Tumor Microenvironment‐Specific Driven Nanoagents for Synergistic Mitochondria Damage‐Related Immunogenic Cell Death and Alleviated Immunosuppression

Abstract Despite significant breakthroughs in immunotherapy, the limitations of inadequate immune stimulation and stubborn immune resistance continue to present opportunities and challenges. Therefore, a two‐pronged approach, encompassing the activation of immunogenic cell death (ICD) and blocking the indoleamine 2,3‐dioxygenase (IDO)‐mediated pathway, is devised to elicit systemic anti‐tumor immunity and alleviate immunosuppression. Herein, a tumor microenvironment (TME)‐specific driven nanoagent is composed of a tetrasulfide bond‐bridged mesoporous silica layer (MON) coated up‐conversion nanoparticles as a nano‐carrier, combines Fe 2+ , curcumin, and indoximod for operating chemodynamic therapy/chemotherapy/immunotherapy. The consumption of glutathione (GSH) caused by MON degradation, the Fenton reaction of Fe 2+ , and curcumin triggering mitochondrial damage collectively exacerbate the oxidative stress, leading to a violent immunoreaction and reversal of the immunosuppressive TME through a combination of IDO‐inhibitors. Meanwhile, upconversion luminescence (UCL) imaging serves as a significant guiding tool for drug delivery and the treatment of nanoagents. In vivo and in vitro experiment results demonstrate that the nanosystem not only effectively inhibits the growth of primary tumors but also induces immune priming and memory effects to reject re‐challenged tumors. The strategy as a complementary approach displays great potential for future immunotherapy along with other multimodal treatment modes.