Preparation And Osteogenic Properties Of Magnetic Apatite/chitosan Composite Scaffolds

For the repair of large bone defects,artificial organic/inorganic composite scaffolds have been widely studied because of similar pore structure and composition with natural bone,but the traditional scaffold material lacks bone induction.The magnetic particles SrFe₁₂O₁₉were added to the composite magnetic apatite composite scaffold,and the magnetic particles were oriented in the scaffold to enhance their magnetic properties.The phase structure,functional group,microstructure,crystal shape,thermal stability and magnetic properties of the magnetic apatite composite scaffold were studied by means of XRD,FTIR,SEM,TEM,BET,TG-DTA and VSM,and the biological activity and bone properties were discussed in this study.Mesoporous hydroxyapatite powder?MHAP?was prepared by coprecipitation method using brominated sixteen alkane three methyl ammonium?CTAB?as template.MHAP powders are short bars with a length of about 100-300 nm and a diameter of about 40-60 nm.The MHAP is monocrystalline,with clear crystal striations,and is aligned along?100?and?002?surface orientation,with the lattice spacing of⁰.82 nm and⁰.34 nm respectively,along the c axis.The crystallinity of MHAP is lower than that of HAP.The pure high crystallinity SrFe₁₂O₁₉ was prepared by melting transformation method,with high coercivity Hcm?6191 Oe?and residual magnetization Mr?32 emu/g?.Thus,it was concluded that SrFe₁₂O₁₉ was permanent magnetic material.Chitosan?Cs?as the organic composition and SrFe₁₂O₁₉ as a magnetic particle,the magnetic mesoporous hydroxyapatite/chitosan composite scaffold?MMHA 1:x;x=3,5,7?was prepared by the freeze drying technology.MMHA 1:3,MMHA 1:5 and MMHA 1:7 magnetic composite scaffolds with magnetic field strength are 0.53 mT,0.36 mT and 0.26 mT respectively.MMHA composite scaffolds have a connectedthree-dimensional porous structure,with a pore size of about 100-300?m.In vitro,bone marrow mesenchymal stem cells?BMSCs?have good spreading morphology on MHAP and MMHA composite scaffolds.Besides MHAP and MMHA composite scaffolds have good proliferation effect on BMSCs,which shows that both MHAP and MMHA composite scaffolds have good biocompatibility.In addition,MMHA 1:3,MMHA 1:5 and MMHA 1:7 magnetic composite scaffolds have higher alkaline phosphatase?ALP?activity than pure MHAP composite scaffolds,and have higher expression levels of RUNX 2,Collagen1 and OCN genes.In vivo,sterile MHAP,MMHA 1:3,MMHA 1:5 and MMHA 1:7magnetic composite scaffolds were implanted into the skull of bone defects.Micro-CT scan for skull defect area,MMHA composite scaffoldshave more new bone formation and higher BV/TV and BMD than pure MHAP composite scaffold.In vitro and in vivo studies show that the MMHA composite scaffold has excellent bone promoting performance,and its bone ability is affected by SrFe₁₂O₁₉.As the proportion of SrFe₁₂O₁₉ increases in MMHA composite scaffolds,Bone regeneration capacityis enhanced.for MMHA composite scaffolds.In this study,?-tricalcium phosphate??-TCP?powder was prepared by high temperature sintering.The powder of?-TCP is irregular granular with a diameter of about 2-4?m.The magnetic?-tricalcium phosphate/chitosan composite scaffold?MTCP 1:x;x=3,5,7?scaffold was prepared by using the chitosan?Cs?as an organic component and SrFe₁₂O₁₉ as a magnetic particles.The magnetic field strength of MTCP 1:3,MTCP 1:5 and MTCP 1:7 magnetic composite scaffolds is 0.57 mT,0.39mT and 0.23 mT,respectively.Bone marrow mesenchymal stem cells?BMSCs?have good spreading morphology on the composite scaffold of?-TCP and MTCP.Besides?-TCP and MTCP composite scaffolds have good proliferation effect on BMSCs,which shows that?-TCP and MTCP composite scaffolds have good biocompatibility.In addition,MTCP has higher alkaline phosphatase?ALP?activity than pure MTCP composite scaffolds.In addition,MTCP 1:3,MTCP 1:5 and MTCP1:7 magnetic composite scaffolds have higher alkaline phosphatase?ALP?activity than pure?-TCP composite scaffolds,and have higher expression levels of RUNX 2,Collagen 1 and OCN genes.In vivo,sterile MTCP 1:3,MTCP 1:5 and MTCP 1:7magnetic composite scaffolds were implanted into the skull of bone defects.Micro-CT scan for skull defect area,MTCP composite scaffoldshave more new bone formation and higher BV/TV and BMD than pure?-TCP composite scaffold.In vitro and in vivo studies show that the MTCP composite scaffold has excellent bone promoting performance,and its bone regeneration capacity is affected by SrFe₁₂O₁₉.Magnetic apatite composite scaffold has excellent bone healing properties,which provides an effective new method for the treatment of bone defects.