Co₃O₄ nanocrystals as an efficient catalase mimic for the colorimetric detection of glutathione

Nanomaterial-based artificial enzymes (nanozymes), as an emerging generation of artificial enzymes, have received extensive attention in recent years owing to their striking merits. In this study, the obtained Co₃O₄ nanocrystals exhibited catalase-like activity and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, and a clear absorption peak at 652 nm can be observed. It was verified that the catalytic activity for the oxidation of TMB originated from the oxygen, which is generated by Co₃O₄ catalyzed H₂O₂ decomposition. Upon addition of glutathione (GSH), the catalytic ability of the Co₃O₄ nanocrystals was inhibited. And, the changes of absorbance at 652 nm could be utilized to quantify the concentration of GSH. Under the optimized conditions, the proposed assay showed good linear relationships and a low detection limit towards GSH. Moreover, the Co₃O₄ nanocrystals had excellent stability and can maintain the catalytic activity for a long time. Thus, a simple, sensitive and selective nanozyme-based biosensor was developed for the colorimetric detection of GSH.