BioMEMS Laboratory, Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey 08854, USA.
Lab Chip. 2012 Jan 7;12(1):99-108. doi: 10.1039/c1lc20605b. Epub 2011 Nov 1.
Sample pre-concentration can be a critical element to improve sensitivity of integrated microchip assays. In this work a converging Y-inlet microfluidic channel with integrated coplanar electrodes was used to investigate transverse DNA and protein migration under uniform direct current (DC) electric fields to assess the ability to concentrate a sample prior to other enzymatic modifications or capillary electrophoretic separations. Employing a pressure-driven flow to perfuse the microchannel, negatively charged samples diluted in low and high ionic strength buffers were co-infused with a receiving buffer of the same ionic strength into a main daughter channel. Experimental results demonstrated that, depending of the buffer selection, different DNA migration and accumulation dynamics were seen. Charged analytes could traverse the channel width and accumulate at the positive bias electrode in a low electroosmotic mobility, high electrophoretic mobility, high ionic strength buffer or migrated towards an equilibrium position within the channel in a high electroosmotic mobility, high electrophoretic mobility, low ionic strength buffer. The various migration behaviours are the result of a balance between the electrophoretic force and a drag force induced by a recirculating electroosmotic flow generated across the channel width due to the bounding walls. Under continuous flow conditions, DNA samples were concentrated several-fold by balancing these transverse electrokinetic forces. The electrokinetic trapping technique presented here is a simple technique which could be expanded to concentrate or separate other analytes as a preconditioning step for downstream processes.
样品预浓缩可以是提高集成微芯片分析灵敏度的关键因素。在这项工作中，采用具有集成共面电极的会聚 Y 型入口微流道来研究在均匀直流 (DC) 电场下横向 DNA 和蛋白质的迁移，以评估在其他酶修饰或毛细管电泳分离之前浓缩样品的能力。采用压力驱动的流动来灌注微通道，将在低离子强度和高离子强度缓冲液中稀释的带负电荷的样品与具有相同离子强度的接收缓冲液一起共注入主支流道中。实验结果表明，根据缓冲液的选择，可以看到不同的 DNA 迁移和积累动力学。带电荷的分析物可以穿过通道宽度，并在低电渗流迁移率、高电泳迁移率、高离子强度缓冲液中在正偏压电极处积累，或者在高电渗流迁移率、高电泳迁移率、低离子强度缓冲液中在通道内迁移到平衡位置。各种迁移行为是电泳力和由于边界壁在整个通道宽度上产生的循环电渗流引起的阻力之间平衡的结果。在连续流动条件下，通过平衡这些横向电动力量，可以将 DNA 样品浓缩数倍。这里提出的电动捕获技术是一种简单的技术，可以扩展为浓缩或分离其他分析物，作为下游过程的预处理步骤。
