A novel Cu2+-quenched fluorescent probe for turn-on detection of biothiols in food samples and cell imaging

A novel Schiff base fluorescent probe J-Y with a large Stokes shift (158 nm) and visible-region emission (575 nm) was developed. • J-Y forms a 1:1 complex with Cu 2+ through multiple chelation sites, enabling efficient fluorescence quenching via a PET mechanism. • Biothiols (Cys, GSH, Hcy) restore fluorescence by synergistic reduction of Cu 2+ and competitive coordination, achieving a highly sensitive “turn-on” response. • Dual-channel detection (UV–vis and fluorescence) with fluorescence LODs as low as 0.018 μM was demonstrated. • Practical applicability was validated through test strip assays, real food sample analysis and live-cell imaging. Biothiols play crucial roles in numerous physiological processes, making the development of novel fluorescent sensors for their detection highly valuable. Herein, a new fluorescent probe, J-Y, was designed, synthesized, and structurally characterized. The probe exhibits emission in the visible region (575 nm), a large Stokes shift (158 nm), and a wide applicable pH range. The probe J-Y can form a stable complex with Cu 2+ , and the competitive coordination ability of biothiols toward Cu 2+ lead to fluorescence recovery, enabling dual-channel UV–vis and fluorescence detection of biothiols (GSH, Cys, and Hcy). In a CH 3 CN/H 2 O system, the [ J-Y -Cu 2+ ] complex displays a fluorescence turn-on response toward the three biothiols. The UV–vis limits of detection are 0.034 μM (GSH), 0.031 μM (Cys), and 0.043 μM (Hcy), while the fluorescence limits of detection are 0.018 μM (GSH), 0.022 μM (Cys), and 0.031 μM (Hcy), respectively. More importantly, the probe J-Y has been successfully applied to test strip assays, real food sample analysis, and live-cell fluorescence imaging. Download: Download high-res image (205KB) Download: Download full-size image