Laboratory of Surface Reactivity, CNRS UMR 7197, University of Pierre & Marie Curie - Paris VI, 4 Place Jussieu, case 178, 75252 Paris Cedex 05, France.
Phys Chem Chem Phys. 2013 Jun 7;15(21):8429-40. doi: 10.1039/c3cp00137g. Epub 2013 Apr 29.
We investigate the nanoscale organization of a superficially hydroxylated Al substrate and its effect on subsequent protein adsorption using atomic force microscopy (AFM). For this purpose we used a mode which allows a direct mapping of a variety of surface properties (adhesion, elasticity, dissipation, etc.) to be probed simultaneously with topographical images. The hydroxylation treatment leads to a drastic modification of the surface morphology, owing to the formation of AlOOH compounds. In air, AFM images revealed the formation of regular nanorod-like structures randomly distributed, inducing the appearance of nanoporous domains on the surface. In buffer solution, prior to the adsorption of proteins, the surface nanoscale organization is preserved, mainly due to the chemical stability of AlOOH compounds under these conditions. The adsorption of proteins on the obtained nanostructured surface was performed using either a globular (β-lactoglobulin) or a fibrillar (collagen) protein and by modulating the adsorbed amount through the incubation time or the concentration of proteins in solution. At low amounts, collagen adsorbs on the whole surface without preferential localization. The surface topography remains similar to the bare surface, while significant changes were evidenced on adhesion and elasticity maps. This is due to the fact that the surface became adhesive and less stiff, owing to the presence of a soft and hydrated protein layer. By contrast, β-lactoglobulin tends to diffuse into the nanoporous domains, leading to their filling up, and the surface is blurred with a thick and dense protein layer upon increasing the amount of adsorbed molecules. Our findings demonstrate the interest in using AFM for surface mapping to investigate the mechanism of protein adsorption at the nanoscale on materials with high surface roughness.
我们使用原子力显微镜（AFM）研究了表面经羟基化处理的 Al 基底的纳米级结构及其对后续蛋白质吸附的影响。为此，我们使用了一种模式，可以同时对各种表面特性（粘附力、弹性、耗散等）进行直接映射，并对形貌图像进行探测。由于 AlOOH 化合物的形成，羟基化处理导致表面形貌发生了剧烈的变化。在空气中，AFM 图像显示出规则的纳米棒状结构随机分布，导致表面出现纳米多孔区域。在缓冲溶液中，在蛋白质吸附之前，表面的纳米级结构得以保持，这主要是由于 AlOOH 化合物在这些条件下具有化学稳定性。通过调节孵育时间或溶液中蛋白质的浓度，可以使用球状（β-乳球蛋白）或纤维状（胶原蛋白）蛋白质在获得的纳米结构表面上进行蛋白质吸附。在低浓度下，胶原蛋白在整个表面上吸附而没有优先定位。表面形貌与裸表面相似，而在粘附力和弹性图谱上则出现了明显的变化。这是因为表面变得具有粘性且硬度降低，这是由于存在柔软且水合的蛋白质层。相比之下，β-乳球蛋白倾向于扩散到纳米多孔区域，导致其被填满，并且随着吸附分子数量的增加，表面变得模糊，形成了一层厚而致密的蛋白质层。我们的研究结果表明，在具有高表面粗糙度的材料上，使用 AFM 进行表面映射以研究蛋白质在纳米尺度上吸附的机制是很有意义的。
