A fluorescent probe with high selectivity to glutathione over cysteine and homocysteine based on positive effect of carboxyl on nucleophilic substitution in CTAB

A new fluorescent probe based on fluorescein fluorophore displays an excellent selectivity and sensitivity for GSH in buffer solution containing CTAB. The fluorescence intensity of sensor is linearly proportional to GSH concentrations ranging from 0 to 10 μM, and as low as 22 nM concentration of GSH was evaluated with 3.3 σ/s. The optical changes are attributed to the release of free fluorescein after the electron withdrawing dinitrophenyl ether reacted efficiently with GSH in CTAB micelles. The enhanced selectivity toward GSH over Cys and Hcy considered to be related to the carboxyl groups in thiols. The confocal microscopy experiments implied that this probe is a promising candidate for imaging of GSH in living cells.