After manufacturing and collecting a quantity of the silk proteins, the Nexia scientists sent the material to microbiologist Steven Arcidiacono of the U.S. Army Soldier Biological Chemical Command in Natick, Massachusetts, where researchers had developed a "spinning" technique.
The proteins were placed in a syringe and squeezed through a tiny tube, which forced the proteins into the shape of a silk fiber. "You can actually see the silk fiber. It looks a little thinner than a human hair—it's about ten to 40 microns in diameter," said Arcidiacono.
Lewis said the resulting fiber is similar to natural spider silk but not a duplicate. "The silk they have spun is about three times more elastic and not quite as strong as natural spider silk," he explained. "It is short of the real thing, but better than anything everyone else has been able to do."
The diameter of Nexia's silk is slightly larger than a spider's. Thinner silk tends to be stronger, but scientists are not sure why.
Manufacturing Benefits
One of the biggest advantages of Nexia's technique, Lewis said, is that the silk proteins that are made in mammal cells do not clump or gel in water, which would make it impossible to shape the proteins into a fiber. "The rest of us had to use really toxic chemicals to keep silk proteins dissolved," said Lewis. "This opens the possibility for environmentally friendly manufacturing."
Lewis is now trying to insert silk genes into plants, specifically alfalfa, which would be a cheap way of producing artificial spider silk. Alfalfa was chosen because it produces large amounts of protein (the plant is 24 percent protein by weight).
"One of our goals is to create designer silks that are stronger and stretchier than spider silks," said Nexia scientist Anthoula Lazaris, the lead author of the report.
Among orb-weaving spiders—about one quarter of all spider species—the genes responsible for producing dragline silk have remained essentially unchanged through 125 million years of evolution, said Lewis.
Lazaris said: "Mother Nature knows what she's doing, and our goal is to bio-mimic her creations."
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