Originally Published MPMN March 2002

EDITOR'S PAGE

Oh, What a Tensile Web We Weave

I grew up thinking that being bitten by a radioactive spider was the only way to produce synthetic spider silk. Now I learn that all you really need is a genetically modified goat and some leading-edge extrusion equipment. Working collaboratively, a Canadian biotech firm and the U.S. Army have succeeded in manufacturing spider-silk protein in transgenic goats and spinning the silk in a laboratory for the first time. Medical devices are among the initial applications, according to a report published in the January 18 issue of Science magazine. Biotechnology triumphs again, and not a moment too soon. Radiated arachnids and hormonal mutations . . . that's so Cold War.

Spider silk—more specifically, the dragline material that frames the radiating spokes of the spider web—features a combination of strength and toughness unmatched by synthetic fibers. Five times stronger by weight than steel, spider silk can stop a bee traveling 20 miles per hour without breaking. Researchers have long dreamt about mass-producing this remarkable material. Attempts to harvest silk on spider "farms" have been thwarted by the creature's territorial nature. In the lab, scientists have had some success producing spider-silk proteins, but they were unable to weave fibers with the desirable properties. Their attempts to genetically engineer spider silk relied on the use of bacterial, yeast, or plant cells. By contrast, Nexia Biotechnologies Inc. (Montreal) and the U.S. Army Soldier Biological Chemical Command used mammalian cells to produce monomers and spun the fibers in an aqueous environment.

Nexia's proprietary silk production technology relies on the anatomical similarities between the spider's silk gland and the goat's mammary gland. The company is currently breeding genetically engineered goats with a spider gene. Spider silk proteins in the goats' milk are formed into insoluble threads by means of a microextrusion process, which forces the solution through a very fine opening.

Having achieved a proof of principle, Nexia is now moving toward commercial development of the fiber, called BioSteel, for applications such as medical sutures, biodegradable fishing lines, and soft body armor, according to Nexia president and CEO Jeffrey Turner.

Wound-closure systems and ligament prosthetic devices are the two most immediate medical applications of the silk, Nexia reports. Because of its strength and biodegradability in water, BioSteel may quickly develop a niche in markets for vascular wound repair devices, hemostatic dressings, and sutures. Long-term implantables as well as resorbable products also stand to benefit from the structural properties of spider silk, according to the firm.

The company intends to explore the use of spider silk in these and other applications through partnerships.

For more recent developments in materials as well as electronics and surface treatments, be sure to read the Special Section on Emerging Technologies. If you think small farm animals secreting spider silk is wild, wait until you read about the electroactive polymer that wants to challenge you to an arm-wrestling match.

Norbert Sparrow

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