Vacancy-enhanced generation of singlet oxygen for photodynamic therapy

Oxygen vacancy (OV) engineering in semiconductors can greatly enhance the separation of photo-induced electron-hole pairs, thereby enhancing the photocatalytic activity. Taking inspiration from this, we prepared a novel BiOBr-H/Rub₂d composite by functionalizing OV-rich BiOBr (named BiOBr-H) with a carboxyl functionalized ruthenium photosensitizer (Ru(bpy)₂C-pyCl₂, abbreviated as Rub₂d), which was then successfully applied for photodynamic therapy (PDT). Density functional theory (DFT) calculations confirmed efficient electron transfer from the Rub₂d complex to the intermediate energy level of BiOBr-H under visible light irradiation. In vitro and in vivo studies demonstrated that BiOBr-H/Rub₂d was a superior agent for photodynamic therapy compared with the free ruthenium complex. The theoretical and experimental data presented thus reveal for the first time that abundant OVs in BiOBr-H can significantly improve the photocatalytic activity of a photosensitizer, resulting in the generation of more reactive oxygen species to enhance PDT. The findings of this study thus offer a new strategy for the development of highly efficient cancer therapies.