Interstitial Nitrogen Doping in Barium Titanate Amplifies Ultrasound‐Triggered Piezocatalysis for Eradicating Biofilms and Boosting Osseointegration

ABSTRACT Titanium‐based bone implants face significant clinical challenges, including drug‐resistant bacterial infections, biofilm formation, and insufficient bone integration. To overcome these limitations, a hydroxyapatite/nitrogen‐doped barium titanate composite coating (Ti‐HA/N‐BTO) was developed. Interstitial nitrogen doping enhances the piezoelectric performance and ultrasonic catalytic activity of BTO by inducing its lattice distortion and reducing its band gap. Band bending caused by ultrasound and the reduced band gap promote the efficient production of reactive oxygen species (ROS). After 15 min of ultrasonic treatment at 1.5 W cm −2 , Ti‐HA/N‐BTO showed significant inhibitory rates against both Staphylococcus aureus ( S. aureus ) and methicillin‐resistant Staphylococcus aureus (MRSA), and effectively removed mature biofilms. Antibacterial mechanisms include ROS‐mediated bacterial membrane disruption and bacterial electron transfer induced by the piezoelectric effect, which interferes with bacterial respiratory chain function and energy metabolism, resulting in comprehensive damage to bacterial structure and metabolic activity. Moreover, the hydroxyapatite and microcurrents produced by the coating have high osteogenic activity, promoting the osteogenic differentiation of MC3T3‐E1 cells. The coating showed potent antibacterial activity and bone‐promoting abilities in SD rat models of infected femoral defects. This study provides a novel strategy for designing multifunctional implants by leveraging doping engineering in piezoelectric materials to simultaneously address infection control and bone integration.