Scientists Weave Spider Silk Into New Bulletproof Vests.
A product that spiders have been crafting for perhaps 400 million years is being developed to protect military and law enforcement personnel.The material is spider-dragline filament, from which arachnids spin their webs. It is one of the strongest materials in the world--many times stronger than steel--Jeffrey D. Turner, president of Nexia Biotechnologies, in Montreal, told National Defense in a recent interview. Spider silk's tensile strength is such that it can withstand weight of up to 300,000 pounds per square inch, he said.
Scientists currently are developing dragline filament for use in the next generation of bulletproof vests.
Currently, bulletproof vests are made of Kevlar, which provides a dependable barrier against bullets. Soldiers and police personnel, however, report that Kevlar vests are heavy; inflexible and hot to wear. Vests made of dragline filament may resolve these problems, Turner said.
Thus far, no vests have been made of spider silk. The biggest roadblock has been finding a sufficient quantity of filament to weave materiel for ballistic-protection garments, Turner explained.
For many years, scientists have sought a way to mass-produce this filament. The problem is that arachnids are notoriously anti-social, Turner pointed out. They much prefer individual territory to living in social groups. This greatly complicates the task of producing large quantities of the silk.
In 1999, Nexia signed research and development agreements with the U.S. Defense Department and the Canadian Department of National Defense to try to solve this problem.
Boosting Production
Nexia's strategy is to use the latest transgenic animal technology to boost spider silk production. Nexia has cloned several New Zealand miniature goats that have a silk-producing gene added to their genome. These animals will form the foundation for a herd that will share an identical genetic makeup that Nexia scientists anticipate will produce from two to 15 grams of spider silk per liter of milk, a vast increase over the amount provided naturally by individual spiders.
"Two to 15 grams of silk per liter of milk doesn't seem like a lot until you consider that we will be dealing with many thousands of gallons of milk," Turner explained. Eventually, Nexia wants to produce as much as five tons of silk per year, he said.
The silk-producing gene added to the goats is a form of recombinant DNA-- which means they can pass the gene on to their offspring, without the need for technicians to introduce it to each new generation of animals.
The herds are being raised at two Nexia farms, one in St. Telesphore, Quebec, and the other in Plattsburgh, N.Y. The New York farm is the site of a former Strategic Air Command base.
In 1999, Nexia increased its investment in spider silk production. The company declined to disclose specific dollar figures. It bought an exclusive licensing agreement on the existing portfolio of patented spider silk genes from the University of Wyoming at Laramie. Nexia has trademarked the filament as BioSteel. It went a step further and also secured an option on any future gene research currently being conducted by Randolph V. Lewis, research scientist at the University of Wyoming at Laramie.
"The royalties and upfront money will help finance new research," Lewis told National Defense.
Spider silk has been studied for possible use in the non-violent field of medicine, as stitches, replacement tendons and wiring for prosthetic devices. Lewis, however, does not object to its use for more military purposes. The Defense Department, he noted, was instrumental in the early stages of his research. "The Defense Department had confidence in us and made an investment," Lewis said. "I think they deserve to get a return on their money. Besides, we are talking about defensive use here, not offensive. I don't have any particular problem with that."
During the past 15 years, scientists have sought ways to achieve commercially viable silk production, he added.
"Sometimes, we just can't improve on nature's design," said Turner. Researchers already knew that "the silk gland and the milk gland were almost identical," he said. "You have to have humility if you are going to learn from nature."
Scientists first used mice to see if the added silk gene would be passed from one generation to the next, before trying it in larger mammals, Turner said. Cows, which produce greater quantities of milk than goats, were initially rejected because of their size, appetite and long gestation period, said Turner, a former professor and researcher in dairy cattle molecular genetics at McGill University, in Montreal.
Using genetics, Nexia has patented what it calls a breed-early/lactate-early, (BELE) goat, which takes up less space than a cow and eats less food. Turner noted, however, that cows aren't totally out of the picture and might be used in the future.
"With cows, it takes nine months to put a calf on the ground," he explained. "We went with goats for earlier results. We'll have goats producing milk in seven months."
Because of the BELE system, Turner anticipates that this quickly expanding goat herd will be producing a quantity of usable milk some time this fall. This is good news for Steve Arcidiacono, a molecular biologist with the Soldier Biological Chemical Command, (SBCCOM), in Natick, Mass.
According to the agreement between Nexia and the Defense Department, the firm will be responsible for production of the goat's milk, the medium containing the spider silk. The spider-silk research section of the SBCCOM laboratory will assist Nexin refining methods for extracting the filament from the milk, spinning it into fiber and testing it for tensile strength.
A patent for the spinning procedure is being sought, Arcidiacono said.
It may take more than two years to produce enough fiber to make the first bulletproof vest, he said.
