Self-supplying of hydrogen peroxide nanozyme-based colorimetric sensing array as electronic tongue for biothiol...

Developing a highly reliably and sensitive nanozyme-based colorimetric sensor array for biothiols analysis is critical owing to they play an essential role in diagnosing disease. The required procedure of introducing hydrogen peroxide (H₂O₂) directly into the colorimetric reaction systems in traditional biothiols array analysis limits its applicability due to its poor stability and inhibition in biomolecular activity by using the high-concentration H₂O₂. Herein, we carried out a "green" and convenient approach to propose for the biothiol detection and disease discrimination through nanozymes-based colorimetric sensor technique without adding the high-concentration H₂O₂ for the first time. The copper peroxide nanodots (CPNs) and graphene oxide (GO) modified CPNs (GO@CPNs) are as sensing units to release H₂O₂ and Cu²⁺ under acidic conditions, which triggered a Fenton-like reaction, generating hydroxyl radical (•OH) to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) accompanied by a change in TMB color from colorless to blue. Due to the synergistic effect of Cu²⁺ and GO, GO@CPNs showed increased the activity of peroxidase-like compared to CPNs. Therefore, the catalytic abilities of nanozymes-based colorimetric sensing array were inhibited to different degrees by different biothiols (i.e., glutathione (GSH), cysteine (Cys) and homocysteine (Hcy)) with a detection limit of 50 nM, which could be precisely distinguished by using pattern recognition method. Besides, the detection of a single biothiol at different concentrations and mixtures of biothiols has also been achieved. Moreover, the real biological samples (cells and human serum) can be accurately discriminated through array method, which demonstrated its potential application of medical diagnosis.