Construction And Optimization Of Porous Zirconia Based On Bone Tissue Engineering

Objective:Bio inert ceramic zirconia（ZrO₂）is widely used in bone tissue engineering materials because of its high mechanical strength,corrosion resistance,fracture toughness and good biocompatibility.However,as a bio inert material,ZrO₂ is not easy to form an effective bond with bone tissue and does not have the function of bone conduction.Therefore,in order to solve this problem,in the first part of this paper,porous structure was introduced to improve the mechanical bonding between the matrix and bone tissue,and to provide reference for cell infiltration,nutrition transportation,waste treatment and the formation of new tissue for the host environment.Also,through the systematic design of the experimental scheme and continuous optimization of the molding conditions of porous ZrO₂,the foundation for the preparation of bone implant structure is laid;In the second part,porous ZrO₂ was combined with polymer to improve the bonding strength between bone tissue and implant,and endowed the matrix with new biological functions.Methods:In the first part of the study,the molding conditions of porous ZrO₂ were studied.These conditions include the content of ZrO₂ powder,the pore size of polyurethane,the number of impregnation and the introduction and proportion of adhesive.Through controlling these parameters,porous ZrO₂ ceramic scaffolds with good mechanical properties,controllable porosity and good molding morphology can be obtained.The porous ZrO₂ scaffolds were characterized by X-ray diffraction（XRD）and scanning electron microscopy（SEM）.The mechanical properties and capillary phenomenon of porous ZrO₂ scaffolds were tested.In the second part of the study,a porous scaffold made of ZrO₂ scaffolds was used as the substrate,and the composite scaffolds were constructed by filling different concentrations of methacrylated gelatin（Gel MA）hydrogel and sodium alginate（SA）hydrogel.The morphology,phase,mechanical properties and biological properties of the composites were systematically studied.Results:Part I:porous ZrO₂ scaffolds with controllable pore size and porosity,relatively high compressive strength,good scaffold morphology and capillary phenomenon were successfully prepared by template replication method.The pore size and porosity of the stent can be effectively controlled by adjusting the content of ZrO₂,the pore size of the template and the times of slurry hanging;the compressive strength of the stent can be enhanced by introducing the adhesive PVA and adjusting the ratio of the adhesive content and ZrO₂ content,and the stent with better shape can be obtained;the porous ZrO₂ stent has capillary phenomenon,which can promote angiogenesis.Part II:the composite scaffolds with different proportions were prepared by vacuum infiltration combined with single cross-linking and double cross-linking.The results showed that the morphology and biological properties of all composite scaffolds were better than that of porous ZrO₂ scaffolds,and the filling of hydrogels had achieved the purpose of functional modification.Compared with ZrO₂-SA composite,in the aspect of morphological characteristics,ZrO₂-Gel MA and ZrO₂-GM/SA have ideal morphology characteristics between the composite scaffolds,especially the size and uniform pore size distribution of ZrO₂-10Gel MA and ZrO₂-10GM/1SA two kinds of gel,which is an important part of cell growth and adhesion and transportation.In terms of mechanical,swelling and degradation properties,ZrO₂-SA has higher swelling degree,but lower compressive strength.Both ZrO₂-Gel MA and ZrO₂-GM/SA showed proper swelling degree and controllable degradation.In terms of cell biological properties,the cell proliferation of ZrO₂-GM/SA was the most obvious.Conclusions:Part I:porous ZrO₂ scaffolds with controllable pore size and porosity,relatively high compressive strength,good scaffold morphology and capillary phenomenon can be prepared by template replication method.Part II:the filling of Gel MA hydrogel and SA hydrogel can achieve the purpose of functional modification of porous ZrO₂ scaffolds,and is suitable for the preparation of bone tissue engineering scaffolds.