The extraction of silk will involve conventional dairy processes, using milking machines. The milk will be skimmed for cream and whey. Once the protein fat has been separated by a 50 percent filtration process, the milk will be pure enough to produce a film that contains silk.
Until now, efforts to extract a high-tensile strength fiber have been hampered by an inferior quality of silk that is produced in bacterial fermentation vats, Arcidiacono said. This method works well for other types of recombinant proteins, but tends to produce shorter, weaker strands of spider silk. While the fermentation method, so far, has proven inadequate, he said, the process has remained his main source of material for conducting experiments. While a higher quality silk can be extracted from tissue culture, the amount is too small for spinning purposes, Arcidiacono explained. Research on making a synthetic version of spider silk continues, he confirmed.
This is one of the three areas that royalties from Nexia will help fund at the University of Wyoming spider silk laboratory, said Lewis. "An artificial-gene construct that is expressed in bacteria is a method that will allow us to combine two spider silk proteins," he explained. In spite of its obvious shortcomings, Lewis continued, the bacterial fermentation process gives scientists the opportunity to study the structural aspects, which is easier to accomplish using the shorter strands.
Spinning Fiber
Arcidiacono indicated that the program has reached a stage where scientists can actually begin to think about spinning fiber. Getting away from near total dependence on the bacterial fermentation process will be a major boost for this part of the project, he said.
It is the pulling action that the spider employs, while weaving and stretching a web, that serves to strengthen individual strands of filament, scientists explained. This post-spinning, "extensibility" process is needed, if the end product is to be as strong as advertised, Arcidiacono said.
In nature, both male and female spiders produce silk-generating protein.
By Turner's estimate, one gram--approximately a teaspoon of silk--can be stretched to almost three miles.
Scientists, however, have not been able to accomplish this feat yet, because of a lack of spider silk, Arcidiacono said. This shortage should be relieved later this year as more BELE goats begin lactating, he said.
Nexia's initial goal is to increase the herd to 700 goats Turner said. Ultimately, the company will maintain several thousand animals, he said.
In addition to spider silk, the goats will produce antibodies in their milk that can be used to treat people injured by biological/chemical attacks or industrial accidents, Nexia officials said. Enzymes to make products to neutralize chemical and biological hazards will also be produced in this medium.
Following the extraction of spider silk and other products, many thousands of gallons of goats' milk will be composted and spread on fields that grow feed for the goat herd, Turner explained. It also can be converted directly into goat feed. "Spider silk is a nontoxic substance," said Turner.
The extraction process is environmentally friendly, because the filament is water-soluble, Arcidiacono said. "We won't be using chemical solvents." Once the fibers are formed outside of solution, however, "they are no longer water soluble," he said. This is a desirable characteristic, according to Arcidiacono, because it helps to preserve the filament.
Common Standards Sought for Chem-Bio Protective Equipment
A one-year-old federal joint-agency pilot program--called the National Protection Center (NPC)--aims to provide common standards for protective clothing and equipment for local fire, rescue workers and law enforcement personnel, who would be called in for assistance following terrorist attacks with chemical/biological weapons or accidental industrial chemical spills in the United States.
"We see ourselves as a kind of GSA (General Services Administration) for providing information and networking for the first responder," said Rita Gonzales, NPC acting director. "We act as a liaison, putting together technical working groups around specific technologies. Our job is to cut down on redundancy in developing specialized equipment for the first-responders. We don't believe that duplicating efforts is cost effective."
The NPC is part of the Soldier and Biological Chemical Command (SBCCOM) at the U.S. Army Soldier Systems Center, in Natick, Mass.
The agency works with local fire and rescue detachments, hazardous- material containment and cleanup units, and law-enforcement agencies, stated Bill Haskell, NPC technical program development manager. NPC is a joint effort between the Army, NASA-Ames Research Center and the National Institute for Justice.
"We don't procure or sell anything," Gonzales explained. "However, we do know where to get the best prices. This would have the effect of driving down prices due to cooperation by combining forces and putting in for procurements en masse. It the Defense Department is buying in bulk and civilians are able to get in on it, this will help to drive down cost to the communities."
Community first responders need to have access to the right kind information, continued Gonzales. These days, it is necessary to sift through a plethora of information on an overwhelming array of available products, Gonzales added. "Our goal is to build a user database, driven by the needs and concerns of the users," Gonzales said.
Eventually NPC wants to get more involved with product evaluation for the first responder in much the same way Underwriter Laboratories evaluates electrical equipment and appliances for consumers, Gonzales said.
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| Author: | Willingham, Stephen |
|---|---|
| Publication: | National Defense |
| Geographic Code: | 1CANA |
| Date: | Sep 1, 2000 |
| Words: | 1839 |
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