▎ 摘　　要

Radiation therapy is a kind of tumor treatment that has been widely employed in clinics, but its therapeutic effect is largely hampered by various factors. Currently, considerable efforts are being made in the search for effective and safe radiosensitizers. A nano-radiosensitizer is an ideal choice for improving the effects of tumor radiotherapy due to its high degree of tumor tissue uptake and secondary electrons' productivity. Herein, highly oxidized graphene quantum dots (GQDs) with a good oxidative stress response and significantly high phototoxicity were prepared and purified via the photo-Fenton reaction of graphene oxide. The enhanced radiosensitization effects were systematically evaluated by monitoring colorectal carcinoma cell cycle and the degree of apoptosis, and the possible mechanism of the GQD irradiating enhancement of cell apoptosis was preliminarily investigated. Our data showed that the GQD synergy with ionizing radiation (IR) could noticeably enhance the G2/M stage arrest of cells, inhibit cell proliferation, and improve apoptosis. This is mainly due to the overproduction of reactive oxygen species by GQDs in combination with the IR, which activates the apoptosis-related regulation proteins and results in tumor cell apoptosis. This study suggests that the GQDs can act as a new nano-radiosensitizer in tumor radiotherapy.