Preparation and characterization of chitosan-g-poly(vinyl alcohol)/poly(vinyl alcohol) blends used for the evaluation of blood-contacting compatibility

To increase the physicochemical compatibility between chitosan and poly(vinyl alcohol), chitosan-g-poly(vinyl alcohol)/poly(vinyl alcohol) (CS-g-PVA/PVA) blends were prepared via a two-step reaction. In the first step, chitosan-g-poly(vinyl acetate)/poly(vinyl acetate) (CS-g-PVAc/PVAc) blends were produced in situ by adding 100 g of VAc monomer to acetic aqueous solutions with different amounts of CS, using a ceric ion as the initiator. The polymerization was carried out at 60 °C for 2 h, where grafting of VAc monomers onto chitosan and homopolymerization of VAc monomers occurred simultaneously. Monomer conversion, grafting efficiency and grafting ratio were all measured by gravimetric analysis. In the second step, CS-g-PVA/PVA blends were obtained by converting PVAc chains to PVA through alcoholysis in an alkali methanol solution. After oven drying process, the morphology of CS-g-PVAc/PVAc and CS-g-PVA/PVA blends were observed to be particulate and dense membrane, respectively. The cellular and blood compatibility of pure PVA, pure chitosan, and CS-g-PVA/PVA blends were tested separately by the viability of osteoblasts and the adhesion of platelets. Our results showed the cellular compatibility of PVA was improved due to the incorporation of chitosan. For platelet adhesion, pure PVA offered a good blood-contact property, while pure chitosan did very poor. However, interesting enough, the blends of a small amount of CS-g-PVA with PVA further improved the blood compatibility. An optimum composition of CS-g-PVA/PVA blend was determined in this study for its use in blood-contacting biomedical devices.