submitted to a chemical cross-linking treatment by adding 10% (w/w) of the crosslinking agent (1,6 diisocyanatohexane, 98%). HPC films were then prepared with the help of a calibrated ruler moving at a controlled rate (v = 6 mm.s-1). The non-biological characterization of these films included physico-chemical and structural characterization. HPCi and HPCa film characterization was performed by optical microscopy, determination of the gel fraction, mechanical properties, contact angle measurements, infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The biological experimental characterization included cytotoxicity evaluation, cell adhesion, morphology, proliferation and viability assays. The band texture of HPCa films, formed during the shear, was easily observed using polarized light transmission microscopy. The mechanical anisotropy of HPCa films was also easily identified. FTIR and XPS showed that the surface chemistry of both films is similar, as well as the contact angles measured on both surfaces. SEM results showed a characteristic topography on the HPCa surface, which was verified and quantified by AFM. The interaction of these biomaterials with human mesenchymal stem cells (hMSC) was also investigated. HPC films were also tested for in vitro cytotoxicity and were found to be non-cytotoxic. The results showed that the percentage of adherent cells on HPC films was almost zero and that cells were not able to proliferate on these substrates. MSCs became round and aggregated on both HPC films, but remained aggregated and viable. This study has shown that it is possible to prepare sterile and biocompatible HPC films with potential use as coatings for anti-adhesive purposes in medical devices.