Colorimetric detection of glutathione based on its inhibitory effect on the peroxidase-mimicking properties of WS2 nanosheets.

A highly sensitive colorimetric assay is described for the determination of glutathione (GSH). It is based on the use of tungsten disulfide (WS2) which is a peroxidase mimic. It catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide to form a blue-colored product (oxTMB) at near neutral pH values. In the presence of the analyte GSH, it is transformed to its oxidized form (GSSG), while the blue oxTMB is increasingly reduced and eventually is converted to colorless TMB. This can readily be detected with bare eyes. GSH can be determined spectroscopically (at 652 nm) by this method at concentrations down to 61 pM, and the response is linear in the 100 pM to 10 nM GSH concentration range. The assay is cost-effective and simple. Conceivably, it provides a promising tool for the determination of GSH in food and medical samples. Graphical abstract Schemaric of a sensitive method for colorimetric detection of glutathione (GSH) based on WS2-catalyzed oxidation of TMB by H2O2 and the reduction of blue oxTMB by GSH.