Structural studies and macro-performances of hydroxyapatite-reinforced keratin thin films for biological applications

In this work, a series of wool keratin/hydroxyapatite (HA) composite films with different component ratios were fabricated by a modified solution casting technique. During the film-forming process, HAs deposited on the keratin matrix and bonded with amino acids of keratin molecules via electrostatic and intermolecular/water-bridged hydrogen bond interaction, which can be verified by the different morphologies of HA particles in water and keratin solution from scanning electron microscope and transmission electron microscope images. The microstructural transitions of hybrid films were examined by Fourier transform infrared spectroscopy and X-ray diffraction, indicating that HA particles expanded the crystalline area of composites without disrupting the original structures of keratin, and eventually enhanced the macro-performance of hybrid film. Nevertheless, excessive HA particles in keratin were liable to agglomerate and accumulate on the surface of films, which led to the weakening of tensile strength to some extent but improved the wettability of films and the biocompatibility and bioactivity compared to the pure keratin film. The composite films with 5 wt% HA granules were taken to be the optimum composition for practical application with good mechanical strength and biocompatibility; moreover, thermo gravimetric analysis was used to confirm the good thermostability of this kind of film.