Ultrasensitive near-infrared fluorescence-enhanced probe for discriminative detection of GSH and Cys from different emission channels

Aberrant levels of glutathione (GSH) and cysteine (Cys) are key risk indicators for some diseases, hence monitoring the levels of GSH and Cys is of great significance in clinical diagnosis. Herein, a water soluble near-infrared fluorescent probe (CFL-NDB) was readily prepared for fast, sensitive and discriminative detection of GSH and Cys. The probe was constructed with a near-infrared semi-heptamethine cyanine attached to 7-nitrobenzofurazan (NBD) via an ether bond. Upon substitution of NBD with GSH, this probe exhibits a significant fluorescence “turn-on” signal towards GSH at 702 nm with fast response (within 5 min) and low limit of detection (81 nM). In contrast, the probe not only displays the emission at 702 nm but also shows another emission band at 540 nm in the presence of cysteine (Cys). Therefore, this probe can be used to simultaneously detect Cys and GSH from different emission channels. Such capability of the probe has been demonstrated for quantitative determination of Cys and GSH in human plasmas. Furthermore, fluorescence imaging of HeLa cell indicated that the probe could be used for visualizing GSH and Cys in living cells.