Synthetic and Biodegradable Molybdenum(IV) Diselenide Triggers the Cascade Photo‐ and Immunotherapy of Tumor

Abstract In this study, a polyvinylpyrrolidone (PVP)‐decorated MoSe 2 (MoSe 2 ‐PVP) nanoparticle with excellent photothermal transforming ability and chlorin E6 (Ce6) loading capacity is designed for combined tumor photothermal therapy (PTT), tumor photodynamic therapy (PDT), and immunotherapy. The light‐to‐heat conversion efficiency under irradiation with an 808 nm near‐infrared laser is as high as 59.28%. The MoSe 2 ‐PVP NPs could function as an artificial catalase and catalyze the decomposition of H 2 O 2 . Their catalytic activity and thermal durability are higher than the native catalase, which relieve the tumor hypoxia status and sensitize the tumor PDT. The data show that the synthetic MoSe 2 ‐PVP is biodegradable, owing to the oxidation of the Mo 4+ to Mo 6+ . Moreover, its degradation products could increase the proportion of mature dendritic cells and CD8 + thymus (T) cells and promote the infiltration of active CD8 + T cells in tumors. The immune checkpoint inhibitor, programmed cell death protein 1 monoclonal antibody is combined with MoSe 2 ‐PVP and it is found that its degradation product could efficiently change the immune microenvironment of the tumor.