A retrievable, water-soluble and biocompatible fluorescent probe for recognition of Cu(II) and sulfide based on a peptide receptor.

A novel fluorescent probe C-GGH for recognition of Cu(2+) and S(2-) was designed and synthesized by incorporation a natural tripeptide GGH (Gly-Gly-His) moiety, which acts as a recognition unit for Cu(2+), to a coumarin fluorophore. C-GGH displayed ON-OFF type fluorescence response towards Cu(2+) with high selectivity in 100% aqueous solution. Furthermore, the in situ generated non-fluorescent C-GGH-Cu(2+) complex can serve as an effective OFF-ON type fluorescent probe for selective sensing sulfide anion. Due to the strong binding affinity of S(2-) to Cu(2+), sulfide anion can extract Cu(2+) from C-GGH-Cu(2+) complex, resulting the release of C-GGH and the revival of fluorescent emission of the system. Techniques of emission spectrometry, NMR, mass spectrometry, and HPLC were used to confirm the displacement mechanism of C-GGH-Cu(2+) for sensing sulfide anion. The probe C-GGH-Cu(2+) allowed detection of S(2-) in aqueous buffer solution with a LOD (limit of detection) of 0.44μM. By taking advantages of the natural tripeptide GGH, the sensor exhibits excellent biocompatibility and water solubility. Moreover, the cell imaging study demonstrated that the probe can be exploited to detect sulfur anion in biological systems.