Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
Anal Methods. 2020 Nov 21;12(43):5177-5185. doi: 10.1039/d0ay01523g. Epub 2020 Oct 19.
Microfluidic magnetophoresis is a powerful technique that is used to separate and/or isolate cells of interest from complex matrices for analysis. However, mechanical pumps are required to drive flow, limiting portability and making translation to point-of-care (POC) settings difficult. Microfluidic paper-based analytical devices (μPADs) offer an alternative to traditional microfluidic devices that do not require external pumps to generate flow. However, μPADs are not typically used for particle analysis because most particles become trapped in the porous fiber network. Here we report the ability of newly developed fast-flow microfluidic paper-based analytical devices (ffPADs) to perform magnetophoresis. ffPADs use capillary action in a gap between stacked layers of paper and transparency sheets to drive flow at higher velocities than traditional μPADs. The multi-layer ffPADs allow particles and cells to move through the gap without being trapped in the paper layers. We first demonstrate that ffPADs enable magnetic particle separations in a μPAD with a neodymium permanent magnet and study key factors that affect performance. To demonstrate utility, E. coli was used as a model analyte and was isolated from human urine before detection with a fluorescently labeled antibody. A capture efficiency of 61.5% was then obtained of E. coli labeled magnetic beads in human urine. Future studies will look at the improvement of the capture efficiency and to make this assay completely off-chip without the need of a fluorescent label. The assay and device described here demonstrate the first example of magnetophoresis in a paper based, pump free microfluidic device.
微流控磁泳是一种强大的技术，用于从复杂基质中分离和/或分离有兴趣的细胞进行分析。然而，需要机械泵来驱动流动，这限制了其便携性，使得难以将其转化为即时护理（POC）环境。微流控纸基分析器件（μPADs）提供了一种替代传统微流控器件的方法，传统微流控器件不需要外部泵来产生流动。然而，μPADs 通常不用于颗粒分析，因为大多数颗粒会被困在多孔纤维网络中。在这里，我们报告了新开发的快速流动微流控纸基分析器件（ffPADs）进行磁泳的能力。ffPADs 使用堆叠纸层和透明片之间的间隙中的毛细作用以比传统 μPADs 更高的速度驱动流动。多层 ffPADs 允许颗粒和细胞通过间隙移动而不会被困在纸层中。我们首先证明 ffPADs 可以在使用钕永久磁铁的 μPAD 中实现磁性颗粒分离，并研究了影响性能的关键因素。为了证明其用途，我们使用大肠杆菌作为模型分析物，并在使用荧光标记抗体进行检测之前从人尿中分离出来。然后，在人尿中获得了大肠杆菌标记的磁性珠的捕获效率为 61.5％。未来的研究将着眼于提高捕获效率，并使该测定完全在没有荧光标记的情况下在芯片外进行。这里描述的测定和器件展示了基于纸张的无泵微流控器件中磁泳的第一个实例。
