The Study Of Dual Multi-Scale Construction And Performance Of Biomimetic Bone Haversian Structure Scaffold

Human skeleton supports body weight and protects the organs around the body.Its excellent mechanical and biological properties all come from its organic and inorganic composite components and unique Haversian bone structure.At present,artificial bone scaffolds with both mechanical and biological properties cannot fully meet the needs of clinical bone repair.Therefore,organic and inorganic composite components similar to bone are selected to simulate the structure,in an attempt to obtain a new type of bone scaffolds whose composition,structure and performance are similar to human bones.In this paper,bionic the Haversian hierarchical bone structure from micro to macro.First,a micron biomimetic Haversian bone motif was prepared and assembled from the synthetic Col/HA nanocomposite fiber membrane and the decellularized submucosa(SIS)membrane of the small intestine with complex calcium phosphate bone cement(CPC),and then bone motifs were arranged and constructed bone scaffolds with millimeter scale,realizing the primary multiscale construction of bone scaffolds.Second,Nanometer hydroxyapatite(nHA)was synthesized by mineralization to grow in situ on the various structures of the scaffold,A new type of bone scaffold with dual multi-scale Haversian bone structure has been constructed.The effects of structural parameters on mineralization,degradation,mechanical and biological properties of scaffolds were discussed.Based on the first principle calculation,the mineralization nucleation mechanism of scaffolds is revealed at the atomic level.The mechanical strengthening mechanism of scaffolds is expounded.The main achievements are as follows:(1)Electrostatic spinning,calcination and impregnation process is presented prepare the Col/HA composite nanofibers of orderly arrangement in this paper.The fiber membrane was coiled,assembled into 4 kinds of diameter of micron grade bionic Haversian bone motifs by layer upon layer,the motifs were arranged orderly and build 4 kinds structure of bone scaffolds with millimeter scale.Compared the scaffold with layered structure bone scaffold,Mechanical strength was increased.its compression strength increased 1.47 folds,elastic modulus increased 5 times;Through the study of the mineralization of the scaffolds,the realization of the bionic Haversian bone structure Col/HA composite scaffolds constuct by dual multi-scale.Its compression strength and elastic modulus increased 10.1 and 16.12 times respectively.The mechanical properties of the scaffolds enhanced twice due to the near bone composition and imitation Haversian bone structure.And the scaffolds have good biological performance.(2)SIS membrane is mainly composed of ordered arrangement collagen type I fibers,The matrix membrane mimics the collagen components of bone and its nanofiber structure.In situ synthesis of HA by using SIS membrance as biological template to restrain ion diffusion and mineralization methods separately,the former has low nucleation rate and few chemical bonds formed between the SIS membrance and the HA,and HA grows bigger and forms thicker composite film,resulting in weak binding force between HA and SIS film.The latter,due to the explosive nucleation of HA,has a high nucleation probability and forms rich chemical bonds with SIS films.Moreover,HA particles are small and the composite film formed is thin.The binding force between the two is strong.Using natural membrane SIS as biological template and restricting ion diffusion,the single-crystal c-axis similar to bone HA was prepared,and the growth mechanism of rod-shaped HA self-assembled from lamellar c-axis single-crystal HA induced by regular carboxyl and carbonyl functional groups in SIS membrane was proposed.(3)Calcium phosphate bone cement(CPC)slurry for clinical use was coated with SIS matrix film,which was rolled up by layer by layer and assembled into the bionic Haversian bone motifs.The motifs were arranged orderly,realizing the initial multi-scale construction of SIS/CPC composite scaffold.The SIS/CPC scaffold was constructed by bionics with dual multi-scale by mineralization.The compression strength of the dual-constructed scaffolds was 42.41 MPa,69.67 MPa,8.32 MPa and 27.17 MPa respectively,which were much higher than that of the scaffolds constructed for the first time.SIS/CPC composite bone scaffold building with the inner and outer diameter is 100 microns and 500 microns of bionic bone motifs before and after double construction,the compression strength and young’s modulus were 8.43 MPa to 69.67 MPa,159 MPa and 519 MPa,far higher than corresponding to Col/HA scaffolds’s,increase 2.77,2.26,8.33 and 1.69 times respectively.And the SIS/CPC composite bionic scaffold has excellent biological properties.(4)The primary principle reveals mineralization nuclear mechanism of the scaffold.That is,the carboxyl group at the amino acid terminal and the carbonyl group of Col provide the nucleation of O atom and Ca2+ in HA,respectively.In situ growth of nHA in multi-scale scaffolds was realized.The in situ growth of nHA on these characteristic structures enhances the mechanical properties of the scaffold.The mechanical strengthening mechanism of the scaffold mainly is in-situ growth of a large number of nHA on the nanoscale structure of Col/HA nanofibers,membrane interlayer of micron grade bionic Haversian bone motifs and among bionic bone motifs of milimeter scaffolds,the nHA and Col components at all levels structure of scaffolds form interface with chemical bonds,the combination to enhance the bonding strength of the interface.And the cumulative effects of in situ deposition of nHA on multi-scale structure of scaffolds,The mechanical properties of the composite scaffolds were strengthened for the second time.