Got some special milk, plastic tubing, some red beads and salt water?
What’s needed to spin spider silk proteins may seem pedestrian, but walking to the nearest hardware store for supplies and trying isn’t recommended.
The spider silk research prowess of Professor Randy Lewis and his team in the Department of Molecular Biology at the University of Wyoming draws world-wide interest. For example, a presentation about his research was selected as a Top 5 hot talks/cool paper during the Materials Research Society’s international fall meeting in Boston, Massachusetts. The Top 5 were selected from nearly 5,000 oral and poster presentations.
The renewal of a half-million dollar Air Force grant and a $1.5 million grant from National Institutes of Health will enable the Lewis team in the College of Agriculture to examine using spider silk as sutures, and there is also interest in using spider silk technology as scaffolding for regenerating ligaments and tendons in humans. The grant will help the team continue research into production of spider silk for various commercial purposes.
They have to have the proteins first. The Lewis team derived small amounts from E. coli and is experimenting with alfalfa, but the mother lode of spider silk proteins may be using transgenic goats.
The team received about 600 gallons of the milk from Nexia Biotechnologies Inc. in Montreal, Canada, and began processing the goat’s milk containing the spider silk protein for the production of recombinant spider silk – BioSteel® – for Nexia.
Fourth-year doctoral students Daniela Bittencourt of Brasilia, Brazil, and Melinda Creager of Green River began processing the milk this past winter and will eventually spin the protein fibers.
The two in a special cooler in the Animal Science/Molecular Biology building watched in January as a pump drew milk through a tube to eventually separate the protein from the milk. It was slow going. The milk had arrived frozen. When it thawed, fat globs formed and began plugging the system.
To obtain the milk from Nexia, UW agreed to process and provide 50 grams of protein to a company in Europe. “That doesn’t sound like a lot,” said Creager, “but it is. The protein is for a medical products company trying to coat latex gloves with the silk-latex mix for stronger gloves. The rest of the milk is ours.”
Difficulties had to be overcome before the team could proceed. “We had to figure out how to do it,” Creager said. “The fat comes out and creates lots of problems.”
Fifteen gallons of milk provided the 50 grams of protein, said Lewis, and the process took about four days.
A plastic tube with microscopic holes lets proteins through but traps the fats. The liquid is then placed in another tube with much smaller holes that retains and concentrates the spider silk proteins.
The final step involves putting the concentrated solution with those afore-mentioned red beads. “For reasons unknown to anybody, the spider silk proteins stick to the red dye,” said Lewis. A salt solution is poured over the beads, which washes away the wanted proteins.
The proteins naturally stick together and are put through a device that looks like a cake decorator’s funnel for squeezing frosting. The fibers squirt out and are wound around a spool.
The process is not unique. “Nexia does it all the time,” said Lewis. “They do hundreds of meters. We are more interested in the properties of the fibers. How strong and how far will they stretch?”
From milk to spinning fibers team members are happy about could take a year to 18 months.
“There are so many things we have to learn at each step to do it right to produce fibers with properties superior to anything out there,” said Lewis. “At each step, there are things we have to solve.”
Back in a laboratory, Bittencourt and Creager took “Persephone” out of her cage for photographs. She proved only a little camera shy as she crawled over their arms while being photographed. Named for the goddess of the underworld, Persephone is a Nephila clavipes, or a golden orb weaver.
Creager said the team uses five types of spiders regularly in the lab: the golden orb weaver, Argiope aurantia, also known as a black and yellow garden spider, Argiope trifasciata, native to Wyoming and commonly known as a grass spider, Araneus gemmoides, known as cat-faced or barn spiders, and Latrodectus geometricus, commonly known as the brown widow. They also have wolf spiders and three types of tarantulas.
The stable provides natural silk Creager, Bittencourt, and the team can compare to the artificial spider silk, both mechanically and structurally.
“Another use is that we’re still looking at some of the other types of silk; there are still three silks we do not have a definite protein sequence for, although we’re getting close, but we have to have the silk or glandular content to determine the sequence of these silks,” said Creager.
The research by Lewis was a magnet for Creager and Bittencourt.
Bittencourt was interested in transgenic animals but switched emphasis to spider silk research and is attending UW on a fellowship. “If not the best, Randy is one of the best in the world in spider silk research,” said Bittencourt, seeking a doctorate degree in molecular biology.
Both said Lewis is good to work for. “He is very open to your ideas and will give you guidance,” said Creager, pursuing degrees in molecular biology and physical chemistry. “He knows what others have done and is always open to let you try something.”