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

Abstract

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 experiments. 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 × 10−8 A/cm2 to 3.18 × 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 potential for biological application, especially as orthopedic implants.