An 'off-on' fluorescein-based colormetric and fluorescent probe for the detection of glutathione and cysteine over homocysteine and its application for cell imaging

A new fluorescein-based probe (Py-F) was designed and synthesized to develop an optical and fluorescent sensor for biological thiols. Py-F possessed the thiol-responsed disulfide group and displayed selectivity and sensitivity for glutathione (GSH) and cysteine (Cys) over homocysteine (Hcy) in the CH3CN/PBS buffer solution, and the fluorescence detection limit was calculated to be 0.12 μM and 0.13 μM, respectively. Besides, the recognition mechanism was explained by density functional theory (DFT) calculation, and confirmed by mass spectroscope measurement. Furthermore, the thiols detection application in cellular imaging assays indicated that the probe has appreciable cell permeability and can serve as a fluorescent probe for detecting biothiols in living cells.