ACS Appl Mater Interfaces. 2019 Jan 9;11(1):320-330. doi: 10.1021/acsami.8b18302. Epub 2018 Dec 29.
Surface-associated transport of flowing bacteria, including cell rolling, is a mechanism for otherwise immobile bacteria to migrate on surfaces and could be associated with biofilm formation or the spread of infection. This work demonstrates how the moduli and/or local polymer concentration play critical roles in sustaining contact, dynamic adhesion, and transport of bacterial cells along a hydrogel or hydrated brush surface. In particular, stiffer more concentrated hydrogels and brushes maintained the greatest dynamic contact, still allowing cells to travel along the surface in flow. This study addressed how the mechanical properties, molecular architectures, and thicknesses of minimally adhesive poly(ethylene glycol) (PEG)-based coatings influence the flow-driven surface motion of Staphylococcus aureus MS2 cells. Three protein-repellant PEG-dimethylacrylate hydrogel films (∼100 μm thick) and two protein-repellant PEG brushes (8-16 nm thick) were sufficiently fouling-resistant to prevent the accumulation of flowing bacteria. However, the rolling or hopping-like motions of gently flowing S. aureus cells along the surfaces were specific to the particular hydrogel or brush, distinguishing these coatings in terms of their mechanical properties (with moduli from 2 to 1300 kPa) or local PEG concentrations (in the range 10-50% PEG). On the stiffer hydrogel coatings having higher PEG concentrations, S. aureus exhibited long runs of surface rolling, 20-50 μm in length, an increased tendency of cells to repeatedly return to some surfaces after rolling and escaping, and relatively long integrated contact times. By contrast, on the softer more dilute hydrogels, bacteria tended to encounter the surface for brief periods before escaping without return. The dynamic adhesion and motion signatures of the cells on the two brushes were bracketed by those on the soft and stiff hydrogels, demonstrating that PEG coating thickness was not important in these studies where the vertically oriented surfaces minimized the impact of gravitational forces. Control studies with similarly sized poly(ethylene oxide)-coated rigid spherical microparticles, that also did not arrest on the PEG coatings, established that the bacterial skipping and rolling signatures were specific to the S. aureus cells and not simply diffusive. Dynamic adhesion of the S. aureus cells on the PEG hydrogel surfaces correlated well with quiescent 24 h adhesion studies in the literature, despite the orientation of the flow studies that eliminated the influence of gravity on bacteria-coating normal forces.
细菌在表面的相关输运,包括细胞滚动,是一种使原本不活动的细菌在表面迁移的机制,可能与生物膜形成或感染传播有关。这项工作展示了模量和/或局部聚合物浓度如何在维持接触、动态粘附以及细菌细胞沿着水凝胶或水合刷表面的输运中发挥关键作用。特别是,更硬、更集中的水凝胶和刷子保持了最大的动态接触,仍然允许细胞在流动中沿表面移动。这项研究探讨了机械性能、分子结构和最小粘附性聚乙二醇 (PEG) 基涂层的厚度如何影响金黄色葡萄球菌 MS2 细胞的流动驱动表面运动。三种抗蛋白的 PEG-二甲基丙烯酸酯水凝胶膜(约 100 µm 厚)和两种抗蛋白的 PEG 刷(8-16 nm 厚)具有足够的抗污染能力,可防止流动细菌的积累。然而,轻轻流动的金黄色葡萄球菌细胞沿着表面的滚动或类似跳跃的运动是特定于特定水凝胶或刷子的,这表明这些涂层在机械性能(模量从 2 到 1300 kPa)或局部 PEG 浓度(在 10-50%PEG 的范围内)方面有所不同。在具有较高 PEG 浓度的较硬水凝胶涂层上,金黄色葡萄球菌表现出表面滚动的长运行,长度为 20-50 µm,细胞在滚动和逃脱后再次返回某些表面的趋势增加,以及相对较长的整体接触时间。相比之下,在较软且稀释度较高的水凝胶上,细菌在逃脱之前往往会在很短的时间内与表面接触而不返回。细胞在两种刷子上的动态粘附和运动特征介于软和硬水凝胶之间,这表明在这些研究中,垂直定向的表面最大限度地减少了重力的影响,PEG 涂层的厚度并不重要。用具有相似尺寸的聚环氧乙烷涂层刚性球形微球进行的对照研究也没有在 PEG 涂层上停止,这表明细菌跳跃和滚动的特征是金黄色葡萄球菌细胞特有的,而不仅仅是扩散。金黄色葡萄球菌细胞在 PEG 水凝胶表面的动态粘附与文献中 24 小时静态粘附研究密切相关,尽管流动研究的方向消除了重力对细菌-涂层法向力的影响。