Technische Universität Darmstadt, Fachbereich Maschinenbau, Alarich-Weiss-Str. 10, 64287 Darmstadt, Germany.
Soft Matter. 2021 Apr 14;17(14):3929-3936. doi: 10.1039/d0sm01921f. Epub 2021 Mar 15.
The electric-field driven transport of proteins across the liquid-liquid interface in an aqueous two-phase system (ATPS) is studied in a microfluidic device using fluorescence microscopy. An ATPS containing polyethylene glycol (PEG) and dextran is employed, and bovine serum albumin (BSA) and bovine γ-globulins (BγG) are considered as model proteins. It is shown that both proteins, initially in the dextran-rich phase, accumulate at the liquid-liquid interface, preferably close to the three-phase contact line between the two liquid phases and the microchannel wall. It is in these regions where the proteins penetrate into the PEG-rich phase. The transport resistance of the liquid-liquid interface is higher for BγG than for BSA, such that a much larger molar flux of BSA into the PEG phase is observed. This opens up the opportunity of separating different protein species by utilizing differences in the transport resistance at the interface. A mathematical model is developed, accounting for adsorption and desorption processes at the liquid-liquid interface. The underlying theoretical concept is that of an electrostatic potential minimum formed by superposing the applied electric field and the field due to the Donnan potential at the interface. A fit of the model parameters to the experimental data results in good agreement between theory and experiments, thereby corroborating the underlying picture.
在微流控装置中使用荧光显微镜研究了在水相双相体系（ATPS）中电场驱动蛋白质穿过液-液界面的传输。使用含有聚乙二醇（PEG）和葡聚糖的 ATPS，牛血清白蛋白（BSA）和牛γ-球蛋白（BγG）被视为模型蛋白。结果表明，两种蛋白质最初都在葡聚糖丰富相中，在液-液界面处积累，优选靠近两相和微通道壁之间的三相接触线。正是在这些区域，蛋白质渗透到富含 PEG 的相中。与 BSA 相比，BγG 在液-液界面处的传输阻力更高，因此观察到 BSA 进入 PEG 相的摩尔通量要大得多。这为通过利用界面处的传输阻力差异来分离不同的蛋白质物种提供了机会。开发了一个数学模型，该模型考虑了在液-液界面处的吸附和解吸过程。基本理论概念是通过叠加施加的电场和界面处的Donnan 势场来形成静电势能最小值。模型参数与实验数据的拟合结果表明，理论与实验之间存在良好的一致性，从而证实了基本情况。
