Computer Simulations of Fibronectin Adsorption on Graphene Modified Titanium Dioxide Surfaces

Abstract

Fibronectin (FN) could be used to modify the transplant of titanium dioxide. However, the hydrophilicity of tita- nium dioxide may prevent the stable adsorption of protein. Suitable hydrophobic modification of the surface can promote protein adsorption. In this work, all-atom molecular dynamics (MD) simulations were used to study the adsorption of FN on rutile surface, 23% graphene layer modified rutile surface, 92% graphene layer modified rutile surface and the graphite sur- face. The graphene layer can change the surface chemistry of rutile and break the strong interactions between rutile and water molecules. Parallel tempering Monte Carlo algorithm was used firstly to identify the global-minimum-energy orientation of FN. Subsequently, the orientation and conformation of adsorbed FN on modified titanium dioxide surfaces were studied by MD simulations. The simulation results show that FN can hardly adsorb on the rutile surface. Graphene layer deposited on titanium dioxide can reduce the surface hydrophilicity. When the rutile surface is covered by the graphene layer, FN adsorbs on the surface stably. The specific recognition site of FN faces toward the solution when FN is adsorbed on 23% graphene layer modified rutile surface, which is conducive to the identification of integrin. However, if too much graphene layer de- posited on rutile, the specific recognition site of FN would get close to the surface due to the stronger adsorption. The mini- mum distance between FN and various surfaces can indicate the stability of protein adsorption on surfaces. DSSP analysis shows that the seven β-sheets of FN do not change much in all systems during the 40 ns MD simulations. Due to the deposi- tion of graphene layer, the density of water molecules near the surface decreases. The adsorption energy of FN on different surfaces increases with higher surface graphene composition. Graphene modification could promote the fibronectin adsorp- tion on rutile surfaces. This work can provide some guidance for the design and development of modified implant biomate- rials.