A fluorescent dansyl-based peptide probe for highly selective and sensitive detect Cd²⁺ ions and its application in...

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.