Bacteria-targeted delivery of black phosphorus quantum dots facilitates photothermal therapy against hypoxic tumors and complementary low-dose radiotherapy.

Many approaches have been employed to relieve hypoxia in solid tumors to enhance sensitivity to radiotherapy (RT), including O 2 delivery or hydrogen peroxide (H 2 O 2 ) decomposition strategies. To date, however, these modalities have been restricted by poor O 2 loading, rapid O 2 leakage, and limited endogenous H 2 O 2 levels. To overcome these limitations, we therefore sought to develop an effective approach for the oxygen-independent treatment of hypoxic tumors. In this study, we designed a novel black phosphorus quantum dot (BPQD)/ Escherichia coli ( E. coli ) hybrid system (BE) capable of facilitating the photothermal therapy (PTT) of hypoxic tumors. A simple electrostatic adsorption approach was used to conjugate BPQDs to E. coli . BE is capable of reliably targeting hypoxic tumors and mediating PTT. BPQDs in BE can directly facilitate X-ray-mediated radiosensitization of tumors, thereby achieving significant RT efficacy in response to lower doses of radiation, effectively and specifically damaging hypoxic tumor tissues to suppress the growth of tumors. Our results highlight this BE system as a novel approach to tumor radiosensitization with great potential for clinical application.