Enhanced mechanical, antibacterial, and osteogenic performance of zinc-doped micro-nano porous layer on Ti6Al4V: Realized by ion exchange and induction heating

Abstract

Titanium (Ti)-based implants still face the issues including insufficient early osseointegration and bacterial infection in clinical applications. In this study, zinc (Zn)-doped micro-nano porous layer is in-situ constructed on Ti6Al4V surface, through ion exchange followed by induction heating at 600–800 °C to realize that the substrate is first heated and then the surface layer is heated. The effects of induction heating on phase, microstructure, physicochemical properties, antibacterial effectiveness, and cell responses of the films are explored. As induction heating temperature increases, the porous architecture interlaced by needle-shaped structures changes into a coral-like porous structure with a few spherical particles. The composite layer consists of ZnTiO₃ porous layer and Rutile-TiO₂ intermediate layer containing nanopores, with a total thickness of about 600–700 nm after induction heating at 800 °C. Induction heating improves hydrophilicity, hardness, elastic modulus, and adhesion strength of the films, as well as apatite-formation ability, and reduces Zn²⁺ release rate. Compared to Ti6Al4V substrate, the composite layers exhibit significantly enhanced adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells, as well as antibacterial activity against Staphylococcus aureus and Escherichia coli. These findings and their correlation provide a new perception for the microstructure and phase evolution of Zn-doped micro-nano porous layer induced by induction heating, as well as a promising strategy to enhance osteogenic and antimicrobial properties of Ti-based implants.