Red-emitting fluorescent turn-on probe with specific isothiocyanate recognition site for cysteine imaging in living systems

[Display omitted] •An ITC-based fluorophore, TMN-NCS, is developed for Cys detection.•The sensor presents high sensitivity and selectivity in a wide pH range.•TMN-NCS can detect Cys with high specificity and no interferences from biothiols.•With low toxicity, TMN-NCS can be used for imaging in live systems. Cysteine (Cys) is an effective biomarker in life systems and is closely related to a variety of diseases, so developing a specific and efficient detection method for Cys is of great significance. To date, extensive work has been undertaken toward this goal. However, the differentiation of Cys from other biothiols still represents a challenge from an experimental point of view. Toward this end, a selective and sensitive red-emitting probe (TMN-NCS) with an isothiocyanate (ITC)-based structure was proposed in this paper. A large Stokes shift (210 nm) was observed upon addition of Cys to a solution of TMN-NCS. In addition, TMN-NCS showed low toxicity, a low detection limit (120 nM), and excellent cell permeability. The results suggested that TMN-NCS holds great promise for biological applications.