Recyclable Endogenous H2 S Activation of Self-Assembled Nanoprobe with Controllable Biodegradation for Synergistically Enhanced Colon Cancer-Specific Therapy.

Excessive production of hydrogen sulfide (H2 S) plays a crucial role in the progress of colon cancer. Construction of tumor-specific H2 S-activated smart nanoplatform with controllable biodegradation is of great significance for precise and sustainable treatment of colon cancer. Herein, an endogenous H2 S triggered Co-doped polyoxometalate (POM-Co) cluster with self-adjustable size, controlled biodegradation, and sustainable cyclic depletion of H2 S/glutathione (GSH) is designed for synergistic enhanced tumor-specific photothermal and chemodynamic therapy. The designed POM-Co nanocluster holds H2 S responsive "turn-on" photothermal property in colon cancer via self-assembling to form large-sized POM-CoS, enhancing the accumulation at tumor sites. Furthermore, the formed POM-CoS can gradually biodegrade, resulting in release of Co2+ and Mo6+ for Co(II)-catalyzed •OH production and Russell mechanism-enabled 1 O2 generation with GSH consumption, respectively. More importantly, the degraded POM-CoS is reactivated by endogenous H2 S for recyclable and sustainable consumption of H2 S and GSH, resulting in tumor-specific photothermal/chemodynamic continuous therapy. Therefore, this study provides an opportunity of designing tumor microenvironment-driven nanoprobes with controllable biodegradation for precise and sustainable anti-tumor therapy.