Biocompatibility of sol-gel hydroxyapatite-titania composite and bilayer coatings

Titania-Hydroxyapatite (TiO₂/HAP) reinforced coatings are proposed to enhance the bioactivity and corrosion resistance of 316L stainless steel (316L SS). Herein, spin- and dip-coating sol-gel processes were investigated to construct two kinds of coatings: TiO₂/HAP composite and TiO₂/HAP bilayer. Physicochemical characterization highlighted the bioactivity response of the TiO₂/HAP composite once incubated in physiological conditions for 7days whereas the TiO₂/HAP bilayer showed instability and dissolution. Biological analysis revealed a failure in human stem cells adhesion on TiO₂/HAP bilayer whereas on TiO₂/HAP composite the presence of polygonal shaped cells, possessing good behaviour attested a good biocompatibility of the composite coating. Finally, TiO₂/HAP composite with hardness up to 0.6GPa and elastic modulus up to 18GPa, showed an increased corrosion resistance of 316L SS. In conclusion, the user-friendly sol-gel processes led to bioactive TiO₂/HAP composite buildup suitable for biomedical applications.