A quinoline-based probe for the ratiometric fluorescent detection of sulfite in lysosomes of living cells

A lysosome-targeting ratiometric fluorescent probe was synthesized for detecting sulfite based on sulfite-triggered nucleophilic addition reaction. Due to the specific reaction, the fluorescence intensity ratio (I530/I390) of the probe in an almost aqueous solution (0.5% DMSO) changed significantly after the addition of HSO3-, corresponding to the change in the fluorescence color of the solution from green to blue. The recognition was conducted using high-resolution mass spectrometry, proton nuclear magnetic resonance, and density functional theory calculations. The fluorescent probe could be utilized to quantitatively monitor HSO3- in lysosomes of living C6 glioma cells and real-water samples.