Biocompatible 7-nitro-2,1,3-benzoxadiazole-embedded naphthalimide for exploring endogenous H2S in living cells.

Hydrogen sulfide (H2S) is a central signaling and antioxidant biomolecule involved in various biological processes. As inappropriate levels of H2S in the human body are closely related to various diseases, including cancer, a tool capable of detecting H2S with high selectivity and sensitivity in living systems is urgently required. In this work, we intended to develop a biocompatible and activatable fluorescent molecular probe for detecting H2S generation in living cells. The 7-nitro-2,1,3-benzoxadiazole-imbedded naphthalimide (1) probe presented here responds specifically to H2S and produces readily detectable fluorescence at 530 nm. Interestingly, probe 1 exhibited significant fluorescence responses to changes in endogenous H2S levels as well as high biocompatibility and permeability in living HeLa cells. This allowed for the real-time monitoring of endogenous H2S generation as an antioxidant defense response in the oxidatively stressed cells.