Single-nanozyme single-readout enabled efficient identification of polyphenols for Chinese tea authentication and brewing evaluation

Abstract

With the popularity of health-conscious tea drinking, precise sensing of polyphenols as a main class of antioxidants in tea becomes critical for tea authentication and brewing evaluation. Sensor arrays show great potential for the goal, but currently available sensor arrays always need multiple sensing units and/or multi-dimensional signals, resulting in cumbersome sensor construction and operation as well as data processing. Developing easy-to-fabricate and easy-to-use sensor arrays for efficient discrimination is still challenging. Here we propose a new sensor array that only uses a single signal collected dynamically with oxidase-like MnOOH as a sole sensing material. The synthesized MnOOH nanowires exhibit favorable activity to catalyze the chromogenic oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB. By taking gallic acid, tannic acid, L-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate as models, the six tea polyphenols show discrepant inhibitory effects on the above catalytic system. As a result, these polyphenols, no matter as a single component at various concentrations or multi-component mixtures with different ratios, can be well distinguished by the single-nanozyme single-readout sensor array. Besides, different Chinese tea species, black tea varieties and impacts of brewing methods are accurately identified. Evidently, our sensor array avoids the requirement for multiple sensing units and multi-dimensional signals, greatly simplifying the fabrication of sensor arrays and their use, which provides an efficient yet facile tool for tea authentication and brewing evaluation.

Keywords: Nanozyme; Sensor array; Tea authentication; Tea brewing evaluation; Tea polyphenol.