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A novel sensor array was developed based on the enzyme/nanozyme hybridization for the identification of tea polyphenols (TPs) and Chinese teas. The enzyme/nanozyme with polyphenol oxidase activity can catalyze the reaction between TPs and 4-aminoantipyrine (4-AAP) to produce differences in color, and the sensor array was thus constructed to accurately identify TPs mixed in different species, concentrations, or ratios. In addition, a machine learning based dual output model was further used to effectively predict the classes and concentrations of unknown samples. Therefore, the qualitative and quantitative detection of TPs can be realized continuously and quickly. Furthermore, the sensor array combining the machine learning based dual output model was also utilized for the identification of Chinese teas. The method can distinguish the six teas series in China, and then precisely differentiate the more specific tea varieties. This study provides an efficient and facile strategy for the identification of teas and tea products. [Display omitted] • A novel sensor array was developed based on the enzyme/nanozyme hybridization. • Six TPs in Chinese tea were successfully distinguished. • Effective identification of six major teas series and more specific 17 tea varieties. • Machine learning based dual output model for TPs' qualitation and quantitation. • Machine learning based dual output model for identifying tea samples. [ABSTRACT FROM AUTHOR]

In this work, 2-methylimidazole (MI) was doped into the Bpy-Cu nanozyme as a second ligand to form a novel laccase-mimicking enzyme (MI-Bpy-Cu). By comparison, MI-Bpy-Cu nanozyme was identified to have excellent laccase-mimicking activity, high stability and catalytic kinetic properties. It may be that the incorporation of 2-methylimidazole helped the nanozymes to build a structure closer to natural laccase and accelerate the electron transfer rate, thereby achieving the purpose of enhancing the activity. Furthermore, we observed that MI-Bpy-Cu nanozymes could oxidize the colorless (+)-Catechin to generate a yellow radical product, and a novel colorimetric sensing strategy for (+)-Catechin was successfully developed. The method had excellent selectivity and anti-interference properties, and also had good application in the analysis of (+)-Catechin in dairy products. [Display omitted] • The 2-methylimidazole was first incorporated as a second ligand to enhance the activity of laccase-mimicking enzymes. • The nanozyme was modified close to the natural laccase composition. • The colorimetric method was successfully established for the analysis of (+)-Catechin in dairy products. • The method has high selectivity and interference resistance. [ABSTRACT FROM AUTHOR]

A selective and sensitive colorimetric strategy for sulfide analysis was developed using GMP-Cu nanozymes with a laccase-like activity. This research discovered for the first time that sulfide could significantly enhance the catalytic activity of the GMP-Cu nanozymes by about 3.5 folds. The enhanced laccase activities duo to two reasons. First, Cu2+ in GMP-Cu nanozymes was reduced to Cu+. The other reason was the formation of Cu–S bond which was beneficial to accelerate the electron transfer rate to improve catalytic activity. Therefore, this method showed an excellent selectivity for sulfide. And it had a linear relationship in the sulfide concentration range of 0–220 μmol/L with a detection limit of 0.67 μmol/L. Furthermore, the proposed method was successfully applied to examine sulfide in the food systems. This new method may be used in sulfide detection to improve food quality and safety. [Display omitted] • A method of sulfide detection based on Cu-Nucleotide nanozymes with laccase-like activity is first constructed. • The catalytic activity of nanozymes is enhanced by bifunctional sulfide accelerating the electron transfer rate. • This study develops a facile sensing method for the detection of sulfide in food system. • The sensor detects sufide with good selectivity and sensitivity. [ABSTRACT FROM AUTHOR]