Highly selective fluorescent detection platform based on isoquinoline Schiff base ligand monitors glutathione in biological systems

Aberrant levels of intracellular glutathione (GSH) have been held responsible for various disease and pathological processes, and existing evidence underscores the significance of GSH detection in biological systems. The recognition, discrimination, and precise detection of GSH in the cellular matrix and living organisms can revolutionize our understanding of the physiological and pathological processes of GSH. Herein, we reported a new isoquinoline Schiff base fluorescence probe, N'-((7-(diethylamino)-2-oxo-2H-chromene)methylene) isoquinoline-3-carbohydrazide (NCMC), which can selectively recognize GSH by its ensemble complex NCMC-Cu2+ with a low nanomolar level detection limit (4.16 × 10−8 M) in the aqueous environment. Moreover, the binding behavior and "ON-OFF-ON" fluorescence probing pattern were illustrated in detail by UV–vis titration, ESI-MS spectroscopy, and density functional theory calculations. Notably, the nontoxic NCMC-Cu2+ ensemble platform showed great potential for detecting GSH distribution in cells and zebrafish larvae, and can also be applied in differentiating endogenous GSH in both cancer cells and normal cells, which may represent a promising GSH fluorescence probe in bioimaging and disease diagnosis.