"Reactive" probe for hydrogen sulfite: "turn-on" fluorescent sensing and bioimaging application

Taking advantage of the special nucleophilic addition reaction with aldehyde, a "switching-on" fluorescent probe (C1) for hydrogen sulfite was synthesized using intramolecular charge transfer (ICT) as a signal mechanism. Upon the addition of HSO₃ ^- ions, the probe displayed apparent fluorescence changes from non-emission to strong green fluorescence. C1 gave response to hydrogen sulfite with high sensitivity and the detection limit was determined to be as low as 3.0 μM. In addition to its high selectivity for hydrogen sulfite rather than other common anions, C1 was successfully applied to the detection of hydrogen sulfite in HeLa cells with turn-on fluorescent methods.