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.

[Display omitted] • The fluorescent probe DSD based on the dipeptide receptor was synthesized. • DSD exhibited fluorescent quenching for Cu2+ and recovered rapidly by adding CN−. • The detection limit of 2.4 nM for Cu2+ and 41.9 nM for CN−. • DSD was successfully applied for detecting and imaging Cu2+ and CN− in live cells. A novel fluorescent probe (DSD) was reasonably designed and synthesized with dansyl-labeled dipeptide (Dan-Ser-Asp-NH 2). 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. [ABSTRACT FROM AUTHOR]