Study On The Spinnability Of Regenerated Silk Fibroin With Different Molecular Weights In Centrifugal Spinning

Natural silk is a traditional textile fiber with outstanding performance. However, when the diameter of silk is reduced to submicron or nanoscale, silk will be widely used in many fields, including drug delivery, tissue engineering, wound dressing, due to the increase of specific surface area and excellent biocompatibility. Several methods have been explored to spin artificial silk or reduce silk diameter, for examples, dry spinning, wet spinning, electrospinning, and so on. In addition, a newly-developed approach, centrifugal spinning, has been used to fabricate regenerated silk fibroin. However, the performances of fibroin will be different due to the various techniques to extract fibroin, which will influence spinning process. Therefore, the centrifugal spinnability of regenerated silk fibroin extracted from same system will be researched in this article.Cocoon shells are degummed with Na2CO3 solution and dissolved in CaCl2-CH3CH2OH-H2 O solution. The different regenerated silk fibroins are obtained through changing the concentration of Na2CO3 solution, the dissolving temperature, and the dissolving time. The molecular weights of silk fibroin and secondary structure are characterized by SDS-PAGE Gel Electrophoresis, Ubbelohde Viscometer, and Fourier Transform Infrared Spectroscopy, Wide Angle X-ray Diffraction, respectively. The higher Na2CO3 solution concentration, the higher temperature, and the longer dissolving time result in smaller molecular weights, whereas they are in favor of random coils transform to ?-sheets.In centrifugal spinning, the major effect factors are divided into the properties of solution and spinning parameters. Therefore, we focus on the effect of viscosity and surface tension of spinning solution, and rotational speed. The solution viscosity and surface tension can be characterized by viscometer and surface tension meter, respectively. The centrifugal spinnability of different silk fibroin can be observed from the morphologies measured by Field-Emission Scanning Electron Microscopy on aluminum foil. When molecular weight is small and concentration is low, few fibers can be fabricated due to short and limited silk fibroin segmers can not entangle with each other to form a stable jet. In contrast, many fibers can be obtained when molecular weight or solution concentration is high.Silk fibroin with low molecular weight can be fabricated a small number of fibers with beads in high concentration, which reduces the utilization of silk fibroin. Polycaprolactone(PCL) has excellent biocompatibility and also can be dissolved into formic acid. Hence, we attempt to add PCL to regenerated silk fibroin spinning solution and hope to improve the spinnability of fibroin with low molecular weight. Fibers can be spun when the mass ratio of regenerated silk fibroin and PCL is 5:1, and the spinnability is better with the increasing of PCL. Fourier Transform Infrared Spectroscopy, Wide Angle X-ray Diffraction, Field-Emission Scanning Electron Microscopy, and Thermogravimetric Analysis are used to characterize the secondary structure, crystalline, morphology and thermodynamic property of RSF/PCL fibers, respectively.According to our results, the conditions of extracting regenerated silk fibroin will directly affect the properties of raw materials, which will influence the centrifugal spinning. In this article, we systematically research the effect of conditions, analyze the spinnability of RSF with different molecular weights, and enhance the repeatability. In addition, low molecular weights RSF can be spun by adding to some PCL, which advantages the applications of regenerated silk fibroin.