One-step activated fluorescence bioimaging of gamma-glutamyltransferase activity in living cancer cells based on chloro-rhodamine probe

In this article, we report a chloro-rhodamine (ClR) dye as a potential novel probe scaffold that possesses a specific intra-subspiral cyclization behavior: the acetylation of ClR (ClR-Ac) features a closed-loop structure in an aqueous solution, while the ClR itself is an open-loop structure. ClR-Ac is colorless and completely nonfluorescent, while ClR is yellowish and strongly fluorescent. This discovery has led to the development of a general design strategy to develop highly sensitive fluorescence probes for peptidase. We designed and synthesized the probe ClR-Glu by peptidase represented by gamma-glutamyl-transpeptidase (GGT) to verify this strategy. Experimental results show that ClR is easier to synthesize and has better environmental pH stability than the GGT probe based on HMRG. Furthermore, in addition, we expect that ClR-based probes will be widely used for the detection of peptidases and other analyses.