Nanomedical Sonocatalyst Tailored for Enhanced Hypoxic Tumor Therapy Based on Crystal Facet Engineering Strategy

Strategically exposing active crystal facets significantly enhances the catalytic performance of the catalyst. Here, we design ultrathin BiOCl nanosheets (NSs) with nearly completely exposed active (001) crystal facets and investigate the facet-dependent catalytic activity and the underlying mechanism. With the exposure extent of active facets increased, the defect type changed from the single atom Bi vacancy defect to the adjacent Bi–O–Bi triatom association vacancy. These vacancy associates provide active sites for the adsorption and activation of the catalytic substrate on the surface, which promotes the catalytic reaction. Meanwhile, the adjustment of surface electronic structure and band structure is conducive to the decrease of the charge transfer barrier and the enhancement of carrier separation ability. In a mouse breast cancer model, ultrasound-mediated BiOCl NSs facilitated a trimodal synergistic treatment regimen comprising carbon monoxide gas therapy, sonodynamic therapy, and starvation therapy to effectively inhibit hypoxic tumor growth and proliferation.