Silkworms genetically engineered to produce pure spider silk

Silkworms have been genetically engineered with CRISPR to produce pure spider silk for the first time. The worms could offer a scalable way to create things like surgical thread or bulletproof vests from spider silk, which is prized for its strength, flexibility and lightness.

Spider silk has been eyed as a greener alternative to synthetic fibres, which are derived from fossil fuels and leach harmful microplastics into the environment. Farming silk from spiders themselves is difficult, however, because they tend to eat each other and only produce a small amount of silk fibre to make their webs. A 4-square-metre spider silk shawl that was displayed at the Victoria and Albert Museum in London, for example, had to be created from the silk of over 1 million golden orb-weaver spiders.

As a result, several groups have tried to genetically engineer silkworms so that they make spider silk instead of their own silk, since silkworms are easier to farm and spin much larger quantities of fibre. But until now, the silk produced by these modified silkworms has been less than 36 per cent spider silk.

Now, Junpeng Mi at Donghua University in China and his colleagues have used a more advanced genetic engineering technique – CRISPR – to insert the genes responsible for making spider silk proteins into silkworms.

The resulting silkworms produced silk that was 100 per cent spider silk and could withstand a stretching force of 1299 megapascals without breaking, making it 1.3 times stronger than nylon. Its toughness – the energy it could absorb under impact – was 319 megajoules per cubic metre, making it six times tougher than Kevlar.

As a bonus, the silkworms also naturally applied a protective coating to the spider silk, resembling that produced by spiders themselves. This is likely to result in the fibres being more durable than artificially created spider silk, says Mi. “This makes silkworms an all-in-one station for spider silk fibre production,” he says.

The engineered silkworms could enable cheap mass production of spider silk, which may be used as surgical suturing thread or in bulletproof vests, says Mi. The team has already experimented with using the spider silk as a suturing thread for stitching up incisions in rats and found that their wounds healed better than when traditional nylon threads were used, he says.