Study On Preparation And Osteogenic Properties Of Oriented Porous Functional Scaffold

Bone is an important part of the human body,and plays the role in supporting and protection.However,bone injuries caused by traumatic injuries and other factors can also have difficulty self-healing.Bone tissue engineering is devoted to the reconstruction of the structure and function of bone through implantation of scaffolds.The ideal scaffolds generally have a bionic structure and can repair bone,blood vessels and nerves simultaneously.Cryogel is a kind of hydrogel prepared by freezing technology,which has high pore connectivity.Therefore,in this study,a microspherecryogel composite with an oriented macroporous structure and sustainably release of Mg²⁺ was prepared,and its effects on osteogenesis,vascularization and neurogenesis were investigated in vivo and in vitro.The main contents are as follows:The first chapter briefly describes the basic content of bone tissue engineering,and introduces the commonly used materials（natural polymer,synthetic polymer and bioceramics）and requirements（orientation bionic structure,pore size,biocompatibility and ability of promoting tissue regeneration）of bone tissue engineering scaffolds.Then,the requirements of bone tissue engineering scaffolds and the effects of Mg²⁺ on bone regeneration,angiogenesis and nerve regeneration were introduced.Finally,the thesis topic and research content were proposed.In the second chapter,norborne-modified gelatin（GB）,chitosan/sodium alginate microspheres loaded with magnesium L-threonate（MgT-MCS）and dithiothreitol（DTT）were used as prepolymers,and the oriented microsphere-cryogel composite（MgT-MCS/GB）was prepared by bidirectional freezing method.The composite has a oriented macroporous structure（>100 μm）and can sustainably release Mg²⁺in 28 days.The composite also has high equilibrium swelling rate and fast material exchange rate.In the third chapter,the effects of MgT-MCS/GB at different Mg²⁺concentrations on osteogenic differentiation,vascularization and neural differentiation were explored.The results showed that:（1）The composite has good biocompatibility.（2）Composite with higher concentration of Mg²⁺ can promote the osteogenic differentiation of bone marrow mesenchymal stem cells（BMSCs）,improve the activity of alkaline phosphatase,and promote the expression of osteogenic genes.（3）Composite with higher concentration of Mg²⁺ can promote the migration and tubule formation of human umbilical vein endothelial cells（HUVECs）;（4）Composite with higher concentration of Mg²⁺ can promote the migration of rat Schwann cells（RSC96）and the differentiation of neural cells.In the fourth chapter,it was verified that MgT-MCS/GB cryogel composite can promote bone regeneration in vivo.Micro-CT images,HE staining,Masson staining and OCN immunohistochemical staining showed that the oriented macroporous structure and Mg²⁺could synergically promote the formation of new bone.CD31 immunohistochemical staining showed that the oriented macroporous structure and Mg²⁺ may act synergically,and NGF immunohistochemical staining showed that Mg²⁺could promote nerve regeneration.In summary,this paper reported the prepareation of oriented microsphere-cryogel composite with macroporous structure and sustainably released Mg²⁺,and verified that it can simultaneously promote osteogenesis,vascularization and nerve regeneration,and achieve bone repair through the osteogenic-angiogenic-neural coupling effect.