An ESIPT coupled AIE fluorescent probe for biothiols detection and imaging based on a chalcone fluorophore

Biothiols are closely related to numerous physiological and pathological processes in living organisms and cells. Fluorescent probes are powerful tools for sensitive detection and imaging of biothiols in biological samples. In this work, we developed a novel turn-on fluorescent probe DNBS-HCA for biothiols detection based on the simple 2′-Hydroxychalcone (HCA) fluorophore, which possesses an excited-state intramolecular proton transfer (ESIPT) coupled aggregation-induced emission (AIE) characteristic. The 2′-hydroxyl group of HCA fluorophore is caged with a biothiols reactive 2,4-dinitrobenzenesulfonyl (DNBS) moiety, which blocks the ESIPT process and quenches the fluorescence. The reaction between probe and biothiols will produce the HCA fluorophore with large Stokes shift and long-wavelength red fluorescence emission. The biothiols in solutions and living cells can be conveniently detected with the probe DNBS-HCA due to its excellent properties such as simple synthetic procedure, remarkable fluorescence enhancement, good sensitivity, high selectivity and low cytotoxicity. Benefiting from the AIE characteristic, the probe is also applied for biothiols detection on indicator papers with RGB color red values, which can be handily obtained by smartphone app.