| Hydroxyapatite and titanium are successful biocompatible materials that are extensively used today for manufacturing bone replacement. Since metallic biomaterials used for orthopedic and dental implants possess a paucity of reactive functional groups, biomolecular modification of these materials is challenging. Hydroxyapatite, the same as the main inorganic component of bone, has problems as used for bone filler and bone tissue engineering scaffold due to brittleness and low dissolution rate. In order to improve their biocompatibility, we immobilized collagen on surfaces of both materials by irradiation grafting. Active centers on surfaces of hydroxyapatite and titanium that induced by radiation reacted with organic monomers 2-Hydroxyethyl acrylate (HEMA). Then collagen was coupled with HEMA monomers. So collagen was covalently linked to the surfaces of hydroapatite and titanium by a surface modification process that radiation grafting with HEMA. The properties of surface-modified materials were investigated by a number of surface sensitive techniques: IR, XPS, SEM and other methods.The iso-phase grafting polymerization is a kinetic controlling process. The radiation dose, radiation ratio and organic monomer concentration are main effect factors to the grafting yields when the. materials properties fix on. Compared with graft yields of congener materials of different specific surface areas in the same radiation conditions, the graft yields are obviously affected by the specific surface area and the absorbent capacity of materials surface and the diffusive rate of HEMA monomer in the iso-phase graft polymerization. The bigger the specific surface areas are, the bigger the differences of chemical bonds and electronical states on surface are with material inner. The specific surface area and theabsorbent capacity of materials surface and the diffusive rate of organic monomer influence the reactive graft yields. The surface structures of the materials have especially an influence to stereochemistry of graft polymeric chain. And the structure responds to the environment by expanding to make new polymeric method. Besides, the grafting reaction is also a preparing biofimctional materials method with cell recognizability. The grafting yield of hydroapatite was better than titanium's on the same situation. The quantity of collagen coupling depended on the HEMA grafting yield. We got the best condition of HEMA radiation grafting that can direct the following work.The result of BSA adsorption on materials indicated the adsorbent capability of materials was changed after surface modification. That maybe due to the collagen film on the materials. A comparative study of the in vitro formation on the materials was finished in a simulated body fluid (SBF). After surface modification, there were mineral layer on the surface of materials dipped in SBF for 3days. And the crystalloid-like mineral was found after a longer time. All of above indicated that the bioacitive of materials were improved through surface modification.In practice, the immobilized biomelecules, such as collagen, and the overall interfacial structure increase the information contact of the surface and the degrees of freedom as compared to the inorganic surface. Graft polymerization by irradiation is one of the important modification methods, in the presence of chemical bond between inorganic particles and surface modified agents. In this paper, collagen was immobilized on the hydroxyapatite and titanium surface by irradiation. It is possible to improve the interface of inorganic-organic composite materials and to make bioactive materials by using radiation induced-grafting copolymerization. |
