Single-atom Zr doped heterojunction enhanced piezocatalysis for implant infection therapy through synergistic metal immunotherapy with sonodynamic and physical puncture

Recent common clinical treatments for implant bacterial infections involve replacing inert implants and using antibiotics. However, these methods remain limited in their effectiveness for pathogen clearance, immune regulation, and osteogenesis. In this study, we developed a Zr-doped heterointerface of SrTiO₃ and Hap (SrTiZrO₃/Hap) heterojunction coating with single-atom Zr doping and heterogeneous interfaces designed for ultrasound-responsive antimicrobial activity and bone formation. Under ultrasound, the mechanical force exerted by SrTiZrO₃/Hap enhances its physical puncture and sonodynamic activity, synergizing with the metalloimmunotherapy effect of Zr⁴⁺ for efficient antimicrobial activity. The primary mechanism enhancing sonodynamic activity involves local interfacial polarization from single-atom Zr doping, achieving piezoelectric catalysis in conjunction with electronic polarization from the built-in electric field. SrTiZrO₃/Hap achieved a 99.3% antibacterial rate against S. aureus and 99.7% against E. coli under ultrasound. Additionally, SrTiZrO₃/Hap promoted osteogenic differentiation after ultrasound irradiation by activating the PI3K/Akt pathway via its piezoelectric, needle-like topological surface and the release of functional ions, thus accelerating bone repair.