Solutions of Bombyx mori gland silk can be electrospun with the addition of some polyethylene oxide (PEO). Green fluorescent protein (GFP) can also be incorporated and electrospun without apparent phase separation from the silk. The dimensions of the fibers with and without the GFP are qualitatively similar. The results indicate the possibility of making fibers with uniform non-linear optical properties. (c) 2006 Published by Elsevier Ltd.