Thienothiophene-Benzopyran Derivative and AQ4N-Assembled Liposomes for Near-Infrared II Fluorescence Imaging-Guided Phototherapy, Chemotherapy, and Immune Activation

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has attracted wide attention in tumor treatment. However, the hypoxic tumor microenvironment and the heat shock proteins produced by tumor cells significantly reduce their efficacy. Developing effective phototherapy agents that have high reactive oxygen species generation efficiency and photothermal conversion efficiency (PCE) while simultaneously utilizing the hypoxic tumor microenvironment is of great importance. Here, a thienothiophene-benzopyran derivative, BTPIC4F-C10 is designed and synthesized, with near-infrared (NIR) absorption and fluorescence. Then the lipid nanoparticles (LipBFCA NPs) which encapsulated BTPIC4F-C10 in a phospholipid bilayer together with hypoxia-activated prodrug banoxanthrone (AQ4N) are constructed for NIR-II fluorescence imaging-guided synergistic PDT/PTT/chemotherapy and immune activation. Under 808 nm laser irradiation, LipBFCA NPs is a high singlet oxygen quantum yield of 20.2% and PCE of 78.8%. With ultra-high photon energy utilization efficiency of 99%, LipBFCA NPs is an excellent phototherapy effect. The hypoxic environment caused by phototherapy can further activate AQ4N to transform into chemically toxic AQ4 radicals to kill tumor cells. Moreover, phototherapy can induce immunogenic cell death, release tumor-associated antigens, and activate immune responses. This work provides a new way for the clinical application of fluorescence imaging in guiding tumor diagnosis and treatment.