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Abstract We reported a novel and readily synthesized fluorescent "turn-on" probe L (Dansyl-Glu-Pro-Gly-Cys) based on dansyl group combine tetrapeptide. The probe L exhibited highly sensitive fluorescent recognition to Cd2+ ions in HEPES buffer solutions (10.0 mM, pH 7.4). The 2:1 binding stoichiometry of L with Cd2+ were determined based on fluorescence titration and the Job's plot investigation. The competitive experiments were found to be highly selective for the Cd2+ ions even in the existence of excess competing metal ions including Zn2+, Pb2+, Hg2+ and Cu2+ ions. The binding constant of the complex L -Cd was calculated to be 5.18 × 1010 M−2, and showed great affinity compared to other probes. In addition, the detection limit of the probe L for Cd2+ ions was calculated to be 45 nM, which presented a pronounced sensitivity toward Cd2+ ions. Most importantly, the probe L had wide range of pH and good biocompatibility, and were successfully applied to selectively detected Cd2+ ions within pH range of 7–12 and bioimaging studies in live cells. Graphical Abstract Unlabelled Image Highlights • A novel fluorescent peptide-based probe (L) was synthesized. • L exhibited exclusively selective fluorescent "turn-on" response toward Cd2+ ions. • L displayed high sensitivity for Cd(II) with a low detection limit of 45 nM. • L could serve as a potential probe to detect Cd2+ ions in living cells. [ABSTRACT FROM AUTHOR]

• A new peptide-based fluorescent probe DCH was synthesized. • DCH exhibited high sensitivity to Zn2+, with detection limits of 30.49 nM. • DCH was utilized for detecting Zn2+ in two real samples with high reliability. • DCH was low toxicity and could be used to monitor Zn2+ in two living cells. Zinc (Zn2+) ions play a very important role in the environment and organisms, and it is of great significance to realize the high sensitivity and selectivity detection of Zn2+ ions. Herein, a new peptide-based fluorescent probe named DCH was rationally designed and synthesized by solid phase peptide synthesis with Fmoc chemistry. DCH exhibited excellent fluorescent "turn-on" responding to Zn2+ with highly selective and exhilaratingly sensitive in aqueous media, with detection limits (LOD) as low as 30.49 nM. ESI-MS, Job's plot curves and fluorescence titration results indicated that the stoichiometric ratio between DCH and Zn2+ was 2:1. DCH could be regenerated by adding EDTA solutions to the complex formed during interaction, and indicated that DCH was promising reversibility probe. Furthermore, DCH has excellent practical application potential through two actual water sample experiments. Importantly, DCH was successfully used in monitor cellular Zn2+ and EDTA in living HK2 cells and SV-HUC-1 cells based on good biocompatibility and exciting low toxicity. [ABSTRACT FROM AUTHOR]

[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]

[Display omitted] • A novel peptide fluorescent probe DGGH was synthesized. • DGGH -Cu2+ system showed highly selective and "turn-on" response to S2−. • The detection limit of DGGH -Cu2+ for sensing S2− was calculated to be 13.7 nM. • DGGH -Cu2+ was successfully applied to monitor Cu2+ and S2− in real samples and living cells. We report a new fluorescent probe named DGGH with dansyl-labeled tripeptide (Dan-Gly-Gly-His-NH 2). DGGH showed obvious fluorescence quenching after the addition of Cu2+ ions and a 1:1 ensemble system (DGGH -Cu2+) was formed, the limit of detection was 37.9 nM. As expected, DGGH -Cu2+ ensemble system exhibited high selectivity and rapid response for S2− in 100% aqueous solutions, as a result of the addition of S2− immediately replaced Cu2+ from the DGGH -Cu2+ ensemble system. The limit of detection of the DGGH -Cu2+ ensemble for S2− was determined to be 13.7 nM. In addition, DGGH -Cu2+ has excellent detection performance within a wide pH range of 6 to 12, and its outstanding response time of less than 50s. Furthermore, we demonstrated the usability of the present approach for detecting Cu2+ and S2− in two water samples. What's more, DGGH was successfully applied to monitor Cu2+ and S2− in living LNcap cells based on good cells permeability and low toxicity. [ABSTRACT FROM AUTHOR]