A NIR colorimetric-fluorescent probe for cysteine detection with applications in plant imaging and portable food analysis.

Cysteine (Cys) is crucial for redox balance and metabolism but real-time in situ detection of Cys in plants limited by tissue penetration, sensitivity, and response time. Herein, a novel fluorescent probe, DCI-Cys, is developed for the detection of Cys, which exhibits characteristics of near-infrared emission (650 nm), high sensitivity (30.32 nM), and rapid response (80 s). With the aid of DCI-Cys, real-time imaging of Cys in various plant tissues is innovatively achieved, and fluctuations in endogenous Cys levels in Nicotiana tabacum L. seedlings during exposure to chromium (Cr) and drought stress are detected. Furthermore, test strips based on DCI-Cys enable rapid qualitative detection of Cys in food samples. When integrated with a smartphone-based portable device, the system permits convenient and quantitative Cys analysis through dual colorimetric and fluorescent modes. This work demonstrates the broad utility of the DCI-Cys platform for Cys detection in both plant biology and food science.