Biomolecule Functionalization of Diamond Surfaces for Implant Applications - A Theoretical Study

Abstract: Diamond is a promising material with unique chemical properties. In this thesis, nano-scale diamond quantum size effects were investigated using several chemical property indicators. The results show that the chemical properties are strongly dependent on size for film thicknesses smaller than 1 nm (1D), and for nanodiamond particle diameters less than 2 nm (3D). When the sizes exceed these ranges there are no longer any quantum effects.The influence of surface termination coverage on the surface chemical properties has been calculated for the 2×1 reconstructed diamond (100) surface and for the diamond (111) surface. The terminating species included COOH and NH2 groups, which both are beneficial for the immobilization of biomolecules. The results of the calculations show that it is energetically possible to terminate the diamond surfaces up to 100% with NH2, while it is only possible to cover the surfaces up to 50% with COOH species. The reason for the latter result is most probably the larger sterical hindrance amongst the adsorbates. Both types of termination species were shown to influence the diamond surface electronic properties (e.g., HOMO/LUMO levels).In order to extend the diamond utility for biomedical applications, especially implant design, interactions of various growth factors with the diamond surfaces were also simulated. For non-solvent diamond-biomolecule systems, the results show that adhesion affinities are strongly dependent on biomolecule molecular weights. When including a water based solvent in the systems, the results show good physisorption affinities between proteins and diamond. Proteins structures, before and after physisorption, were visualized, and further investigated with respect to electrostatic properties and functional groups. By comparing the biomolecular structural changes during the adhesion processes, it can be concluded that both the general structures, as well as the binding pocket structures, were kept intact after the adhesion to the diamond surfaces (regardless of the adhesion affinities). In addition, the surface electronic potential distributions were maintained, which indicate preserved biomolecule functionalities.