The enhanced mechano-corrosion and biological properties of the electrodeposited hydroxyapatite-titania coatings on nitinol

Since the first orthopedic application of nitinol (NiTi) in the mid-1970s, it has occupied a prominent position among metallic biomaterials market due to its appropriate features. However, the use of NiTi as a permanent orthopedic implant remains challenging due to some post implantation concerns. These limitations have motivated researchers to modify its surface with favorable bioactive coatings, such as hydroxyapatite (HAp). The inherent drawbacks of the HAp films, including poor mechanical properties associated with their brittle ceramic nature together with moderate corrosion resistance, must be addressed to enable their reliable use in this surgery filed. This contribution attempts to study the surface, chemistry, mechanical, electrochemical, and biological characteristics of the titania included HAp coatings galvanostatically electrodeposited onto NiTi. Titania nanoparticles, added to the HAp electrolyte at concentrations ranging from 0 to 1 g/L, were included in the coatings and distributed both on surface of and between the plate-like HAp crystals, resulting in a smoother surface topography. The nanoparticle-containing coatings showed higher microhardness up to 59% greater than that of pure HAp. In addition, they increased the bonding strength between the HAp layer and NiTi substrate by ≈ 10 MPa. The corrosion resistance of the composite samples is 99% higher than that of titania-free HAp coating. Moreover, enhanced viability and proliferation of the osteoblastic cells on the titania nanoparticle-containing coatings confirmed the constructive effect of the titania on biological properties of the layers. The findings suggest that the proposed surface modification approach improves the final performance of the NiTi implants and their suitability for orthopedic applications.