Highly selective and sensitive detection of glutathione based on anti-aggregation of gold nanoparticles via pH regulation

•A facile and highly sensitive colorimetric assay for glutathione (GSH) based on AuNPs was presented.•The assay was based on anti-aggregation of AuNPs via pH regulation.•Discriminative detection of GSH over Cys/Hcy was developed.•The assay was applied to detect GSH in serum and urine samples.

Glutathione (GSH) plays a key role in biological systems and serves many cellular functions. Since biothiols all incorporate thiol, carboxylic and amino groups, discriminative detection of GSH over cysteine (Cys) and homocysteine (Hcy) is still challenging. Both Cys and Hcy can induce aggregation of AuNPs via the formation of zwitterionic networks, which is different from GSH. GSH induced aggregation of AuNPs by the hydrogen bonding between the carboxylic groups when pH <4.5, so pH plays a crucial part in our present work. By regulating the pH to 5.8, our proposed sensing system exhibits high selectivity and sensitivity towards GSH even in the presence of other biothiols, realizing the discriminative detection of GSH over Cys/Hcy based on anti-aggregation of AuNPs. In our work, 2-mercapto-1-methylimidazole (MMI) and GSH took the role of aggregation and anti-aggregation agent, respectively. A linear relationship between the intensity ratio A650 nm/A520 nm and the GSH concentration is obtained (R2 = 0.998) with a detection limit of 12.0 nM.