Possible to spin artificial spider silk

Being able to produce artificial spider silk has long been a dream of many scientists, but all attempts have until now involved harsh chemicals and have resulted in fibers of limited use. Now, a team of researchers from the Swedish University of Agricultural Sciences and Karolinska Institutet has, step by step, developed a method that works. In a new study in Nature Chemical Biology, they now report that they can produce kilometer long threads that for the first time resemble real spider silk.

Spider silk is an attractive material–it is well tolerated when implanted in tissues, it is light-weight but stronger than steel, and it is also biodegradable. However, spiders are difficult to keep in captivity and they spin small amounts of silk. Therefore, any large scale production must involve the use of artificial silk proteins and spinning processes.

A biomimetic spinning process (that mimics nature) is probably the best way to manufacture fibers that resemble real spider silk. Until now, this has not been possible because of difficulties to obtain water soluble spider silk proteins from bacteria and other production systems, and therefore strong solvents has been used in previously described spinning processes.

Large quantities in bacteria

Spider silk is made of proteins that are stored as an aqueous solution in the silk glands, before being spun into a fiber. Principal Invetigator Anna Rising and her colleagues at the Swedish University of Agricultural Sciences and at Karolinska Institutet have previously shown that there is an impressive pH gradient in the spider silk gland, and that this well-regulated pH gradient affects specific parts of the spider silk proteins and ensures that the fiber forms rapidly in a defined place of the silk production apparatus.

This knowledge has now been used to design an artificial spider silk protein that can be produced in large quantities in bacteria, which makes the production scalable and interesting from an industrial perspective.

"To our surprise, this artificial protein is as water soluble as the natural spider silk proteins, which means that it is possible to keep the proteins soluble at extreme concentrations", says Anna Rising in a press release.

Among the authors are also researchers from Donghua University (China), Universidad Politécnica de Madrid (Spain), University of Oxford (UK), KTH Royal Institute of Technology (Sweden), Uppsala University (Sweden) and Lund University (Sweden). The research has been funded by the Swedish Research Council, Center for Innovative Medicine (CIMED) at Karolinska Institutet and FORMAS, among others.

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Publication

Biomimetic spinning of artificial spider silk from a chimeric minispidroin
Marlene Andersson, Qiupin Jia, Ana Abella, Xiau-Yeen Lee, Michael Landreh, Pasi Purhonen, Hans Hebert, Maria Tenje, Carol V Robinson, Qing Meng, Gustavo R Plaza, Jan Johansson, Anna Rising
Nature Chemical Biology, online 9 January 2017, doi: 10.1038/nchembio.2269