de Vos Wiebe M, Biesheuvel P Maarten, de Keizer Arie, Kleijn J Mieke, Cohen Stuart Martien A
Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
Langmuir. 2008 Jun 1;24(13):6575-84. doi: 10.1021/la8006469. Epub 2008 May 29.
The adsorption of bovine serum albumin (BSA) in a planar poly(acrylic acid) (PAA) brush layer has been studied by fixed-angle optical reflectometry. The influence of polymer length, grafting density, and salt concentration is studied as a function of pH. The results are compared with predictions of an analytical polyelectrolyte brush model, which incorporates charge regulation and excluded volume interactions. A maximum in adsorption is found near the point of zero charge (pzc) of the protein. At the maximum, BSA accumulates in a PAA brush to at least 30 vol %. Substantial adsorption continues above the pzc, that is, in the pH range where a net negatively charged protein adsorbs into a negatively charged brush layer, up to a critical pH value. This critical pH value decreases with increasing ionic strength. The adsorbed amount increases strongly with both increasing PAA chain length and increasing grafting density. Experimental data compare well with the analytical model without having to include a nonhomogeneous charge distribution on the protein surface. Instead, charge regulation, which implies that the protein adjusts its charge due to the negative electrostatic potential in the brush, plays an important role in the interpretation of the adsorbed amounts. Together with nonelectrostatic interactions, it explains the significant protein adsorption above the pzc.
通过固定角度光学反射法研究了牛血清白蛋白（BSA）在平面聚丙烯酸（PAA）刷层中的吸附情况。研究了聚合物长度、接枝密度和盐浓度作为pH函数的影响。将结果与包含电荷调节和排除体积相互作用的分析聚电解质刷模型的预测进行了比较。在蛋白质的零电荷点（pzc）附近发现吸附量最大。在最大值处，BSA在PAA刷层中积累至至少30体积%。在pzc以上，即净带负电荷的蛋白质吸附到带负电荷的刷层的pH范围内，直至临界pH值，仍有大量吸附继续发生。该临界pH值随离子强度的增加而降低。吸附量随PAA链长和接枝密度的增加而强烈增加。实验数据与分析模型吻合良好，无需考虑蛋白质表面的非均匀电荷分布。相反，电荷调节（即蛋白质由于刷层中的负静电势而调整其电荷）在解释吸附量方面起着重要作用。与非静电相互作用一起，它解释了pzc以上显著的蛋白质吸附现象。
