Carbon monoxide-based immunogenic cell death amplifier remodels the hypoxic microenvironment for tumor sono-immunotherapy

Ultrasound-activated tumor catalytic therapy has great potential in clinical cancer treatment. However, the hypoxic and immunosuppressive tumor microenvironment impairs the efficacy of solid tumor treatment, leading to a high recurrence rate of metastatic cancer. Thus, reversing the tumor microenvironment remains a formidable challenge. To circumvent these critical issues, we employ ultrasound-activable carbon monoxide (CO) gas therapy and reactive oxygen species (ROS) production to trigger immunogenic cell death (ICD) and alleviate tumor hypoxia, achieving a combination of tumor therapy and reversal of immunosuppression to overcome the limitations of monotherapy and control tumor metastasis and recurrence. In brief, we first use copper sulfide (CuS) nanosheet as a highly efficient ultrasound-controllable catalytic nanomaterial, which can catalyze carbon dioxide, water, and oxygen to produce CO, oxygen, and ROS. Moreover, as a Fenton-like catalyst, it can catalyze hydrogen peroxide at tumor sites to generate ROS. The generated CO can attack mitochondria to accelerate their metabolism and produce more ROS, thus inducing ICD. In addition, the generation of oxygen can not only serve as the source of ROS, but it can also relieve tumor hypoxia and normalize the tumor immunosuppressive microenvironment. This results in the maturation of dendritic cells and the enhancement of T-lymphocyte recruitment and infiltration, further stimulating the antitumor immune response, mediating the regression of primary and distal tumors, and inhibiting lung metastasis. This in situ sono-activable catalytic therapy strategy minimizes the toxicity of CO and ROS leakage and provides a novel approach for designing new ICD inducers and improving therapeutic effects.