Piezopotential and vacancies co-enhanced sonodynamic response of a ZnO-TiO2- heterojunction array for osteointegration in MRSA-infected osteomyelitis

Preventing multidrug-resistant bacteria-related osteomyelitis and simultaneously improving osseointegration are in great demand for orthopedic implants. Herein, an ultrasound (US)-responsive array of nanorod-like core–shell heterojunctions is developed on Ti substrate, in which oxygen vacancies (OVs) and residual compressive stresses are respectively introduced into TiO2 shells and ZnO cores via annealing in argon and ice cooling. The OVs narrow TiO2 band gap to enhance the formation of US-excited electron-hole pairs, while the ZnO-generated piezoelectric field by the residual compressive stress efficiently separates these electron-hole pairs. The combination of these two effects in the array leads to much more generation of reactive oxygen species than either under US irradiation, in which the piezoelectric field-derived separation of electron-hole pairs plays a crucial role. Consequently, the array exhibits high bacteria-killing and biofilm-eradicating efficacy of methicillin-resistant Staphylococcus aureus (MRSA), possessing strong osseointegration in MRSA-infected osteomyelitis of rat.