Spider twist leads to hybrid silk yarn

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  • Published 3.01.12

Jan. 2: Scientists say they have coaxed silkworms to spin mechanically superior spider yarn and moved a step closer to efforts at commercial spider silk farming abandoned as unviable more than 300 years ago.

A team of Chinese and US researchers has created genetically-engineered silkworms that spin hybrid silk, a material that is part-silkworm fibre and part-spider silk and significantly tougher than natural fibre from silkworms.

The scientists injected silkworm embryos with gene sequences for elasticity and tensile strength of spider silk that allowed the resulting adult silkworms to spin hybrid fibres, 95 per cent silkworm and 5 per cent spider proteins.

This is the first time spider silk proteins have been incorporated into composite fibres with a beneficial impact on the mechanical properties of the fibres, said team member Donald Jarvis, a professor of molecular biology at the University of Wyoming in the US. Jarvis and his colleagues published their results today in the US journal Proceedings of the National Academy of Sciences.

Their announcement comes at a time when the Victoria and Albert Museum in London is preparing to display later this month a large hand-woven brocaded textile made from natural spider silk that highlights the difficulty of harnessing spiders.

Eighty spider handlers extracted silk from Golden Orb spiders from Madagascar for five years to accumulate enough of the silk to make the four-metre long woven textile that will be on display from January 25 to June 5, the museum said in a press release.

“Spider silk is dramatically superior to silkworm fibre,” said Javaregowda Nagaraju, a biologist at the Centre for DNA Fingerprinting in Hyderabad, and an expert on silkworm genetics, who was not associated with the Chinese-US project. Spider silk is viewed as a futuristic material that could be used to make sutures for cosmetic surgery to scaffolds for biomedical engineering to bullet-proof vests, he said.

“But spider farming had long been given up as unviable,” Nagaraju told The Telegraph. The French science academy dismissed spider farming as unviable in 1710 after a series of experiments to fashion stockings and gloves from spider egg sac silk, he said.

A major drawback of spiders is their inability to spin particularly long lengths of fibres. While silkworms can produce 600 metres to 1,200 metres of fibres, spiders make just 130 metres of silk from their silk glands and 12 metres from their webs, Nagaraju said.

While silkworms can be cultivated in the thousands, spiders are territorial and eat each other, making spider farming difficult. Although spider silk has earlier been produced in bacteria, yeast and insect cells, most processes have been expensive to scale up.

The new results suggest that genetically engineered silkworms could be used as tiny factories to make composite silkworm and spider silk fibre with predictable properties, Jarvis said.

But Jarvis cautioned that commercial production of such composite fibre might still be some years away. “We still need to produce transgenic silkworms that produce fibres mostly or solely of spider silk proteins,” Jarvis said.