Protein-Functionalized Diamond Surfaces in a Water Solvent: A Theoretical Approach

In order to improve the performance of a diamond-based implant material, surface functionalization with different proteins is a promising approach. The main goal of the present study has been to theoretically investigate the diamond functionalization by physisorption of different proteins onto different surface planes. The protein candidates selected are growth factors which can promote cell adhesion and growth and subsequent vascularization surrounding the implanted materials. They include Bone Morphogenetic Protein 2 (BMP2), Vascular Endothelial Growth Factor (VEGF), Fibronectin (FN), and Angiopoietin (AGP). Moreover, it is well-known that diamond surface properties are strongly dependent on diamond surface planes and surface terminations. Therefore, the following two different diamond surface planes [diamond (100)-2 × 1 and diamond (111)] and four different kinds of terminations species (H, OH, COOH, and NH₂) were used in the present study. The results from force-field calculations show that the surface wettability is crucial for the protein adhesion onto the diamond surfaces, and the different proteins possess distinct preferences for diamond surface planes and terminations. For the identification of protein functionality, the atomic structures, in addition to corresponding electrostatic maps, were also visualized in the comparison of protein structures before and after adhesion to the diamond surfaces. It could be concluded that the protein structures and binding pocket electrostatic distributions are maintained as a result of the functionalization process, regardless of adhesion energy strength. These results provide a solid base for experimental protein functionalization of the diamond surfaces.