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

• A novel retrievable fluorescent probe was developed for recognition of Cu(II) and sulfide based on a displacement mechanism.
• A natural tripeptide GGH (Gly-Gly-His) moiety was used as a recognition unit in the probe.
• The constructed probe displayed excellent water-solubility and biocompatibility.

A novel fluorescent probe C–GGH for recognition of Cu2+ and S2− was designed and synthesized by incorporation a natural tripeptide GGH (Gly-Gly-His) moiety, which acts as a recognition unit for Cu2+, to a coumarin fluorophore. C–GGH displayed ON–OFF type fluorescence response towards Cu2+ with high selectivity in 100% aqueous solution. Furthermore, the in situ generated non-fluorescent C–GGH–Cu2+ complex can serve as an effective OFF–ON type fluorescent probe for selective sensing sulfide anion. Due to the strong binding affinity of S2− to Cu2+, sulfide anion can extract Cu2+ from C–GGH–Cu2+ 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–Cu2+ for sensing sulfide anion. The probe C–GGH–Cu2+ allowed detection of S2− in aqueous buffer solution with a LOD (limit of detection) of 0.44 μM. 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.

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