Here is the Randy Lewis interview by Sander Olson. Dr. Lewis is a molecular biologist who teaches at the University of Wyoming. His group has sequenced the genome of the orb spider, which has silk which is 10x as strong as steel. Dr. Lewis group aims to inject orb spider genes into silkworms in order to have silkworms produce pure spider silk. Dr. Lewis is also investigating combining orb spider silk with carbon nanotubes, which could yield materials which have unprecedented properties of strength and elasticity.
Question: Your lab has recently made some major advances in sequencing spider silk. What properties does spider silk have that make it so potentially valuable?
Answer: Our research is focused on cloning and sequencing spider silk genes. The gene sequence tells us what the silk proteins look like. Then we produce these proteins in bulk and turn them into fibers. We want to create fibers that are high in tensile strength and elasticity, a combination not found in manmade fibers, with the ultimate aim of mass producing fibers with the same properties as silk.
Question: How long have researchers been studying silk?
Answer: The first scientific paper on silk was published in 1907. In 1990 the first gene sequencing of silk was published. That was the first step towards creating artificial silk, since we knew at that point the proteins that made up the silk.
Question: How many different types of silk exist? How many types does your lab use?
Answer: Every species of spider makes its own silk. The orb-web spider makes 6 different types of silk, and each silk has different mechanical properties. The orb-web spider has the strongest type of silk that we have tested, although we haven’t yet tested most spider silks since there are 40,000 species of spiders. So we can’t say for sure which is the strongest.
Question: How does the strength of spider silk compare with that of steel or Kevlar?
Answer: There are different ways of measuring strength. Tensile strength provides a good indication of how much weight a thread can carry. The tensile strength of spider dragline silk is comparable to that of kevlar. For bulletproof vests, strength is measured in how much energy the material can absorb before it breaks. By that measure, spider dragline silk is about 10 times as strong as steel, and 3 times as strong as kevlar.
Question: What about elasticity?
Answer: Some spider silks stretch considerably more than kevlar or steel. By stretching the spider silk absorbs substantial amounts of energy, and this is one of the properties that makes silk so valuable.
Question: How does spider silk compare with that of silk from silkworms?
Answer: There are different varieties of spider silk with varying properties. Some spider silks have no elasticity, and other silks will stretch to almost double their length. Silkworm silk is about 1/10 as strong as the strongest spider silk, and has virtually no elasticity.
Question: Your recent study added spider silk genes to silkworms. What properties did the resulting silk have?
Answer: We actually created several spider silk genes ourselves designed for strength, or for elasticity. We injected the genes for elastic protein into transgenic silkworms, in order for them to produce the silk with the different properties. The ultimate goal is to have a silkworm produce spider silk.
Question: How long before the first silkworm produces pure spider silk?
Answer: It will probably take 3 years before we succeed. We know that we can inject all of the necessary genes, but we aren’t 100% certain that the silkworm can produce pure spider silk. It may not be necessary for the needed properties to have pure spider silk, some combination may work just fine.
Question: What do you see as the first application for this spider silk?
Answer: We see the first application in biomaterials, such as ligament replacement and tendon repair materials. We know that spider silk is strong enough to perform that task. Parachute chords and reinforced airbags that absorb energy could also be early applications. High-tech clothing, fly fishing lines, and ropes are another possibility. Bullet proof vests will come eventually but we don’t see them as being an initial application.
Question: How much will pure spider silk cost?
Answer: It will cost modestly more than silkworm silk. Although I can’t provide precise estimates, it won’t cost 10 times as much as raw silk. I’m confident that we’ll eventually be able to produce enough silkworms to satisfy demand.
Question: Could other animals, such as transgenic goats, or spiders produce the necessary quantities of spider silk?
Answer: We do use transgenic goats to produce certain proteins. But there isn’t any feasible way to use animals other than silkworms to produce the silk fibers so we have to purify the spider silk proteins and spin our own fibers. Silk from orb spiders is prohibitively expensive since they are territorial and cannibalistic, and don’t produce much silk.
Question: How does the strength of orb spider silk compare with that of carbon nanotubes?
Answer: Carbon nanotubes are considerably stronger than any silk. However, nanotubes are stiff, and can’t be made into the same types of fibers as silk. We are currently examining the possibility of combining nanotubes with silk to see if we can increase the strength without impeding the elasticity. If we succeed, we will create a material with the strength of nanotubes combined with the elasticity of spider silk, which would be quite valuable.
Question: Will it ever be feasible to create spider silk using vats of bacteria?
Answer: Genetically engineered bacteria might be useful for specialty applications, but I doubt that it would be cost-effective for large-scale production. There are actually a huge variety of plants that could be used to make spider silk, and we are looking at alfalfa, cottonseed, soybeans, and even tobacco. We have demonstrated that we can produce the necessary proteins using alfalfa, and we have our own spinning apparatus. So we don’t actually need silkworms – we can produce the silk on our own using alfalfa and our spinning machines.
Question: How does the spider silk feel? Does it have the same softness as silkworm silk?
Answer: Yes, it feels the same. But it is much stronger and more elastic. We can tailor the properties of the silk, such as increasing tensile strength or elasticity. But it is probably too expensive to be used in sheets or standard clothing unless we use the fibers produced by the transgenic silkworms.
Question: Have you created any startups?
Answer: Yes, it is called WyoBiGen. I am the founder and President. I formed this company to commercialize spider silk production. Currently it is an R&D company. If this technology progresses the way I hope, WyoBiGEN will be instrumental in the mass-production of spider silk