Department of Inorganic and Analytical Chemistry , University of Geneva , Sciences II, 30 Quai Ernest-Ansermet , 1205 Geneva , Switzerland.
Langmuir. 2019 Sep 17;35(37):12042-12052. doi: 10.1021/acs.langmuir.9b02149. Epub 2019 Sep 9.
Various physicochemical parameters of poly-l-lysine (PLL) solutions comprising the diffusion coefficient, the electrophoretic mobility, the density, and the intrinsic viscosity were determined for the pH range 3.0-9.2. This allowed us to calculate derivative parameters characterizing the PLL molecule such as: zeta potential, the number of electrokinetic charges, ionization degree, contour length, and cross section area. These data were exploited in theoretical calculations of PLL adsorption kinetics on solid substrates under diffusion transport. A hybrid approach was used comprising a blocking function derived from the random sequential adsorption (RSA) model. In experiments, the PLL adsorption on mica was studied using the streaming potential measurements and interpreted in terms of a general electrokinetic model. This confirmed a side-on adsorption mechanism of the macroion molecules at the examined pH range. Additionally, using this method, the stability of PLL monolayers was determined performing in situ desorption kinetic experiments. In this way, the equilibrium adsorption constant and the energy minimum depth were determined. It was confirmed that the monolayer stability decreases with pH following the decrease in the number of electrokinetic charges per molecule. This confirmed the electrostatic interaction driven adsorption mechanism of PLL. It is also predicted that at pH 5.7-7.4 the monolayers were stable under diffusion-controlled desorption over the time exceeding 100 h. In addition to their significance for basic science, the results obtained in this work can be exploited for developing procedures for preparing stable PLL monolayers of well controlled coverage and electrokinetic properties.
各种聚赖氨酸（PLL）溶液的物理化学参数，包括扩散系数、电泳迁移率、密度和特性粘度，在 pH 值范围 3.0-9.2 下进行了测定。这使我们能够计算出表征 PLL 分子的导数参数，如：zeta 电位、动电电荷数、电离度、轮廓长度和横截面积。这些数据被用于在扩散输运下理论计算 PLL 在固体基底上的吸附动力学。采用了一种混合方法，其中包括源自随机顺序吸附（RSA）模型的阻塞函数。在实验中，使用流动电势测量研究了 PLL 在云母上的吸附，并根据一般的电动模型进行了解释。这证实了在研究的 pH 范围内，大分子分子的侧吸附机制。此外，通过这种方法，通过原位解吸动力学实验确定了 PLL 单层的稳定性。通过这种方式，确定了平衡吸附常数和能量最小深度。证实了单层稳定性随 pH 值的降低而降低，这与每个分子的动电电荷数的降低有关。这证实了 PLL 的静电相互作用驱动的吸附机制。还预测在 pH 5.7-7.4 下，在超过 100 小时的时间内，单层在扩散控制解吸下是稳定的。除了对基础科学的重要性之外，这项工作的结果还可以用于开发制备具有良好控制覆盖率和电动特性的稳定 PLL 单层的程序。
