An “on–off–on” fluorescent peptide probe for the specific detection of Cu2+ and S2− in living cells and zebrafish†
Abstract
Cu2+ plays an important role as the third most abundant essential trace element in normal physiological activities and metabolism of organisms. S2− participates in a variety of physiological processes, such as cell apoptosis, intracellular redox balance, insulin secretion and vasodilation. Herein, a novel fluorescent peptide probe P composed of six amino acids and Dansyl chloride dye (Dansyl–Asp–Asp–Gly–Gly–Glu–Glu) has been constructed to detect Cu2+ and S2−. P can specifically recognize Cu2+ without the interference of Hg2+ and other metal ions. The mixture of P and Cu2+ leads to the formation of a 1 : 1 complex and pronounced fluorescence quenching of the Dansyl-labeled peptide. Molecular simulation has revealed the structural details of the P–Cu complex, indicating that the binding of Cu2+ and P is mediated by two coordination sites (O atom of Glu and Asp). The continuous addition of S2− is to recover the fluorescence since it can release the Cu2+ from the P–Cu complex. P has been demonstrated as an “on–off–on” biosensor for Cu2+ and S2− with the detection limits of 47 nM and 57 nM, respectively. Furthermore, P has been successfully used for the imaging of Cu2+ and S2− in the living HeLa cells and zebrafish. The newly developed P has extraordinary features such as good biocompatibility, low biotoxicity, and high specificity of Cu2+ and S2−, which shows great potential in the studies of various Cu2+/S2−-involved diseases.