Numerical-Simulation-Based Buffer Design for Microchip Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

IF 5.5 3区工程技术 Q1 BIOCHEMICAL RESEARCH METHODS BioChip Journal Pub Date : 2024-01-03 DOI:10.1007/s13206-023-00135-x

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Abstract

We present a numerical simulation method for designing a buffer system in microchip electrophoresis (MCE) equipped with capacitively-coupled-contactless-conductivity detection (C4D). One of the key design considerations for MCE-C4D is background electrolyte (BGE). This is because a C4D typically exhibits low sensitivity, and optimizing BGE conditions (e.g., base and acid species, pH, and ionic strength) can improve its sensitivity. However, BGE has been traditionally designed through experience or trial and error, which is time- and reagent-consuming. In this study, we employ Simul 5, an open-source electrophoresis simulation software, for rational BGE design. Four BGEs including trimethylamine (TEA)/acetic acid (AcOH, pH 10.6), MES/His (pH 6.1), MES/TRIS (pH 8.1), and TRIS/HCl (pH 7.4), previously used in electrophoresis-C4D of amino acids and protein, were selected for evaluation of our numerical method. Glutamic acid (Glu) was selected as a model analyte for initial simulation verification. Our numerical simulation revealed that the best achievable detection sensitivity was 1.046 × 10^–5 S/(m µM) in the TRIS/HCl buffer because anionic Glu species with a low mobility (27 × 10^–9 m²/Vs) replaced Cl⁻ co-ion of a high mobility (79.1 × 10^–9 m²/Vs) in the analyte zone, leading to a significant negative conductivity peak. TEA/AcOH, MES/His, and MES/TRIS buffers exhibited progressively lower sensitivity. After the initial evaluation, trypsin inhibitor (TI), a more complex proteinous analyte was tested in the MES/His and MES/TRIS BGEs. The best detection sensitivity was 1.032 × 10^–4 S/(m µM) in the MES/TRIS buffer because counter-ionic species TRIS⁺ of a high mobility (29.5 × 10^–9 m²/Vs) was replaced by the ionic TI, characterized by a large charge (− 11.5) and a low mobility (8.08 × 10^–9 m²/Vs), resulting in a strong negative peak. Based on a comprehensive analysis of the impacts of compositional changes in each ionic species of the analyte zone on conductivity-peak height, we propose a BGE design guideline for enhanced sensitivity. Subsequent MCE-C4D confirmation experiments demonstrated excellent qualitative agreement with the simulation results for the Glu and TI analytes. We anticipate that our numerical analysis method will find wide application in designing BGEs for portable MCE-C4D systems by enhancing sensitivity.

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基于数值模拟的微芯片电泳缓冲器设计与电容耦合非接触式电导检测

摘要我们提出了一种数值模拟方法，用于设计配备电容耦合无触点电导检测（C4D）的微芯片电泳（MCE）缓冲系统。MCE-C4D 的关键设计因素之一是背景电解质 (BGE)。这是因为 C4D 通常灵敏度较低，而优化 BGE 条件（如碱和酸种类、pH 值和离子强度）可以提高灵敏度。然而，传统的 BGE 设计是通过经验或反复试验来实现的，这既耗时又耗费试剂。本研究采用开源电泳模拟软件 Simul 5 对 BGE 进行合理设计。我们选择了以前用于氨基酸和蛋白质电泳-C4D 的四种 BGE 进行评估，包括三甲胺（TEA）/乙酸（AcOH，pH 10.6）、MES/His（pH 6.1）、MES/TRIS（pH 8.1）和 TRIS/HCl（pH 7.4）。谷氨酸（Glu）被选为模型分析物，用于初步模拟验证。我们的数值模拟结果表明，在 TRIS/HCl 缓冲液中，可达到的最佳检测灵敏度为 1.046 × 10-5 S/(m µM)，这是因为在分析物区域，低迁移率（27 × 10-9 m2/Vs）的阴离子 Glu 取代了高迁移率（79.1 × 10-9 m2/Vs）的 Cl-共离子，从而导致了一个显著的负电导峰。TEA/AcOH、MES/His 和 MES/TRIS 缓冲液的灵敏度逐渐降低。经过初步评估后，又在 MES/His 和 MES/TRIS BGE 中测试了胰蛋白酶抑制剂（TI）这种更复杂的蛋白质分析物。在 MES/TRIS 缓冲液中，最佳检测灵敏度为 1.032 × 10-4 S/(m µM)，这是因为高迁移率（29.5 × 10-9 m2/Vs）的反离子物种 TRIS+ 被离子型 TI 取代，TI 的特点是电荷量大（- 11.5）、迁移率低（8.08 × 10-9 m2/Vs），从而产生了一个强烈的负峰。在全面分析分析区各离子种类的组成变化对电导率-峰高的影响的基础上，我们提出了一个提高灵敏度的 BGE 设计指南。随后进行的 MCE-C4D 确认实验表明，Glu 和 TI 分析物的质量与模拟结果非常吻合。我们预计，通过提高灵敏度，我们的数值分析方法将在便携式 MCE-C4D 系统的 BGE 设计中得到广泛应用。

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来源期刊

BioChip Journal 生物-生化研究方法

CiteScore

7.70

自引率

16.30%

发文量

审稿时长

6-12 weeks

期刊介绍： BioChip Journal publishes original research and reviews in all areas of the biochip technology in the following disciplines, including protein chip, DNA chip, cell chip, lab-on-a-chip, bio-MEMS, biosensor, micro/nano mechanics, microfluidics, high-throughput screening technology, medical science, genomics, proteomics, bioinformatics, medical diagnostics, environmental monitoring and micro/nanotechnology. The Journal is committed to rapid peer review to ensure the publication of highest quality original research and timely news and review articles.