Electrospun Bombyx mori gland silk
Introduction
Since the electrospinning of silk was first reported [1], there has been an increasing interest in such work. However, all the efforts have used reconstituted silks from biologically spun fibers. In this short note, we report the use of Bombyx mori silk dissolved in water directly from the gland and spun. Some PEO is added to the solution to facilitate spinning.
We have previously shown that GFP, which exhibits non-linear optical properties can be incorporated into cast silk films [2]. However, the GFP and silk phases separated somewhat thereby yielding non-uniform results in optical transmission measurements. Therefore, experiments to determine whether GFP molecules could be incorporated into electrospun gland silk fibers were done. It was hypothesized that the relatively large size of the GFP molecule [3] compared to the size of the fibers [1] might limit the possible separation. Further, the large surface area to volume ratio of the fibers was expected to speed the evaporation of the water, thereby quickly reducing the GFP mobility and hence reducing the opportunity for phase separation.
Section snippets
Experimental
The eggs of B. mori were obtained from NIAS, CREST, Japan. The worms were hatched in a laboratory at about 24 °C and at 36–42% RH. They were fed fresh mulberry leaves and reared according to USDA regulations. After the fourth moulting, but before cocoon spinning, the silk gland was removed and rinsed in distilled water. Thereafter, the membrane was removed and the contents were slowly dissolved in deionized water at 5 °C. The GFP was made using an encoding Vector produced by Clontech. It was
Results and discussion
Electrospun fibers prepared from the silk and PEO solution (sample number 1) and observed under visible light are shown in Fig. 1. The beads that sometimes form on the fibers can be eliminated by variation of the spinning parameters [6]. Fig. 2 is a higher magnification SEM image. The fibers are in the range of 80–270 nm as can be seen in the histogram in Fig. 3. The average dimension of the fibers is 158±46 nm.
Fig. 4a is an image observed under visible light of a sparse layer of electrospun
Conclusions
Solutions of B. mori gland silk can be electrospun with the addition of some PEO to facilitate the spinning. The results show that GFP can be incorporated relatively uniformly in the fibers without phase separation. This indicates the possibility of making fibers with uniform non-linear optical properties.
Acknowledgements
The authors acknowledge the support of AFOSR award no. F49620-03-1-0169. They also thank Y. Magoshi and J. Magoshi of NIAS, Tsukuba, Japan, and Prof. M. Becker, Fukui University, Japan.
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