| Bone is an organ that the human body mainly uses to withstand external forces and plays an important role in people's healthy life.In recent years,the number of patients with bone defects caused by diseases and traffic accidents has been increasing.Currently,the commonly used treatment method is implanted with bone repair materials.?-tricalcium phosphate(?-TCP)has been extensively studied as a bone substitute material.But P-TCP has poor molding performance and biological activity.Octacalcium phosphate(Ca8(HPO4)2(PO4)·5H2O,OCP)has good bone conduction properties and excellent biological activity,and has no stimulation or rejection effect with tissues.Sr,as a trace element necessary for the human body,can effectively reduce the impact of osteoclasts on the human body,at the same time promote the osteogenic ability of the cells,and also enhance the mechanical properties of the material.Therefore,in this project,a new composite biomaterial is prepared by combining ?-TCP with OCP to improve its molding performance,biological activity and osteogenic performance,and then to further enhance the mechanical and biological properties of the material by doping Sr.The specific contents are as follows:(1)Pure ?-TCP,P-TCP powders with different amounts of Sr doped and OCP were prepared by chemical co-precipitation method.XRD analysis results show that we have prepared powder with good crystallinity and high purity.The pH,reaction temperature and ion concentration of the solution have a significant effect on the synthesis of OCP.pH=4.5,temperature 75?,ion concentration 0.08 mol/L are the best conditions for OCP synthesis.Sr doping causes Sr2+to replace Ca2+in the ?-TCP lattice,causing lattice distortion and shifting the position of the diffraction peak to a low angle as a whole.The results of FTIR analysis show that Sr doping significantly weakened the peak intensity of ?-TCP and moved towards a low wavenumber.The results of SEM and TEM analysis show that ?-TCP is granular and OCP sheet is flaky.The results of nanometer particle size analysis indicate that the average particle size of?-TCP powder is around 300nm.The average particle size of the OCP powder is around 280 nm,and Sr doping can slightly increase the particle size.The results of specific surface area analysis show that the specific surface area of OCP is more than twice that of ?-TCP.This is caused by the difference in density between the two.And the doping of Sr makes the specific surface area of ?-TCP decrease.(2)?-TCP/OCP composites with different Sr contents were prepared by cold compression molding followed by isostatic compression molding.The SEM results of the surface morphology of the composite materials with different Sr doping levels show that the undoped Sr ?-TCP particles retain the granular morphology,and as the Sr content increases,the granular ?-TCP becomes more and more flatter.In the compressive strength test,as the forming pressure increases,the compressive strength of the material also increases.Generally speaking,as the OCP content increases,the strength of the material also increases.In the porosity test,the material's porosity is exactly the opposite of the compressive strength.At a molding pressure of 80 MPa,the P-TCP:OCP=7:3 material has a porosity of about 45%and a compressive strength of more than 40 MPa,and has the best comprehensive performance.Sr doping can increase the strength of the material and reduce the porosity of the material.Variance analysis shows that different molding ratios,different molding pressures and Sr doping have significant effects on compressive strength and porosity.(3)The effect of steam hydrothermal treatment on the morphology and properties of composite materials was studied.The study finds that OCP grows up from the initial sheet shape,gradually becomes thicker and thicker,and finally turns into a rectangular parallelepiped shape.?-TCP changes from granular to fibrous,and becomes short rod shape at 195?.When the time of steam hydrothermal treatment exceeds 8h,an irregular polyhedron block is formed.All in all.steam hydrothermal treatment at 195? for 4h has the best appearance and performance.At the same time,the effect of the calcination process on the morphology and properties of the composite materials was studied.After the calcination treatment.OCP is transformed into[3-TCP.The compressive strength of the composite material is slightly lower than that of pure ?-TCP material,but much higher than that of pure OCP material.The porosity of all materials is densified due to calcination,but no more than 40%.Variance analysis shows that the calcination temperature has an important effect on the compressive strength and porosity of the material.(4)In vitro degradation tests indicate that a layer of bone-like substance HA can be deposited on the surface of the composite material.And the ability of OCP to induce the production of bone-like substance HA is significantly stronger than that of?-TCP.Sr doping can increase the deposition of bone-like substance,but will inhibit the degradation of ?-TCP.Biological experiments show that the doping of Sr can significantly improve the biocompatibility and osteogenic ability of the material.Among them,the 3%Sr group has the best biological performance,and high concentration of Sr will reduce the biological performance of the material.In the analysis of variance,different molding ratio,degradation time and the doping of Sr all have significant effects on the quality change and pH change after degradation,and the doping of Sr and culture time have significant effects on cell proliferation and the expression of osteoblast related gene. |
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