Black Phosphorus-Synergic Nitric Oxide Nanogasholder Spatiotemporally Regulates Tumor Microenvironments for Self-Amplifying Immunotherapy.

The lack of tumor immunogenicity coupled with the presence of tumor immunosuppression severely hinders antitumor immunity, especially in the treatment of "immune cold" tumors. Here, we have developed a drug-free and NIR-enabled nitric oxide (NO)-releasing nanogasholder (NO PS @BP) composed of an outer cloak of nitrate-containing polymeric NO donor and an inner core of black phosphorus (BP) as the energy converter to spatiotemporally regulate NO-mediated tumor microenvironment remodeling and achieve multimodal therapy. Following NIR-irradiation, BP-induced photothermia and its intrinsic reducing property accelerate NO release from the outer cloak, by which the instantaneous NO burst concomitant with mild photothermia, on the one hand, induces immunogenic cell death (ICD), thereby provoking antitumor responses such as the maturation of dendritic cells (DCs) and the infiltration of cytotoxic T lymphocytes (CTLs); on the other hand, it reverses tumor immunosuppression via Treg inhibition, M2 macrophage restraint, and PD-L1 downregulation, further strengthening antitumor immunity. Therefore, this drug-free NO PS @BP by means of multimodal therapy (NO gas therapy, immune therapy, photothermal therapy) realizes extremely significant curative effects against primary and distant tumors and even metastasis in B16F10 tumor models, providing a new modality to conquer immune cold tumors by NO-potentiated ICD and immunosuppression reversal.