Laminin adsorption on nanostructures: Switching the molecular orientation by local curvature changes

This work addresses the influence that the nanometric features of biologically relevant surfaces have on the conformation and properties of adsorbed laminin. It was observed that the adsorption kinetics and the nanomorphology of laminin were affected by the change in local curvature of chemically homogeneousnanostructured surfaces. The nanostructured surfaces were prepared by exploiting the self-assembly process of carboxylated polystyrene NPs, with diameters of 45, 109, and 209 nm, onto a polyelectrolyte multilayer formed by alternate deposition of poly(acrylic acid) and poly(allylamine hydrochloride) on gold. The anchored polymeric NPs were finally coated with a homogeneous layer of poly(allylamine hydrochloride), providing three surfaces with different nanometriclocal curvature. Atomic force microscopy was employed to characterize the relevant morphological parameters of the nanostructured surfaces. Quartz crystal microbalance with dissipationmonitoring was employed to determine the adsorbed mass of laminin as well as its adsorption rate as a function of the localsurface curvature. A model is proposed to explain the higher and faster laminin adsorption on surfaces with lower local curvature,where a switching of laminin anchoring orientation from a side-on to an end-on geometry can be predicted by a simple curvature-dependent parameter, γ, connecting the average nanostructure height h and the macromolecule radius of gyration Rg. The results provide a framework to understand the dependence of biomolecule orientation on local nanostructure.