Silk tougher than Kevlar thanks to genetically modified silkworms

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In a piece of amazing science, researchers in China successfully genetically modified silkworms to produce spider silk. The silk fibres produced were 6 times tougher than the Kevlar used in bulletproof vests.

The result might bring manufacture of a sustainable alternative to synthetic fibres a step closer.

Spider silk has a higher tensile strength than nylon and greater toughness than Kevlar, and has long been of interest to material scientists.

The research, published in Matter, could also have implications for the production of synthetic fibres that are both high-strength and ultra-tough.

Like silkworm silk, spider silk is a natural polyamide fibre – nylon and Kevlar are synthetic polyamide fibres – but commercialising it has been problematic due to limited understanding of the spinning mechanism, technical complexities in the process, and engineering hurdles in low-cost mass production. There’s also the pesky problem of spiders’ cannibalistic nature.

“Silkworm silk is presently the only animal silk fibre commercialised on a large scale, with well-established rearing techniques,” says lead author and PhD candidate Junpeng Mi.

“Consequently, employing genetically modified silkworms to produce spider silk fibre enables low-cost, large-scale commercialisation.”

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Mi and his team introduced spider silk protein genes into the DNA of silkworms using a combination of CRISPR-Cas9 gene editing technology, via hundreds of thousands of microinjections into fertilised silkworm eggs.

The researchers also needed to perform modifications on the spider silk proteins so that they would interact properly with proteins in the silkworm glands, ensuring that the fibre would be spun properly.

Two silkworm glands sit in a petri dish. They look like bright yellow worms with a silk thread coming out the end.
Domestic silkworm silk glands. Credit: Junpeng Mi.

The silk fibres produced had exceptionally high mechanical performance.

As well as applications in smart materials for the military and aerospace, Mi says there are also applications in biomedical engineering. “This type of fibre can be utilised as surgical sutures, addressing a global demand exceeding 300 million procedures annually.”

Future research will build on the insights into the toughness and strength of spider silk fibres developed in the current study by developing genetically modified silkworms that produce spider silk fibres from both natural and engineered amino acids.

“The introduction of over one hundred engineered amino acids holds boundless potential for engineered spider silk fibres,” says Mi.

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