Hydrogen sulfide (H2S) is an important gasotransmitter. Although a large number of fluorescent probes for cellular H2S have been reported, only a few can detect H2S in mitochondria, a cellular organelle connecting H2S with mitochondrial function and metabolic pathways. We hereby describe a novel near-infrared fluorescent probe, nimazide, by introducing sulfonyl azide to the core structure of a QSY-21 dark quencher. Nimazide responded quickly to H2S, resulting in robust fluorescence turn-off changes. This conversion displayed high specificity and fast kinetics. More impressively, we observed a robust fluorescence decrease in live cells loaded with mitochondrial nimazide in response to extracellular addition of nanomolar H2S, and successfully imaged biologically generated mitochondrial H2S in live mammalian cells. Nimazide is one of the most sensitive fluorescent probes for mitochondrial H2S.
Keywords: fluorescence imaging; membrane activation; mitochondrial targeting; nanomolar hydrogen sulfide; near-infrared fluorescent sensor.