Nanozyme Inhibited Sensor Array for Biothiol Detection and Disease Discrimination Based on Metal Ion-Doped Carbon Dots

Developing highly active and sensitive nanozymes for biothiol analysis is of vital significance due to their essential roles in disease diagnosis. Herein, two metal ion-doped carbon dots (M-CDs) with high peroxidase-like activity were designed and prepared for biothiol detection and identification through the colorimetric sensor array technique. The two M-CDs can strongly catalyze the decomposition of H₂O₂, accompanied by color changes of 3,3',5,5'-tetramethylbenzidine (TMB) from colorless to blue, indicating peroxidase-mimicking activities of M-CDs. Compared with pure carbon dots (CDs), M-CDs exhibited enhanced peroxidase-like activity owing to the synergistic effect between metal ions and CDs. However, due to the strong binding affinity between biothiols and metal ions, the catalytic activities of M-CDs could be inhibited by different biothiols to diverse degrees. Therefore, using TMB as a chromogenic substrate in the presence of H₂O₂, the developed colorimetric sensor array can form differential fingerprints for the three most important biothiols (i.e., cysteine (Cys), homocysteine (Hcy), and glutathione (GSH)), which can be accurately discriminated through pattern recognition methods (i.e., hierarchical clustering analysis (HCA) and principal component analysis (PCA)) with a detection limit of 5 nM. Moreover, the recognition of a single biothiol with various concentrations and biothiol mixtures was also realized. Furthermore, actual samples such as cells and sera can also be well distinguished by the as-fabricated sensor array, demonstrating its potential in disease diagnosis.