Synthesis And Bioactivity Characterization Of HA/CS Composites

Hydroxyapatite(HA) is the main inorganic composition of human bonesand teeth. It has a good ability to bond with bone and biological activity.Synthetic HA is non-toxic, safety and has a good biological activity andbiocompatibility and can well combine with bone. So it’s a good bone repairsubstitue materials. But because of the brittleness and low toughness, thestrength of HA is less than human bones. As a result, it cannot be directly usedas bearing parts in a bone defect repairation. Therefore, in order to improve theHA mechanic properties, and make it as the ideal bone graft substitute materials,it is necessary to compound with other materials. It can improve mechanicalstrength and toughness of HA for combine a natural or synthetic organicmolecule with HA. Chitosan(CS) is a kind of alkaline polysaccharide positivelycharged in nature. It is obtained by a deacetylation of Chitin. CS is similar tosugar glycosaminoglycan in structure and can be degradated and absorged inhuman body. CS has a variety of biological activity, but the ability of bonebonding is poor. This topic research aim is to synethesize a composite of HAand CS—HA/CS, having the advantages of HA and CS, good at biologicalactivity, biocompatibility and mechanical properties. To improve thecomprehensive performance of HA/CS materials as a bone repairIn this study, a combination method of even co-precipitation andhydrothermal method was used to synthesize HA/CS composite in a short time.The factors affecting the morphology and biocompatibility of HA/CS crystalswere investigated. The mechanic properties, composition, and morphology ofHA/CS crystal were characterized by XRD, FTIR, SEM. And also wet-thermaltesty were conducted to enhance the resistence to water of HA/CS composite.The fibroblasts of chicken embryos and rats’ osteoblast were used to observe thebiocompatibility and biological activity of HA/CS by primary cell culture.The results indicated that:1) Using even co-precipitation in a water bath to prepare HA/CS crystal isfeasible. Concentration of reaction solution and pH value has significant influence on the crystal morphology. Crystal can be changed fromneedle(bar)-like and sphere to almost all spherical shape when concentration ofreaction solution or pH value were raised. CS average molecular weight and CSaddition have slight effect on the morphology of HA/CS.2) The internal stress of HA/CS disks are improved by wet-thermalprocessing, so the HA/CS water resistance performance are also improved.3) When the response system pH=8, mass concentration is0.1mol/L, CSadd content is30%, CS for any molecular weight, HA/CS particle have gooddispersion, and compressive strength from176.7MPa~179.8MPa.4) Cell culture experiments show that, HA/CS is non-toxic materials, andfibroblasts and osteoblasts have very good compatibility with HA/CS.5) When the response system pH=8, mass concentration is0.1mol/L, CSmolecular weight is250000~300000, CS in any proportion to add, theosteoblast compatibility with HA/CS is overall better. Among them, when CSaddition is40%, the relative rate of cell proliferation in the composite materialis supreme, the cell compatibility and biological activity is the best; When CSaddition is30%, cell compatibility is second only to addition of40%CS amount.But it has the best particle dispersion, and the compressive strength is176.7MPa.