Spider silk is famously strong—comparable to steel or Kevlar yet many times lighter—but there's a limit to how much of the natural supermaterial you can harvest from our eight-legged pals. That's why researchers have been looking for ways to make their own silk, and one group reports that they've successfully made lab samples of fibres that could be greatly scaled up and used in medical applications.
A paper in Nature Communications describes their efforts to design the perfect silk using computer simulations and make samples, no spiders needed.
"Spiders are not easily farmed, in fact they cannot be farmed at all," said Markus Buehler, an MIT engineer and author on the paper. Spiders are territorial and don't like to share space (they don't have many qualms about eating each other), so while you can get a bit of silk from an odd spider caught here and there, scaling up to a useful amount is difficult.
To make the silk without the need for a leggy menagerie, Buehler explained that the team broke it down into its basic building blocks: the proteins that spiders spin into webs. They genetically modified bacteria to make these, then extruded the material through a syringe needle to mimic the natural spinning process.
"This particular work is geared towards medical applications," said Buehler. "Silk is almost a perfect biomaterial—unlike polymers or some metals it is completely biocompatible so our bodies don't reject silk when you put it in an implant or replacement tissues, things like this." The work was funded by the National Institutes of Health (NIH).
Other applications could include things like super-strong composites for cars and trains—which would require a lot of the stuff. While the researchers just made small samples to test their method, Buehler said they could scale up. "Instead of making one batch with, say, one gallon of liquid, we can easily make 10,000 of these in a larger factory," he said.
The team is now playing with the idea of making alloys of silk and elastin, another biomaterial that is known for being elastic (it's the stuff that makes your skin ping back into place after you pinch it). "We're sort of tricking nature and adding different protein motifs into the silk structure," said Buehler. That could make new materials with different functions, like synthetic tissues also for medical applications.
Computer simulations, which made up a pivotal part of the current research, are also important here. As it can take a long time to synthesise a protein, it's good to know beforehand whether it's going to have the properties you want.
Buehler said that just a couple of years ago there wouldn't have been sufficient computational efficiency to simulate the proteins to this molecular level, which requires simulating billions of particles.
This could help them come up with designs for new materials that are still inspired by spider silk, but actually can't be found in nature. And given the choice between a computer simulation and a "spider farm," I know which I'd rather work with.