A Reversible Fluorescent Probe for Real‐Time Quantitative Monitoring of Cellular Glutathione

The ability to monitor and quantify glutathione (GSH) in live cells is essential in order to gain a detailed understanding of GSH‐related pathological events. However, owing to their irreversible response mechanisms, most existing fluorescent GSH probes are not suitable for this purpose. We have developed a ratiometric fluorescent probe (QG‐ 1 ) for quantitatively monitoring cellular GSH. The probe responds specifically and reversibility to GSH with an ideal dissociation constant ( K d ) of 2.59 m m and a fast response time ( t 1/2 =5.82 s). We also demonstrate that QG‐ 1 detection of GSH is feasible in a model protein system. QG‐ 1 was found to have extremely low cytotoxicity and was applied to determine the GSH concentration in live HeLa cells (5.40±0.87 m m ).