A rhodamine-based fluorescent probe with high water solubility and its application in the detection of glutathione with unique specificity

Rhodamine dyes are ideal material to construct off-on-type probes for recognizing various analytes with high sensitivity. However, most of them were operated in either pure organic or organic-aqueous solutions, which limited their practical applications in physiological environment. Herein, a universal strategy is provided to improve the water solubility of rhodamine-based fluorescent probe by structural modification. In this strategy, a carboxyl group is introduced to the chemical structure of probe. It is expected that the design strategy could be widely applied to improve the water solubility of all the existing rhodamine-based fluorescent probes. A fluorescent probe named Rh-COOH is designed and synthesized through attaching a carboxyl to the structure of this probe. Rh-COOH is used to recognize glutathione (GSH), which is the most abundant cellular thiol and plays crucial roles in physiological processes. The characteristics of this probe are as following: (1) Rh-COOH operates well in aqueous solution without organic solvent. (2) The probe exhibits high sensitivity toward GSH with 69-fold fluorescence enhancement. (3) The probe is highly selective, which will not be interfered by the other 2 biological thiols (Cys, Hcy) and other 19 amino acids. (4) The probe displays selective detection of GSH in living cells.