Development of near-infrared fluorescent sensor and portable measuring device for on-site quantitation of Cys in food samples

Cys plays significant roles in food industries. It is very necessary to on-site quantify Cys content in food samples. Herein, we rationally developed a fluorescent sensor, YF, for on-site measurement of Cys in various foodstuffs. Sensor YF showed fluorescence response to Cys in near infrared (NIR) region, which could dramatically mitigate the interference of autofluorescence in foodstuffs. Moreover, sensor YF exhibited obvious colorimetric change to Cys. Accordingly, the sensor YF was capable of detecting Cys via both fluorescence method and colorimetric method, making the detection more reliable. Sensor YF also presented high selectivity and sensitivity to Cys, and its detection limits was measured to be 88 nM. The practical application demonstrated that sensor YF was able to monitor Cys in live cells and zebrafish via fluorescence imaging. Moreover, variations of Cys concentration in spinach leaves under different Cd2+ stress were effectively tracked. To accomplish on-site quantitation of Cys content in foodstuffs, a simple and portable measuring device was made. Sensor YF and the portable measuring device were successfully utilized for quantitation of Cys in food samples such as dry red pepper, tomato and soy bean. The detection method established herein will be conveniently employed for on-site quantitation of Cys in various food samples.