Oxygen-carrying nanoplatform to reprogram tumor immunosuppressive microenvironment and enhance photothermal-immunotherapy.

Immunotherapy shows great promise on treating tumors. However, insufficient antigen exposure and immunosuppressive tumor microenvironment (TME) caused by hypoxia impose a serial of constraints on the therapeutic efficacy. In this study, we developed an oxygen-carrying nanoplatform loaded with perfluorooctyl bromide (PFOB, a second-generation of perfluorocarbon-based blood substitute), IR780 (a photosensitizer) and imiquimod (R837, an immune adjuvant) to reprogram immunosuppressive TME and reinforce photothermal-immunotherapy. The obtained oxygen-carrying nanoplatforms (abbreviated as IR-R@LIP/PFOB) show highly efficient oxygen release behavior and excellent hyperthermia performance upon laser irradiation, thus achieving the attenuation of the inherent tumor hypoxia and the exposure of tumor associated antigens , and transforming the immunosuppressive TME to an immunosupportive one. We found that the photothermal therapy of IR-R@LIP/PFOB together with anti-programmed cell death protein-1 (anti-PD-1) would elicit a robust antitumor immunity by increasing the tumor-infiltrating frequencies of cytotoxic CD8 T cells and tumoricidal M1-phenotype macrophages, while reducing immunosuppressive M2-phenotype macrophages and regulatory T cells (Tregs). This study presents these oxygen-carrying IR-R@LIP/PFOB nanoplatforms are potent in removing some negative impacts of immunosuppressive TME caused by hypoxia, and suppressing tumor growth by initiating antitumor immune responses, especially in combination with anti-PD-1 immunotherapy.