A Novel Peptide-Based Fluorescent Probe with Large Stokes Shift for the Simultaneous Detection of Ag+ and Cu2+ Ions Through Differential Response and its Practical Applications

Abstract

Achieving highly selective detection of silver (Ag+) and copper (Cu2+) ions is important because their large emissions can cause many diseases. Herein, a new fluorescent probe DGCA (Dansyl-Gly-Cys-Ala-OH) with large Stokes shift was synthesized using solid-phase peptide synthesis (SPPS) with Fmoc chemistry. DGCA acts as a bi-functional probe for simultaneous detection of Ag+ and Cu2+, which displayed fluorescence enhancement by Ag+ and fluorescence quenching by Cu2+ in 100% aqueous solution. In addition, DGCA predominantly exhibited high sensitivity recognition of Ag+ and Cu2+, with the limit of detections (LODs) were 7.4 nM and 5.9 nM, respectively. Furthermore, the stoichiometry between DGCA and Ag+/Cu2+ were 1:1 by means of fluorometric titration, Job's plot, high resolution mass spectrometry and theoretical calculation. DGCA was successfully used for bioimaging Ag+ and Cu2+ in living cells based on differential response. Moreover, it was also demonstrated that DGCA was suitable for the simultaneous detection of Ag+ and Cu2+ in three water samples. More importantly, the smartphone with RGB Color Picker was employed to analyze the concentration of Ag+ and Cu2+ with satisfactory results.

Keywords: Peptide-based probe, Ag+, Cu2+, Bioimaging, Smartphone App