Many silk-based materials today are used in the biomedical field as material for stitches and surgical mesh. Producing silk strong enough for these purposes has been a challenge. Most silk comes from silkworms, but their silk is not as strong as spider silk.
Unfortunately, harvesting silk from spiders is more difficult due to their aggression. There is a process in which spider DNA is incorporated into silkworms to make their silk more robust. However, this procedure is costly and hard to grow in the desired quantities.
A recent study published in the journal Matter describes an alternative method for producing strong materials by boiling silkworm silk in a chemical bath to remove the outer layer of silk glue. Then, the strands are fortified by bathing them in metals and sugars. By using this process, the researchers found that silk naturally produced by silkworms can be made 70 percent stronger than spider silks.
“Dragline silk is the main structural silk of a spider web. It is also used as a lifeline for a spider to fall from trees,” explained study senior author Zhi Lin, a biochemist at Tianjin University.
“Since silkworm silk is very structurally similar to eggcase spider silk, which has previously been demonstrated to do well in a mix of zinc and iron baths, we thought to test this alternative method to avoid hazardous conditions used elsewhere. Sucrose, a form of sugar, may increase the density and viscosity of the coagulation bath, which consequently affects the formation of the fibers.”
Once these artificial silk fibers have been spun, they are nearly the same length as spider silk, and are “smooth and strong” enough to resist physical force, according to Lin.
“Our finding reverses the previous perception that silkworm silk cannot compete with spider silks on mechanical performance,” said Lin. “We hope that this work opens up a promising way to produce profitable high-performance artificial silks.”
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