A novel NIR fluorescence probe with cysteine-activated structure for specific detection of cysteine and its application in vitro and in vivo

Cysteine (Cys) as a vital antioxidant molecule and an effective biomarker for illness, plays an essential role in physiological functions and pathological processes. Extensive work has been done to explore the physiological functions of Cys and develop probes for detection of biothiols. However, the challenge to differentiate Cys from glutathione and homocystine remains. In this work, we constructed a novel near-infrared (NIR) probe, termed TMN-Cys, using TMN-NH2 and thionoesters. The probe could selectively detect Cys over homocysteine and glutathione in solution. It displayed a large Stokes shift (210 nm) upon treatment with Cys, and its detection limit was as low as 79 nM. Moreover, this probe showed low toxicity and was successfully employed in monitoring endogenous Cys in living cells and mice. [Display omitted] •TMN-Cys, a novel red-emitting fluorescent probe based onthionoesters, was designed.•TMN-Cys selectively monitored Cys both in vitro and in vivo.•TMN-Cys exhibited high sensitivity and a large Strokes shift after reacting with Cys.•The detection limit of TMN-Cys was as low as 79 nM.