The Research On 3D Printing Fabrication And Properties Of Strengthening Sodium Alginate/Chitosan Hydrogel Scaffolds By Silica Fume

Background:Repairing large-scale defects of the jaw caused by trauma,tumor,infection or developmental deformity is a major clinical problem.Traditional autologous bone graft repair has disadvantages of limited bone mass and secondary injury.Therefore,bone tissue engineering is becoming the most promising treatment.However,the challenges of restricting its application and development lies in the lengthy preparation process of bone tissue engineering scaffolds,the difficulty in realizing personalized shapes and the high cost output,at the same time,non-adjustable pore size of the scaffold is harmful to its mechanical properties.So the clinical application of bone tissue engineering technology is still far away.Objective:In order to solve the problems of poor mechanical properties,excessive swelling rate and fast degradation rate of sodium alginate（SA）and chitosan（Chitosan,CS）composite scaffolds,so as to meet the performance requirements of bone tissue engineering scaffolds.MethodsThis project intends to use nano-scale silicon dioxide（SiO₂）purified by industrial waste microsilica fume as a reinforcing material,and use 3D printing technology to prepare a low-cost,high-strength,low-swelling,controllable degradation and excellent biocompatibility.The new bone tissue engineering scaffold provides a new idea for the bone tissue repair scaffold.1.The industrial solid waste product Silica Fume（SF）was purified by high temperature sintering combined with acid leaching（hydrochloric acid,sulfuric acid）to obtain non-toxic silicon dioxide（SiO₂）nanoparticles.Use scanning electron microscope（SEM）,X-ray diffractometer（XRD）and X-ray fluorescence spectrometer（XRF）to characterize and analyze its morphology,structure and composition;2.SA-CS base paste is suitable for 3D printing,prepare 3D printing structure with good plastic properties,explore the effect of cross-linking treatment on hydrogel scaffolds,and optimize cross-linking formula;Effect of SA-CS scaffold on mechanical properties,obtained high-strength SA-CS hydrogel scaffold;3.Silica（SiO₂）nanoparticles were doped into SA-CS base slurry in different proportions,and composite bone tissue scaffolds were prepared by 3D printing technology.Scanning electron microscope（SEM）was used to characterize its morphology and structure,and the swelling rate and degradation rate of scaffolds were tested.Alkaline phosphatase（ALP）and alizarin red staining（ARS）were used to evaluate the in vitro osteogenic effect of the hydrogel scaffolds.Results1.The microsilica fume（SF）was sintered at 500°C for 5h,placed in a 2mol/L HCl solution,stirred continuously for 5h at a speed of 300r/min in a water bath at60°C,and subjected to deacidification after three cycles of pickling.,to obtain nano-scale SiO₂particles.SEM results show that SiO₂presents a nano-scale spherical structure with uniform size and clean surface;XRF and XRD results show that SiO₂nanoparticles are still amorphous and have not crystallized;the purity of SiO₂is as high as 94.93%,eliminating 26.86%of impurities.Therefore,it is proved that the purification of SiO₂nanoparticles from SF is a low-cost and efficient processing method;2.After the rheological property test,the viscosity of the paste is 1000 Pa.s-10Pa.s,which is a typical shear thinning paste,suitable for printing;soak the SA-CS stent in 2mol/L calcium acetate for 30min and transfer it to In 2wt%calcium acetate,the optimal cross-linking formula was obtained.Compression test results show that when the diameter of the stent is 0.6 mm,the compressive strength is 0.46 MPa;when the diameter of the needle is 0.34 mm,the compressive strength is 0.49 MPa,and the structure with the best mechanical properties is obtained;3.Based on the research in the previous section,the addition of nano-SiO₂to the base slurry significantly reduced the stent swelling rate and degradation rate,and further improved its mechanical and biological properties.There is an optimum dosage for biocompatibility.The SA-CS-3%SF hydrogel scaffold not only has the most significant proliferation effect and osteogenic potential on MC3T3-E1 cells,but also has a compressive strength of 0.61 MPa,realizing a scaffold with high strength and good biocompatibility Structural design.Conclusion:In this study,SiO₂was finally used in the base slurry through solid waste purification treatment,proportioning and cross-linking design.The SA-CS-3%SF composite hydrogel scaffold obtained by 3D printing technology has high strength,low swelling,low degradation rate and good biocompatibility,and can be used as a good scaffold material for bone tissue engineering.