Fabrication Of Wood/Hydroxyapatite Composite As Bone Substitution Material

As one of the important subjects, biomaterials especially man-made bones are attracting more and more attention. Hydroxyapatite is one of the most attractive biomaterials for bone repairing due to its good biocompatibility and bioactivity. However, hydroxyapatite is difficult to be used as the weight-bearing bone owing to its weak mechanical property. Hence, it is significant to fabricate a new composite biomaterial with good mechanical property. Wood is a common natural biomass material and possesses excellent biocompatibility, bioactivity, mechanical property and porosity, therefore it is suitable to be used as the substrate of the composite biomaterials. And the pores with differnent sizes in the wood can allow bone cells adhesion and differentiation. In this thesis, two new fabrication approaches of wood/hydroxyapatite composite material are developed. The structure and the properties of the resulting materials are investigated, in order to obtain the possibility of their applications in biocompatible materials. The main contents are as followed:1. Chinese Glossy Privet was selected as the substrate of the composite material. The wood surface was inert to fabricate hydroxyapatite, it was necessary to activation the surface of wood. After the pre-treatment of the wood, polyethylene glycol was grafted onto the surface of the wood. Polyethylene glycol can help enhance the protein adsorption, cell adhesion, growth and proliferation, which making it an important biomaterial with good biocompatibility, minimal toxicity and immunogenicity. Then the deposited hydrated calcium hydrogen phosphate was transformed into hydroxyapatite successfully by hydrothermal vapor treatment. Fourier transform infrared spectrometer, X-ray diffractometer, field emission scanning electron microscope with energy dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectroscopy were used to detect the properties of the wood/hydroxyapatite composite biomaterial. The surface morphology of the sample was observed by Sirion200Field Emission Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy. The structure and compositions were analyzed using TTR-Ⅲ X-ray Diffractometer and Fourier Transform Infrared Spectrometer. The concentrations of Ca2+in the phosphate buffer solution were measured by inductively coupled plasma atomic emission spectroscopy. The hydroxyapatite particles on the wood surface showed a flower-like appearance with high crystallinity and regular pattern. And the in vitro experiment indicated that the hydroxyapatite paticles were tightly adhered to the surface of the wood, which was beneficial for its application as artificial bone. This work provides a new fabricating approach of biocompatible material which may have some potential applications as bone-repairing material.2. Chitosan is a widely used biomaterial with good biocompatibility and renewability, and it can be easily mixed with hydroxyaptite to fabricate chitosan/hydroxyaptite gel. The gel could tightly adhere to the wood surface to get a porous chitosan/hydroxyapatite coating through air-drying and chemical foaming. Chitosan/hydroxyapatite coating could closely adhere to wood surface because wood has a good hydrophilicity. Meanwhile, the thickness of coating and the size or amounts of pores could be adjusted by adding different amount of chitsan/hydroxyapatite or sodium bicarbonate, sodium bicarbonate could make the chitosan/hydroxyapatite gel porous in acidic surrounding through effervescence effect. Therefore, due to the rigidity and biocompatibility, Chinese Glossy Privet was chosen as the substrate in this work for fabricating chitosan/hydroxyapatite coating. Such wood/chitosan/hydroxyapatite composite materials were measured by Fourier transform infrared spectrometer, Field emission scanning electron microscope and thermogravimetric analyzer. The morphology of the sample was observed by field emission scanning electron microscope, the structure and composition were analyzed using Fourier transform infrared spectrometer and thermogravimetric analyzer. Fourier transform infrared spectra analysis indicated that the interaction between chitosan and hydroxyapatite might exist. The degradation of the wood/chitosan/hydroxyapatite composite material was measured by the loss of sample’s weight through immersing in the phosphate buffer solution.In this thesis, two fabrication methods of wood-hydroxyapatite composite materials were developed, which were proved to be with high efficiency, convenience, compactness and stability. The obtained wood-hydroxyapatite composite materials could be potentially used as artificial bone. The main innovation of this thesis is the fabrication of hydroxyapatite using physicochemical modified wood as the substrate.