Three-in-one type fluorescent sensor based on a pyrene pyridoxal cascade for the selective detection of Zn(<scp>ii</scp>), hydrogen phosphate and cysteine

Abstract

A novel fluorescent receptor L was synthesized by Schiff base condensation of 1-pyrenemethylamine with the vitamin B₆ cofactor pyridoxal. The receptor L is highly selective and sensitive towards Zn²⁺ ions among other tested metal ions. Upon interaction with Zn²⁺, the receptor L showed a distinct fluorescence enhancement at 485 nm due to the excimer formation leading to the fluorescent colour change from blue to bluish-green. Subsequently, when the in situ generated ZnL₂ complex interacted with various anions and amino acids, the addition of H₂PO₄^- and cysteine reinstated the fluorescence of the receptor L due to the demetalation of Zn²⁺ from the ZnL₂ complex. Accordingly, the receptor L was developed for the highly selective, specific and sensitive detection of three important bioactive analytes, i.e., Zn²⁺, H₂PO₄^- and cysteine with a detection limit down to 2.3 × 10^-6 M, 2.18 × 10^-7 M and 1.59 × 10^-7 M, respectively. Additionally, the receptor L was applied to the detection of intracellular Zn²⁺ ions in live HeLa cells.