†Department of Polymer Science and Engineering, ‡Department of Chemical Engineering, and §Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, United States.
ACS Appl Mater Interfaces. 2015 May 20;7(19):10275-82. doi: 10.1021/acsami.5b00864. Epub 2015 May 8.
Active surfaces that form the basis for bacterial sensors for threat detection, food safety, or certain diagnostic applications rely on bacterial adhesion. However, bacteria capture from complex fluids on the active surfaces can be reduced by the competing adsorption of proteins and other large molecules. Such adsorption can also interfere with device performance. As a result, multiple upstream processing steps are frequently employed to separate macromolecules from any cells, which remain in the buffer. Here, we present an economical approach to capture bacteria, without competitive adsorption by proteins, on engineered surfaces that do not employ biomolecular recognition, antibodies, or other molecules with engineered sequences. The surfaces are based on polyethylene glycol (PEG) brushes that, on their own, repel both proteins and bacteria. These PEG brushes backfill the surface around sparsely adsorbed cationic polymer coils (here, poly-L-lysine (PLL)). The PLL coils are effectively embedded within the brush and produce locally cationic nanoscale regions that attract negatively charged regions of proteins or cells against the steric background repulsion from the PEG brush. By carefully designing the surfaces to include just enough PLL to capture bacteria, but not enough to capture proteins, we achieve sharp selectivity where S. aureus is captured from albumin- or fibrinogen-containing solutions, but free albumin or fibrinogen molecules are rejected from the surface. Bacterial adhesion on these surfaces is not reduced by competitive protein adsorption, in contrast to performance of more uniformly cationic surfaces. Also, protein adsorption to the bacteria does not interfere with capture, at least for the case of S. aureus, to which fibrinogen binds through a specific receptor.
形成细菌传感器基础的活性表面可用于威胁检测、食品安全或某些诊断应用，其依赖于细菌黏附。然而，在活性表面上从复杂流体中捕获细菌会被蛋白质和其他大分子的竞争吸附所削弱。这种吸附也会干扰器件性能。因此，通常采用多种上游处理步骤将大分子与任何仍在缓冲液中的细胞分离。在这里，我们提出了一种经济的方法，可以在不使用生物分子识别、抗体或其他具有工程序列的分子的情况下，在不通过蛋白质竞争吸附的情况下，在工程表面上捕获细菌。这些表面基于聚乙二醇 (PEG) 刷，单独使用时，既排斥蛋白质又排斥细菌。这些 PEG 刷会填充稀疏吸附的阳离子聚合物线圈（此处为聚-L-赖氨酸 (PLL)）周围的表面。PLL 线圈有效地嵌入在刷内，并产生局部带正电的纳米级区域，吸引蛋白质或细胞的带负电荷区域，克服来自 PEG 刷的空间位阻排斥。通过仔细设计表面，使其包含刚好足以捕获细菌但不足以捕获蛋白质的 PLL，我们实现了尖锐的选择性，例如从含有白蛋白或纤维蛋白原的溶液中捕获金黄色葡萄球菌，但从表面排斥游离的白蛋白或纤维蛋白原分子。与更均匀带正电的表面相比，这些表面上的细菌黏附不受竞争蛋白质吸附的影响。此外，对于至少结合纤维蛋白原的金黄色葡萄球菌，蛋白质吸附到细菌上不会干扰捕获，纤维蛋白原通过特定受体与金黄色葡萄球菌结合。
