Department of Chemistry, University of California Irvine, Irvine, California 92697, USA.
ACS Appl Mater Interfaces. 2013 Jan 23;5(2):374-9. doi: 10.1021/am302404q. Epub 2013 Jan 4.
Cationic-functionalized polymer nanoparticles (NPs) show strikingly distinct affinities to proteins depending on the nature of the cationic functional group. N-Isopropylacrylamide (NIPAm) polymer NPs incorporating three types of positively charged functional groups (guanidinium, primary amino, and quaternary ammonium groups) were prepared by precipitation polymerization. The affinities to fibrinogen, a protein with an isoelectric point (pI) of 5.5, were compared using UV-vis spectrometry and a quartz crystal microbalance (QCM). Guanidinium-containing NPs showed the highest affinity to fibrinogen. The observation is attributed to strong, specific interactions with carboxylate groups on the protein surface. The affinity of the positively charged NPs to proteins with a range of pIs revealed that protein-NP affinity is due to a combination of ionic, hydrogen bonding, and hydrophobic interactions. Protein affinity can be modulated by varying the composition of these functional monomers in the acrylamide NPs. Engineered NPs containing the guanidinium group with hydrophobic and hydrogen bonding functional groups were used in an affinity precipitation for the selective separation of fibrinogen from a plasma protein mixture. Circular dichroism (CD) revealed that the protein was not denatured in the process of binding or release.
阳离子功能化聚合物纳米粒子 (NPs) 根据阳离子官能团的性质对蛋白质表现出明显不同的亲和力。通过沉淀聚合制备了含有三种带正电荷官能团（胍基、伯氨基和季铵基）的 N-异丙基丙烯酰胺 (NIPAm) 聚合物 NPs。使用紫外-可见分光光度法和石英晶体微天平 (QCM) 比较了它们与等电点 (pI) 为 5.5 的纤维蛋白原的亲和力。含胍基的 NPs 对纤维蛋白原表现出最高的亲和力。这一观察结果归因于与蛋白质表面上的羧酸盐基团之间的强、特异性相互作用。带正电荷的 NPs 对具有一系列 pI 的蛋白质的亲和力表明，蛋白质-NP 亲和力是由于离子、氢键和疏水相互作用的组合。通过改变丙烯酰胺 NPs 中这些官能单体的组成，可以调节蛋白质的亲和力。含有胍基和疏水及氢键官能团的工程化 NPs 用于亲和沉淀，可从血浆蛋白质混合物中选择性分离纤维蛋白原。圆二色性 (CD) 表明，在结合或释放过程中蛋白质没有变性。
