A turn-on mitochondria-targeted iridium (Ⅲ) Complex-Based probe for glutathione detection and photodynamic therapy of cancer cells

As one of the most abundant biothiols in cells, glutathione (GSH) usually exists in a dynamic equilibrium of oxidized glutathione (GSSG) and reduces glutathione redox, and plays an essential reducing substance to maintain the REDOX balance of the microenvironment. So, the development of a reliable GSH sensor will be important for living cells and organisms. We fabricated a mitochondria targeted "turn-on" fluorescent sensor based on Ir (III) complex and successfully detected endogenous and exogenous GSH in living cells and zebrafish. For the probe Ir-DINI, a robust electron-withdrawing group 2,4-dinitrobenzoyl was introduced to quench the fluorescence, which could be broken through electrostatic interaction with GSH, following exposing a strong fluorescent Ir (Ⅲ) complex Ir-OH. On the other hand, photodynamic therapy (PDT) has attracted much attention in recent years due to its minimally invasive treatment. We found that singlet oxygen yields of probe Ir-DINI displayed an enhancement before and after the detection of GSH. Additionally, photodynamic studies in living cells illustrated that after reacting with GSH, probe Ir-DINI exhibited more obvious phototoxicity than before the detection of GSH. So the probe Ir-DINI could be served as a GSH sensor and potential GSH-activated photosensitizer for photodynamic therapy.