Molecular Modeling of Fibronectin Adsorption on Topographically Nanostructured Rutile (110) Surfaces

To investigate the topographical dependency of protein adsorption, molecular dynamics (MD) simulations were employed to describe the biological behavior of the tenth type-III cell adhesion module of fibronectin (FN–III₁₀) on nanostructured rutile (110) surfaces. The simulation results indicated that the protein segments had a tendency to adsorb preferentially along the nanostructural features (protrusion, cavity and groove), compared to the planar reference regions of substrate. The residence time of adsorbed FN–III₁₀ largely relied on its binding mode (direct or indirect) with the substrate and the region for protein migration on the periphery (protrusion) or in the interior (cavity or groove ) of nanostructures. In the direct binding mode, FN–III₁₀ molecules directly connected to the rutile surface were found to be ‘trapped’ at the anchoring sites, or even penetrate deep into the interior of nanostructures, regardless of the geometrical features presented on substrate. In the indirect binding mode, FN–III₁₀ molecules were observed to be indirectly connected to the substrate via a hydrogen–bond network linking FN–III₁₀ and the mediating interfacial hydrations together. In the indirect mode, our results suggested that a suitable number of facets created by nanostructures that exerted restraints on protein migration played a role in the stability of the indirect binding between FN–III₁₀ and the substrate. However, a doubly unfavorable situation—indirect FN–III₁₀–rutile connections bridged solely by a small number of water molecules and few constraints on movement of protein provided by nanostructures —would result in an early desorption of FN–III₁₀ molecules.