A thermosensitive chitosan/poly(vinyl alcohol) hydrogel containing hydroxyapatite for protein delivery

The synthesis and characterization of a thermosensitive chitosan/poly(vinyl alcohol) (PVA) hydrogel containing hydroxyapatite for protein delivery were first reported. Two synthetic processes were introduced, that is, in situ and ex situ routes. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and rheological analysis were employed to characterize the hydrogel. The gel formation decreased the crystallinity of the hydroxyapatite crystal. FTIR results showed that the hydroxyapatite crystals were partially substituted by carbonate. It was supposed that the structural features of hydroxyapatite were close to those of biological apatites. The thermosensitive property of the gels was evaluated by rheological analysis, which indicated that the strength of hydroxyapatite-chitosan/PVA composite gels was notably enhanced in comparison with that of pure chitosan/PVA gel, especially for hydroxyapatite-chitosan/PVA composite gels synthesized through the in situ process. The performances of composite gels containing different amounts of hydroxyapatite were further studied. For the hydroxyapatite-chitosan/PVA composite gels containing 0.1 mM hydroxyapatite synthesized through in situ process, the swelling degree was the lowest, and the speed of protein release was the slowest. Therefore, the composite gels are attractive for applications as protein delivery, artificial bones, and scaffolds for tissue engineering.