Structure Changes of Silk Fibroin（SF） by Blending with Poly（ε-caprolactone）（PCL）：Characterization of SF and PCL Blended Electrospinning Films

The mechanical properties and water solubility of electrospinning SF films limit their use as biomaterials. In order to develop a tissue engineering biomaterial with both satisfying biological properties and sufficient biomechanical properties,blended films composed of silk fibroin（ SF） and poly（ ε-caprolactone）（ PCL） were fabricated by electrospinning in this study. Scanning electron microscope（ SEM）, X-ray diffraction（ XRD）,thermal analysis,Fourier transform-infrared（ FT-IR）,Raman spectra,mechanical testing,and water solubility were used to characterize the morphological, structural and mechanical properties of the blended electrospinning films. Results showed that the diameter of the blended fiber was distributed between 600 and1000 nm,and the fiber diameter increased as the PCL content increased. There is no obvious phase separation due to the similarity and intermiscibility,as well as the interactions（ mainly hydrogen bonds）, between the two polymers. Meanwhile, the secondary structures of SF changed from random coils and Silk I to Silk II because of the interactions between SF and PCL. For this reason,the tensile strength and elongation at break of the electrospinning films improved significantly,and the water solubility decreased. In conclusion,the blended electrospinning films fabricated in this study showed satisfying mechanical properties and water insolubilities,and they may be promising biomaterials for applications in tissue engineering for blood vessels,nerve conduits,tendons,ligaments and other tissues.