Synthesis And Characterization Of Hydroxyapatite With A Sheet Morphology And Its Composite Material

Hydroxyapatite (HAP) has the similar chemical composition and structure to human bones and teeth in major inorganic components. HAP is widely used as bone substitute materials in the field of orthopedic surgery and hard tissue repair due to its good bone conductivity, biocompatibility and biological activity. A problem, however, is that they create an acidic environment at the implant site that induces an inflammatory response.To enhance the mechanical strength and to prevent infection of HAP implants a silver and lanthanum doped hydroxyapatite/silk fibroin composite materials (Ag/La/HAP/SF) composite was synthesized by hydrothermal synthesis method. Silk fibroin fiber was dissolved in the mix solution of ternary solvent (CaCl2, C2H5OH and H2O molar ratio of 1:2:8). After desalination by dialysis it become silk fibroin solution (SF sols) which was directly added into the reaction system to synthesize a different ratio of HAP/SF fibroin composite materials. According to the ratio of urea mass to reaction solution system, 1g/160ml urea was added in reaction solution to control pH value. Sorbitol as a template agent was also used:The phase composition and morphology of HAP and Ag/La/HAP/SF composites were observed using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR). The effects of the concentration of starting reactants, reaction time and temperature, pH value, the amount of urea used, the pH control agents, the template agent of sorbitol on the growth, chemical composition, size and morphology as well as the stability of obtained crystal, were investigated. The antibacterial properties of doped antibacterial HAP were detected using the minimum inhibitory concentration method (MIC). The bioactivity and biocompatibility of the metal-ions-doped HAP material were observed through cell culture method of osteoblasts from a mouse.The results show that, the better starting materials for preparation of HAP are 0.1mol/L of CaCl2 solution and (NH4)2HPO4 solution. A single HAP crystal with high purity and a unique sheet morphology was obtained by hydrothermal method at 120℃, reacted for 2h. Over-extension of reaction time was not good for formation of the sheet morphology HAP. Silver ions (Ag+) has a strong anti-bacterial properties and lanthanum ions (La3+) can refine and improve the crystal stability of crystal. These two ions in the hydrothermal reaction system can be adopted by co-precipitation and ion exchange into the HAP. The control of pH value is very important for synthesis of Ag-doped HAP. The pH value in reaction system was changed from the starting value 10-11 down to 7-8. Urea was a good agent to control pH value of synthesis solution. We can dope La in HAP crystal under a wide range of alkaline conditions.The sheet HAP/SF composites were composed of many unique needle bars and whiskers, which can significantly improve the mechanical properties of HAP. The increase of SF in composite enhance the cross links between HAP crystal and SF. The MIC testing results showed that Ag/La/HAP has efficient antibacterial properties against to Escherichia coli and Staphylococcus aureus and the MIC is 30.32ppm. The osteoblast cells grew well on the Ag/La/HAP and HAP/SF composite surface showed that the prepared doped antibacterial HAP and HAP/SF composite material having a good biocompatibility.