Department of Electrical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Biomaterials. 2011 Feb;32(4):969-78. doi: 10.1016/j.biomaterials.2010.09.075. Epub 2010 Oct 28.
The maximum capacity of a hydrophobic adsorbent is interpreted in terms of square or hexagonal (cubic and face-centered-cubic, FCC) interfacial packing models of adsorbed blood proteins in a way that accommodates experimental measurements by the solution-depletion method and quartz-crystal-microbalance (QCM) for the human proteins serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa). A simple analysis shows that adsorbent capacity is capped by a fixed mass/volume (e.g. mg/mL) surface-region (interphase) concentration and not molar concentration. Nearly analytical agreement between the packing models and experiment suggests that, at surface saturation, above-mentioned proteins assemble within the interphase in a manner that approximates a well-ordered array. HSA saturates a hydrophobic adsorbent with the equivalent of a single square or hexagonally-packed layer of hydrated molecules whereas the larger proteins occupy two-or-more layers, depending on the specific protein under consideration and analytical method used to measure adsorbate mass (solution depletion or QCM). Square or hexagonal (cubic and FCC) packing models cannot be clearly distinguished by comparison to experimental data. QCM measurement of adsorbent capacity is shown to be significantly different than that measured by solution depletion for similar hydrophobic adsorbents. The underlying reason is traced to the fact that QCM measures contribution of both core protein, water of hydration, and interphase water whereas solution depletion measures only the contribution of core protein. It is further shown that thickness of the interphase directly measured by QCM systematically exceeds that inferred from solution-depletion measurements, presumably because the static model used to interpret solution depletion does not accurately capture the complexities of the viscoelastic interfacial environment probed by QCM.
疏水性吸附剂的最大容量是根据吸附蛋白质在界面处的方形或六方（立方和面心立方，FCC）堆积模型来解释的，该模型可以通过溶液耗尽法和石英晶体微天平（QCM）实验测量来容纳人血清白蛋白（HSA，66 kDa）、免疫球蛋白 G（IgG，160 kDa）、纤维蛋白原（Fib，341 kDa）和免疫球蛋白 M（IgM，1000 kDa）等蛋白质。简单的分析表明，吸附剂的容量受到固定的质量/体积（例如 mg/mL）表面区域（相间）浓度的限制，而不是摩尔浓度的限制。堆积模型与实验之间几乎完全一致的吻合表明，在表面饱和时，上述蛋白质在相间以近似有序排列的方式组装。HSA 使疏水性吸附剂饱和，相当于单个水合分子的正方形或六方层，而较大的蛋白质则根据特定的蛋白质和用于测量吸附物质量的分析方法（溶液耗尽或 QCM）占据两个或更多层。通过与实验数据的比较，无法清楚地区分方形或六方（立方和 FCC）堆积模型。实验表明，QCM 测量的吸附剂容量与溶液耗尽法测量的结果明显不同。其根本原因在于 QCM 测量的是核心蛋白、水合水和相间水的贡献，而溶液耗尽法仅测量核心蛋白的贡献。进一步表明，通过 QCM 直接测量的相间厚度系统地超过从溶液耗尽测量推断的厚度，这可能是因为用于解释溶液耗尽的静态模型不能准确地捕捉到 QCM 探测到的粘弹性界面环境的复杂性。
