Biomimetic Mineralization Of Hydroxyapatite Composites By Organic Templates Via Simulate Body Fluid

As a thermodynamic stable crystalline phase, hydroxyapatite is the most similar to the mineral in bone tissue and is a key ingredient in various vertebrate bones. Because of not only the excellent bioactivity and compatibility but also the conduction of regeneration of bone tissue,hydroxyapatite has been studied widely. However,due to the structure and poor mechanical properties of natural hydroxyapatite which are not comparable to the native bone,the application of natural hydroxyapatite is still limited. Hence we are engaging in these problems in this dissertation. In order to prepare the hydroxyapatite organic/inorganic hybrid materials, the organics templates are employed to regulate and control the formation of hydroxyapatite in a moderate circumstance. In this dissertation,different organic templates are employed and the effects of both concentration of template and time of biomineralization are investigated. An organic/inorganic hybrid materials of which the structure and properties are close to bone tissue are obtainedFunctionalized graphene is a natural layer structure and the functional groups on the surface can effectively induce mineral deposits. While the monomer firstly self-assemble into nano-fibre structure via quadruple hydrogen-bonding interaction, and the nano-fibre again intertwine and interweave into other sec-structure according to the concentration of monomer via the hydrogen bonding of terminal group.Functionalized graphene layers and template self-assembled by aspartic acid ending-group monomer (UPy-Asp) are both thin film material, and the functional group on the surface can induced nucleation and crystallization of hydroxyapatite. With the time pass by, the crystallization of hydroxyapatite grow gradually and the template layers wrap the crystal and fuse them together to get organic/inorganic hybrid materials. The mass fraction of hydroxyapatite on functionalized graphene layer template is about 22.3 % while on the UPy-Asp template is about more than 60 %. Cell culture experiments show that the product has a good biocompatibility and the elastic modulus can reach about 5.0 GPa.The template formed by the glycerol ending-group monomer (UPy-Gly) shows a porous hierarchical self-assembly structure under the condition that the template concentration is close to the solubility. Hydroxyapatite firstly nucleation and crystallization in the microvoid and then grow gradually and fuse mineral and template together to get organic/inorganic hybrid materials. The mass fraction of hydroxyapatite on the UPy-Asp template is about more than 60 % and the elastic modulus can reach about 3.2 GPa.The optimal concentration of self-assembly templates inducing the mineralization is about the solubility, mean 2.5×10-4 M. The structure, relative contents of mineral and mechanical properties of the product are very similar to the human bone tissue so that it has a broad prospect in biomedical field and has a great significance in studying growth process of bone tissue .