Multifunctional nanomedicines for synergistic photodynamic immunotherapy based on tumor immune microenvironment

Cancer immunotherapy, which harnesses the host immune system to identify, attack, and remove tumor cells, has emerged as one of the most promising cancer therapies. Nevertheless, the further applications of clinic-approved immunotherapies have been hindered due to their low response rates and adverse reactions. Recently, photodynamic therapy (PDT)-based photonanomedicines (PNMs) have gained much attention as they have been reported to participate in immunotherapy by triggering the death of immunogenic tumor cells. This contributes to the initiation of the immune response and the infiltration of toxic T lymphocytes, thereby eliminating metastatic tumor cells. When combined with conventional immunotherapy, such immunostimulatory properties of PNMs offer opportunities to enhance anti-cancer immunity. This review elaborates on the latest strategies for PNMs to enhance the anti-cancer efficiency of immunotherapy, with emphasis on PNM-synergized immunotherapy, PNM-based nano-drug delivery systems in synergistic immunotherapy and PNM-based improved infiltration of toxic T lymphocytes in synergistic immunotherapy. Moreover, the current challenges and prospective developments for PNM-synergized immunotherapy to realize the transition from bench to bedside are also discussed.