Khairulina Kateryna, Chung Ung-Il, Sakai Takamasa
Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Mater Chem B. 2017 Jun 21;5(23):4526-4534. doi: 10.1039/c7tb00064b. Epub 2017 May 16.
Electro-osmosis is the bulk fluid flow of electrolyte solution generated by an electric field in contact with charged immobile objects, such as the surface of polymer gels. Electro-osmosis may be used to assist in analytical separation, and plays an important role in biological tissues. Despite its importance, the contribution of electro-osmosis to the overall solute transport has never been fully understood because of the complexity of the biological systems. To understand the electro-osmosis, a model system with controlled charge density, charge composition and stiffness is necessary. In this paper, we propose a new design of a gel-based system (tetra-PEG gel) with well controlled electro-osmotic properties. Tetra-PEG gels are formed by two four-armed poly(ethylene)glycol units with mutually reactive end groups, allowing the introduction of positive or negative charges by variation in the monomer stoichiometric ratio. Using this system, we for the first time succeeded in preparing a series of hydrogels with precisely and independently tuned charge densities and stiffness. Electro-osmotic flows of these gels were distinctly different from each other, and varied linearly with the total charge amount. Interestingly, a hydrogel with the same amount of positive and negative charges did not show any electro-osmotic flow. Our new hydrogel system provides an important basis for understanding the electro-osmotic flow as an additional mechanism in mass transport and will find use in biomaterials and analytical separations, and as a model system for biological tissues.
电渗是指在与带电固定物体（如聚合物凝胶表面）接触的电场作用下，电解质溶液产生的整体流体流动。电渗可用于辅助分析分离，在生物组织中发挥着重要作用。尽管其很重要，但由于生物系统的复杂性，电渗对整体溶质传输的贡献尚未得到充分理解。为了理解电渗，需要一个具有可控电荷密度、电荷组成和刚度的模型系统。在本文中，我们提出了一种基于凝胶的系统（四聚乙二醇凝胶）的新设计，该系统具有良好控制的电渗特性。四聚乙二醇凝胶由两个带有相互反应端基的四臂聚（乙二醇）单元形成，通过改变单体化学计量比可以引入正电荷或负电荷。利用这个系统，我们首次成功制备了一系列电荷密度和刚度可精确且独立调节的水凝胶。这些凝胶的电渗流彼此明显不同，并且随总电荷量呈线性变化。有趣的是，具有相同数量正电荷和负电荷的水凝胶没有显示出任何电渗流。我们的新型水凝胶系统为理解电渗流作为质量传输中的一种附加机制提供了重要基础，并将在生物材料和分析分离中得到应用，还可作为生物组织的模型系统。
