Peptide-based probe for colorimetric and fluorescent detection of Cu²⁺ and S^2- in environmental and biological...

Pollution caused by Copper and hydrogen sulfide pollution has severe adverse effects on the environment and organisms. Real-time, fast and accurate monitoring of Cu²⁺ and S^2- faces serious challenges. In this study, we designed a novel biosensor and synthesized it by mimicking the structure of the main Cu(II)-binding site on bovine serum albumin. As a peptide-based sensor, FGGH (FITC-Gly-Gly-His-NH₂) can perform the sequential detection of Cu²⁺ and S^2- by fluorescence and colorimetry. The high water solubility and selectivity make it suitable for monitoring Cu²⁺ and S^2- in environmental water samples with high sensitivity; its limit of detection (LOD) is as low as 1.42 nM for Cu²⁺ and 22.2 nM for S^2-. The paper-based sensing platform of this probe was found to be a promising tool for the on-site visualization of real-time quantitative analysis of Cu²⁺ and S^2- due to its rapid response and recyclable detection characteristics. Additionally, FGGH was successfully used to image Cu²⁺ and S^2- in living cells and zebrafish models with adequate fluorescence stability and low cytotoxicity, providing the first visual evidence of the effect of the interactions between Cu²⁺ and S^2- on the redox homeostasis of organisms.