Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
ACS Nano. 2011 Oct 25;5(10):7775-80. doi: 10.1021/nn2030379. Epub 2011 Sep 14.
Here we report that nanopillar array structures have an intrinsic ability to suppress electroosmotic flow (EOF). Currently using glass chips for electrophoresis requires laborious surface coating to control EOF, which works as a counterflow to the electrophoresis mobility of negatively charged samples such as DNA and sodium dodecyl sulfate (SDS) denatured proteins. Due to the intrinsic ability of the nanopillar array to suppress the EOF, we carried out electrophoresis of SDS-protein complexes in nanopillar chips without adding any reagent to suppress protein adsorption and the EOF. We also show that the EOF profile inside a nanopillar region was deformed to an inverse parabolic flow. We used a combination of EOF measurements and fluorescence observations to compare EOF in microchannel, nanochannel, and nanopillar array chips. Our results of EOF measurements in micro- and nanochannel chips were in complete agreement with the conventional equation of the EOF mobility (μ(EOF-channel) = αC(i)(-0.5), where C(i) is the bulk concentration of the i-ions and α differs in micro- and nanochannels), whereas EOF in the nanopillar chips did not follow this equation. Therefore we developed a new modified form of the conventional EOF equation, μ(EOF-nanopillar) ≈ β[C(i) - (C(i)(2)/N(i))], where N(i) is the number of sites available to i-ions and β differs for each nanopillar chip because of different spacings or patterns, etc. The modified equation of the EOF mobility that we proposed here was in good agreement with our experimental results. In this equation, we showed that the charge density of the nanopillar region, that is, the total number of nanopillars inside the microchannel, affected the suppression of EOF, and the arrangement of nanopillars into a tilted or square array had no effect on it.
我们在此报告，纳米柱阵列结构具有内在的抑制电动流（EOF）的能力。目前使用玻璃芯片进行电泳需要费力的表面涂层来控制 EOF，EOF 作为一种与带负电荷的样品（如 DNA 和十二烷基硫酸钠（SDS）变性蛋白质）电泳迁移率相反的逆流。由于纳米柱阵列具有抑制 EOF 的内在能力，我们在纳米柱芯片中进行 SDS-蛋白质复合物的电泳，而无需添加任何抑制蛋白质吸附和 EOF 的试剂。我们还表明，纳米柱区域内的 EOF 轮廓变形为反向抛物线流。我们使用 EOF 测量和荧光观察的组合来比较微通道、纳米通道和纳米柱阵列芯片中的 EOF。我们在微通道和纳米通道芯片中的 EOF 测量结果与 EOF 迁移率的常规方程（μ（EOF-channel）=αC（i）（-0.5）完全一致，其中 C（i）是 i-离子的体相浓度，α 在微通道和纳米通道中不同），而 EOF 在纳米柱芯片中不遵循该方程。因此，我们开发了传统 EOF 方程的一种新的修正形式，μ（EOF-nanopillar）≈β[C（i）-（C（i）（2）/N（i））]，其中 N（i）是 i-离子可用的位点数，并且由于每个纳米柱芯片的间距或图案等不同，β 也不同。我们提出的 EOF 迁移率修正方程与我们的实验结果非常吻合。在该方程中，我们表明纳米柱区域的电荷密度，即微通道内的纳米柱总数，影响 EOF 的抑制，而纳米柱排列成倾斜或正方形阵列对其没有影响。
