The SF/PCL/nHA Composite Scaffolds For Guiding Periodontal Tissue Regeneration

Guiding periodontal tissue regeneration with biomaterials is a potential and effective way to repair periodontal tissue defects.The scaffold material used for periodontal tissue regeneration should provide suitable conditions for seed cells growth.In addition,it should prevent fast-growing gingival epithelial cells from growing into the defect area and provide adequate time and space to ensure the normal regeneration of the defect tissue.The destination of this task is to construct a silk fibroin(SF)/polycaprolactone(PCL)/nano-hydroxyapatite(nHA)double-layer composite material that may be used for the regeneration of periodontal tissue in the future.It is assembled by the upper and lower layers,and the lower layer is a SF/nHA composite porous material prepared by freeze-drying method.This layer as a scaffold material for guiding cell adhesion,proliferation,angiogenesis and bone tissue regeneration,take full advantage of the osteoconductivity,osteoinductivity of nHA and excellent cell adhesion of silk fibroin materials and the materials formability;The upper layer as the isolation layer preventing gingival epithelial cells and surrounding connective tissue from growing into the porous material,is a dense silk fibroin film reinforced by SF/PCL blended fiber mat,which makes full use of SF good biocompatibility,and makes good use of PCL good mechanical properties to make up for the deficiency of SF membrane.Firstly,SF/PCL blended fiber mesh was spun by electrospinning technology with hexafluoroisopropanol as a co-solvent of silk fibroin and polycaprolactone,and the tensile properties of the fiber mat were tested and analyzed.The results show that the dry and wet tensile strength and elongation at break of SF/PCL fiber mat are significantly larger than that of SF fiber mat,indicating that the blending of PCL and SF can significantly improve the toughness of SF fiber mat.On this basis,SF/PCL composite film reinforced by SF/PCL blended fiber mat was prepared by casting method.The effect and mechanism of fiber mat on silk fibroin film were studied.The results of electron microscopy showed that the fibers in the film and the silk fibroin could be tightly combined.The tensile test results showed that the tensile strength and elongation at break of the composite film,especially elongation at break,were significantly higher than those of pure silk fibroin film.SF/PCL fiber can achieve a significant enhancement of silk fibroin film through fiber bridging.Secondly,the SF/nHA composite porous material was prepared by freeze-drying method.The results of electron microscopy showed that the connectivity between the pores of the material increases,as the proportion of nano-hydroxyapatite in the porous material increases.The pore size test results show that the pore size and porosity increase with the proportion of nano-hydroxyapatite when the proportion of nHA in the porous material is less than 30%.When the mass ratio of SF/nHA is 70/30,the pore size and porosity are maximized,the average pore diameter is 213.5 μm,and the porosity is 81.2%.The wet compression test results show that the compressive stress and compressive modulus increase with the proportion of nHA,when the proportion of nHA in the porous material is less than 30%.At a mass ratio of SF/nHA of 70/30,the compressive stress was 7.16 kPa and the compressive modulus was 12.8 kPa.The compressive stress and modulus were significantly increased compared with the pure silk fibroin porous material.Finally,using silk fibroin solution as binder,SF/PCL composite membrane and SF/nHA composite porous material were assembled into SF/PCL/nHA double-layer composite scaffolds,and the wet tensile properties,the cytocompatibility of scaffold was tested initially.The results showed that the proliferation rate of bone marrow mesenchymal stem cells on the double-layer composite scaffold was significantly faster than that of the control group.In this paper,SF/PCL composite membrane and SF/nHA composite porous material were prepared firstly.Then the two layers were assembled into SF/PCL/nHA double-layer composite scaffolds.This scaffold provides the basis for material preparation techniques for subsequent use of the composite scaffold to guide periodontal tissue regeneration.