Department of Mechanical Engineering, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering (FB40), Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
ACS Appl Mater Interfaces. 2017 Apr 5;9(13):12118-12129. doi: 10.1021/acsami.7b01322. Epub 2017 Mar 27.
Bacterial adhesion and biofilm formation on surfaces are troublesome in many industrial processes. Here, nanoporous and nanopillared aluminum surfaces were engineered by anodizing and postetching processes and made hydrophilic (using the inherent oxide layer) or hydrophobic (applying a Teflon coating) with the aim of discouraging bacterial adhesion. Adhesion of Staphylococcus aureus ATCC 12600 (Gram-positive, spherically shaped) and Escherichia coli K-12 (Gram-negative, rod-shaped) was evaluated to the nanoengineered surfaces under both static and flow conditions (fluid shear rate of 37 s). Compared to a nonstructured electropolished flat surface, the nanostructured surfaces significantly reduced the number of adhering colony forming units (CFUs) for both species, as measured using agar plating. For the hydrophilic surfaces, this was attributed to a decreased contact area, reducing bacterial adhesion forces on nanoporous and nanopillared surfaces to 4 and 2 nN, respectively, from 8 nN on flat surfaces. Reductions in the numbers of adhering CFUs were more marked on hydrophobic surfaces under flow, amounting to more than 99.9% and 99.4% for S. aureus and E. coli on nanopillared surfaces, respectively. Scanning electron microscopy revealed a few bacteria found on the hydrophobic nanopillared surfaces adhered predominantly to defective or damaged areas, whereas the intact area preserving the original nanopillared morphology was virtually devoid of adhering bacteria. The greater decrease in bacterial adhesion to hydrophobic nanopillared surfaces than to hydrophilic or nanoporous ones is attributed to effective air entrapment in the three-dimensional pillar morphology, rendering them superhydrophobic and slippery, in addition to providing a minimized contact area for bacteria to adhere to.
细菌在表面的黏附和生物膜形成在许多工业过程中都是令人烦恼的问题。在这里，通过阳极氧化和后刻蚀工艺对纳米多孔和纳米柱形的铝表面进行了工程改造，使其亲水（利用固有氧化物层）或疏水（涂覆特氟隆涂层），目的是阻止细菌黏附。评估了金黄色葡萄球菌 ATCC 12600（革兰氏阳性，球形）和大肠杆菌 K-12（革兰氏阴性，杆状）在静态和流动条件下（流体剪切速率为 37 s）对纳米工程表面的黏附。与非结构化的电化学抛光平面表面相比，纳米结构表面显著减少了两种细菌的附着菌落形成单位（CFU）数量，这是通过琼脂平板测量得出的。对于亲水表面，这归因于接触面积的减小，从而将纳米多孔和纳米柱形表面上的细菌黏附力分别降低到 4 和 2 nN，而在平面表面上则为 8 nN。在流动条件下，疏水表面上附着的 CFU 数量减少更为明显，对于纳米柱形表面，金黄色葡萄球菌和大肠杆菌的数量分别减少了 99.9%和 99.4%。扫描电子显微镜显示，在疏水纳米柱形表面上发现的少数细菌主要附着在有缺陷或损坏的区域，而保持原始纳米柱形形态的完整区域几乎没有附着的细菌。与亲水或纳米多孔表面相比，疏水纳米柱形表面上细菌黏附的减少幅度更大，这归因于三维柱形形态中有效捕获空气，使其具有超疏水性和滑溜性，此外还为细菌提供了最小的附着接触面积。
