A reaction-activated near-infrared hemicyanine probe for tandem detection of copper(II) and glutathione in food systems and living cells

Reaction-based fluorescent strategies offer improved selectivity for chemically interrelated analytes but remain underexplored for the sequential detection of Cu 2+ and glutathione (GSH) in complex food and biological systems. Herein, we report a hemicyanine-derived near-infrared probe (HC-TPA) that operates through a Cu 2+ -activated chemical transformation followed by GSH-triggered fluorescence restoration, enabling cascade sensing within a single molecular platform. Coordination of Cu 2+ to the tris(2-pyridyl)methylamine unit induces rapid fluorescence quenching, while subsequent GSH-mediated reaction releases the emissive hemicyanine species, producing distinct near-infrared signals at 668 and 696 nm. The probe responds within 1 min to Cu 2+ and within 20 min to GSH. Quantitative analysis revealed linear detection ranges of 100–800 nM for Cu 2+ and 6–30 μM for GSH, with limits of detection of 48 nM and 0.56 μM, respectively. The reaction-based mechanism affords excellent selectivity and minimizes interference from competing species. Practical applicability was demonstrated through accurate determination of Cu 2+ and GSH in food samples and successful fluorescence imaging in living cells. This work establishes a mechanistically driven tandem sensing strategy for food safety monitoring and bioanalytical applications.