Microcomposite fibers of regenerated silk fibroin (RSF) and multiwalled carbon nanotubes (MWNTs) were successfully prepared by an electrospinning process from aqueous solutions. A quiescent blended solution and a three-dimensional Raman image of the composite fibers showed that functionalized MWNTs (F-MWNTs) were well dispersed in the solutions and the RSF fibers, respectively. Raman spectra and wide-angle X-ray diffraction (WAXD) patterns of RSF/F-MWNT electrospun fibers indicated that the composite fibers had higher β-sheet content and crystallinity than the pure RSF electrospun fibers, respectively. The mechanical properties of the RSF electrospun fibers were improved drastically by incorporating F-MWNTs. Compared with the pure RSF electrospun fibers, the composite fibers with 1.0 wt % F-MWNTs exhibited a 2.8-fold increase in breaking strength, a 4.4-fold increase in Young's modulus, and a 2.1-fold increase in breaking energy. Cytotoxicity test preliminarily demonstrated that the electrospun fiber mats have good biocompatibility for tissue engineering scaffolds.

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The conventional process for preparing dry spinnable regenerated silk fibroin (RSF) aqueous solution needs not only an addition of Ca 21 but also an adjustment of pH value. In this work, an RSF dry spinning dope was prepared by using a simplified method with solely adding Ca 21 . Compared with the conventional RSF solution, the simply prepared aqueous solution showed similar content of b-sheet conformation and diameter of RSF aggregates but lower viscosity. Furthermore, the posttreated RSF fiber dry-spun from this simply prepared solution showed higher crystallinity and crystalline orientation, smaller crystallite size, and better mechanical properties. It could be concluded that Ca 21 played a much more important role than pH value in improving the structures and properties of RSF spinning solution and fibers. Therefore, the step of adjusting pH value could be excluded in the process of preparing high performance RSF fibers.

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