Mitochondria-targeted fluorescent probe for imaging endogenous hydrogen sulfide in cellular antioxidant stress

Hydrogen sulfide (H₂S) is believed to play an important role in maintaining cellular redox homeostasis and avoiding oxidative damage caused by abnormally raised ROS levels. Highly selective and sensitive fluorescent probes for the detection and imaging of endogenous H₂S in living cells over other biological thiols are desirable. Herein, we developed a mitochondria-targeted fluorescent probe L, a thioxanthene-benzo[e]indolium derivative, for the discrimination of H₂S from other chemically similar biothiols. Based on the nucleophilic addition of H₂S and the charged electron-deficient C[double bond, length as m-dash]N double bond within the benzo[e]indolium moiety, the generation of L-HS with a shortened π-conjugated system led to significant spectral changes in the visible region. Importantly, the probe L with mitochondria-targeting ability has been successfully used for imaging the endogenous H₂S biosynthesized from Cys and GSH and in cellular antioxidant stress.