| Research backgroundThe development of 3D printed artificial bone graft materials provides a new way for the treatment of large bone defects.Synthetic polymer materials are the most widely used bone three-dimensional printing materials.These materials can meet the requirements of bone tissue engineering for mechanical strength,complex structure,degradation rate and so on.However,synthetic polymer materials often lack bone induction performance.Introduction of bioactive factors provides a wat to address this problem,which is a promising in bone tissue regenerative medicine.ObjectiveIn this study,a new composite core shell microsphere(CSMs)containing bone morphogenetic protein-2(BMP-2)was designed and fabricated.The microsphere has heparin cores,which can mimic the storage of growth factor in vivo and achieve sustained release of BMP-2.Besides,an effective strategy was developed to integrate composite microspheres into three-dimensional printed polycaprolactone scaffolds,aiming to promote the repair performance of composite scaffolds in the treatment of large bone defects.Method1.Heparinized polylactic acid pellets with diameters of 5-20μm were prepared by solvent volatilization,dopamine coating and amide reaction.The morphology and structure of heparinized polylactic acid pellets were observed by scanning electron microscope,and the surface chemical components were analyzed by X-ray photoelectron spectroscopy;alginate hydrogel microspheres containing heparinized polylactic acid pellets were prepared by electrostatic spray technology.The morphological characteristics of alginate hydrogel microspheres were observed by optical microscope and scanning electron microscope,and their cytotoxicity was detected by CCK-8 assay.2.The fluorescent labeled BMP-2 was loaded into the core/shell microspheres,and the distribution and loading level of BMP-2 in the microspheres were analyzed;The release kinetics of BMP-2 was detected by ELISA assay in vitro;the microspheres were co-cultured with MC3T3-E1 cells,and the effect of BMP-2 loaded composite microspheres on the osteogenic differentiation of MC3T3-E1 cells was analyzed;3.The three-dimensional porous polycaprolactone scaffolds were prepared by 3D printing technology,and the hydrophilicity was improved by dopamine coating technology.The structures were analyzed under scanning electron microscope;the cytocompatibility of the modified scaffold was studied;Using the self-expansion of microspheres,the microspheres were loaded into the scaffold,and its assembly stability was studied.The effect of hybrid scaffolds on the osteogenic differentiation of MC3T3-E1 cells was analyzed;4.The scaffolds were implanted into the rat skull critical defect model.12 weeks after operation,the bone repair was evaluated by imaging,histology and immunology,and the bone repair performance of the hybrid scaffolds was evaluated in vivo.Result1.Alginate/heparinized polylactic acid composite microspheres is morphologically uniformed with the size of 150μm in diameter;2.BMP-2 was loaded inside the microspheres.It was found that long-term sustained release of BMP-2 from the composite microspheres was achieved and effectively promote the osteogenic differentiation of MC3T3-E1 cells in vitro;3.3D polycaprolactone scaffolds were printed.The hydrophilicity and cell compatibility of the scaffolds were significantly improved after coated with polydopamine.It was found that the microspheres could be firmly combined into the scaffolds with its self-expansion property.The hybrid scaffold could enhance osteogenic differentiation of MC3T3-E1 cells in vitro;4.The hybrid scaffold implanted into the critical defect of rat skull can significantly promote the bone repair of the defect.ConclusionThe results show that the composite microsphere is an effective BMP-2 carrier and can be effectively integrated into 3D printing scaffolds.This composite scaffold showed significant potential in bone tissue engineering. |
PDF Full Text Request