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

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.