Research On Hydroxyapatite-based Bone Tissue Engineering Composite Scaffolds With Macroscopic Pore Structure

In the field of bone repair,bone tissue engineering is currently recognized as the most potential and promising bone defect repair trial.As a key factor in bone tissue engineering,bone tissue engineering scaffold is a significant research direction.In order to study the preparation of bone tissue engineering scaffold with more excellent properties,this thesis intensively researched on the optimization of fabrication process of scaffolds.Hydroxyapatite was used as matrix material to analyze the aspects of structure and composition,based on extrusion deposition technology.Some new processing methods and optimization of scaffolds were studied in this paper.At first,the process to obtain biogenic hydroxyapatite from bovine bone is introduced in detail.After degreasing and deproteinization,the bovine bone was milled by using a planetary ball mill to obtain nanometer particles.The bovine bone powder(BHA)compounded with sodium alginate(SA)was applied to prepare the BHA-SA composite scaffolds.The scaffolds were sintered at 1000,1100,1200 and 1300℃ respectively.The properties of scaffold was tested in aspects of structural,physical,chemical and biological fields,and the feasibility of application of biogenic hydroxyapatite was demonstrated.Secondly,as the degradation performance of hydroxyapatite scaffold after sintering is poor,this thesis gelatin was added(GA)to control printing slurry viscosity due to its thermo sensitivity.The alginate with excellent biological performance was added to regulate the proportion of HA.The crosslinking curing process was employed to modify the property of GA and SA,to avoid absorbing or dissolving in water,and also to ensure the stability of the scaffolds.In this thesis,the structural and physicochemical properties of the HA-GA-SA scaffolds prepared in different proportions were systematically compared.The results showed that the degradation performance and structure function of the un-sintered HA-GA-SA composite have some advantages.Finally,the freeze drying and extrusion deposition technology were employed to prepare the HA-GA-SA scaffolds with macro and micro holes.The trial of freeze-drying technology could avoid the shrinkage of the scaffold and the uneven components in the process of dehydration.A comprehensive comparison of HA-GA-SA scaffolds prepared in four different proportion in aspects of structural,physical,chemical and biological properties was made in this thesis.The freezing drying provided rich micro pore structure in HA-GA-SA scaffolds,and good biological properties compared to the scaffolds without freeze drying.The preparation technology of the scaffold is of great significance to the study of bone tissue engineering from sintering to normal temperature and to freeze drying.