A reversible pyrene-based fluorescent probe for visual detection of cysteine in food samples

A reversible fluorescent probe Pyr-1 was developed by integrating pyrene and oxime functional groups and applied for visual detection of Cysteine (Cys). By featuring three binding sites, Pyr-1 exhibited selective fluorescence quenching response towards Fe3+ through the formation of 1:1 coordination complex. The ensemble Pyr-1-Fe3+ was further applied to detect Cys. Among the various test species, Cys induced unique fluorescence enhancement through the decomplexation process. The detection of Cys exhibited a fluorescence “turn-off-on” phenomenon within 50 s and reversible cycle performed up to at least 32 times. The detection limit was calculated as 0.446 µM. Due to the excellent stability in wide pH range (2−11), Pyr-1-Fe3+ was successfully applied in detection of Cys in diverse food samples. In practical applications, an obvious fluorescent color difference was observed on paper-based device modified by Pyr-1-Fe3+, which was convenient and could be used for on-site evaluation of Cys in food samples.