Highly sensitive and selective detection and intracellular imaging of glutathione using MnO2 nanosheets assisted enhanced fluorescence of gold nanoclusters

Glutathione (GSH) plays a critical role in biological defense system and is associated with numerous human pathologies. However, it still remains a challenge for fluorescent detection of GSH over cysteine (Cys) and homocysteine (Hcy) because of their similar structures. In this work, MnO2 nanosheets can efficiently quench the fluorescence of gold nanoclusters (Met-AuNCs) prepared by blending methionine and HAuCl4 owing to their superior absorption capability. However, GSH can reduce MnO2 nanosheets into Mn2+ which leads to the fluorescence recovery of Met-AuNCs. More intriguingly, GSH can dramatically and selectively enhance the fluorescence intensity of Met-AuNCs. Hence, a low background, ultrasensitive fluorescent detection of GSH was obtained with a detection limit of 68 nM. Moreover, the assay has been successfully used for GSH detection in human serum samples and cellular imaging with high selectivity over Cys and Hcy.