A mitochondria-targetable fluorescent probe for detection of bisulfite in living cells

A new colorimetric semi-cyanine fluorescent probe (3) based on benzo[g]indolium was designed and prepared. Probe 3 exhibited a clear OFF-ON fluorescence response at 460 nm toward HSO3- (0-8.0 eq.) within a short response time (3 min). In addition, probe 3 had good selectivity and competitiveness, with excellent sensitivity and a low detection limit (4.4 nM). The detection mechanism relied on nucleophilic HSO3- attacking the C?C double bond in a 1,4-nucleophilic addition reaction. Importantly, the confocal fluorescence results indicated that probe 3 targeted mitochondria and could detect HSO3- in living cells.