Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Lab Chip. 2011 Dec 7;11(23):4036-40. doi: 10.1039/c1lc20600a. Epub 2011 Oct 14.
We report a novel DNA separation method by tethering DNA chains to a solid surface and then stretching the DNA chains with an electric field. The anchor is such designed that the critical force to detach a DNA chain is independent of its size. Because the stretching force is proportional to the DNA net charge, a gradual increase of the electric field leads to size-based removal of the DNA strands from the surface and thus DNA separation. Here we show that this method, originally proposed for separation of long double-stranded DNA chains (>10,000 base pairs), is also applicable to single-stranded (ss) DNA fragments with less than 100 nucleotides (nt). Theoretical analysis indicates that the separation resolution is limited by the fluctuation forces on tethered DNA chains. By employing a microfluidic platform with narrow channels filled with a buffer of low ionic conductivity, we are able to apply a strong electric field to the DNA fragments with negligible Joule heating. Upon stepwise increments of the electric field, we demonstrate efficient separation of short ssDNA fragments at a 10-nt resolution.
我们报告了一种通过将 DNA 链固定在固体表面上并使用电场拉伸 DNA 链来分离 DNA 的新方法。该锚的设计使得分离 DNA 链的临界力与其大小无关。由于拉伸力与 DNA 的净电荷成正比，因此电场的逐渐增加会导致 DNA 链从表面上按大小顺序去除，从而实现 DNA 分离。在这里，我们表明，这种最初用于分离长双链 DNA 链（> 10,000 个碱基对）的方法也适用于小于 100 个核苷酸（nt）的单链（ss）DNA 片段。理论分析表明，分离分辨率受固定化 DNA 链上的波动力限制。通过采用填充低离子电导率缓冲液的狭窄通道的微流控平台，我们能够对 DNA 片段施加强电场，而焦耳加热可忽略不计。通过逐步增加电场，我们在 10-nt 的分辨率下证明了短 ssDNA 片段的有效分离。
