Artificial Spider Silk Can Now Be Made
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A team of researchers from the Swedish University of Agricultural Sciences and Karolinska Institutet has have developed a method for making artificial spider silk. The reported that they can produce kilometer long threads that for the first time resemble real spider silk.
Spider silk is well tolerated when implanted in tissues, light-weight but stronger than steel, and is also biodegradable. However, spiders are difficult to keep in captivity and they spin small amounts of silk. Any large-scale production must involve the use of artificial silk proteins and spinning processes. 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.
Spider silk is made of proteins that are stored as an aqueous solution in the silk glands, before being spun into a fibre. Researcher Anna Rising and her colleagues Jan Johansson and Marlene Andersson at the Swedish University of Agricultural Sciences and at Karolinska Institutet have previously shown that there is a pH gradient in the spider silk gland. This well-regulated pH gradient affects specific parts of the spider silk proteins, ensuring that the fibre 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. To mimic the spider silk gland, the research team constructed a simple but very efficient and biomimetic spinning apparatus in which they can spin kilometre-long fibres only by lowering the pH.
"This is the first successful example of biomimetic spider silk spinning. We have designed a process that recapitulates many of the complex molecular mechanisms of native silk spinning. In the future, this may allow industrial production of artificial spider silk for biomaterial applications or for the manufacture of advanced textiles", says Anna Rising.
Andersson, M., Jia, Q., Abella, A., Lee, X.-Y., Landreh, M., Purhonen, P., … Rising, A. (2017). Biomimetic spinning of artificial spider silk from a chimeric minispidroin. Nature Chemical Biology. doi:10.1038/nchembio.2269
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