A highly selective ratiometric fluorescent probe for cysteine detection

A novel coumarin-based ratiometric fluorescent probe, NPCN, was developed for the highly selective and sensitive detection of cysteine (Cys). The dual reaction site design of the probe enables effective differentiation of Cys from other biothiols, such as homocysteine (Hcy) and glutathione (GSH). Upon reacting with Cys, the probe exhibited a significant blue shift in its emission spectrum, allowing for ratiometric detection at 472 nm and 590 nm with a good linear relationship (0–100 μM) and a low detection limit (0.18 μM). Further investigations demonstrated excellent selectivity and biocompatibility of NPCN for Cys detection. In cell imaging experiments, NPCN effectively visualized both endogenous and exogenous Cys, showing outstanding cellular permeability and low cytotoxicity. Moreover, using a zebrafish model, NPCN successfully achieved in vivo imaging of Cys, exhibiting a concentration-dependent fluorescence response. Overall, NPCN represents a promising tool for real-time imaging and analysis of Cys in biological samples, providing critical technological support for disease diagnosis and therapeutic research.