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People have been using silkworm silk to make stuff for thousands of years, but spider silk could potentially be even more useful. It's stronger than steel, super stretchy, and could be made into anything from bridge cables to biodegradable water bottles... if only we could figure out how to cultivate it.

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Sources:
https://www.wired.com/2015/06/bolt-threads-spider-silk/
https://finance.yahoo.com/news/314-necktie-made-spider-silk-201500116.html
https://www.forbes.com/sites/amyfeldman/2018/08/14/clothes-from-a-petri-dish-700-million-bolt-threads-may-have-cracked-the-code-on-spider-silk/#4ad46bc8bda1
https://www.smithsonianmag.com/innovation/new-artificial-spider-silk-stronger-steel-and-98-percent-water-180964176/
http://www.kraiglabs.com/spider-silk/
https://www.technologyreview.com/s/541361/spinning-synthetic-spider-silk/
https://www.technologyreview.com/s/420070/making-spider-strength-materials/
http://www.bbc.co.uk/science/0/21685308
https://cen.acs.org/articles/92/i9/Spider-Silk-Poised-Commercial-Entry.html
https://www.nature.com/articles/nbt.3894/tables/1
https://texeresilk.com/article/silk_making_how_to_make_silk
https://phys.org/news/2018-07-genetic-silkworm-unravel-history-domestication.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5000687/
https://www.britannica.com/animal/silkworm-moth
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https://labiotech.eu/industrial/adidas-amsilk-biodegradable-sneakers/
https://phys.org/news/2018-04-spider-silk-key-bone-fixing-composite.html
https://www.wired.com/story/bolt-threads-synthetic-spider-silk-hat/
https://www.bbc.com/news/av/science-environment-16554357/the-goats-with-spider-genes-and-silk-in-their-milk
♪.

The last time you knocked a cobweb out of your window, you probably weren’t thinking, “I sure wish I had a necktie made out of that stuff.” Scientists, though, think cobweb neckties, and cobweb lots-of-other-things, would be pretty useful. They’ve been trying to mass produce spider silk for decades, but they still haven’t quite figured out how to do it.

So what is it about the fine, stretchy stuff that comes out of a spider’s backside that makes it such a manufacturing challenge? And more importantly, why do scientists think it’s worth doing in the first place? If the idea of harvesting and using the secretions of an arthropod sounds vaguely familiar to you, it’s because humans already do it.

We’ve been using silkworm silk to make clothing and textiles for around 5,000 years. And it’s actually pretty easy to do, because silkworms can be farmed in groups. They produce a lot of silk, too — each one spins a cocoon from a single strand that can be up to 1,000 meters long.

Silkworm silk is tough, but spider silk is stronger and stretchier, and in theory should be much more versatile. A spider’s dragline silk, which is what it uses to stealthily drop onto your face while you’re sleeping, is lightweight and stronger than steel. We could make all sorts of things out of spider silk, like bridge cables, bulletproof vests, airplanes, and biodegradable bottles.

With its antimicrobial properties, spider silk has potential medical uses, too. We can use silk to treat wounds, and researchers are working on ways to use it to repair broken bones. So why not just raise an army of golden orb weavers to spin an endless supply of wonder-web?

Well, besides being a sort of terrifying idea, it’s just not that simple. Each spider needs a lot of space to build its web. The amount of silk a single spider produces compared to a single silkworm is pretty pathetic, and spiders also like to eat their webs when they’re done with them.

They’re deeply territorial, too, and they tend to resolve property disputes by eating each other, which makes spider farming not-very-practical. They're just not social animals. So if we’re going to harness the power of spider silk, we have to find ways to manufacture it.

Which, as it turns out, is also not simple. Here’s how spiders do it: They store proteins called “spidroins” in a liquid crystalline solution called “dope.” As the dope travels through a duct in the spider’s abdomen, the spidroins form chains and other structures. When the spider pulls the dope through a spinning valve in its body, it dries into a spinnable fiber, which it then strategically leaves in the air where you will be most likely to just stumble into it and be like "oh my god!

OH MY GOD!" So to make silk ourselves, we not only have to figure out a way to replicate the dope — we also have to figure out how to spin it. There are a couple of ways we could go about this. We could take dope directly from spiders.

Or, we could engineer bacteria or other organisms to make dope for us. Both alternatives have problems. Individual spiders — even enormous ones — can’t really give us a useful amount of dope.

And tiny bacteria will have trouble secreting the larger spidroin proteins. When other organisms do succeed in producing spidroin proteins, they just aren’t as good as the real thing. The truth is that we just don’t know enough about the spidroin-encoding genes, or the biological process of transforming dope into silk.

So we can approximate what the spider does, but we can’t copy it with precision. We are getting closer, and some companies have even claimed success, though it’s hard to know just how close their products are to the real thing, because they don’t usually like to share that kind of proprietary information. So far, researchers have created silkworms that carry the spider silk gene.

But the worms don’t produce spider silk, either, just better silkworm silk. And in the early 2000s, a company genetically engineered dairy goats that produce orb weaver silk protein in their milk. But you still needed to spin it into thread, and the company eventually went bankrupt, with other scientists taking over some of that research.

Another company uses a yeast fermentation process to make spider silk protein, but their silk has to be stabilized with wool or cellulose. This company has used their revolutionary process to make — wait for it — really, really, expensive neckties and hats. And they only made 50-100 of each, so the silk is not exactly in mass production.

So there are plenty of hurdles left to overcome before we can even make enough spider silk for a steady supply of hats, let alone turn it into bulletproof vests and bridge cables. But if we could just figure out a practical way to make a decent amount of it, we’ll have a pretty awesome material on our hands. Thanks for watching this episode of SciShow, which was brought to you by our community on Patreon!

We love exploring fascinating questions like this, and we wouldn’t be able to do it without your help. If you’re interested in learning more about Patreon and some of the awesome rewards that we share with our patrons, just check out patreon.com/scishow. ♪.