Carbon dot sensitized hollow Co ₉ S _{8− <i>x</i>} for enhanced sonodynamic cancer therapy

Sonodynamic therapy activates sonosensitizers through US to generate a large amount of reactive oxygen species (ROS), which causes apoptosis of tumor cells and achieves a therapeutic effect against tumors. However, the excessively wide bandgap of inorganic sonosensitizers and the easy recombination of electron-hole pairs limit the yield of ROS of sonosensitizers. Herein, for the first time, we report carbon dot (CD)-sensitized hollow Co₉S_8-<i>x</i> as a novel inorganic sonosensitizer for enhanced sonodynamic tumor therapy. The presence of sulfur vacancies endows Co₉S₈ with excellent sonodynamic and chemodynamic activities. Furthermore, CDs with good sonodynamic activity are utilized to form CD@Co₉S_8-<i>x</i> heterojunctions with hollow Co₉S_8-<i>x</i>, realizing the cascaded amplification of the ROS yield. The significantly increased ROS level induces a powerful effect of cell apoptosis, thus completely eradicating tumors. Overall, this work delivers useful insights for utilizing vacancy engineering and heterojunction engineering to achieve enhanced sonodynamic tumor therapy.