Device Spins Super-Strong Spider Silk That Could One Day Repair Nerves

Researchers made a device that extrudes silk just like a spider gland.

At high magnification, the structure of silk-tougher-than-steel-1822242055.html">silk proteins from a special South African spider resemble dumbbells. It's an appropriate shape given how strong the fibers are. This particular kind of silk doesn't contract in water, either, unlike the fibers from other spiders.

That's a crucial property considering that one day a material produced efficiently in the lab from these proteins could be inside your body, healing it.

"I think that our fiber has a good potential to become like a scaffold to guide nerve regeneration. We are looking mainly at spinal cord injuries for the moment, but also peripheral nerve damage," Anna Rising, an assistant professor of translational medicine at the Swedish University of Agricultural Sciences and the Karolinska Institutet, told me.

She and her colleague Jan Johansson combined a silk gene from the South African spider Euprosthenops australis with DNA from a Chinese spider called Araneus ventricosus. They used bacteria to produce new hybrid silk proteins, turned them into a highly concentrated solution and extruded the solution through a spinning device they created to mimic a spider gland.

The resulting fiber is stronger and more efficient than most other artificial lab-produced versions, and about a third as strong as real spider silk. Their results were published today in the journal Nature Chemical Biology.

Besides being beautiful, natural spider silk is unbelievably strong, biodegradable, and has myriad potential applications. But it's expensive and challenging to obtain. So scientists like Rising and Johansson want to generate an artificial version in the lab that's just like the real thing.

The Swedish team has their sights on biomedical applications, starting with nerve repair. Rising cited published studies, including one where about two inches of peripheral nerves were removed from sheep. Left alone, the nerve endings couldn't regenerate. Then the scientists added spider silk fibers. "The animal got the function of the nerve back, which is quite remarkable," Rising said.

Other researchers typically take spider silk proteins and put them in harsh chemicals to make them more soluble, Johansson said. Instead, he and Rising sought to replicate the conditions in a spider silk gland using only water and a low pH bath. They put a high concentration of the protein solution into Rising's device, which pumped it through tubing into a pointy glass tip. As the proteins passed through the capillary's narrow end, they got sheared, which spun fiber into the low pH aqueous buffer.

This new biomimicry system is highly efficient. "From one liter of E. coli culture, which costs a few dollars to produce, we could make protein enough for making a kilometer of silk fiber," Johansson explained.

Next, Johansson and Rising want to improve the spinning process and redefine the silk protein structures to make them even stronger. They'd also like to get their protein and device into a 3-D printer, Rising said. "In theory, we can print anything now."

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