Au-Modified SrTiO3 Nanoarray Featuring Enhanced Ultrasound-Responsive Mott–Schottky Heterojunction Speeds Bone Regeneration Through Sonodynamic Antibacterial and Inflammatory Management

Eradicating the bacteria on the surface of titanium-based (Ti) implants and optimizing the local immune environment is urgently needed to minimize the clinical implantation failures. Here, an ultrasound (US)-responsive Ti implant aiming at killing bacteria is prepared by building strontium titanate (SrTiO 3 ) nanoarrays on Ti substrate through a multi-step hydrothermal method and the subsequent decoration of Au nanoparticles (Au NPs). As an n-type semiconductor, SrTiO 3 can combine with Au NPs to form a Mott–Schottky heterostructure. The results reveal that the built-in electric field of the M–S heterojunction composed of Au NPs and SrTiO 3 significantly promotes the separation of electrons and holes while reducing the bandgap. Under US irradiation, Au@SrTiO 3 generates a large amount of reactive oxygen species (ROS) to kill bacteria, meanwhile eliminating bacterial biofilms that adhere to the implant surface. Besides, Au NPs accelerate bone remodeling by modulating macrophage polarization toward inflammation-suppressive orientation. Also, SrTiO 3 and Au NPs synergistically directed the osteogenic differentiation. The implantation in vivo shows that continuously optimizing the osteogenic microenvironment can obviously accelerate the osseointegration of Ti implant. Transcriptomic analysis reveals the in vivo pro-osteointegration mechanism of heterostructured Au@SrTiO 3 nanoarrays on Ti implant.