Study On The Preparation And Properties Of Ultrafine Silk Fibroin/ Poly(ε-caprolactone) Composite Fibrous Scaffolds

In this thesis, ultrafine silk fibroin (SF) fibrous membranes were prepared by electrospinning and methanol treatment. Methanol treatment induced inter-fiber conglutinating and leaded to predominantlyβ-sheet structure of SF fibers. Although the tensile strength of electrospun SF fibrous membranes significantly increased after methanol treatment, electrospun SF fibrous membranes became more brittle. Meanwhile, ultrafine poly(ε-caprolactone) (PCL) fibers were also prepared by electrospinning. The ultrafine PCL fibers were bonded by thermal treatment. The bond between the ultrafine electrospun PCL fibers could be obviously found after the 30min or 60min thermal treatment at 55℃. The molecule structure and crystal form of the fibers did not change after thermal treatment, but the crystallinity of the fibers increased after thermal treatment. Thus the mechanical properties of electrospun PCL fibrous membranes after thermal treatment could be significantly improved.The brittleness of electrospun SF fibrous membrane limited its application in the tissue engineering. In order to improve the mechanical properties of SF. Ultrafine SF/PCL composite fibers were prepared by electrospinnig. The results showed that the average diameter of the fibers gradually increased with increasing of PCL content in the blend. With increasing of PCL content in the blend, the crystallization of the fibers became well, but the compatibility between the two polymers became poor. The mechanical properties of the ultrafine composite fibrous membranes were improved by adding PCL. Compared with the ultrafine electrospun SF fibrous membranes which treated by methanol, the ultrafine SF/PCL composite fibrous membranes had higher elongation at break, lower Young's modulus and still well tensile strength. In vitro cell culture results showed that mouse fibroblasts (L929) proliferated well on the ultrafine electrospun SF/PCL composite fibrous scaffolds. The ultrafine electrospun SF/PCL composite fibrous scaffolds were non-toxic, and the cytocompatibility of the ultrafine electrospun SF/PCL composite fibrous scaffolds were favourable. Based on above experiments, we introduced nano-hydroxyapatite (nHA) particles into the SF/PCL matrix. Ultrafine nHA/SF/PCL composite fibers were prepared by electrospinning. The results showed that the crystallinity of PCL in the fibers became poor with increasing of nHA content. Comparing with the ultrafine SF/PCL composite fibrous membranes, the mechanical properties of the ultrafine nHA/SF/PCL composite fibrous membranes were still well when the nHA mass fraction reached 30%. When the nHA mass fraction was 30%, the mechanical properties of the ultrafine composite fibrous membranes were improved with increasing of PCL content. In vitro cell culture results showed that the ultrafine electrospun nHA/SF/PCL composite fibrous scaffolds were non-toxic. The human osteosarcoma cell line (MG63) adhered and proliferated well on the ultrafine electrospun nHA/SF/PCL composite fibrous scaffolds, the cytocompatibility of the ultrafine electrospun nHA/SF/PCL composite fibrous scaffolds were also favourable. And the ultrafine electrospun nHA/SF/PCL composite fibrous scaffolds could well accelerate the osteogenic differentiation.Ultrafine core(PCL)-shell(nHA/SF) and core(MWNTs/PCL)-shell(nHA/SF) composite fibers were successfully prepared by coaxial electrospinning. The results showed that the thermal stability of the ultrafine electrospun core-shell structure composite fibers was improved after MWNTs reinforcement. Compared with the ultrafine core(PCL)-shell(nHA/SF) composite fibrous membranes, the ultrafine core(MWNTs/PCL)-shell(nHA/SF) composite fibrous membranes were more brittle. But the ultimate tensile strength of the ultrafine core(MWNTs/PCL)-shell(nHA/SF) composite fibrous membranes were higher because of MWNTs reinforcement to PCL. In vitro cell culture results showed MG63 cells adhered and proliferated well on the two core-shell structure composite fibrous scaffolds. And the two kinds of core-shell structure composite fibrous scaffolds could accelerate the osteogenic differentiation. Compared with the ultrafine electrospun core(MWNTs/PCL)-shell(nHA/SF) composite fibrous scaffolds, the ultrafine electrospun core(PCL)-shell(nHA/SF) composite fibrous scaffolds were more suitable for MG63 cell adhesion, proliferation and differentiation.