Osteogenic activity, antibacterial ability, and Ni release of Mg-incorporated Ni-Ti-O nanopore coatings on NiTi alloy

Favorable osteogenic activity and antibacterial ability are highly desired for hard tissue repair and replacement materials. However, as a typical implant material, nearly equiatomic nickel-titanium (NiTi) alloy exhibits poor osteogenic and antibacterial capacities despite its good biocompatibility and unique mechanical properties. In this work, nickel-titanium-oxygen (Ni-Ti-O) nanopores (NPs) coatings incorporated with magnesium (NP-Mg) are fabricated on the NiTi alloy by anodization and hydrothermal treatment (HT). The results show the amount of loaded Mg can be regulated by the NPs length (1.8 and 10.4 mu m) and the hydrothermal duration (1 and 5 h). In addition, the surface morphology of the coatings transform to nanosheets after HT for 1 h and to NPs with small diameter after HT for 5 h. Bone marrow mesenchymal stem cells (BMSCs) cultured on NP-Mg-coated NiTi alloy show better proliferation and osteogenic differentiation than that of pristine and as-anodized specimens. Antibacterial experiments show although HT reduces Ni ion release and increase corrosion resistance, the NP-Mg coatings yet maintain potent antibacterial activity especially against adherent bacteria. The NPs coating with thickness of 10.4 mu m and HT for 5 h shows favorable osteogenic activity, antibacterial ability, little Ni ion release, and good corrosion resistance thus is a promising candidate to functionalize the surface of the NiTi alloy for orthopedic applications.