| In our country,number of defects,cataclasis caused by traffic,industrial accidents,trauma and bone tissue necrosis and rheumatic diseases will reach millions,and with the development of the society and aging population in recent years,the problem becomes more serious.Autogenous bone,xenogenic and artificial bone grafts are currently the main methods of clinical treatment for bone defect.One of the most effective methods is autogenous bone graft,but the limited source and functional disorder limited its widely clinical application.Using the xenogenic bone graft has the disadvantage of high price and time-consuming in manufacturing process.Therefore,designing an ideal bone repair scaffold materials with a highly biomimetic structure,good biocompatibility and inducing bone regeneration ability to mimic extracellular matrix materials(ECM)in bone tissue is a hot issue in bone tissue engineering.This paper is around the subject of biomimetic hierarchical structure,composition and function of the natural bone.Based on the nano-textile technology,four kinds of different bionic bone scaffold have been prepared and systematically studied to discuss its potential application in bone tissue engineering through selection of different materials,preparation of scaffolds and characterization methods.The results are shown as follows:Firstly,to mimic the key structure characteristics-the mineralized collagen fiber bundle in natural bone,the aligned nanostructured fibers consisted of a composite particles of hydroxyapatite and tussah silk in a core were fabricated by coaxial electrospinning.Osteoblast-like MG-63 cells were cultivated on the composite to assess its suitability as a scaffold for bone tissue engineering.The results showed that aqueous solution of pure TSF displayed superior spinnability during electrospinning,and the HA-TSF composite nanoparticles in the core could be encased well by TSF in the shell when the ratio of core/shell is 1:2 or 1:1.Additionally,the core/shell nanofibers showed the best mechanical properties when the ratio of HTP/TSF was 1:1.Biological test results corroborated that the TSF/HA-TSF(1:1)nanofiber scaffold showed the best cytocompatibility as compared with that of the pure TSF nanofiber scaffolds and Cover slips,and the aligned construct had an important impact on cell growth direction,which was consistent with nanofiber.To improve the mechanical properties and osteogenesis.poly(lactic-co-glycolic acid(PLGA)composite nanofiber scaffolds were prepared by doping with 1 wt%graphene oxide(GO)nanosheets and 10 wt%TSF.The results showed that the GO nanosheets were overlapping and were aligned along the PLGA/TSF nanofiber axis.After addition 10 wt%TSF and doping 1 wt%GO into PLGA nanofibers,the fiber diameter significantly decreased from 278 to 130nm,and hydrophilicity and the protein adsorption onto the nanofiber scaffolds were remarkably improved.Interestingly,the GO-incorporated nanofibers showed 7-fold and 4-fold improved Young's modulus and tensile strength,respectively,higher than those of pure PLGA.Biological evaluation demonstrated that PLGA/TSG/GO nanofibers showed the highest proliferation,addition of TSF and doping of GO played a key role in accelerating functionally differentiation of mMSCs and formation of new bone.In order to mimic the similar structure and composition of nature bone,the scaffolds with good mechanical properties and biological activity were prepared,and biomineralization had been considered as an important strategy to deposit HA similar to the mineral in nature bone onto the surface of polymers.Based on the above work,three-dimensional multilayer-orthogonal PLGA/TSF/GO nanofiber scaffolds were fabricated and then mineralized in simulated body fluid(SBF)to mimic the structure and composition of lamellar bone.The results showed that addition of TSF into PLGA nanofibers substrate could induce HA mineral crystal to nuclear and grow directionally,The HR-TEM images exhibited the mineral on the surface of nanofibers made up needle shaped crystal with a length of 40-50 nm and a width of 2-5 nm,and many microporous and mesoporous structures existed in fiber.After mineralization,the compressive modulus and stress of multilayer-orthogonal PLGA/TSF/GO/HA nanofiber scaffolds were 1.7-fold and 0.6-fold higher than that of the composite scaffolds with the same composition but random construct,respectively.Human mesenchymal stem cells(hMSCs)were seeded on the surface of composite scaffolds,and the adhesion,proliferation and differentiation of cells were analyzed by confocal laser scanning microscope(CLSM),ALP,flow cytometry and real time PCR(RT-PCR)an so on.The above experiment confirmed that the mineralized nanofiber scaffolds showed the excellent osteogenic activity,and cells could grow into the scaffold.Cell arrangement also presented the multilaye-orthogonal construct.Moreover,it was found that the multilaye-orthogonal construct of the scaffold could enhance cell proliferation and differentiation.To simulate the hierarchical structure of natural bone,the biomimetic bone composite material enhanced by nanofiber fabrics were fabricated,and this kind of hierarchical structure in the order:nanofibers and mineral particles.mineralized nanofibers,mineralized nanofiber yarn,mineralized fabric and the macro-structure biomimetic bone.First by electrospinning technology preparation has certain nanofiber yarn twist,using nano yarn woven textile weaving technology to produce three-dimensional multi-layer fabric,finally by cell culture in vitro of multilayer fabrics after the construction of a fabric reinforced bone biomimetic mineralization bionic materials.Firstly,the nanofiber yarns with a certain twist were prepared by electrospinning technology,and three-dimensional multi-layer fabrics were fabricated by woven textile weaving technology.Secondly.mouse mesenchymal stem cells(mMSCs)were subsequently cultivated on the nanofiber fabric scaffolds to assess their suitability for bone tissue engineering.The results showed that PLA/TSF mixing solution with a mass ratio of 9:1 can be spun continuously,and the result showed nanofiber yarn exhibited a uniform diameter distribution and good mechanical properties.In addition,the hydrophilicity and the protein adsorption onto the nanofiber scaffolds were remarkably improved by addition TSF into PLA substrate.The results of cell culture in vitro showed that cells could grow into the three-dimensional multi-layer fabric scaffolds and attached along the yarn axes.The well-aligned hierarchical structure of nanofiber fabrics could enhance cell proliferation,differentiation and functional expression better as compared with that of the non-woven nanofiber mats.The composite scaffolds mineralized by cells culture in vivo were implanted into bone defects created in the femoral condyle of New Zealand rabbits.The results found that the composite had a good bone repaired effect,and the new bone tissue integrated well with the neighbouring normal tissue.The mineral density of the new bone is 732 ± 56 mg/cm3 after 12 weeks of implantation,a value similar to that of trabecular bone in a femoral condyle(around 800 mg/cm3).Thus,the nanofiber fabrics composite materials with hierarchical structure will be a kind of excellent bone replacement materials,which may used in clinical for bone defect treatment. |
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