Fan Xiao, Zhang Xiaoyu, Ping Jinglei
Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
Institute of Applied Life Sciences, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
ACS Nano. 2022 Jul 26;16(7):10852-10858. doi: 10.1021/acsnano.2c03054. Epub 2022 Jun 17.
Transverse isoelectric focusing, i.e., isoelectric focusing that is normal to the fluid-flow direction, is an electrokinetic method ideal for micro total analysis. However, a major challenge remains: There is no electrode system integrable in a microfluidic device to allow reliable transverse isoelectric focusing and electrokinetic sensing. Here, we overcome this barrier by developing devices that incorporate microelectrodes made of monolayer graphene. We find that the electrolysis stability over time for graphene microelectrodes is >10× improved compared to typical microfabricated inert-metal microelectrodes. Through transverse isoelectric focusing between graphene microelectrodes, within minutes, specific proteins can be separated and concentrated to scales of ∼100 μm. Based on the concentrating effect and the high optical transparency of graphene, we develop a three-dimensional multistream microfluidic strategy for label-free detection of the proteins at same processing position with a sensitivity that is ∼10× higher than those of the state-of-the-art label-free sensors. These results demonstrate the advantage of monolayer-graphene microelectrodes for high-performance electrokinetic analysis to allow lab-on-a-chips of maximal time and size efficiencies.
横向等电聚焦，即垂直于流体流动方向的等电聚焦，是一种适用于微全分析的电动方法。然而，一个主要挑战仍然存在：在微流控装置中没有可集成的电极系统来实现可靠的横向等电聚焦和电动传感。在此，我们通过开发包含由单层石墨烯制成的微电极的装置克服了这一障碍。我们发现，与典型的微加工惰性金属微电极相比，石墨烯微电极随时间的电解稳定性提高了10倍以上。通过石墨烯微电极之间的横向等电聚焦，在几分钟内，特定蛋白质可被分离并浓缩至约100μm的尺度。基于石墨烯的浓缩效应和高光学透明度，我们开发了一种三维多流微流控策略，用于在同一处理位置对蛋白质进行无标记检测，其灵敏度比最先进的无标记传感器高约10倍。这些结果证明了单层石墨烯微电极在高性能电动分析方面的优势，可实现具有最大时间和尺寸效率的芯片实验室。
