Recent strategies for nano-based PTT combined with immunotherapy: from a biomaterial point of view

Cancer has been a great threat to humans for decades. Due to the limitations of monotherapy, combinational therapies such as photothermal therapy (PTT) and immunotherapy have gained increasing attention with expectation to overcome the shortfalls of each other and obtain satisfactory therapeutic outcomes. PTT can inhibit primary tumors by thermal ablation but usually fails to achieve complete eradication and cannot prevent metastasis and recurrence. Meanwhile, the efficacy of immunotherapy is usually attenuated by the weak immunogenicity of tumor and the immunosuppressive tumor microenvironment (ITM). Therefore, many recent studies have attempted to synergize PTT with immunotherapy in order to enhance the therapeutic efficacy. In this review, we aim to summarize the cutting-edge strategies in combining nano-based PTT with immunotherapy for cancer treatment. Herein, the combination strategies were mainly classified into four categories, including 1) nano-based PTT combined with antigens to induce host immune responses; 2) nano-based PTT in combination with immune adjuvants acting as