Mitochondria-targeted cyclometalated iridium (III) complex for H2S-responsive intracellular redox regulation as potent photo-oxidation anticancer agent.

Owing to the safety and low toxicity, photodynamic therapy (PDT) for cancer treatment has received extensive attention. However, the excess H2S in cancer cells reduces the PDT efficiency, because H2S indirectly depletes the reactive oxygen species (ROS). To improve anticancer efficiency, a mitochondria-targeted iridium(III) complex Ir-MMB has been developed as H2S consumer and photo-oxidation anticancer agent. On the one hand, complex Ir-MMB can consume H2S with sensitive phosphorescence turn-on, which has been successfully applied to exogenous and endogenous H2S response imaging in living cells. On the other hand, Ir-MMB can enhance its anticancer activity and cause photo-oxidation damage via catalyzing the oxidation of reduced form of nicotinamide-adenine dinucleotide (NADH) to NAD+ and producing H2O2 under light, and ultimately results in cell apoptosis through mitochondrial depolarization and ROS production.