A novel near-infrared fluorescence probe for selective sensing of cysteine over GSH and bioimaging in cells, zebrafish and plants

As an indispensable sulfur-containing amino acid, cysteine plays a vital role in various physiological processes of animals and plants. Its abnormal levels have been closely associated with the development and progression of serveral diseases. As a result, there is a surge in research focusing on the detection and measurement of cysteine within plants, which has captured significant attention in recent years. While several fluorescent probes have been designed to target cysteine, the majority of these probes face inherent challenges when applied in complicated biological systems. In this study, we have developed a novel fluorescent probe, MN-Cys, based on rhodamine derivative dyes, which can selectively detect Cys against GSH with a NIR-fluorescence turn-on response mode. Notably, MN-Cys shows low cytotoxicity, and possesses the capability to visualize and assess Cys via bioimaging, including NIR fluorescence imaging in both living cells and zebrafish models and two-photon imaging in Arabidopsis thaliana. The findings in this work underline the potential of MN-Cys as a promising NIR fluorescent probe which incorporates unique reaction sites and demonstrates exceptional sensing properties. Overall, this probe holds significant promise for the rapid and accurate detection of Cys both in vitro and in vivo.