We present a novel microfluidic paper-based analytical device (μPAD) which utilizes the native high electroosmotic flow (EOF) in nitrocellulose to achieve stationary isotachophoresis (ITP) focusing. This approach decouples sample accumulation from the length of the channel, resulting in significant focusing over short channel lengths. We provide a brief theory for EOF-balanced ITP focusing under continuous injection from a depleting reservoir and present the design of a short (7 mm) paper-based microfluidic channel, which allows a 200 μL sample to be processed in approximately 6 min, resulting in a 20 000-fold increase in concentration – a full order of magnitude improvement compared to previous paper-based ITP devices. We show the stability of the assay over longer (40 min) durations of time, and using Morpholino probes, we present the applicability of the device for amplification-free detection of nucleic acids, with a limit-of-detection (LoD) of 5 pM in 10 min. Finally, we utilize the small footprint of the channel and show a multiplexed platform in which 12 assays operate in parallel in a 24-well plate format.

中文翻译：

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使用电渗平衡的等速电泳在纸基微流控设备中进行DNA的无扩增检测†

我们提出了一种新颖的基于微流体纸的分析设​​备（μPAD），该设备利用了硝酸纤维素中的天然高电渗流（EOF）来实现固定的等速电泳（ITP）聚焦。这种方法使样品积累与通道长度脱钩，从而在短通道长度上获得了显着的聚焦。我们为从耗尽的油层连续注入下的EOF平衡ITP聚焦提供了简要的理论，并提出了一种短（7毫米）纸基微流体通道的设计，该通道可在大约6分钟内处理200μL样品，从而获得了浓度增加了2万倍–与以前的纸制ITP设备相比，整整提高了一个数量级。我们展示了在更长（40分钟）的时间内，使用Morpholino探针进行分析的稳定性，我们介绍了该设备用于无扩增核酸检测的适用性，在10分钟内检测限（LoD）为5 pM。最后，我们利用通道的小面积显示了一个多路复用平台，其中以24孔板形式并行进行12种测定。