Wijesinghe Manjula B, Warnakula Indika K, Gunasekara Dulan B, Lunte Susan M
Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA.
Department of Chemistry, Faculty of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka.
Sens Actuators Rep. 2025 Jun;9. doi: 10.1016/j.snr.2025.100283. Epub 2025 Jan 14.
Microchip electrophoresis (ME) is a separation method that makes it possible to quickly analyze multiple species in small volume samples in a miniaturized format. Two commonly employed detection approaches for ME are electrochemistry and fluorescence. Electrochemical detection can be employed for direct detection of analytes via redox chemistry, while fluorescence generally offers lower limits of detection but often requires analyte derivatization. The present study uses bipolar electrochemistry to couple the two detection methods into a single device as a detector for that encompasses the advantages of both techniques. This system employs a closed bipolar electrode (BPE) that converts the cathodic amperometric current produced at the separation (sensing) pole to a fluorescence response generated at the reporting pole. Two model analytes, benzoquinone and resazurin, were separated and detected using ME with reductive amperometric detection at the sensing pole of the BPE. A potentiostat was used to control the bipolar electrode. The response was then converted to fluorescence through the oxidation of 2,7-dichlorodihydrofluorescein in the reporting channel. This system was subsequently modified to run without a potentiostat by using the separation voltage to bias the BPE sensing pole. A voltage applied across the reporting channel was used to generate electroosmotic flow as well as bias the corresponding pole of the BPE. This potentiostat-free mode was evaluated for the determination of 3-nitro-l-tyrosine, a reducible biomarker of oxidative stress. Lastly, a sacrificial electrochemically active species, Trolox, was incorporated into the reporting channel to compensate for background current at the sensing channel and lower the limits of detection.
微芯片电泳（ME）是一种分离方法，它能够以小型化形式快速分析小体积样品中的多种物质。ME常用的两种检测方法是电化学检测和荧光检测。电化学检测可通过氧化还原化学用于直接检测分析物，而荧光检测通常具有较低的检测限，但往往需要对分析物进行衍生化处理。本研究采用双极电化学将这两种检测方法结合到一个单一装置中，作为一种检测器，兼具了两种技术的优点。该系统采用封闭双极电极（BPE），将在分离（传感）极产生的阴极安培电流转换为在报告极产生的荧光响应。使用ME在BPE的传感极进行还原安培检测，对两种模型分析物苯醌和刃天青进行了分离和检测。使用恒电位仪控制双极电极。然后通过报告通道中2,7 - 二氯二氢荧光素的氧化将响应转换为荧光。随后对该系统进行了改进，通过使用分离电压对BPE传感极施加偏压，使其无需恒电位仪即可运行。施加在报告通道两端的电压用于产生电渗流以及对BPE的相应极施加偏压。对这种无恒电位仪模式进行了评估，用于测定3 - 硝基 - L - 酪氨酸，一种氧化应激的可还原生物标志物。最后，将一种牺牲性电化学活性物质生育三烯酚（Trolox）加入到报告通道中，以补偿传感通道的背景电流并降低检测限。
