Sista Ramakrishna S, Eckhardt Allen E, Srinivasan Vijay, Pollack Michael G, Palanki Srinivas, Pamula Vamsee K
Advanced Liquid Logic, Inc., Research Triangle Park, NC 27709, USA.
Lab Chip. 2008 Dec;8(12):2188-96. doi: 10.1039/b807855f. Epub 2008 Oct 14.
A digital microfluidic platform for performing heterogeneous sandwich immunoassays based on efficient handling of magnetic beads is presented in this paper. This approach is based on manipulation of discrete droplets of samples and reagents using electrowetting without the need for channels where the droplets are free to move laterally. Droplet-based manipulation of magnetic beads therefore does not suffer from clogging of channels. Immunoassays on a digital microfluidic platform require the following basic operations: bead attraction, bead washing, bead retention, and bead resuspension. Several parameters such as magnetic field strength, pull force, position, and buffer composition were studied for effective bead operations. Dilution-based washing of magnetic beads was demonstrated by immobilizing the magnetic beads using a permanent magnet and splitting the excess supernatant using electrowetting. Almost 100% bead retention was achieved after 7776-fold dilution-based washing of the supernatant. Efficient resuspension of magnetic beads was achieved by transporting a droplet with magnetic beads across five electrodes on the platform and exploiting the flow patterns within the droplet to resuspend the beads. All the magnetic-bead droplet operations were integrated together to generate standard curves for sandwich heterogeneous immunoassays on human insulin and interleukin-6 (IL-6) with a total time to result of 7 min for each assay.
本文介绍了一种基于对磁珠的高效处理来进行异质夹心免疫分析的数字微流控平台。该方法基于利用电润湿对样品和试剂的离散液滴进行操控，无需通道，液滴可在其中自由横向移动。因此，基于液滴的磁珠操控不会出现通道堵塞问题。在数字微流控平台上进行免疫分析需要以下基本操作：磁珠吸引、磁珠洗涤、磁珠保留和磁珠重悬。为了实现有效的磁珠操作，研究了诸如磁场强度、拉力、位置和缓冲液成分等几个参数。通过使用永久磁铁固定磁珠并利用电润湿分离多余的上清液，证明了基于稀释的磁珠洗涤方法。对上清液进行7776倍基于稀释的洗涤后，实现了近100%的磁珠保留。通过在平台上的五个电极上运输带有磁珠的液滴，并利用液滴内的流动模式使磁珠重悬，实现了磁珠的高效重悬。所有磁珠液滴操作整合在一起，生成了人胰岛素和白细胞介素-6（IL-6）夹心异质免疫分析的标准曲线，每次分析获得结果的总时间为7分钟。
