This work outlines a simple fabricated microneedle electrode for sensitive and real sample monitoring of plant polyphenolics. The electrode was fabricated by layer-by-layer assembly (LBL) with nanocomposite of carbon nanotubes (CNT) and cellulose nanocrystals (CNC) as the first layer, followed by polyaniline (PANI), and finally, the 3-(glycidyloxypropyl)trimethoxysilane (GOPS) layer as the binding agent. The microneedle electrodes were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The developed microneedle electrodes were successfully applied for the capacitive detection of gallic acid (GA) and chlorogenic acid (CA) as polyphenol model compounds. The microneedle electrode was also used to quantify polyphenols in orange juice. The electrochemical capacitance responses were linearly proportional to the concentrations of GA and CA in the range of 0.1-87.23 μg/mL for GA and 0.1-78.01 μg/mL for CA. The calculated detection limits (LOD) for GA and CA were found to be 0.29 ± 0.2 μg/mL and 0.34 ± 0.2 μg/mL respectively. As minimally invasive technology, microneedle electrodes were found to be promising for successful in situ screening of antioxidants in different fruit matrices. The microneedle electrodes were also applied to the depth profiling of antioxidant content in fruit samples. Graphical abstract.

中文翻译：

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用于多酚检测的改性不锈钢微针电极。

这项工作概述了一种简单而精巧的微针电极，用于对植物多酚类物质进行敏感而真实的样品监测。该电极是通过以碳纳米管（CNT）和纤维素纳米晶体（CNC）的纳米复合材料为第一层，然后是聚苯胺（PANI），最后是3-（缩水甘油基氧丙基）三甲氧基硅烷的逐层组装（LBL）制造的（GOPS）层作为粘合剂。通过扫描电子显微镜（SEM），电化学阻抗谱（EIS），傅里叶变换红外（FTIR）光谱和拉曼光谱对微针电极进行表征。研制成功的微针电极已成功应用于多酚模型化合物没食子酸（GA）和绿原酸（CA）的电容检测。微针电极还用于定量橙汁中的多酚。电化学电容响应与GA和CA的浓度线性相关，GA的浓度范围为0.1-87.23μg/ mL，CA的浓度范围为0.1-78.01μg/ mL。发现GA和CA的计算检出限（LOD）分别为0.29±0.2μg/ mL和0.34±0.2μg/ mL。作为微创技术，发现微针电极有望成功地在不同水果基质中进行抗氧化剂的原位筛选。微针电极还用于水果样品中抗氧化剂含量的深度分析。图形概要。分别为2μg/ mL。作为微创技术，发现微针电极有望成功地在不同水果基质中进行抗氧化剂的原位筛选。微针电极还用于水果样品中抗氧化剂含量的深度分析。图形概要。分别为2μg/ mL。作为微创技术，发现微针电极有望成功地在不同水果基质中进行抗氧化剂的原位筛选。微针电极还用于水果样品中抗氧化剂含量的深度分析。图形概要。