RGD tripeptide onto perfect and grooved rutile surfaces in aqueous solution: Adsorption behaviors and dynamics

Molecular dynamics (MD) simulations were performed to investigate the adsorption behavior and dynamics of Arg-Gly-Asp (RGD) tripeptide onto the rutile TiO₂ (110) perfect and grooved surfaces in aqueous solution. The simulation results suggest that, driven by the electrostatic attractions between charged groups of the tripeptide and opposite-type charges of the surface atoms, RGD substitutes the adsorbed water molecules and binds to TiO₂ surface strongly through direct interactions of carboxyl oxygen (O _coo-) atoms with nearby titanium atoms in the interface, in agreement with some experimental observations and theoretical data. Once bonded to both perfect and grooved surfaces, RGD tripeptides show a reasonable propensity to remain there with the carboxyl groups providing anchors to the substrate surface, while the amide groups (NH₃⁺ and NH₂) with larger separations from the attached portions, undergo relatively remarkable fluctuations during the whole simulation time. The trajectories for atom-surface distances, backbone dihedral angles and root-mean-squared deviations from the initial structure have revealed less mobility and more stable adsorption of RGD onto grooved surface than onto perfect surface, which is confirmed again by greater values of adsorption energy for available grooved surfaces.