Research On The Fabrication Of HA Bone Scaffold Based On MAM Extrusion Deposition System

Bone defects and failure are the most common disease in the world, and nowadays themain treating methods are limited to the implant of autograft, allograft or somenon-degradable materials such as titanium alloy. As the booming development ofbiomaterials and tissue engineering, degradable bone scaffolds, instead of primaryimplants, are now becoming the most promising approach to regenerate bone defects.Scaffolds for bone tissue engineering should possess3D complex porous structure andexcellent mechanic and biology properties. It is very difficult for traditional manufacturetechnologies such as foaming and leaching to realize the complex controllable structures.3DP (3D printing) or RP (Rapid Prototyping) has finally solved this problem.3DP hasbecome one of the most popular and hot scientific terminology since it was proposed bySachs etc. for the first time in1993, which is also now considered as the main factor topush forward the third industrial revolution. This thesis studied on fabricating HA bonescaffolds with complex porous structures based on MAM precise extrusion technology.Mechanic and biology properties of scaffolds were evaluated. And the whole processingtechnique was also optimized to get a series of proper processing parameters.According to the requirements of HA slurry performance in the extrusion processing,this thesis systemically studied dispersion mechanism of nano HA particles in aqueousmatrix, and concluded the factors which could influence the dispersion. Based on theacquired data from the viscosity and sedimentation experiments, the optimal ingredient ofagents was as follows: dispersant PAA was1.5%, pH=9-10, temperature was25-30°C,glycerol in the solvent was10%, surface active agent PEG was4%.Fluid mechanic analysis of the slurry in the extrusion process was conducted. Factorsand parameters such as nozzle diameter and extrusion speed had some effects on thevelocity of slurry and extrusion swelling phenomenon. Finite element methodPOLYFLOW software was applied to simulate the extrusion process using Binghammodel. And fabrication experiment was also carried out to verify the best parameters. Thebest combination of parameters was: the nozzle diameter φ=0.34mm, scanning speed Vxy=7mm/s, extrusion speed Vt=0.005mm/s.Sintering process was optimized by studying the mechanism of it. Factors that caninfluence the micro structure and properties of scaffold such as sintering method, sinteringtemperature and time were systematically researched. And the best sintering process wasmicrowave sintering in1200°C for30min. Scaffolds after sintering possessed excellentmechanic property, and the compressive strength could reach45.57MPa. Finally, biologytest including in vitro and in vivo experiments were carried out to evaluatebiocompatibilities and osteoinduction. Images of SEM illustrated very good attachment ofMC3T3-E1cells on scaffolds. The CCK-8experiment also showed the evidence of goodproliferation. Osteoinduction of scaffolds in bone defects was primarily explored andverified by animal test in New Zealand rabbit. The results of Micro-CT and florescence ofcalcein showed that there were some new bone components formed in the surface ofscaffold. By combining RP technology with microwave sintering, this thesis realized thefabrication of3D porous scaffolds, which showed promising future in the clinicalapplication after mechanical and biology test.