Clinics and industrialists are trying to make use of the unique fibers of spider webs. But producing the precious molecule that forms it in sufficient quantities isn't easy.
HANNOVER — The female Nephila Clavipes, a spider as big as the palm of the hand and present all across the Southern Hemisphere, weaves huge, golden webs that are worth a lot. Light, surprisingly elastic and flexible, as well as being more resistant than steel or nylon, the natural silk this arachnid produces also has shape retention memory.
Industrialists looking for high-performance technical fibers and textiles have had their eyes on the qualities of this biological material for a long time. But although the weaving of this dazzling yellow thread has been mastered since the 17th century to make sumptuous sets of clothing, supply is a more delicate question.
Gathering by "reeling" consists of painlessly immobilizing these giant weavers and delicately pulling the filament from their abdomen, simultaneously rolling it up around a spool. The technique, which produces 200 meters of silk in 15 minutes, is used by the team of Professor Peter Vogt, lab chief at the Department of Plastic, Hand and Reconstructive Surgery in Hannover, Germany, to experiment with the properties of the silk on sheep.
Biocompatible, biodegradable and hypoallergenic, the natural silk of the Nephila Edulis, bred on site, does not cause any rejection or inflammation. It produces perfect stitching material, aids healing and is a good indicator for the regeneration of skin, cartilage and nerve cells, which adapt to it easily. Clinical trials are set to take place soon.
At the Institute of Physics in Rennes, France, the Nephila Clavipes' web is preferred for its structural characteristics. It has a diameter of just one millionth of a meter and is smooth throughout its whole length. What's more, it's medically neutral and more resistant than glass and silk and could one day replace the optical fibers in fiberscopes and endoscopes.
Industrialists are eagerly awaiting the extraordinary properties of spider silk. But because of the cannibalism of certain species, intensive breeding is complicated, and the artisanal technique of the "trade" excludes large-scale production. This is why specialists are stretching their imagination to try to reproduce these qualities in a biosynthetic way.
Spider silk is a biopolymer comprised of a family of proteins. To produce these proteins, Randy Lewis, the head of the Synthetic Biomanufacturing Institute at the University of Utah, is taking over work on transgenesis that was initiated 15 years ago by the Canadian company Nexia Biotechnologies but that had been stopped.
With genetic modification, he is currently breeding around 30 chimera, surrogate goats carrying the spider silk production gene. These transgenic animals produce up to 4 grams of silk protein per liter of milk. Once grinded down to powder, they are rehydrated and woven.
"The goats produce good quality protein, but the purification still needs to be improved," Lewis explains. "We are also working on the Escherichia coli bacteria, which is easy to manipulate genetically and commonly used for the production of protein. And we are trying to increase the proportion of spider protein secreted by our transgenic silkworms."
The fibers could be used in medicine but also for the manufacturing of clothing and sport gear, automobile parts, transparent film, coating, adhesive and gel. It's a market with enormous potential, and the German company AMSilk has positioned itself well for it after announcing last year that it had succeeded in producing a natural polymer with mechanical properties similar to spider silk, via transgenic bacteria. It plans on commercializing a range of products designed for the cosmetics industry and manufacturing medical products such as breast implants by 2016.
The American company Kraig Biocraft Laboratories is also collecting patents so that it can produce the highly resistant fiber "monster silk." It is working on the development of, construction and protection against explosion materials as well as bulletproof vests.
Finally, silk yarn, which can withstand extremely low and high temperatures, could be used to make spacesuits.