Study On Preparation And Properties Of High Strength-modulus Silk Biocomposites

Hard tissue repair is a long-term clinical need,which is limited by the demanding mechanical and biological properties of bone tissue repair materials.At present,the treatment of large-scale bone defects is still facing challenges.Homogeneous reinforced composites offer a potential solution to the problem of treating large-scale bone deformities,which still poses difficulties today.Due to its superior mechanical qualities,biocompatibility,and degradability,silk fibroin has a lot of potential as an implanted device.In this study,natural silk fibroin nanofibers（SNFs）were extracted efficiently without mechanical approach by chemical pretreatment（DMSO/KOH）of silk fibroin fibers.SNF has the advantages of high aspect ratio,high yield and stable crystal structure of SilkⅡ.SNFs with adjustable diameters from 100 to600 nm may be produced by varying the concentration of the degumming solution and the pretreatment period of DMSO/KOH.The prepared silk nanofiber film still retained the excellent mechanical properties of natural silk.Secondly,based on the homogeneous reinforcement principle,SNF（reinforcing base）was introduced into silk fibroin（SF,matrix）to enhance its mechanical properties.By adjusting the content of SNF,the water absorption ability of the composite membrane was up to 47%,and the membrane with high content of SNF had better water absorption ability.When the amount of SNF was 15%,the tensile strength of the film was 2.1 MPa,which was 129%higher than that of the pure SF film.In vitro cell experiments showed that all materials supported the growth of human umbilical vein endothelial cells,but the growth activity:SNF/SF film≈SNF film>SF film.The introduction of SNF can not only make up for the shortcomings of the low wet strength and elasticity of pure SF membrane,but also significantly improve the biocompatibility of the composite membrane.Again,the SNF/SF composite three-dimensional materials were prepared by introducing SNF based on the formic acid（FA）/CaCl₂ system.The hydrophilic and mechanical properties of the composites were improved by adjusting the content of SNF.Compared with the pure SF three-dimensional material,the compressive strength of the composites could reach 140 MPa,which was increased by 27.3%,and the flexural strength was 65 MPa,which was increased by71.1%,and the secondary structure characterization showed a SilkⅡcrystalline structure with good thermal stability when 10%of SNF was added.In vitro degradation behavior analysis of SNF/SF composite three-dimensional material（SNF10%）The results showed that the compressive strength was still 100 MPa at 90 days of degradation in Proteinase XIV,with a mass loss of about 20%,maintaining good mechanical properties and still meeting the requirements for mechanical properties as bone defect repair.Finally,the SNF/SF three-dimensional material was processed into bone screw using a turning process,and then osteoblasts were cultured in vitro.The results showed that the high specific surface area of SNF in SNF/SF bone screw provided sufficient space for cell growth,which was conducive to cell differentiation and proliferation.In conclusion,this study successfully prepared silk nanofiber-reinforced SNF/SF bone screws,which provides an important basis for the development of silk-based bone repair materials and devices.