Computer Simulation Of Interaction Between Biomolecules And TiO₂/Graphene

Biomaterials will be covered by an abundance of proteins in a very short interval after implantation. When proteins/peptides adsorb on biomaterial surfaces, their configurations will be changed due to interactions with biomaterial surfaces, which affects their final functions. The investigation of interactions between biomaterials and biomolecules is of great importance to surface modification of biomaterials, design of novel biomaterials and medical devices. However, biomaterial and biomolecule interaction mechanism is far from being thoroughly understood in an atomic and electronic level. This study employed the density functional theory (DFT) method to explore the interaction between biomaterials and biomolecules.Graphene is a monolayer of carbon atoms that is tightly packed into a two-dimensional honeycomb lattice. It has fascinating mechanical and electronic properties. Studies have paid considerable attention to the potential biomedical applications of graphene and graphene oxde (GO). Arginine-glycine-aspartic acid (RGD) is a tripeptide that widely exists in several extracellular matrix proteins. RGD is recognized as one of the effective peptide sequences that stimulates cell adhesion on material surfaces. This study investigated the interaction between carbon nanostructures and RGD by density functional theory. The results show that the strongest adsorption is observed when RGD is parallel to graphene surfaces, in which graphene interacts with all three functional groups of RGD, including NH3+, COO-, and guanidine. The interaction of NH3+…π was stronger than that of guanidine-NH2…π and COO-…π. The vacancy improves the ability of graphene to attract RGD because of active dangling C atoms. GO has a stronger interaction with RGD than the pristine and defective graphene because of O-containing groups. Various O-containing groups have distinguishing binding abilities with RGD. Water molecules strengthen the interaction between graphene and RGD, whereas they weaken the interaction between GO and RGD.The surface of Ti can be spontaneously oxidized into TiO2, which is believed to be closely related to the excellent biocompatibility of Ti. Understanding the interaction mechanism between TiO2surfaces and proteins/peptides/amino acids is crucial to the success of Ti implants. Aspartic acid (Asp or D) is one of the most abundant amino acids in nature. This study investigated the interaction of Asp with pure, nitrogen-doped, and calcium-doped rutile (R(110)) surfaces by density functional theory. The effect of water on the interaction was also studied. The results demonstrate that the strongest adsorption happens when both the amino and carboxyl groups of Asp approach the R(110) surfaces and form a bidentate coordination to two surface Ti atoms. Hydrogen bonds from the H atoms of Asp and bridging-O atoms on the surface also contribute to the adsorption. Water hinders the Asp adsorption. N-doping and Ca-doping are not beneficial to Asp adsorption.Both graphene and Tio2have wide potential applications in the field of biomaterials. It is of great significance to study the application of TiO2/graphene composites in biomedical area. Glycine (Gly or G) is the simplest amino acid in nature. This study investigated the interaction of Gly with TiO2/graphene composites by density functional theory. The results show that the interaction is complicated. When TiO2is the main component of the composite, Gly mainly interacts with TiO2, and the crystal from of TiO2has primary effect on Gly adsorption. Otherwise, graphene or graphene oxide has dominant effect on Gly adsorption. Graphene may be not beneficial to the adsorption of Gly on the composite.The results provide useful guidance in designing optimal material surfaces with specific characteristics that could satisfy the demand for diverse applications of biomaterials in biomedical fields.