A novel peptide-based fluorescent probe with a large stokes shift for rapid and sequential detection of Cu2+ and CN- in aqueous systems and live cells

A novel fluorescent probe (DSD) was reasonably designed and synthesized with dansyl-labeled dipeptide (Dan-Ser-Asp-NH2). DSD featured remarkably large Stokes shift (230 nm) and perfect water solubility, and exhibited high selectivity and rapid recognition toward Cu2+ via fluorescence quenching. The detection limit of DSD for Cu2+ was 2.4 nM, indicated that DSD has excellent sensitivity. In addition, the stoichiometry between DSD and Cu2+ were detected as 1:1 by fluorescence titration, Job's plot and ESI-HRMS data. As designed, DSD-Cu2+ system was able to sequentially detect CN according to the displacement approach with fluorescence off-on response, and the detection limit for CN was calculated to be 41.9 nM. Specifically, the response time of DSD with Cu2+ and CN was less than 40 s, which rendered it suitable for real time detection in actual water samples. In addition, with the alternate addition of Cu2+ and CN , the reversible cycles could be repeated for at least 10 times, indicated that DSD was a promising reversibility probe. DSD showed low toxicity and good biocompatibility, and was successfully applied to detect Cu2+ and CN in living cells. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The novel fluorescent probe DSD exhibits high sensitivity towards Cu2+ and CN with high selectivity and rapid recognition. It features a large Stokes shift, perfect water solubility, and the ability to be reversibly cycled at least 10 times.