Preparation Of Nanocarbon-based Magnetic Compsite And Its Application In Calcium Phosphate Cement

With the good biosafety and plasticity,Calcium phosphate cement(CPC)has been widely concerned and studied in the field of bone repair.But CPC has been commonly used in non-bearing bone site of bone repair and bone replacement due to its low compressive strength.which has been greatly limited in clinical application.The CPC as the base material,the functional composite can meet the basic requirements of bone repair materials.Carbon nanotubes(Carbon,nanotubes,CNTs)and graphene(Reduced-graphene oxide,RGO)with high surface area and high free energy,corrosion resistance and other advantages,can increase the toughness of composite.Some studies show that the carbon nanomaterial has good biocompatibility.In addition,magnetic nano-iron oxide(Fe3O4)material as a functional nano-particles with good biocompatibility,can be used for biomedical magnetic hyperthermia,and has been in the field of drug and vaccine release applications.Therefore,nano carbon based magnetic composites with biocompatibility and magnetism can be obtained by compounding Fe3O4 with carbon nano materials.It is possible that the preparation of high compressive strength and magnetic stimulation of the magnetic bone repair material by introducing composite materials into CPC,in which CNTs as an additional material and Fe3O4 as a magnetic material.In this experiment,carbon nano based magnetic composites were prepared by in situ deposition of Fe3O4 on CNTs and RGO,and the effects of different preparation methods and surfactants on the physical and chemical properties of magnetic composites were studied.The magnetosilicate calcium phosphate cement(MCPC)was successfully prepared by adding CNTs/Fe3O4 and RGO/Fe3O4 with high saturation magnetization to calcium phosphate cement and the physical and chemical properties of MCPC were tested.The degradation performance and mineralization properties of MCPC in simulated body fluids(SBF)were studied under the action of static magnetic field with different magnetic properties.The cytocompatibility of MCPC was evaluated by in vitro co-culture experiments of bone marrow mesenchymal stem cells(MSCs)and MCPCs,and the effects of different static magnetic fields on MCPC cell compatibility were investigated.First,the magnetic composites were prepared by boiling reflux and hydrothermal deposition Fe3O4 on CNTs and RGO.It was found that Fe3O4 on CNTs/Fe3O4 had higher crystallinity and stronger magnetic properties.The crystallinity,morphology and dispersion degree of Fe3O4 were controlled by different surfactants and the results show that the saturation magnetization of CNTs/Fe3O4 prepared by adding NaAc+CTAB and NaAc+PEG 2000 is respectively 65.77emu/g and 65.08emu/g,which is at a high level.The magnetic MCPC was successfully prepared by adding different nano carbon based magnetic composites into the solid phase powder of CPC.The results show that the addition of nano magnetic composite has no influence on the phase composition of MCPC,but it will decrease the solidification time of MCPC,and the solidification time of MCPC decreases with the increase of the amount of the additive.The effect of different carbon nano based magnetic composites on MCPC was different.The MCPC of RGO/Fe3O4 showed brittle fracture.The MCPC of CNTs/Fe3O4 was plasticized and MCPC first showed ductile fracture then appears brittle fracture.Compressive strength and modulus of elasticity of the addition of CNTs/Fe3O4 to MCPC increased by 178.4%and 776.5%,respectively.The reinforcing and toughening effect of CNTs/Fe3O4 on MCPC has a great advantage over RGO/Fe3O4.For the composites with CNTs/Fe3O4 addition,the amount of addition has a significant influence on the microstructure,porosity and mechanical properties of MCPC composites.When the amount of added is 9wt%,the compressive strength and elastic modulus of MCPC are the highest,which is 40.15 MPa and 1782 MPa respectively,which is 83.2%and 93.7%higher than that of BCPC without CNTs/Fe3O4.The degradation and mineralization experiments show that MCPC has good anti-collapse ability,and ?-tricalcium phosphate(?-TCP)was continuously converted to hydroxyapatite(HA)in the SBF soaking process.After 5 days of soaking,the addition of 9wt%CNTs/Fe3O4 promoted the preferential growth of HA grains in the(113)crystal plane.In addition,the addition of CNTs/Fe3O4 is beneficial to improve the degradation rate of MCPC.The static magnetic field does not change the final degradation and mineralization behavior of MCPC,but it will affect the degradation and mineralization process of MCPC,which is mainly reflected in the degradation and mineralization rate of MCPC.Such as,80mT static magnetic field is beneficial to improve the degradation rate of MCPC,300mT static magnetic field is conducive to improve the mineralization rate of MCPC.In vitro cell experiments showed that MCPC could inhibit the proliferation of MSCs cells without static magnetic field,and the addition of magnetic composites was not conducive to the enrichment of intracellular Ca2+ in MCPC cells and the different contents of the magnetic composite have no effect on the morphology of the cells.60mT static magnetic field can promote a little the proliferation of MSCs cells on BCPC,and promote more significant the proliferation of MSCs cells on MCPC.MSCs on MCPC9 grew most significantly at 60mT static magnetic field,and the maximum growth rate was 23.6%compared with that in non-magnetic stimulation.MSCs on MCPC were well spread and adhered more closely at 60mT static magnetic field,and their differentiation ability increased with the increase of magnetic composite content,which showing dose-dependent.The effect of different additions of magnetic composites on the intracellular Ca2+ enrichment of MCPC was different under 60mT static magnetic field,and the intracellular Ca2+ enrichment of MCPC was significant improved when the addition amount was 9wt%.Different static magnetic field is not conducive to BCPC intracellular Ca2+ enrichment,and the greater the magnetic strength,the lower the degree of enrichment.Different static magnetic fields can promote the enrichment of Ca2+ on MCPC9 cells,the higher the magnetic force,the higher the enrichment,but the effect of the existence of the threshold.The results showed that the effect of MCPC on MSCs was magnetic response,and its cell compatibility had a window effect.