Out-of-plane faradaic ion concentration polarization: stable focusing of charged analytes at a three-dimensional porous electrode
Out-of-plane faradaic ion concentration polarization: stable focusing of charged analytes at a three-dimensional porous electrode
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DOI：
10.1039/d1lc01011e
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发表时间：
2022-01-04
期刊：
影响因子：
6.1
通讯作者：
Anand, Robbyn K.
中科院分区：
文献类型：
--
作者：
Berzina, Beatrise;Kim, Sungu;Anand, Robbyn K.
离子浓差极化 (ICP) 通过局部消耗电解质离子来实现生物分析的预浓缩，从而产生电场强度梯度，通过带电分析物相对于相反流体流动的电迁移，促进带电分析物的动电聚焦。这种 ICP 聚焦已被证明可以在单级预浓缩器中实现核酸和蛋白质高达百万倍的富集。然而，样品体积的扫掠速率是有限的，需要几个小时才能实现这些高富集因子。这种限制是由两个因素造成的。首先，在平面膜或电极处形成的离子耗尽区(IDZ)在用于聚焦的流速下可能不会延伸穿过整个通道横截面，从而允许分析物“泄漏”通过IDZ。其次，在 IDZ 内，大的流体涡流会导致混合，从而降低分析物富集的效率，并且随着通道尺寸的增加而恶化。在这里，我们通过法拉第 ICP (fICP) 在包含金属微珠的三维 (3D) 电极上解决这些挑战。该 3D 电极分布 IDZ，因此，用于逆流聚焦的电场梯度分布在流体通道的整个高度上，并且其大面积微结构表面支持较小的涡流。额外的绝缘微珠床限制了流动模式，并为离子通过 IDZ 的表面传导提供了大面积。最后，该次生床的阻力通过局部加强隔离力来增强聚焦。这个易于构建的平台为富集与用户定义的填充床和电极材料的集成奠定了基础。
Ion concentration polarization (ICP) accomplishes preconcentration for bioanalysis by localized depletion of electrolyte ions, thereby generating a gradient in electric field strength that facilitates electrokinetic focusing of charged analytes by their electromigration against opposing fluid flow. Such ICP focusing has been shown to accomplish up to a million-fold enrichment of nucleic acids and proteins in single-stage preconcentrators. However, the rate at which the sample volume is swept is limited, requiring several hours to achieve these high enrichment factors. This limitation is caused by two factors. First, an ion depleted zone (IDZ) formed at a planar membrane or electrode may not extend across the full channel cross section under the flow rate employed for focusing, thereby allowing the analyte to "leak" past the IDZ. Second, within the IDZ, large fluid vortices lead to mixing, which decreases the efficiency of analyte enrichment and worsens with increased channel dimensions. Here, we address these challenges with faradaic ICP (fICP) at a three-dimensional (3D) electrode comprising metallic microbeads. This 3D-electrode distributes the IDZ, and therefore, the electric field gradient utilized for counter-flow focusing across the full height of the fluidic channel, and its large area, microstructured surface supports smaller vortices. An additional bed of insulating microbeads restricts flow patterns and supplies a large area for surface conduction of ions through the IDZ. Finally, the resistance of this secondary bed enhances focusing by locally strengthening sequestering forces. This easy-to-build platform lays a foundation for the integration of enrichment with user-defined packed bed and electrode materials.