Graphene oxide/ hydroxyapatite composite coatings on additively manufactured NiTi alloy for biomedical applications

In recent years, additive manufacturing of nickel-titanium (NiTi) alloys as medical implant materials have attracted a lot of interest due to their precise, rapid, and integrated molding. However, the NiTi alloy as a bioinert material exhibits poor osteogenic activity and biomineralization properties. In this work, a graphene oxide (GO) coating containing nano-hydroxyapatite (HA) is fabricated on the NiTi alloys by a one-step DC electrodeposition method. The effects of HA (0.1 g/L) on the corrosion resistance, biomineralization properties and long-term stability of GO composite coating were investigated by electrochemical tests and immersion ex-periments. The result shows that the corrosion current density of GO coating reduces by one order of magnitude due to the introduction of nano-HA (from 2.24 x 10-8 A/cm2 to 3.18 x 10-9 A/cm2), the surface remains dense after 15 days of immersion, and a dense apatite layer is mineralized on the surface. In addition, in vitro MC3T3-E1 cell viability and cell morphology results showed that the coating can effectively enhance the biocompatibility of additively manufactured NiTi alloy because it provides a better microenvironment and interface for cell growth and adhesion. Taken together, the additively manufactured NiTi alloys with GO/HA coating present great po-tential for biological application, especially as orthopedic implants.