Bi₂WO₆ Semiconductor Nanoplates for Tumor Radiosensitization through High- Z Effects and Radiocatalysis

The radioresistance of tumor cells is considered to be an Achilles' heel of cancer radiotherapy. Thus, an effective and biosafe radiosensitizer is highly desired but hitherto remains a big challenge. With the rapid progress of nanomedicine, multifunctional inorganic nanoradiosensitizers offer a new route to overcome the radioresistance and enhance the efficacy of radiotherapy. Herein, poly(vinylpyrrolidone) (PVP)-modified Bi₂WO₆ nanoplates with good biocompatibility were synthesized through a simple hydrothermal process and applied as a radiosensitizer for the enhancement of radiotherapy for the first time. On the one hand, the high- Z elements Bi ( Z = 83) and W ( Z = 74) endow PVP-Bi₂WO₆ with better X-ray energy deposition performance and thus enhance radiation-induced DNA damages. On the other hand, Bi₂WO₆ semiconductors exhibit significant photocurrent and photocatalytic-like radiocatalytic activity under X-ray irradiation, giving rise to the effective separation of electron/hole (e^-/h⁺) pairs and subsequently promoting the generation of cytotoxic reactive oxygen species, especially hydroxyl radicals (^•OH). The γ-H2AX and clonogenic assays demonstrated that PVP-Bi₂WO₆ could efficiently increase cellular DNA damages and colony formations under X-ray irradiation. These versatile features endowed PVP-Bi₂WO₆ nanoplates with enhanced radiotherapy efficacy in animal models. In addition, Bi₂WO₆ nanoplates can also serve as good X-ray computed tomography imaging contrast agents. Our findings provide an alternative nanotechnology strategy for tumor radiosensitization through simultaneous radiation energy deposition and radiocatalysis.