Novel Colorimetric\nand Near-Infrared Ratiometric Fluorescent\nProbe for Sensing Cysteine in Food Samples, Plants, and Living Cells

Cysteine\n(Cys) is a crucial biothiol that acts a significant function\nin food samples and biological systems, including plant roots and\nliving cells. Hence, we developed a novel colorimetric and near-infrared\nratiometric fluorescent probe (CT), composed of coumarin and tetrahydroacridine-conjugated\nindole salt, for the detection of Cys. Upon reaction with Cys, the\nprobe undergoes a specific N-substitution reaction, resulting in a\nnotable colorimetric change and a significant ratiometric fluorescent\nresponse in both visible and near-infrared emission channels. These\ndual-channel ratiometric fluorescence changes are completely independent,\nenabling the probe to obtain great selectivity, sensitivity, and exceptional\ndetection accuracy. Leveraging these attributes, the probe was employed\nto provide accurate quantitative analysis of Cys in food samples.\nFurthermore, confocal imaging demonstrated that the probe could monitor\nboth exogenous and endogenous Cys levels in living cells and track\nCys changes in plant roots under heavy metal stress. This work presents\na dependable and accurate imaging solution for tracking and identifying\nCys of real food, plants, and living cells.