University of California, Berkeley-University of California, San Francisco Graduate Program in Bioengineering, 342 Stanley Hall, Berkeley, California 94720, United States.
Anal Chem. 2012 Oct 16;84(20):8740-7. doi: 10.1021/ac301875e. Epub 2012 Sep 28.
In designing a protein electrophoresis platform composed of a single-inlet, single-outlet microchannel powered solely by voltage control (no pumps, values, injectors), we adapted the original protein electrophoresis format-moving boundary electrophoresis (MBE)-to a high-performance, compact microfluidic format. Key to the microfluidic adaptation is minimization of injection dispersion during sample injection. To reduce injection dispersion, we utilize a photopatterned free-solution-polyacrylamide gel (PAG) stacking interface at the head of the MBE microchannel. The nanoporous PAG molecular sieve physically induces a mobility shift that acts to enrich and sharpen protein fronts as proteins enter the microchannel. Various PAG configurations are characterized, with injection dispersion reduced by up to 85%. When employed for analysis of a model protein sample, microfluidic PAG MBE baseline-resolved species in 5 s and in a separation distance of less than 1 mm. PAG MBE thus demonstrates electrophoretic assays with minimal interfacing and sample handling, while maintaining separation performance. Owing to the short separation lengths needed in PAG MBE, we reduced the separation channel length to demonstrate an electrophoretic immunoassay powered with an off-the-shelf 9 V battery. The electrophoretic immunoassay consumed less than 3 μW of power and was completed in 30 s. To our knowledge, this is the lowest voltage and lowest power electrophoretic protein separation reported. Looking forward, we see the low-power PAG MBE as a basis for highly multiplexed protein separations (mobility shift screening assays) as well as for portable low-power diagnostic assays.
在设计由单入口、单出口微通道组成的蛋白质电泳平台时，我们仅通过电压控制（无泵、阀、注射器）来驱动，从而将原始的蛋白质电泳格式——移动边界电泳（MBE）——应用于高性能、紧凑的微流控格式。微流控适应的关键是在样品注入过程中最小化注入分散。为了减少注入分散，我们在 MBE 微通道的头部利用光图案化的自由溶液聚丙烯酰胺凝胶（PAG）堆积界面。纳米多孔 PAG 分子筛物理上引起迁移率变化，当蛋白质进入微通道时，这种变化会浓缩和锐化蛋白质前沿。对各种 PAG 配置进行了表征，注入分散度降低了多达 85%。当用于分析模型蛋白质样品时，微流控 PAG MBE 在 5 秒内和不到 1 毫米的分离距离内基线分辨物种。因此，PAG MBE 展示了具有最小接口和样品处理的电泳分析，同时保持分离性能。由于 PAG MBE 中需要较短的分离长度，我们将分离通道长度缩短，以展示使用现成的 9 V 电池供电的电泳免疫分析。电泳免疫分析消耗的功率小于 3 μW，完成时间为 30 秒。据我们所知，这是报告的最低电压和最低功率电泳蛋白质分离。展望未来，我们认为低功率 PAG MBE 可作为高度多重蛋白质分离（迁移率变化筛选分析）以及便携式低功率诊断分析的基础。
