Biomimetic Construction Of Bone-like Micro/Nano Structured Surface On Bioactive Cap Substrate And The Effects On Osteogenesis And Vascularization

The micro/nano surface topogrophy of biomaterials is one of the important factors mediating cellular behaviors.The construction of bioactive ceramic materials with surface micro/nano biomimetic structure is the key to the design of bone repair materials and an important way to mediate cell fate in order to achieve bone regeneration.Nevertheless subject to the characteristics of inorganic materials such as brittleness,it is still a challenge to constrict bone-like surface micro/nano surface on the bioactive ceramics and promote the osteogenesis and angiogenesis of the materials.By optimizing and regulating the reaction conditions,the hydrothermal mineralization system without template agent was established,and the bone-like hydroxyapatite micro/nano rod-cluster structure was constructed on the surface of the?-TCP/CaSiO₃ bioactive ceramics.Further combined with 3D print,3D porous scaffolds with bone apatite micro/nano rod-cluster structure layer were fabricated.Then investigated the angiogenesis and osteogenesis of the hierarchical biomimetic scaffolds in vitro and in vivo.The hierarchical biomimetic scaffolds might be a candidate for bone regeneration and it provided reference data for the material design and surface construction of the bioadaptable CaP bioceramics.The main contents included:?1?The synthesis hierarchical HAp particles with micro/nano structured surface and the mediation on stem cell fateVia hydrothermal treatment,propanamide and sodium citrate were utilized to regulate the morphology of the particles.Hydroxyapatite hierarchical microspheres with micro/nano structured surface were obtained by crystal fractal growth,and the average particle size was about 10 microns while the surface of the microsphere was rod-like hydroxyapatite.Then the effects of particles'surface micro/nano structure on stem cell behaviors were studied.Hydroxyapatite microspheres with micro/nano structure were proved to promote the cell proliferation and favor cellular differentiation via up-regulating the gene expression of ALP,Col-I,OCN,OPN and OSX.?2?The construction of bone-like hydroxyapatite micro/nano rod-cluster structure on the surface of the?-TCP/CaSiO₃ bioactive ceramics and the effects on mediating stem cell fateBy optimizing the hydrothermal system and regulating related key parameters in the surface construction such as supersaturation,component of the matrix and the comdition of the hydrothermal treatment,a novel and facile hydrothermal mineralization system without template agent was established.The mineral ions released by the dissolution of the substrate were redeposited on the surface to form the bone-like HAp hybrid micro/nano rod-cluster structure layer on the surface of?-TCP/CaSiO₃ bioactive ceramics in situ.The hydrothermal mineralization system reduced the possibility of inducing impurity phase and simplified the process of treatment.In vitro experiments confirmed that bone-like HAp hybrid micro/nano rod-cluster structure layer could favor the cell adhesion,promote the cell proliferation and facilitate the cellular differentiation via up-regulate the concerned gene expression?OSX,ALP,OPN and OCN?and ALP protein secretion.?3?The fabrication of biomimetic hierarchical 3D scaffolds with bone-like HAp micro/nano rod-cluster structure layer and the promotion of angogenesis and osteogenesisBased on the established hydrothermal mineralization system,further combined with 3d printing technology,the hierarchical biomimetic scaffolds with bone-like HAp micro/nano rod-cluster structure layer were fabricated.Systematically researches were operated on the effects bettween the biomimetic hierarchical 3D scaffolds and mesenchymal stem cells?mBMSCs?and between human umbilical vein endothelial cells?hUVECs?.The bone-like HAp hybrid micro/nano rod-cluster structure layer could favor the adhesion of mBMSCs and hUVECs via up-regulating the expression of intergrin.Meanwhile,the bone-like HAp hybrid micro/nano rod-cluster structure layer could could promote the expression of osteogenic related genes?ALP?BMP2?Col-I?OCN?OPN and OSX?and protein?OCN?secretion of mBMSCs.Besides The bone-like HAp hybrid micro/nano rod-cluster structure layer significantly promotes the expression of vascular related genes?CD31?VEGF?KDR?eNOS?bFGF and TGF-??and protein secretion?CD31?.SD rats were utilized in vivo study.Further evaluation was the angiogenesis and osteogenesis of biomimetic hierarchical 3D scaffolds with bone-like HAp micro/nano rod-cluster structure layer.The scaffolds were implanted in different sites?critical bone defect of skull,subcutaneous implantation near periosteum of skull and subcutaneous implantation in back?for analysis.The results indicated that:1.Biomimetic hierarchical 3D scaffolds with bone-like HAp micro/nano rod-cluster structure layer could promote the formation of bone matrix and favor the bone-angmentation;2.The bone-like HAp micro/nano rod-cluster structure layer could facilitate the secretion of collagen I,osteocalcin and CD31 at the defect site;3.The bone-like HAp micro/nano rod-cluster structure layer could accelerate the formation of capillary structures.In this research,a novel and facile hydrothermal mineralization system was established.A bone-like?both structure and component?HAp hybrid micro/nano rod-cluster structure layer were constructed on the bioactive matrix.Furthermore the hierarchical biomimetic scaffolds were fabricated via combining with the 3D print,and the obtained hierarchical biomimetic scaffolds were endowed with osteogenesis and angiogenesis.The hierarchical biomimetic scaffolds might be an candidate for bone regeneration and the established synthetic process might provide a significant guide for the structural design of bioadaptable bioactive CaP scaffolds.