Cytidine-gold nanoclusters as peroxidase mimetic for colorimetric detection of glutathione (GSH), glutathione disulfide (GSSG) and glutathione reductase (GR)

Label-free sensing assays based on the enzyme-mimicking property of Cytidine-Au nanoclusters were demonstrated for colorimetric detection of glutathione (GSH), glutathione oxidized (GSSG) and glutathione reductase (GR). The method displayed rapid response, easy procedure and high selectivity. [Display omitted] •Peroxidase-like activity of Cytidine-Au nanoclusters was investigated.•The Cy-AuNCs nanozyme follows Michaelis-Menten behaviors and shows strong affinity to H2O2.•GSH can inhibit the catalytic activity of Cy-AuNCs.•Lable-free colorimetric sensors for the detection of GSH, GSSG and GR were developed. Abnormal levels of glutathione (GSH) and glutathione oxidized (GSSG) usually relates to some diseases, thus quantifying the amount of GSH or GSSG is of great significance. A label-free sensing assay based on the enzyme-mimicking property of Cytidine-Au nanoclusters (Cy-AuNCs) was demonstrated for colorimetric detection of GSH, GSSG and glutathione reductase (GR). Firstly, obvious blue color accompanied with an absorption peak at 652 nm was observed due to the high peroxidase-like activity of Cy-AuNCs toward 3,3′,5,5′-tetramethylbenzidine (TMB). Then, in the presence of target, the mimetic activity of Cy-AuNCs could be strongly inhibited and used to achieve the visualization detection. The inhibition effect arose from the surface interaction between GSH and Cy-AuNCs. Linear relationships between absorbance response and concentration were obtained between 0 and 0.4 mM for GSH, 0–2.5 mM for GSSG and 0–0.2 U/mL for GR. The limit of detection (LOD) was calculated as low as 0.01 mM, 0.03 mM and 0.003 U/mL for GSH, GSSG and GR, respectively. Furthermore, the proposed method displayed rapid response, easy procedure and high selectivity.