In situ forming hydrogel incorporating celastrol-loaded copper-doped Prussian blue nanoparticles for oxidative stress amplified multimodal breast cancer therapy.

Breast cancer therapy is often hindered by limited tumor-specific accumulation of therapeutic agents, strong antioxidant defenses within the tumor microenvironment (TME), and the limitations of single-modal therapeutic strategies, which collectively reduce efficacy and increase systemic toxicity. In this study, we developed an injectable, thermosensitive hydrogel (CuPB@Cel-CG), composed of a chitosan (CS)/β-glycerophosphate disodium salt (β-GP) matrix incorporating celastrol-loaded, copper-doped Prussian blue nanoparticles (CuPB). After intratumoral injection, the hydrogel forms in situ, enabling sustained local retention and controlled drug release. Under near-infrared (NIR) irradiation, the system produces a mild photothermal therapy (PTT) that promotes Cu2+-mediated glutathione (GSH) depletion and triggers chemodynamic therapy (CDT), while the released celastrol disrupts tumor antioxidant defenses, amplifying oxidative stress and enhancing tumor cell apoptosis. In 4T1 tumor-bearing mice, CuPB@Cel-CG combined with NIR irradiation significantly inhibited tumor growth (∼84.9% inhibition) and caused extensive tumor necrosis without noticeable damage to major organs, demonstrating good biosafety. Overall, this work presents an innovative injectable hydrogel that integrates celastrol-loaded CuPB nanoparticles to realize localized tumor therapy through combined photothermal-chemodynamic effects and celastrol-induced oxidative stress amplification, providing a safe and effective strategy for multimodal breast cancer treatment.