Gallium loading into a polydopamine-functionalised SrTiO3 nanotube with Combined osteoinductive and antimicrobial activities

Ti-based implant materials still face implant-related infections and poor osseointegration as two major clinical challenges; thus, high-quality implantation demands a strategy that can provide Ti-based implants with longterm antibacterial ability and high osteogenic activity. In this study, gallium was successfully loaded into polydopamine-functionalised SrTiO3 nanotubes (PDA-SrTiO3 NTs) on a titanium substrate through a facile immersion method. The release of strontium and gallium from gallium-doped SrTiO3 NTs was controllably constant and had negligible cytotoxicity. The antibacterial efficacy of the NT coating was demonstrated by the inhibition zones of Escherichia coli and Staphylococcus aureus. The optimum contents of gallium and strontium in the coating led to enhanced cytocompatibility, osteoblast spreading and osseointegration because of the synergistic effects of strontium as a bioactive element and the porous topography of the coating surface. As observed in vivo, bone formation in rabbit-bone-defect models was improved by the proposed coating four weeks after it was implanted. According to literature, the present results show for the first time that the gallium doping of PDA-SrTiO3 NTs can effectively stimulate osteointegration-thanks to its efficacy in enhancing implant osteoinductivity-and can prevent infections. Therefore, gallium-doped PDA-SrTiO3 NT coatings can potentially function as promising bone implants for clinical applications.