Pyro-piezoelectric effect of BaTiO₃ bio-nanocarrier for osteomyelitis therapy

Implant-related osteomyelitis harms patients' health and lives. Non-invasive treatments triggered by external physical stimuli have been brought into focus in antibiosis. Herein, a therapeutic strategy through coupling piezoelectricity and pyroelectricity of BaTiO3 nanotubes (BNT) by synchronous treatments of ultrasound (US) and near-infrared light (NIR) is applied to kill bacteria in an osteomyelitis model. NIR or US treatment reduces spontaneous polarization of BNT, inducing pyroelectric/piezoelectric field and energy band tilting. Compared with single treatment, their synergistic effect further enhances charge transfer and electron-hole pair separation, improving the pyro-piezoelectric catalysis and thus the yield of reactive oxygen species (ROS); meanwhile, the tilting of energy bands induces an irreversible conductive circuit from bacteria to BNT, resulting in membrane electron loss and the disrupted bacterial metabolic balance. As a result, 99.8% of bacteria are killed under the pyro-piezoelectric therapy of BNT. Additionally, BNT with nanotubular structure acts as nanocarriers to load and release bone morphogenetic protein-2 (BMP-2), improving bone regeneration obviously after antibacterial therapy. This study provides a promising pyro-piezoelectric therapy by BMP-2 loaded BaTiO3 nanotubes for antibiosis and bone regeneration in treating osteomyelitis. It also brings new insight for developing pyropiezoelectric sensors to deal with tissue infection.