Self-exploding tumor microenvironment-responsive nanomedicine as "ROS Bomb" ignites STING pathway for triple-negative breast cancer immunotherapy.

Conventional reactive oxygen species (ROS)-mediated tumor therapies such as photo-, sono-, and chemodynamic therapies are often limited by inadequate penetration depth of external stimuli and insufficient endogenous ROS substrates (e.g., O₂ and H₂O₂). Here, we report that horseradish peroxidase (HRP) can catalyze artemisinin to generate ROS. Based on this, a "ROS bomb" nanomedicine was designed for antitumor immunotherapy. The nanocarrier consists of silica cross-linked micelles incorporating ROS-cleavable thioketal bonds and encapsulated artemisinin as the payload, with surface-immobilized HRP serving as the trigger. Within the tumor microenvironment with elevated H₂O₂, the thioketal linkers are cleaved to release artemisinin, initiating an HRP-catalyzed ROS cascade. The ROS burst induces immunogenic cell death and activates the STING pathway in dendritic cells assisted by the co-released drug SN38, effectively suppressing the growth of immunosuppressive triple-negative breast tumors. This exogenous ROS delivery strategy overcomes the restrictions of conventional ROS therapies, offering a potent approach for treating deep-seated tumors.