Precise Regulation of Reactive Oxygen Species in Tumor Microenvironment for Alleviating Inhibitory Immunogenic Cell Death.

High level of reactive oxygen species (ROS) within the tumor microenvironment (TME) not only damage tumor cells but also diminish the efficacy of immunogenic cell death (ICD) and the activity of tumor-infiltrating T lymphocytes, thereby limiting the effectiveness of immunotherapy. Therefore, precise modulation of ROS level is crucial to effectively eliminate tumor cells and activate ICD-induced immunotherapy. Here, an intelligent yolk shell nanoplatform (SPCCM) that features calcium carbonate shells capable of decomposing under acidic TME conditions, thereby releasing the natural antioxidant proanthocyanidins (PAs) and the photosensitizer Ce6 is designed. PAs scavenge ROS within tumors, extending the survival time of T lymphocytes, while Ce6, as an ICD inducer, generates high ROS concentrations upon laser irradiation, thus reaching the toxic threshold within tumor cells and inducing apoptosis. The resulting apoptotic cells serve as tumor-associated antigens, promoting dendritic cells (DCs) maturation, and activating ICD. By effectively neutralizing ROS in the TME, PAs sustainably reduce ROS level, thereby enhancing DCs activation and restoring antitumor immune cell activity suppressed by ROS (resulting in an eightfold increase in DCs activation). This study demonstrates effective synergistic effects between photodynamic therapy and immunotherapy by precisely modulating ROS level.