Efficient control of protein assembly on materials is a major challenge affecting functionality and performance of various implant materials. Nanostructured surfaces with topographical features comparable in size to the physical dimensions of proteins have been recognized as a powerful tool to control protein assembly. However, the mechanism and dynamics of how nanostructures induce order in the adsorbed protein assemblies are still enigmatic. In this work, we used single-molecule mapping by accumulated probe trajectories and complementary atomic force microscopy to shed light on the dynamic in situ assembly of human plasma fibrinogen (HPF) adsorbed on nanostructured polybutene-1 (PB-1) and nanostructured polyethylene (PE) surfaces. We found a distinct lateral heterogeneity of HPF - polymer interactions (surface occupancy, residence time, and diffusion coefficient) that allows identifying the interplay between protein topographical nanoconfinement, protein diffusion mechanism, and ordered protein self-assembly. The direction-dependent analysis of HPF diffusion revealed anisotropic lateral mobility without correlation to the anisotropic friction characteristic of the polymeric surfaces. This suggests that HPF molecules confined on the nanosized PB-1 needle crystals and PE shish-kebab crystals, respectively, undergo partial detachment and diffuse via a Sansetsukon-like nanocrawling mechanism. This mechanism is based on the intrinsic flexibility of HPF in the coiled-coil regions. We conclude that nanostructured surfaces that support nanoconfinement and this distinctive surface mobility are more likely to lead to the formation of ordered protein assemblies and may be useful for advanced nanobiomaterials.
Literature: X. Zhang et al. Nanoconfinement and Sansetsukon-like Nanocrawling Govern Fibrinogen Dynamics and Self-Assembly on Nanostructured Polymeric Surfaces. Langmuir 2018