A photoswitchable phase-reversible gel engine for systemic redox homeostasis remodeling and on-demand chemodynamic immunotherapy with sustainable immunostimulation

Chemodynamic therapy (CDT) efficacy in the tumor microenvironment (TME) remains compromised. Inspired by the potential of fever-like heat to activate a redox-favorable microenvironment, mild photothermal therapy (mPTT) is expected to sensitize tumors to CDT, turning “redox-cold” tumors into “redox-hot” ones. Herein, an injectable gel engine (LMFT@SG-R) is meticulously constructed based on the co-encapsulation of R848 and β-lapachone (LAP)-loaded metal–organic framework-199 (MOF-199) within a lipidic gel reservoir with the unique ability of thermally reversible sol–gel phase transformation. With mPTT reprogramming TME, the custom-designed LMFT@SG-R can realize systemic redox homeostasis remodeling through mPTT-activated chemodynamic immunotherapy (MPCIT). Once reaching the TME, LMFT@SG-R quickly hydrates into solid gel and subsequently undergoes gel-to-sol transformation under mild NIR laser irradiation, resulting in on-demand release of LMFT and R848 for controllable CDT and immunostimulation. LMFT undergoes stepwise degradation for sequential release of Fe³⁺, Cu²⁺ and LAP, which can promote ROS cascade amplification owing to the upregulation of HSP70/NQO1 axis upon mild hyperthermia, resulting in robust ICD effects and T lymphocytes infiltrations together with R848. Notably, the controllable immunostimulation can facilitate robust abscopal effects and prominent suppression of distal tumors. The well-designed LMFT@SG-R may represent an updated CDT catalyst with the highly-integrated gel engine for chained-cooperative MPCIT.