Indirect colorimetric detection of glutathione based on its radical restoration ability using carbon nanodots as nanozymes

This work addresses a colorimetric sensor for glutathione (GSH). In this study carbon nanodots (CDs) were used as the peroxidase mimetic catalysts. The blue colored free cation radicals were generated simply by an oxidation reaction of tetramethyl benzidine (TMB) which was catalyzed by CDs as the catalysts. So, the key role of the CDs was the enhancement in radical generation thereby enhancing the system sensitivity. The results in this study showed that the free radical cation concentration was inversely related to the GSH concentration in the range of 0-7 mu M with a detection limit of 0.3 mu M. Moreover, this system showed a perfect selectivity over non-thiolated biological molecules. As a practical application, this chemosensor was used to measure the GSH content of the whole human blood with the results consistent with that of a classical Ellman method. (C) 2014 Elsevier B.V. All rights reserved.