Department of Physics, University of Massachusetts, Amherst, MA 01003, United States.
Colloids Surf B Biointerfaces. 2010 Apr 1;76(2):489-95. doi: 10.1016/j.colsurfb.2009.12.009. Epub 2009 Dec 22.
This study investigated the initial adhesion of Staphylococcus aureus from flowing buffer onto modified albumin films with the objective of probing the influence of electrostatic heterogeneity on bacterial adhesion. Electrostatic heterogeneity, on the lengthscale of 10-100 nm, was incorporated into the protein film through the irreversible random deposition of small amounts of polycation coils to produce isolated positive "patches" on the otherwise negative albumin surface before exposure to bacteria, which also possess a net negative surface charge. The system was benchmarked against an appropriate analog using 1 microm silica spheres and the same cationic patches on a silica substrate. Bacterial adhesion from flow was measured with the surface oriented vertically to eliminate gravitational forces between the bacteria and collector. In both systems, a threshold in the surface density of polycation patches needed for bacterial (or silica particle) capture indicated multivalent binding: multiple polycation patches were needed to adhere the bacteria (particles). The shifting of the threshold to greater patch concentrations at lower ionic strengths confirmed that the electrostatic interaction area (zone of influence) was a key factor in modulating the interactions. The role of the contact area in this manner is important because it enables a quantitative explanation of counterintuitive bacterial adhesion onto net negative surfaces. The study further revealed a hydrodynamic crossover from a regime where flow aids bacterial adhesion to one where flow impedes adhesion. An explanation is put forth in terms of the relative hydrodynamic and surface forces.
本研究旨在探究流动缓冲液中的金黄色葡萄球菌初始黏附到经修饰的白蛋白膜上的情况，以探究静电异质性对细菌黏附的影响。通过不可逆的随机沉积少量聚阳离子线圈，在白蛋白表面形成离散的正“斑”，从而在暴露于细菌之前引入静电异质性（在 10-100nm 的长度尺度上），而细菌本身带有净负表面电荷。通过使用 1μm 的二氧化硅球和二氧化硅基底上的相同阳离子斑来对标适当的模拟物，对该系统进行了基准测试。细菌（或二氧化硅颗粒）从流动中黏附的情况是通过将表面垂直取向来测量的，以消除细菌和收集器之间的重力。在这两个系统中，细菌（或二氧化硅颗粒）捕获所需的聚阳离子斑的表面密度都存在一个阈值，这表明存在多价结合：需要多个聚阳离子斑才能黏附细菌（颗粒）。在较低离子强度下，阈值向更高的斑浓度移动，这证实了静电相互作用面积（影响区）是调节相互作用的关键因素。这种方式下接触面积的作用很重要，因为它能够定量解释细菌在净负表面上的反直觉黏附现象。该研究进一步揭示了从一个有利于细菌黏附的流动状态到一个阻碍黏附的流动状态的流体力学转变。从相对流体力和表面力的角度解释了这一现象。
