A mitochondria-targeted ratiometric fluorescent probe for rapid, sensitive and specific detection of biological SO2 derivatives in living cells.

In this study, we report a ratiometric fluorescent probe (CZBI) for sulfur dioxide (SO2) derivatives based on the conjugate of carbazole and benzo[e]indolium, which displays colorimetric and ratiometric fluorescence dual response to HSO3(-). The probe can quantitatively detect HSO3(-) with high specificity, fast response (within 40s) as well as low detection limit (10nM). A 1,4-nucleophilic addition reaction was proposed for the sensing mechanism of this probe, which was confirmed by (1)H NMR and HR-MS spectra. Fluorescence co-localization studies demonstrated that CZBI was a specific mitochondria-targeted fluorescent probe for SO2 derivatives with excellent cell membrane permeability. Furthermore, fluorescence imaging of HeLa cells indicated that CZBI could be used for monitoring the intrinsically generated intracellular SO2 derivatives in living cells by ratiometric fluorescence imaging. Thus, CZBI has a great potential application for exploring the role played by SO2 derivatives in biology.