Rational Design of a Peptide-Based Fluorescent Probe for Selective Recognition of Ag+ and Cu2+ Ions and Its Multifunctional Applications

Abstract

Herein, a new large Stokes shift fluorescent probe DGCA based on dansyl group modified tripeptide molecule (Gly–Cys–Ala–NH₂) was successfully synthesized. DGCA acts as a promising probe for simultaneous detection of Ag⁺ and Cu²⁺ based on different response modes, which displayed fluorescence enhancement by Ag⁺ and fluorescence quenching by Cu²⁺ in 100% aqueous solution. In addition, DGCA exhibited high sensitivity recognition of Ag⁺ and Cu²⁺, with the limits of detections (LODs) being 7.4 nM and 5.9 nM, respectively. Furthermore, the stoichiometry between DGCA and Ag⁺/Cu²⁺ 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 Cu²⁺ 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 Cu²⁺ in living cells and zebrafish larvae. Moreover, it was also demonstrated that DGCA was suitable for the simultaneous detection of Ag⁺ and Cu²⁺ in real samples. More importantly, the smartphone App with RGB Color Picker was employed to analyze the concentration of Ag⁺ and Cu²⁺ with satisfactory results.