Enhanced Generation of Non-Oxygen Dependent Free Radicals by Schottky-type Heterostructures of Au–Bi₂S₃ Nanoparticles via X-ray-Induced Catalytic Reaction for Radiosensitization

Despite the development of nanomaterials with high-Z elements for radiosensitizers, most of them suffer from their oxygen-dependent behavior in hypoxic tumor, nonideal selectivity to tumor, or inevasible damages to normal tissue, greatly limiting their further applications. Herein, we develop a Schottky-type heterostructure of Au-Bi₂S₃ with promising ability of reactive free radicals generation under X-ray irradiation for selectively enhancing radiotherapeutic efficacy by catalyzing intracellular H₂O₂ in tumor. On the one hand, like many other nanomaterials with rich high-Z elements, Au-Bi₂S₃ can deposit higher radiation dose within tumors in the form of high energy electrons. On the other hand, Au-Bi₂S₃ can remarkably improve the utilization of a large number of X-ray-induced low energy electrons during radiotherapy for nonoxygen dependent free radicals generation even in hypoxic condition. This feature of Schottky-type heterostructures Au-Bi₂S₃ attributes to the generated Schottky barrier between metal Au and semiconductor Bi₂S₃, which can trap the X-ray-generated electrons and transfer them to Au, resulting in efficient separation of the electron-hole pairs. Then, because of the matched potential between the conduction band of Bi₂S₃ and overexpressed H₂O₂ within tumor, the Au-Bi₂S₃ HNSCs can decompose the intracellular H₂O₂ into highly toxic •OH for selective radiosensitization in tumor. As a consequence, this kind of nanoparticle provides an idea to develop rational designed Schottky-type heterostructures as efficient radiosensitizers for enhanced radiotherapy of cancer.