Scientists spin new version of silk

01 Jun '15

3 min read

After years of research decoding the complex structure and production of spider silk, researchers have now succeeded in producing samples of this exceptionally strong and resilient material in the laboratory.

The new development could lead to a variety of biomedical materials — from sutures to scaffolding for organ replacements — made from synthesized silk with properties specifically tuned for their intended uses.

The findings have been published this week in the journal Nature Communications by Massachusetts Institute of Technology (MIT) professor of civil and environmental engineering (CEE) Markus Buehler, post-doctorates Shangchao Lin and Seunghwa Ryu, and others at MIT, Tufts University, Boston University, and in Germany, Italy, and the UK.

The research, which involved a combination of simulations and experiments, paves the way for “creating new fibers with improved characteristics” beyond those of natural silk, says Buehler, who is also the department head in CEE. The work, he says, should make it possible to design fibers with specific characteristics of strength, elasticity, and toughness.

The new synthetic fibers’ proteins — the basic building blocks of the material — were created by genetically modifying bacteria to make the proteins normally produced by spiders. These proteins were then extruded through microfluidic channels designed to mimic the effect of an organ, called a spinneret, that spiders use to produce natural silk fibres.

While spider silk has long been recognized as among the strongest known materials, spiders cannot practically be bred to produce harvestable fibers — so this new approach to producing a synthetic, yet spider-like, silk could make such strong and flexible fibers available for biomedical applications. By their nature, spider silks are fully biocompatible and can be used in the body without risk of adverse reactions; they are ultimately simply absorbed by the body.

The researchers’ “spinning” process, in which the constituent proteins dissolved in water are extruded through a tiny opening at a controlled rate, causes the molecules to line up in a way that produces strong fibers. The molecules themselves are a mixture of hydrophobic and hydrophilic compounds, blended so as to naturally align to form fibers much stronger than their constituent parts. “When you spin it, you create very strong bonds in one direction,” Buehler said.

The team found that getting the blend of proteins right was crucial. “We found out that when there was a high proportion of hydrophobic proteins, it would not spin any fibers, it would just make an ugly mass,” said Ryu, who worked on the project as a post-doctorate at MIT and is now an assistant professor at the Korea Advanced Institute of Science and Technology. “We had to find the right mix” in order to produce strong fibers, he said.

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