Genetically engineered silk eyed as coating for implants

March 2013. Source:

A German company is raising the ante on potential medical and industrial uses of silk polymers through development of a genetically engineered spider silk fiber it is commercializing under the name “Biosteel”.

According to AMSilk (Martinsreid, Germany), Biosteel has six times more toughness than carbon fiber while having elasticity comparable to rubber. The material is said to be scalable in industrial processes.

“Of all the many applications for spider silk, the spinning of a viable commercial fiber has always been technically the most challenging. With the current process, we have shown that a commercial spider silk fiber is possible,” said Lin Römer, who heads R&D at AMSilk. “Next we will optimize the fiber further and scale raw material production and spinning in our new pilot plant.”

Target medical applications for Biosteel include implant coatings, medical textiles and surgical products such as meshes, support textiles or wound coverings. Other potential targets include high-performance technical textiles and sporting goods.

In an interview with PlasticsToday, Chief Business Officer Mathias U. Woker described the raw material technology behind Biosteel as an E. coli fermentation process. He said the company does not provide details to describe how E. coli can be genetically engineered to mimic the system used by spiders to produce proteins that form the basis of fibers for its web.

Technologies under development elsewhere such as Tufts University (Medford, MA) focus on silk produced directly by silkworms.

Silk is a natural polymer produced by the silk moth, silk worm, bees, wasps, ants, and spiders. Each species produces a type of silk with a unique properties’ signature. Silk produced from silk moths has been a valued fashion material for centuries.

Silk from spiders has not been commercially available because they are cannibals, and cannot be bred on a large scale. It would also be too expensive to harvest the thread.

Recombinant proteins

It is possible to produce spider silk as recombinant proteins using engineered host organisms. That process has been slowed by lack of complete gene sequencing for spiders. A synthetic sequence that mimics or even enhances the original silk proteins can also be used.

Thomas Scheibel, chair of Biomaterials at the University of Bayreuth, is the main inventor of the AMSilk technology and serves as chief scientific advisor for AMSilk. He spent three years as a researcher at the University of Chicago and developed spider silk technologies at the Technische Universität München.

Once the silk is produced it needs to be drawn in order to achieve useable properties. Drawing of the fiber mimics the way a spider pulls dope from its gland.

Woker said that the company currently can only make the material on a kilogram scale, but plans to develop tons-scale capacity, either internally or through third-party manufacturers, within two years. He would not disclose current fiber spinning capacity or plans for production development.

Biocompatibility, resiliency and toughness are Biosteel’s trump cards.

“Our first focus is on a coating for breast implants,” said Woker.

“A coating for a silicone breast implant would prevent capsular fibrosis.” The tightening of the fibrous capsule around the implants making them less mobile takes place in a process called capsular fibrosis. Woker expects clinical trials to commence within two years.

AMSilk was founded in 2008 and is located near Munich. Key investors are MIG Funds and AT Newtec, Munich. Projects are partially funded through grants from the German Federal Ministry of Education and Research and the Bavarian Ministry of Economic Affairs, Infrastructure, Transport and Technology.