A coumarin-quinoline-derived fast and highly sensitive turn on fluorescent probe for sniffing sulfite in food, living cells and zebrafish.

Building on the precursor probe BMQ-1 with A-π-A configuration, a new optimized fluorescent probe, XYT, for the determination of sulfur dioxide was developed by extending the π-conjugation through replacing the electron acceptor 1-(4-dimethylaminophenyl)-2-cyanoacrylonitrile with 1-(7-diethylaminocoumarin-3-yl)-2-cyanoacrylonitrile. This modification resulted in a redshift of XYT in emission wavelength from 590 nm to 603 nm upon reaction with sulfite. The probe demonstrated rapid colorimetric and fluorogenic changes (≈ 10 s), with the solution turning from colorless to red and emitting strong red fluorescence. XYT exhibited high selectivity, photostability, and sensitivity, achieving a detection limit as low as 49.9 nM. In practical detection scenarios, XYT was adopted to measure residual SO2 contents in commercially available food samples, among which the analytical data of some specimens were verified via comparative analysis with the official Chinese national standard GB 5009.34-2022. Beyond in vitro assays on food matrices, XYT also enables fluorescence imaging of exogenous and endogenous SO2 in live cells and zebrafish. These properties suggest that XYT holds substantial potential for pathological studies and clinical diagnostics involving SO2.