An ESIPT-based fluorescent probe for highly selective detection of glutathione in aqueous solution and living cells

In this paper, highly sensitive and selective fluorescent probe 1 for GSH is designed and synthesized based on modulation of the excited-state intramolecular proton transfer (ESIPT) process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole. Upon introducing GSH in neutral solution containing CTAB micelles, dinitrophenyl, the protecting group of the probe, is removed via the nucleophilic substitution, thereby retrieving the ESIPT process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole, which results in a fluorescence enhancement at 485 nm. Additionally, the fluorescence intensity of the probe is linearly proportional to GSH concentration ranging from 0 to 100 μM and the obtained detection limit is as low as 0.81 μM. The enhanced selectivity toward GSH over Cys and Hcy is also attributed to one more carboxyl group in GSH. Importantly, the probe is successfully utilized for monitoring GSH in living HeLa cells.