Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Langmuir. 2011 Dec 20;27(24):15083-91. doi: 10.1021/la203293k. Epub 2011 Nov 21.
Patchy polymer brushes contain nanoscale (5-15 nm) adhesive elements, such as polymer coils or nanoparticles, embedded at their base at random positions on the surface. The competition between the brush's steric (protein resistant) repulsions and the attractions from the discrete adhesive elements provides a precise means to control bioadhesion. This differs from the classical approach, where functionality is placed on the brush's periphery. The current study demonstrates the impact of poly(etheylene glycol) (PEG) brush architecture and ionic strength on fibrinogen adsorption on brushes containing embedded poly-l-lysine (PLL, 20K MW) coils or "patches". The consistent appearance of a fibrinogen adsorption threshold, a minimum loading of patches on the surface, below which protein adsorption does not occur, suggests multivalent protein capture: Adsorbing proteins simultaneously engage several patches. The surface composition (patch loading) at the threshold is extremely sensitive to the brush height and ionic strength, varying up to a factor of 5 in the surface loading of the PLL patches (~50% of the range of possible surfaces). Variations in ionic strength have a similar effect, with the smallest thresholds seen for the largest Debye lengths. While trends with brush height were the clearest and most dominant, consideration of the PEG loading within the brush or its persistence length did not reveal a critical brush parameter for the onset of adsorption. The lack of straightforward correlation on brush physics was likely a result of multivalent binding, (producing an additional dependence on patch loading), and might be resolved for univalent adsorption onto more strongly binding patches. While studies with similar brushes placed uniformly on a surface revealed that the PEG loading within the brush is the best indicator of protein resistance, the current results suggest that brush height is more important for patchy brushes. Likely the interactions producing brush extension normal to the interface act similarly to drive lateral tether extension to obstruct patches.
有 斑点的聚合物刷包含纳米级（5-15nm）的黏附单元，例如聚合物线圈或纳米粒子，随机地嵌入在其表面的基底处。刷的位阻（抗蛋白质）排斥力与离散黏附单元之间的吸引力之间的竞争提供了一种精确控制生物黏附的方法。这与经典方法不同，在经典方法中，功能位于刷的外围。本研究表明了聚乙二醇（PEG）刷结构和离子强度对含有嵌入式聚-l-赖氨酸（PLL，20KMW）线圈或“斑点”的纤维蛋白原吸附的影响。纤维蛋白原吸附阈值的一致出现，即表面上的斑点最小负载，低于该负载，蛋白质吸附不会发生，这表明多价蛋白质捕获：吸附的蛋白质同时与几个斑点结合。在阈值处的表面组成（斑点负载）对刷的高度和离子强度极其敏感，在 PLL 斑点的表面负载中变化高达 5 倍（在可能的表面范围内变化约 50%）。离子强度的变化具有相似的效果，其中看到的 Debye 长度最大的阈值最小。虽然刷高的趋势最清晰和最占主导地位，但考虑到刷内的 PEG 负载或其持久长度并没有揭示出吸附起始的临界刷参数。缺乏直接的刷物理相关可能是多价结合的结果（产生对斑点负载的额外依赖），并且可能会在更强烈结合的斑点上的单价吸附得到解决。虽然具有类似刷的均匀放置在表面上的研究表明刷内的 PEG 负载是蛋白质抵抗的最佳指标，但当前结果表明刷高对于有斑点的刷更为重要。可能是产生垂直于界面的刷延伸的相互作用类似地驱动横向系绳延伸以阻碍斑点。
