Molecular Dynamics Simulations of Biological Molecules on the Natively Oxidized Titanium Surface

In order to investigate the surface properties of metals in a realistic fashion it is crucial to take into account the thin oxide layer that forms spontaneously when the surface is exposed to an oxidising environment. Starting from reference oxide layer structures obtained in extensive first-principles molecular dynamics simulations, we have developed a novel classical potential which is able to reproduce the topological binding features of the amorphous oxide network on Ti as well as the interfacial behaviour of the TiOx/water interface. By combination of this specific potential with well-established biomolecular force fields, we have performed classical simulations of small organic molecules on the oxide surface and successfully compared their results to DFT calculations. The final model is applied to elucidate the microscopic mechanisms that take place at experimentally relevant bio-interfaces. In particular, we focus on the titanium-binding peptide motif minTBP-1. By using advanced simulation techniques, such as metadynamics, replica exchange molecular dynamics, as well as steered molecular dynamics, we have quantified the adhesion strength to the oxidized titanium surface and to the oxidized silicon surface in excellent agreement with experimental results. A microscopical analysis of the simulations reveals that the stronger adhesion to titanium compared to silicon is primarily caused by differences in the interfacial water structure. Furthermore, we have employed the model to calculate the contact forces between two water-covered titania nanoparticles and compared the results to the findings from AFM experiments.