A ratiometric dual-channel fluorescent probe for selective Zn2+/Cd2+ sensing: Applications in food quality control, real-time monitoring in living cells, and mice

Background

Zinc (Zn²⁺) and cadmium (Cd²⁺) ions are ubiquitous in industrial and daily life. Despite their critical impact on food safety and human health, current probes face significant limitations in simultaneously detecting both ions in complex food matrices.

Results

Herein, we successfully developed a pyrene-based FRET ratiometric fluorescent probe QP for the highly selective detection of Zn²⁺ and Cd²⁺. The probe possesses low detection limits (1.85 × 10⁻⁸ M for Zn²⁺ and 1.83 × 10⁻⁸ M for Cd²⁺) and rapid response times (25 s for Zn²⁺ and 30 s for Cd²⁺). ESI-MS, NMR titration, Job's plot, and DFT calculations were employed to propose the fluorescence resonance energy transfer (FRET) mechanism. Probe QP has demonstrated versatile practical applications, including on-site rapid detection using QP-loaded swabs, accurate determination of Zn²⁺/Cd²⁺ levels in environmental water samples, visual monitoring of Zn²⁺ distribution in rice and apples, and quantitative evaluation of Zn²⁺ content in food samples (white radish, pork, and oysters) and pharmaceuticals (zinc gluconate oral liquid). The probe's potential in bioimaging is further solidified by its successful performance in vivo mouse imaging experiments and in vitro studies, notably the real-time detection of both dynamic fluctuations of endogenous Zn²⁺ and exogenous Zn²⁺/Cd²⁺, and concentration-dependent responses to exogenous Zn²⁺/Cd²⁺ in 4T1 cells.

Significance

This work unveils new opportunities of dual-channel fluorescent probes for selective Zn²⁺/Cd²⁺ sensing and their applications in food quality control.