Pre- and post-irradiation mild hyperthermia enabled by NIR-II for sensitizing radiotherapy

The clinical application of cancer radiotherapy is critically impeded by hypoxia-induced radioresistance, insufficient DNA damage, and multiple DNA repair mechanisms. Herein we demonstrate a dual-hyperthermia strategy to potentiate radiotherapy by relieving tumor hypoxia and preventing irradiation-induced DNA damage repair. The tumor hyperthermia temperature was well-controlled by a near infrared laser with minimal side effects using PEGylated nanobipyramids (PNBys) as the photo-transducer. PNBys have narrow longitudinal localized surface plasmon resonance peak in NIR-II window with a high extinction coefficient (2.0 × 1011 M-1 cm-1) and an excellent photothermal conversion efficiency (44.2%). PNBys-induced mild hyperthermia (MHt) prior to radiotherapy enables vessel dilation, blood perfusion, and hypoxia relief, resulting in an increased susceptibility of tumor cells response to radiotherapy. On the other hand, MHt after radiotherapy inhibits the repair of DNA damage generated by irradiation. The PNBys exert hierarchically superior antitumor effects by the combination of MHt pre- and post-radiotherapy in murine mammary tumor EMT-6 model. Consequently, different from the simple combination of RT and MHt, the coupling of pre- and post-MHt with RT by PNBys open intriguing avenues towards new promising antitumor efficacy.