A Novel Composite Materials-Preparation And Biocompatibility Of Graded Zirconia-Hydroxyapatite Composite Bioceramic

The fractures caused by tumour, inflection, abrasion are ordinary in the clinic. The traditional repair of the fractures, such as self-transplant and non-self-transplant, can not be conventionally used in the clinic because of ache and sequelae of self-transplant and repellency of the non-self-transplant. While the artificial synthetical bone substitute, for example, hydroxyapatite(HA) ,is often used in the bone transplant as the bone substitute for its semblable structure as the inorganic-mineralized structure of the bone. But the adverse factors of HAP restriction in clinic application are the frangibility, weak tensibility and tension, and the material will spread when transplanted on the wound.To improve the mechanical properties based on the excellent biologic activity of HAP, HAP coating on the surface of metal materials is used. The coating method includes ion-disordered method, electrochemistry deposition method, plasma spray coating, etc. The most popular method is the plasma spray coating for it forming a strong bond between the HAP and the metal. But this method asks for a strict temperature condition. When the temperature condition alters, the HAP coating will desquamate, and at the same time, it can not avoid the problems of erosion in the human organic environment, dissociation of the metallic ion towards the organic organization, which leads to the inflammation and hyper susceptibility of organic organization. The methods of adding the 2nd phase granule intensifier, such as metal, bioceremics, glass, SiC crystal, and carbonic fibre has no obvious effect on improving the mechanic performance. The functional graded composite method is a simple but efficient method which is carried out under a low temperature. This method is conducive to enhancing the tight combination between interfaces of two kinds of heterogeneous solid material, which make good for minimizing but effecting the hear stress, preventing from cracking.Sponsored by Science and Technology Office of Zhejiang Province, our office and material research Institute of Shanghai University developed a novel biomaterial -Graded zirconia-hydroxyapatite composite bioceremics. Zirconia has excellent intensity and biocompatibility because of its special tenacity-improving mechanism, better than otherbioceremics material. Under the room temperature the 3mol%Y2O3 Zirconia bioceremics has excellent intensity (bending resistance: 12000 MPa) and high fracture toughness property (K I C reaches to 15MPa*ml/2). The composite materials based on Zirconia can meet the standards at the loading parts of the human body. The graded zirconia-hydroxyapatite composite—a novel biomaterials—were synthesized by dry-laying and sintering method which combine the intension, toughness, HA biologic activity.In the clinic, the precondition and foundation of the application of biologic materials which are transplanted into the body and contact the blood are their biologic security and the biocompatibility. According to the international standard organization standard and request of ISO 10993-1: 1992medical instrumental biology, we have done series of experiments on the graded zirconia-hydroxyapatite composite, observing the biocompatibility as well as the effect of boned-inducement and boned-conduction, which establish the foundation of clinic application.The experiments are divided into five parts:1. The preparation and characterization of graded HA/ZrCh composite. Graded HA/ZrC>2 composite is synthesized by dry-laying and sintering method. SEM, XRD, TEM and EDAX were used to characterize the morphology, composition, cross-section, bond strength of coating and bending resistance.2. The biocompatibility of graded HA/ZrC>2 composite. According to "Technical requirements for biological evaluation of biomaterials and medical equipment, Ministry of Health, China", several experiments, including acute toxic tests, hemolytic test, muscle and implantation tests, are performed to evaluate the biocompatibility of the graded materials.3. The immunocompatibility of graded HA/ZrO2 composite. The newly separated PBMCs of the healthy young were cultured in the extracts of the materials. The apoptosis of PBMC, expression of CD3/CD69, lymphocyte Transformation and change of cell factors were tested to evaluate the immunocompatibility of graded HA/Z1O2 composite bioceramics.4. The bone cell compatibility of graded HA/ZrC>2 composite. Through in Vitro cell culture, the osteogenic cells of mice were planted in the graded HA/ZrC>2 composite, and optical microscope and SEM were used to observe the growth of cells andcorrelation between cells and materials.5. The biological link between graded HA/ZrC>2 composite and bone interface. The biological link between two materials were evaluated through the measurements of osseous bond ratio and shear stress, and the biological observation of interface.The study provided a theoretical and experimental basis for the clinical application of the new bio-composite—graded HA/ZrO2 composite.The main results and conclusions of experiments are as follows:1. The osteo-conductive ZrO2 and osteo-inductive HA graded composite—a new composite bioceremics—were synthesized by dry-laying and sintering method for the first time. The main phase at the surface layers were J3-Ca3(PC>4)2 (J5-TCP), a-Ca3(PO4)2 (a-TCP) and CaZrO3;the average bending strength is 868.04Mpa with the maximum up to 1027.27Mpa;the surface roughness is 1.95um.2. The graded HA/ZrC>2 composite is proved to be a kind of bioceramics with good histocompatibility, which has no cytotoxicity or acute in vivo toxicity, and causes no hemolysis. The implantation of the materials leaded to the formation of new bones, and the bone tissues directly grew on its surfaces. No transitional layer was found. The new-grown bone tissues interweaved and thereby improved the bond strength between materials and bone interface. The new-grown bone finally spread over the whole surface of the implanted materials, and the bone trabeculae can be reshaped according to the mechanic requirements. Therefore, this graded composite is an ideal bioceramics for bone implantation.3. The graded composite technique used to prepare HA/ ZrC>2 bioceramics is conducive for improving the immunocompatibility of the materials.4. The cultured osteogenic mice cells can agglutinate, extend, and propagate on the surface of graded zirconia-hydroxyapatite composite bioceremics, which form the inchoate bone interface. With the time increased (2-7 days), the density of the surface of Graded zirconia-hydroxyapatite composite bioceremics increased, the osteogenic mice cells firmly adhered to the material surface with the anchor-shaped, and secreted the cytoplasm, which completely overlayed the materials. Such phenomena explained the excellent biocompatibility of Graded zirconia-hydroxyapatite compositebioceremics.5. The graded HA/ZrC>2 composite has good osteo-conductivity, osteo-inductivity, biocompatibility and immunocompatibility. The graded composite has excellent osteogenic effect, and can form a good biological link with bone interface.