Computer Simulation Of Biomaterial Surface And Interface

An essential feature of the behaviour of artificial materials that are inserted into most places within a living body is that they will become covered by proteins and blood after a very short interval. The chemical and morphological properties will change while the biomaterial surfaces turn into the interface between the artificial materials and the living body. During this process, the protein adsorption can not be avioded. Thus, the biomedical surface and interface interactions are one of the most important problems in biomaterial research areas. However, the experimental researches could hardly invesitgate the interactions between the biomaterial surfaces and the biological tissue. This study applied the molecule dynamics (MD) and density functional theory (DFT) methods to explore the mechanism at the biomaterials surface and interface.Titanium and titanium alloys were widely used as medical implants for their excellent mechanical property, corrision resistance and biocompatibility. Titanium oxide as a nature layer exsiting on the titanium based materials was related with its good biocompatibility. Peptide Arg-Gly-Asp (RGD) sequence is a ubiquitous adhesive motif found in various bone extracellular matrix proteins and is crucial in the biomaterial surface/interface reaction. The interactions between Arg-Gly-Asp (RGD) peptides and titanium oxide (TiO2) surfaces are of considerable interest to medical technological and fundamental researchers. A molecular dynamics (MD) simulation was used to study the interfacial interaction between RGD and TiO2 at an atomistic level. Four important factors affecting RGD adsorption were considered: the initial configuration of the RGD, the crystal structure of the TiO2 materials, the presence of surface defects, and water environment. Three types of RGD initial configurations were considered:lying and standing on the N or O end in order to investigate the effect of the RGD initial configurations on the interfacial interactions. First, RGD adsorptions on ideal rutile (110) and anatase (101) surfaces in a vacuum and in a water environment were studied; then the step edge effects were considered; finally, the synergistic effects of water and surface defects on RGD adsorption were investigated.The simulation results indicate that the RGD peptide binds strongly with anatase (001) and rutile (010). RGD conformation changes due to the variation of the backbone torsion angle in the middle of the RGD chain. Pair correlation function analysis indicates that the interaction of the RGD peptide and the titanium oxide results from hydrogen bonding and the groups in RGD play different roles during the adsorption process. The results from the vacuum indicate that the crystal structure of the surface is more important than the initial RGD configuration. The interaction between RGD and the anatase (101) surface is stronger than that between RGD and the rutile (110) surface according the energy analysis. Atomic step edges on TiO2 surfaces could greatly affect the adsorption of the RGD peptide. Water limits the interaction between the RGD peptide and the TiO2 substrate and helps to sustain the initial configuration of the former. The findings should be helpful in understanding the RGD-TiO2 interaction mechanisms and should provide useful theoretical guidelines for titanium surface treatments in orthopedic applications. DFT methods have been utilized to investigate the interactions between Arginine acids(R) and rutile surface. The in-plane oxygen atom and the bridging oxygen atom deficiencies on the rutile surface have been considered in order to explore the effections of the oxygen deficiency on the interactions between rutile and arginine. Furthermore, the water environment also has been investigated here. The study provide the several basical informations on the arginine adsorption on the rutile surface.Molecular dynamics (MD) simulation was used to study chitosan (CS) behaviors on different hydroxyapatite (HA) crystallographic planes at the atomic level. The interaction energy between the chitosan chain and different HA surfaces indicates that the interaction of the chitosan chain and HA(100) surfaces is stronger than that of HA(001) and HA(110) surfaces. The chemical interactions between chitosan and HA were analyzed through the concentration profile and pair correlation function of nitrogen and oxygen atoms in chitosan. The results show that there might be chemical interaction between nitrogen and calcium atoms, and hydrogen bonding between oxygen atoms and hydroxyl groups. This study provides useful information in understanding the HA/CS interfacial interaction mechanism at the atomistic scale.Hydroxyapatite/biopolymer interface interactions in composites for biomedical applications were investigated by molecular dynamics (MD) simulations in oder to understand the role of coupling agents. The study analyzed the binding energies between hydroxyapatite (HA) and three polymers:polyethylene (PE), polyamide (PA) and polylactic acid (PLA). The interactions of polymers on HA crystallographic planes (001). (100) and (110) were simulated. The effects of the silane coupling agent (A 174) on interfacial binding energies were also examined. The results show that HA (110) has the highest binding energy with these polymers because of its higher planar atom density than that of HA (001) and (100). The binding energies of PA/HA and PLA/HA are much higher than that of PE/HA. which might be attributed to large number of polar groups in PA and PLA chains. The silane coupling agent A174 increases the binding energy between PE and HA. but not for the PA/HA and PLA/HA systems. The MD results can be used to guide the design of polymer/HA composites and to select proper coupling agents.All in all. computer simulation is a very usefully technology in the biomaterials surface and interface research areas. It could study the effects of biomaterials microenvironments on the interactions between biomaterial surfaces and biological tissue, also the electrons transfer occuring there.