Department of Electrical Engineering, ‡Department of Mechanical and Nuclear Engineering, §Materials Research Institute, ∥Department of Chemistry, and ⊥Department of Biomedical Engineering, The Pennsylvania State University , University Park, Pennsylvania 16801, United States.
Langmuir. 2017 Jul 25;33(29):7215-7224. doi: 10.1021/acs.langmuir.7b00523. Epub 2017 Jul 12.
In this Article, we experimentally measure the adsorption kinetics of human serum albumin (HSA) on a hydrophobic hexadecanethiolated gold surface. We use micromachined quartz crystal resonators with fundamental frequency of 83 MHz to accomplish these measurements in real time. In this work, we focus on two key results: (i) asymptotic behavior of the sensor responses upon HSA adsorption and (ii) the jamming limit of adsorbed layer formed by both single-injection and multi-injection experiments with the same value of final concentration. We develop a new interface-depletion modified random sequential adsorption (RSA) model to elucidate the adsorption kinetics and the transport properties of the protein molecules. Analysis of the experimentally measured data shows that the results can be explained on the basis of the exponentially depleting interfacial layer RSA model. To better understand the origin of the formation of the interfacial depletion region where the supply of protein molecules is dramatically reduced, we performed a series of molecular dynamics (MD) simulations using the ReaxFF method. These simulations predict that the resulting adsorption of the protein molecules on the thiolated surface results in a specific orientation at the interface and the diffusion constant of the protein molecules in this layer is significantly reduced. This interplay between the surface adsorption rate and the reduced diffusion coefficient leads to the depletion of the protein molecules in the interfacial layer where the concentration of the protein molecules is much less than the bulk concentration and explains the observed slowdown of the HSA adsorption characteristics on a hydrophobic surface.
在本文中，我们通过实验测量了人血清白蛋白（HSA）在疏水十六硫醇金表面上的吸附动力学。我们使用具有 83MHz 基频的微加工石英晶体谐振器来实时完成这些测量。在这项工作中，我们重点关注两个关键结果：（i）HSA 吸附时传感器响应的渐近行为，以及（ii）单次和多次注射实验在相同最终浓度下形成的吸附层的堵塞极限。我们开发了一种新的界面耗尽修正随机顺序吸附（RSA）模型，以阐明蛋白质分子的吸附动力学和输运性质。对实验测量数据的分析表明，结果可以基于指数耗尽界面层 RSA 模型来解释。为了更好地理解蛋白质分子供应急剧减少的界面耗尽区域形成的原因，我们使用 ReaxFF 方法进行了一系列分子动力学（MD）模拟。这些模拟预测，蛋白质分子在疏水性表面上的吸附会导致界面处的特定取向，并且该层中蛋白质分子的扩散常数显著降低。这种表面吸附速率和降低的扩散系数之间的相互作用导致了界面层中蛋白质分子的耗尽，其中蛋白质分子的浓度远低于体相浓度，并解释了在疏水表面上观察到的 HSA 吸附特征的减缓。
