A coumarin-based water-soluble fluorescent probe for tandem detection of Cu2+ and glutathione with application in bioimaging and real sample analysis.

This study developed a new water-soluble fluorescent probe based on a coumarin scaffold, ALX, by introducing hydrophilic groups such as amino, pyridine, etc., using coumarin as a fluorophore, and verified its rapid (3 s, 50 s) tandem detection of Cu2+ and glutathione (GSH), with good selectivity and immunity to interference. In this case, ALX was specifically fluorescent "on-off" with Cu2+, its fluorescence intensity was linearly correlated with Cu2+ concentration in the range of 0-8 μM, with a detection limit of 5.6 × 10-8 mol/L and a complexation constant of 6.9 × 103 M-1. In contrast, complex ALX-Cu2+ exhibited a fluorescence turn-on response to glutathione, within the GSH concentration range of 0-9 μM, the fluorescence signal intensity of the probe varies linearly with its concentration, achieved a remarkably low detection limit of 4.9 × 10-8 mol/L. To elucidate the mechanism by which probe ALX recognizes copper ions, this study employed density functional theory calculations. In addition, probe ALX could effectively detect Cu2+ and glutathione in red wine and cucumber. This dual-functionality also extended to biological cell imaging, highlighting its significant potential for food quality monitoring and biological control applications.