Rational Design of a Peptide-Based Fluorescent Probe for Selective Recognition of Ag and Cu Ions and Its Multifunctional Applications.

Herein, a new large Stokes shift fluorescent probe DGCA based on dansyl group modified tripeptide molecule (Gly-Cys-Ala-NH) was successfully synthesized. DGCA acts as a promising probe for simultaneous detection of Ag and Cu based on different response modes, which displayed fluorescence enhancement by Ag and fluorescence quenching by Cu in 100% aqueous solution. In addition, DGCA exhibited high sensitivity recognition of Ag and Cu, with the limits of detections (LODs) being 7.4 nM and 5.9 nM, respectively. Furthermore, the stoichiometry between DGCA and Ag/Cu was 1:1 by means of fluorescence titration, Job's plot, electro-spray ionization high-resolution mass spectrometry (ESI-HRMS) and theoretical calculation. The fluorescence changes of DGCA upon the addition of Ag and Cu were applied as an ultrasensitive logic gate at the molecular level. Due to low toxicity and good permeability, DGCA was successfully used for bioimaging Ag and Cu in living cells and zebrafish larvae. Moreover, it was also demonstrated that DGCA was suitable for the simultaneous detection of Ag and Cu in real samples. More importantly, the smartphone App with RGB Color Picker was employed to analyze the concentration of Ag and Cu with satisfactory results.