Study On Preparation Of Porous Ha/ β-TCP/58S Composite Scaffolds

Bone tissue engineering material plays an important role in bone repair materials and always receive broad attention from all related fields. With the development of technology,the bone tissue engineering material has developed from the only natural materials, to synthetics materials, and gradually to porous composites.As one kind of porous biphasic calcium phosphate, porous hydroxyapatite(HA)/β-tricalcium phosphate(β-TCP) has excellent bioactivity, osteogenic induciblity and fine biocompatibility for bone defect repair in clinic. However, its own weakness like low-impact, poor mechanical property limit the scope of application. HA/β-TCP composite with bioactive-glass, may unite the advantages of both sides.That means the Composition may has good bioactivity as well as better compressive strength.In this experiment, we used Ca(NO₃)₂ .4H₂O and (NH₄)₂HPO₄ as raw materials for prepareing HA/β-TCP's precursor d-HA by the method of microwave-aided chemical precipitation; took orthosilicate ethylester and triethylphosphate as precursors, adopted sol-gel method to produce bioactive 58S which has better bioactive properties. We characterized the produced powder by XRD and IR, and observed d-HA powder by SEM.We modified the process of HA/β-TCP/58S preparation. Before 58S formed gel, we added suspension of d-HA.Then, took heat treament after the composite became gel hybrid bulk , adopted slip casted method to cast porous scaffolds. By controling the usage raito of d-HA/58S and porogen amount, we adjusted the porosity, pore-porosity, water absorption, compressive strength of the porous scaffolds, and compared these with porous scaffolds made by presse shaped method. The characters of composites, such as composition ,microstructure, pore-porosity, porosity water absorption ,compressive strength were analyzed with IR,XRD,SEM and some chemistry methods.The results show that, when porogen reached 50% to 60%,(mass fractions) in green body, scaffolds had high porosity about 60% to 70%, pore-porosity about 40% to 50%, water absorption about 40% to 50% by the method of slip casting; however, at the same weight of porogen, scaffolds shaped by press method just reached porosity about 40% to 50%, pore-porosity about 30% to 35%, water absorption about 20% to 30%. SEM indicated that scaffold has connected inner pore with homogeneous pore distribution by the slip casted method and the surface of pore wall of scaffold was rough so that cells may easily get absorbed. Therefore, porous scaffolds made by slip casted method may have better biological properties .Meanwhile, compositing 58S with HA/β-TCP, the scaffolds's compressive strength improved greatly.When the porosity was about 33.2%, the compound's compressive strength was about 6 Mpa, but HA/β-TCP just obtained 2.5Mpa.With the the ratio of 58S in scaffold increased, the better compressive strength was achieved. Even though the compressive strength of porous scaffolds made by the slip casted method could not reach the same level of scaffolds by press casted method, they were still up to 4.1 Mpa with porosity about 46.9%, basically satisfy the compressive requirements of bone-tissue engineering. SBF soaking experiment showed, the pH value of SBF solution had slight increase with time growth,which may benefit for bone apatite growth on scaffold surface.In conclusion, slip casted method is a simple preparation method, can effectively improve the strength of scaffolds, basically meet the needs of tissue engineering method.