Nanocrystal Width Controls Fibrinogen Orientation and Assembly Kinetics on Poly(butene-1) Surfaces

From the view of biomedical relevance, it is known that a specific arrangement of surface-immobilized human plasma fibrinogen (HPF) molecules is required to retain their biological functionality. Here, we demonstrate a topographical effect of chemically identical isotactic poly(butene-1) (iPB-1) semicrystalline nanostructures on the adsorption behavior, i.e., conformation change and orientation of HPF molecules. Using the distinct crystallization of iPB-1 under different shear conditions, polymer thin films consisting of needle-like crystals (NLCs) or shish-kebab crystals (SKCs) having lateral dimension, i.e., width, smaller than or comparable to the HPF major axis, respectively, were fabricated. The protein adsorption kinetic studies by quartz crystal microbalance with dissipation (QCM-D) revealed surface-dependent packing density and assembly configuration of HPF. High-resolution imaging disclosed a "side-on" protein adsorption and anisotropic network formation on the NLCs. With a 2-fold orientation analysis performed at both "single" protein and multiprotein levels, we quantitatively proved the preferential alignment of adsorbed HPF molecules with respect to the axial direction of the NLCs. Remarkably, the iPB-1 surface with SKCs perturbed the "end-to-end" protein-protein interactions and thus hindered the network formation. The distinguished adsorption behavior of HPF molecules on iPB-1 surfaces is explained by the physical effect of crystal width, which is additionally supported by the synergistic effect of crystal curvature and aspect ratio. Our studies provide fundamental insight into purely topography-controlled self-assembly of HPF molecules, which might be further exploited in creating topographically defined implant surfaces for preventing protein aggregation related disorders.