Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077 Göttingen, Germany.
Beilstein J Nanotechnol. 2012;3:475-84. doi: 10.3762/bjnano.3.54. Epub 2012 Jun 28.
Layer-by-layer (LbL) deposition of polyelectrolytes and proteins within the cylindrical nanopores of anodic aluminum oxide (AAO) membranes was studied by optical waveguide spectroscopy (OWS). AAO has aligned cylindrical, nonintersecting pores with a defined pore diameter d(0) and functions as a planar optical waveguide so as to monitor, in situ, the LbL process by OWS. The LbL deposition of globular proteins, i.e., avidin and biotinylated bovine serum albumin was compared with that of linear polyelectrolytes (linear-PEs), both species being of similar molecular weight. LbL deposition within the cylindrical AAO geometry for different pore diameters (d(0) = 25-80 nm) for the various macromolecular species, showed that the multilayer film growth was inhibited at different maximum numbers of LbL steps (n(max)). The value of n(max) was greatest for linear-PEs, while proteins had a lower value. The cylindrical pore geometry imposes a physical limit to LbL growth such that n(max) is strongly dependent on the overall internal structure of the LbL film. For all macromolecular species, deposition was inhibited in native AAO, having pores of d(0) = 25-30 nm. Both, OWS and scanning electron microscopy showed that LbL growth in larger AAO pores (d(0) > 25-30 nm) became inhibited when approaching a pore diameter of d(eff,n_max) = 25-35 nm, a similar size to that of native AAO pores, with d(0) = 25-30 nm. For a reasonable estimation of d(eff,n_max), the actual volume occupied by a macromolecular assembly must be taken into consideration. The results clearly show that electrostatic LbL allowed for compact macromolecular layers, whereas proteins formed loosely packed multilayers.
通过光波导光谱（OWS）研究了在阳极氧化铝（AAO）膜的圆柱形纳米孔内层层（LbL）沉积聚电解质和蛋白质。AAO 具有排列整齐的、不相交的圆柱形孔，具有确定的孔径 d(0)，并作为平面光波导，以便通过 OWS 原位监测 LbL 过程。球形蛋白质（即亲和素和生物素化牛血清白蛋白）的 LbL 沉积与线性聚电解质（线性-PEs）的沉积进行了比较，这两种物质的分子量相似。对于不同的孔径（d(0) = 25-80 nm）和各种大分子物质，在圆柱形 AAO 几何形状内进行 LbL 沉积，结果表明多层膜的生长在不同的 LbL 步骤（n(max)）的最大数量处受到抑制。n(max)的值对于线性-PEs 最大，而对于蛋白质则较小。圆柱形孔几何形状对 LbL 生长施加了物理限制，使得 n(max)强烈依赖于 LbL 膜的整体内部结构。对于所有的大分子物质，在具有孔径 d(0) = 25-30nm 的原始 AAO 中，沉积受到抑制。OWS 和扫描电子显微镜都表明，当接近有效孔径 d(eff,n_max) = 25-35nm 时，较大的 AAO 孔（d(0) > 25-30nm）中的 LbL 生长会受到抑制，这与具有孔径 d(0) = 25-30nm 的原始 AAO 孔的尺寸相似。为了对 d(eff,n_max)进行合理估计，必须考虑大分子组装体实际占据的体积。结果清楚地表明，静电 LbL 允许形成紧密的大分子层，而蛋白质则形成松散堆积的多层。
