Spider Silk Offers Hope to Torn Ligaments : Medicine: Arachnids spin several kinds, using dragline silk for the outer framework of their webs. Its tensile strength is greater than steel. It is more elastic than nylon.

An athlete with a torn ligament receives an artificial ligament in an operation that leaves no scar. Several weeks later, the athlete is back on the field with a knee as strong as before.

Such an operation could be routine one day, according to Randy Lewis, University of Wyoming professor of molecular biology, who says the creature that could make this medical miracle possible is a spider.

Lewis, described by others as a pioneer in the field, has spent six years studying spider silk. His research centers on about a dozen golden orb spiders, measuring about three inches from leg tip to leg tip, encased in small wood-and-Plexiglas enclosures in a laboratory at the university.

Spiders produce several kinds of silk, all intended for different purposes. Lewis has singled out the silk the spiders use for the outer framework of their webs, called dragline silk.

Gram for gram, Lewis said, dragline silk’s tensile strength is greater than that of steel. It’s also more elastic than nylon and can absorb more energy before breaking than any other known substance, he said.

About once a week, researchers anesthetize a spider and immobilize it under a microscope. A strand of dragline silk is drawn out of the spider and attached to a plastic tube spun by a variable-speed drill. Lewis said researchers can obtain up to 100 meters of the silk, about 1/20th the diameter of a human hair, per “silking.”

Lewis began researching spider silk in 1988, when he was approached by a San Diego company interested in possibly synthesizing silkworm silk. That project did not have a chance of becoming economically feasible, Lewis said, because of the low cost of natural silk produced in the Far East.

But the initial research led him to spider silk. When the company involved in the silkworm research lost interest, Lewis obtained federal funding to continue the research.

Since then, Lewis said, he has isolated the two proteins that make up dragline silk. But it has not been easy.

The proteins, Lewis said, are unique in how they are held together. While most proteins are bonded with chemical links, spider-silk proteins have a physical bond, making the silk virtually impervious to water. That means researchers cannot dissolve the silk in a solution to make it easier to study.

Lewis’ efforts to develop ways to study the proteins have led to several offshoots of his research, including four possible patents.

In addition, Lewis’ work on the proteins of the silk have made it possible for others to begin their own research, according to Lynn Jelinski, head of the Center for Biotechnology at Cornell University and a professor of engineering.

“If it weren’t for Randy Lewis, nobody would be doing anything,” she said. “He has done the pioneering work in terms of making the sequence of the protein. He is the kingpin of all this.”

Jelinski said many researchers, using Lewis’ research, are moving ahead with their own efforts to understand the silk and produce their own version of it.

Once the proteins and the genes of the silk were isolated, Lewis faced another problem: trying to figure out how to produce the stuff. Lewis used established genetic procedures to make bacteria absorb the genes responsible for silk production in spiders. The bacteria produce a material that, when purified, becomes a fine white powder which Lewis said could be spun into fibers with dozens of uses.

Some of the most promising possibilities, he said, involve medical technology. The silk could be used for sutures about one-tenth the diameter of current sutures, but with the same strength. Such small stitches could be used to avoid scarring or leakage when used on a blood vessel.

Lewis said studies on animals have indicated that the silk is compatible with implantation in the body, in part because it is so difficult to dissolve.

“There’s virtually no evidence of major tissue response,” he said.

The silk also could be used to make artificial ligaments or tendons, Lewis said, for which there are no effective artificial substitutes now.