Spinning super strong synthetic spider silk

Spiderman will need to upgrade his suit.

A study in Nature Chemical Biology shows a new way to produce synthetic spider silk that comes very close to the strength of nature’s own. Jan Johansson and Anna Rising from Swedish University of Agricultural Sciences have designed a protein that is a hybrid of two natural silk proteins, and a spinning device that mimics the spider’s method of producing silk.

We spoke to the authors about their work.

ResearchGate: What motivated this study?

Jan Johansson & Anna Rising: Spider silk is the toughest fiber known, and it also has favorable properties when implanted in living tissue. This makes it a very attractive material for a wide variety of applications ranging from high performance textiles to medical devices. We aimed to replicate the silk formation process of a spider.

Biomimetic spinning of artificial spider silk. The protein solution is pumped through a glass capillary and into an aqueous buffer at pH 5. Credit: Marlene Andersson
Biomimetic spinning of artificial spider silk. The protein solution is pumped through a glass capillary and into an aqueous buffer at pH 5. Credit: Marlene Andersson

RG: What types of applications does your spider silk have?

Johansson & Rising: Recently, there has been a lot of interest in using artificial spider silk for high performance textiles in things like jackets, shoes, and sporting goods. We are mainly interested in the medical applications of spider silk and are currently working on using spider silk for nerve regeneration associated with spinal cord injuries.

RG: Can you tell us about your new method to produce spider silk?

Johansson & Rising: We have designed a spider silk protein using different spider species to make it optimally water soluble and easy to produce. The design’s success meant we could make unprecedented amounts of the proteins in E. coli bacteria.

We also designed a new spinning apparatus that mimics the changes in pH that the spider uses to make silk fibers. Together this allowed us, for the first time, to spin artificial spider silk fibers without using harsh chemicals. Furthermore, the high amounts of proteins produced in the bacteria allow us to spin a kilometer of the biomimetic fibers from just one liter of E. coli culture.

RG: Why has spider silk been so difficult to produce?

Johansson & Rising: Spiders cannot be used for the industrial production of spider silk, because they are territorial predators. The silk proteins are also very difficult to produce with commonly used production hosts, like bacteria, because the proteins aggregate. To dissolve the aggregates and turn them into fibers, others have tried harsh solvents that denature the proteins. Spider silk is composed of proteins that have assembled into a complex structure that is very different from the disordered state of an aggregate.

Artificial spider silk fibers on spools. Credit: Marlene Andersson
Artificial spider silk fibers on spools. Credit: Marlene Andersson.

RG: What were the biggest challenges you faced?

Johansson & Rising: The first major challenge to overcome in this study was designing a spider silk protein that can be kept at large concentrations. The second major challenge was to design a spinning device that captures the salient features of how the spider spins silk.

A nest of artificial spider silk fibers. Credit: Lena Holm.
A nest of artificial spider silk fibers. Credit: Lena Holm.

RG: Could artificial spider silk ever outperform natural spider silk?

Johansson & Rising: Yes. We will now engineer the protein and work on making the spinning device even better. We are confident that we will be able to produce super fibers that equal or exceed the properties of native spider silk.

Featured image is artificial spider silk fibers rolled up on a frame. Credit: Marlene Andersson.