Two-Step Sensing, Colorimetric and Ratiometric Fluorescent Probe for Rapid Detection of Bisulfite in Aqueous Solutions and in Living Cells

Bisulfite and sulfite (HSO₃ ^-/SO₃ ^2-) are not only widely used toxic chemicals but also active anions with important biological functions. Hence, the development of new detection methods for HSO₃ ^-/SO₃ ^2- is important for environmental security and human health. In this paper, we report a symmetrical hemicyanine for the detection of HSO₃ ^-/SO₃ ^2-, SHC, which is constructed with p-diphthalaldehyde with trimethylbenzoindolium via condensation. The red fluorescent probe can fast respond to HSO₃ ^-/SO₃ ^2- (<30 s) to give cyan fluorescence, and its sensing process is twice nucleophilic additions, which were observed from fluorescence response, initial ratiometric change, and subsequent turn-on increment; especially in a low-concentration level, the ratiometric fluorescence measurement can eliminate environmental interference. This probe can achieve a quantitative detection of HSO₃ ^-/SO₃ ^2- in a wide concentration range. Furthermore, the probe SHC is a mitochondria-specific probe for ratiometric fluorescent detection of HSO₃ ^-/SO₃ ^2- in living cells.