A versatile near-infrared fluorescent probe for Zn²⁺ detection in food and biological matrices

Zinc ions (Zn²⁺) are essential for human health, and their accurate detection in food is critical for dietary safety and nutritional assessment. Although near-infrared fluorescent probes have been widely developed for Zn²⁺ detection, their application in complex food matrices remains underexplored. Herein, we report DCMB, a novel near-infrared probe based on a dicyanomethylene-4H-pyran (DCM) derivative, exhibiting high selectivity for Zn²⁺ with an emission maximum at 640 nm. Anti-interference was systematically evaluated against metal ions, food-relevant small molecules, and biomolecules. DCMB enabled accurate Zn²⁺ quantification in diverse food matrices: fruits (apples, bananas), dairy products (milk), cereals (oats), and pharmaceuticals (zinc gluconate tablets), with results consistent with inductively coupled plasma mass spectrometry. DCMB-loaded test strips allowed rapid and portable naked-eye visual detection and smartphone-based RGB analysis of Zn²⁺ in food and supplement samples. Moreover, DCMB facilitated real-time tracking of endogenous and exogenous Zn²⁺ in 4T1 cells and supported in vivo imaging in mice, with effective suppression of background autofluorescence. Together, DCMB enriches the repertoire of near-infrared fluorescent probes for Zn²⁺ detection in complex food matrices.