H2S-responsive CuSe nanoparticles convert into CuSSe in situ with band gap modulation for oxygen self-supply and enhanced colon cancer phototherapy

Colorectal cancer (CRC) remains a significant challenge due to its aggressive nature and propensity for metastasis. This study presents a novel approach to CRC treatment by improved photothermal/photocatalytic/chemodynamic combination therapy in conjunction with modulation of the cancer microenvironment by scavenging endogenous hydrogen sulfide (H₂S), a gasotransmitter overproduced in CRC cells. Copper selenide nanoparticles (CuSe NPs) scavenge H₂S by sulfidation into copper sulfur selenium (CuSSe) NPs, leading to the in situ band gap modulation from 0.81 eV to 1.03 eV and formation of copper vacancies. These vacancies promote photothermal performances, while the change of band gap enables oxygen production via the oxidation of hydrogen peroxide at the valence band and superoxide radicals (O₂^•-) generation at the conduction band. Profound cytotoxic effect attained by the treatment of murine CT26 colon cancer cells with CuSe NPs and NIR-II laser irradiation corroborates the efficacy of the combined therapy alongside H₂S depletion and disturbance of oxidative stress balance. Selective H₂S depletion and formation of CuSSe NPs in H₂S-rich colon cancer microenvironment efficiently promote the efficacy of the multimodality treatment and eradicate colon cancer in subcutaneous tumor-bearing mice. This strategy highlights the potential of in situ self-engineering nanotherapeutics with tumor microenvironmental remodeling for CRC therapy.