Adsorption of tripeptide RGD on rutile TiO(2) nanotopography surface in aqueous solution.

Molecular dynamics simulations were carried out to investigate the adsorption mechanisms of tripeptide Arg-Gly-Asp (RGD) on the nanotopography and perfect rutile TiO(2) (110) surfaces in aqueous solution. It is shown that the amino groups (NH(2) and NH3+) and carboxyl group (COO(-)) of RGD are the main groups bonding to hydrophilic TiO(2) surface by electrostatic and van der Waals interactions. It is also demonstrated that RGD adsorbs much more rapidly and stably on the nanotopography surface than the perfect surface. On the hydrophilic TiO(2) surface, the water molecules occupy the adsorption sites to form hydration layers, which have a significant influence on RGD adsorption. On the perfect surface, since the fivefold titanium atom is surrounded by surface bridging oxygen atoms above it and has a water molecule bonding to it, the amino group NH(2) is the adsorption group. However, because the pit surface exposes more adsorption sites and has higher surface energy, RGD can adsorb rapidly on the surfaces by amino groups NH(2) and NH3+, and the carboxyl group COO(-) may edge out the adsorbed water molecules and bond to the surface titanium atom. Moreover, the surface with higher surface energy has more adsorption energy of RGD.

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 TiO(2) (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 TiO(2) 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 (NH(3)(+) and NH(2)) 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.

Effect of grooves on adsorption of RGD tripeptide onto rutile TiO(2) (110) surface.

Molecular dynamics (MD) simulations have been performed to investigate the adsorption mechanism of Arg-Gly-Asp (RGD) tripeptide onto perfect and grooved rutile TiO(2) (110) surfaces, respectively. The simulation results suggest that RGD tripeptide can strongly adsorb onto TiO(2) surface through specified Ti coordination sites. Analysis of adsorption energy, mean-squared displacements and radial distribution functions indicates that the adsorption of RGD onto grooved surface is more stable and rapid than that onto the perfect surface, with the adsorption energy around -331.59 kcal/mol. And among the chosen groove surfaces, adsorption energies, adsorption speeds and adsorption depths of RGD onto the surfaces increase evidently with the extension of groove dimensions. For both perfect and grooved surfaces, once bonded to the surfaces by interactions of carboxyl groups or carbonyl groups with nearby surface Ti atoms, RGD tripeptides show a reasonable propensity to remain there and undergo relatively limited hinge-bending motions.