A dual-responsive fluorescent probe for bisulfite and viscosity and its practical detection applications.

This study presents a dual-detection fluorescent probe MCC-DMQ toward both bisulfite and viscosity by strategically conjugating quinolinium salt as an electronic acceptor and 6-methoxychromene as an electronic donor linked through an exocyclic ethylene bridge to form the typical D-π-A conjugated system. The ethylene bridge serves as both reaction site for bisulfite detection and intramolecular rotator responsible for viscosity sensing. MCC-DMQ demonstrates exceptional fluorescence response performances for both analytes with the advantages of large Stokes shifts (160 nm), minimal interference, high selectivity, good sensitivity. Leveraging these superior optical properties, probe MCC-DMQ has been successfully accomplished the quantitative detection of bisulfite levels in food samples and viscosity monitoring in food thickeners systems. Furthermore, we developed a simple, portable and effective analytical platform by integrating a smartphone equipped with a color extraction App and MCC-DMQ-impregnated test strips, successfully achieving the on-site and quantitative analysis of bisulfite in actual samples. Notably, due to its low cytotoxicity and excellent cellular permeability, MCC-DMQ has been subjected to living cell imaging assay and realized the visualization of endo/exogenous bisulfite.