Coaxial Electrospinning of Regenerated Silk Fibroin/Sericin Aqueous
Yichun Hang, Yaopeng Zhang, Huili Shao∗, Xuechao Hu
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of
Material Science and Engineering, Donghua University
Shanghai 201620, China
Corresponding Author E-mail Address: HLShao@dhu.edu.cn
Silkworm silk is composed of a silk fibroin (SF) core and a silk sericin (SS) shell.1 To
biomimic the composition and core/shell (SF/SS) structure of the natural silk, an equipment
(Figure 1) for coaxial electrospinning was designed and fabricated in this work. Regenerated
ultra-fine fibers with a core (SF) -shell (SS) structure were prepared by coaxially
electrospinning SF (22 wt%) and SS (67 wt%) aqueous solutions in inner and outer tubes of
the equipment, respectively.
Figure 1: Experimental setup for coaxial Figure 2: TEM of regenerated SF (with
electrospinning MWCTs)/SS coaxially electrospun fiber with a
core-shell structure. Both flow rates of inner and
outer solutions are 4 μL/min.
To recognize the core-shell structure of the electrospun fiber, 10 wt% regenerated SF
aqueous solution were mixed with aqueous solution of 2 mg/mL Multi-Walled Carbon Tubes
(MWCTs) with a ratio of 1:20 (V/V). Transmission electron microscope (TEM) results
showed that the electrospun fibers had an obvious core-shell structure with a clear boundary
and uniform diameter (Figure 2). Flow rates of the two solutions in inner and outer tubes had
a great influence on the formation of core-shell structure. A higher flow rate ratio of SF/SS
induced an off axis of core fiber or non-coaxiality because of uneven adhesion of SS (shell)
on the SF (core) component (Figure 3)2. According to the Scanning electron microscope
(SEM) observations, it was found that with the increase of the inner flow rate, the electrospun
fibers had a beaded structure and became finer. An appropriate electric field intensity for
coaxial electrospinning was 5 kV/cm with a voltage of 40 kV and a distance of 8 cm. Results
from Raman spectroscopy and differential scanning calorimetry (DSC) indicated that the
crystalline structures of the electrospun fibers and natural silk are much different, though they
have similar core-shell structures.
Figure 3: The TEM images of regenerated silk fibers coaxially electrospun with an outer flow rate of 2
μL/min for SS solution and a inner flow rate of (a) 2 μL/min, (b) 4 μL/min, (c) 6 μL/min and (d) 8 μL/min
for SF solution, respectively.
This work is supported by the National Nature Science Foundation of China
(50803011), Specialized Research Fund for the Doctoral Program of Higher Education
(200802550001), SRF for ROCS, SEM, Shanghai Educational Development Foundation
(2007CG44), and Shanghai Pujiang Program (09PJ1400700), the Programme of Introducing
Talents of Discipline to Universities (111-2-04).
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