A novel fluorescent probe based on a tripeptide-Cu(II) complex system for detection of histidine and its application on test strips and smartphone

Herein, we reported a novel peptide-based fluorescent probe DSSH for highly selective and sensitive detections of both Cu2+ and l-histidine (l-His). DSSH exhibited different color changes and fluorescence “on–off” response toward Cu2+ with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu2+ was calculated to be 22.9 nM. The in situ formed DSSH-Cu2+ ensemble showed obvious fluorescence “off–on” response to l-His based on replacement reaction with Cu2+, as well as the discernable color changes under 365 nm UV lamp irradiation with “naked eye”. The specificity of Cu2+/l-His interactions allowed l-His to be determined without interference from other amino acids, and the detection limit of DSSH-Cu2+ ensemble response to l-His was determined as 25.7 nM. Notably, DSSH was successfully applied for detecting Cu2+ and l-His in RKO living cells owing to its remarkable fluorescence behavior and low cytotoxicity. Test strips experiments suggested that DSSH can recognize Cu2+ and l-His together by a remarkable fluorescence change. More importantly, smartphone was combined with l-His solutions of different concentrations and converted into digital values through RGB channels, which was successfully used for semi-quantitative identification of l-His, and the limit of detection (LOD) was 0.97 μM.