A Highly Sensitive “Off-On” Fluorescent Probe TPA-OH for Rapid Detection of Sulfite/Bisulfite Species in Foods and Cell Imaging

Sulfur dioxide (SO 2 ) and its derivative bisulfite (HSO 3 − ) are widely utilized in food processing but pose potential health hazards at excessive concentrations, highlighting the critical need for rapid and sensitive detection methods for sulfite/bisulfite species. Herein, we report the synthesis of a novel fluorescent probe TPA-OH featuring a donor–π–acceptor (D–π–A) architecture, with triphenylamine (TPA) as the electron-donating unit and 7-hydroxy-1-indanone as the electron-withdrawing moiety. The conjugated C═C double bond enables intramolecular charge transfer (ICT) within the probe. Upon interaction with sulfite/bisulfite species, presumably through nucleophilic addition to the C═C bond, the π-conjugated system is disrupted, resulting in a pronounced fluorescence enhancement accompanied by a distinct blue shift. Under optimized conditions, TPA-OH exhibited a low detection limit of 0.053 µM based on repeated calibration experiments and a broad linear range of 5.0 × 10 − 8 ∼1.0 × 10 − 5 M, along with good stability and strong anti-interference capability toward sulfite/bisulfite detection. This probe was successfully applied for HSO 3 − quantification in real samples and fluorescence imaging of exogenously added HSO 3 − in HepG-2 cells under controlled experimental conditions. Its favorable cytocompatibility supports its use for fluorescence imaging of exogenous sulfite/bisulfite species in living cells under the current experimental conditions. Graphical A novel D–π–A fluorescent probe (TPA-OH) was designed using a triphenylamine donor. The probe detects HSO 3 − via a specific nucleophilic addition disrupting π-conjugation. TPA-OH exhibits an ultralow detection limit of 0.05 nM and broad linear range. Successfully applied for HSO 3 − detection in foods and fluorescence imaging in living cells.