An anthraquinone-imidazole-based colorimetric and fluorescent sensor for the sequential detection of Ag+ and biothiols in living cells

We herein report a simple anthraquinone-imidazole-based compound, 2-(furan-2-yl)-1H-anthra[1,2-d]imidazole-6,11-dione (FAI), as an effective colorimetric and fluorometric Ag+ sensor. In 1,4-dioxane/water (3 : 7, v/v, pH 7.4), FAI could selectively recognize and detect Ag+ ions via significant fluorescence quenching at 606 nm, accompanied by a rapid color change from yellow to orange. FAI exhibited high sensitivity to Ag+ in a linear dynamic range from 0.8–32 μM, with the detection limit of 66 nM. Job's plot analysis and HRMS studies supported the formation of the FAI–Ag+ complex in a ratio of 1 : 1. The in situ generated FAI–Ag+ complex was further utilized as a reversible sensor to detect biothiols (Cys, Hcy, GSH) through a decomplexation reaction, with the detection limit of 89 nM, 174 nM and 208 nM for Cys, Hcy and GSH, respectively. In addition, FAI with low cytotoxicity was efficient in monitoring Ag+ ions and biothiols in living human hepatoma cells SMMC-7721 as demonstrated by fluorescence microscopy imaging.