Silk of the Spider, Thread of the Future

her disposal. A rackney. She's just a wonderful Weaver's an expert weaver, just creates these beautiful tapestries, right, puffed up with pride, I bet, But of course, yeah, In fact, she ends up boasting of her skills, and either, depending on what account you're looking at, either she actually challenges Athena, the Goddess of Wisdom and Crafts, to a weaving competition, or she just kind of talks about how great she is and how she's better than Athena until Athena steps

up and uh, you know, and and accepts this challenge. And of course this is a terrible idea. Right, You're going up against a god who basically like pick axed her way out of Zeus's brain, Right, Yeah, and like all the Greek gods are are are basically terrible. I mean, they're they're vain, they're petty, they're powerful, and uh, and yet she ends up in this competition and then it

just gets it gets even worse from there. Um in Ovid's telling, Athena's resulting tapestry illustrates past incidents where the gods punished more mortals for their arrogance and uh. And then Arachne responds by weaving in accounts of just how massively abusive and just what kind of misleading jerks the gods are towards humans. So, depending on which account you look at, either Athena wins because she is a god and no matter how great your mortal skill, you're gonna

get trump by a god. Or Athena notices that arachney skill is actually superior to hers, and out of spite she just kind of rage quits the entire competition. And in either case she curses Athena and her descendants for forever turning them into these minuscule web slinging arachnids that we know and love today. And what is interesting about that is that in some ways humans are still trying to extend out this metaphor of trying to manipulate nature

for their own gain or go up against it. So here's one from way back, and then we'll talk more recently how we have been trying to do this, all right, So we have one Francois xavier A ban Sae Hilaire, who it turns out, took silk and he tried to do what the gods what nature did, and he tried to extract it and weave it. And in fact he took the silk he boiled their cocoons, extracting the threads

with combs to make socks and gloves. And then in the early nineteenth century along came Jesuit priest Ramondo Maria Tremor, who discovered that threads extracted from the spider itself produced a higher quality silk. And there's an eighteen oh seven engraving showing his extraction device, and we're looking at it

right now. Uh, it kind of looks like a spider guillotine. Yes, it looks a little nefarious, like I'm instantly sympathizing with the spider here, Yeah, because you see that its head is trapped in there in this little half moon device. It's tiny, and it's abdomen is hanging out, and there's a winding machine drawing out a continuous strand from it. Yeah, which instantly makes me think of the paintings of the windlass of the Rasmus. The spindle that was used to

draw Rasmus is guts out of his body. So it looks very much like a torture instrument. Yes, true, right is very nefarious looking, but it's illustrative of the fact that even with this tiny device, it's incredibly labor intensive. And while we now have the technology to make this an easier process, and we have synthetic materials that try to mimic silk, we humans are still laboring, still pulling at the strings of silk. But now it's not in service of our sartorial desires. It's in service of what

we might think of ours, our scientific desires. Yeah. But still a ragney, she doesn't give up her secrets easily.

She does not. So in this episode, we're going to talk a bit about what silk is, what spider silk in particular is, and why it's such a stellar um engineering feat, and then we're going to talk about the various ways that that that humans continue to try and grasp that secret of the silk from the spiders, how to how we try to mimic it and all the various uses that we have for it in our modern

scientific world. That's right. And it's not just spiders. The silkworms so of course, are a huge fixture in this. That's right because we uh start off by just talking about what silk is, and in defining silk, we really need to start more on the insects side of things, uh than the arachnet. For the most part, silk is a fine, continuous protein fiber produced by various insect larva for cocoons, uh. And it's really only produced by a few groups in the insect world. And we also refer

to silk as a bio polymer now. In insects, silk originates as a stored protein liquid and modified saliva glands located in the insect's head. From here it transports via small tubes to the spinneret structure that protrudes beneath the mouth parts on the underside of the head of a given insect. In the case of spiders, however, as we'll discuss, the spinneret is backloaded on the end of the abdomen instead uh And we'll get to the spiders in a bit. But as far as the insects go, the most common

use again is cocooning. That's to contain and protect a defenseless pupil stage of the insect or and or to hold it in place on a leaf or a stem, and also some months build tints out of the material as well. Cocoon is spun from a single thread of silk. It might be just pure silk depending on the species, or it might involve bits of soil or leaf litter uh that are caught up in the silk strand as well.

So let's look a little closer at the silkworm, which is the larva or caterpillar of the domesticated silk moth called bombyx mori, which is Latin for silkworm of the mulberry tree. In fact, there's a Chinese proverb that says, with time and patients, the mulberry leaf becomes a silk gown. Now, the silkworm was once native to China, but now is completely domesticated. One cocoon consists of a single thread that is about one thousand to three thousand feet long, that's

three nine hundred meters. And the manipulation of silkworm, the domestication goes back years. And there's a legend that Lei Zu, wife of the Yellow Emperor, was drinking tea when a cocoon fell from a mulberry tree into her steaming cup

of tea and began to unravel. Yes, she was amazed by its luminosity and strength, and she gathered more and made silk, and China began to export silk and two hundred b c e so much so that the Silk Road, the famous network of trade routes, was created and stretched from China to the Mediterranean, Africa and Middle East in Europe. And the origin of silk was really closely guarded, right because this is the this is the lifeblood of China

at the time. But in five and fifty se some some wily sly monks who had traveled to China brought back silkworm eggs, and the end of the West was forever changed with silk at its disposal. Indeed, now it's rate as insects. Silk is as great as the silkworm. Silk is. None of these guys can really match the arachnids in terms of just pure engineering genius of the thread. Um. I mean, they're just in a class all their own.

So the thing about the spiders, as we've alluded to, is that scientists are continuing to study spider silk making and UH and trying to get all the valuable details out of it. And we still have a lot of questions regarding exactly how it all comes together. UM. But here the basics as we understand it. Spiders, like the like insects, um like the silkworms, have a special special glands to secrete silk proteins dissolved in a water based solution.

The spider pushes the liquid solution through long ducts, leading to microscopic UH bigots on the spiders spinnerets, and generally there are two or three spinneret pairs located in the rear of the admin. Furthermore, each spigot has a valve that controls the thickness and speed of the extruded material. So already we're seeing like these different layers of complexity that are in play when it comes to just pushing

out that that layer of silk. I think it's easy to fall into the trap of thinking of spider silk as kind of like silly string, right, Like there's just a gland, they squeeze it out, and they just squeeze out this thread, and yes, there's some sort of a you know, a hardening of the liquid as it comes out, but we think, well, there's nothing more to that. But really we're talking about a really intense engineering feet just

at the the construction of the material itself. As the spigots pull these silk molecules out of the ducks and excrewed them and extrude them into the air, the molecules are stretched out and linked together to form long strands, and then the spinnerettes wind the strands together to form the sturdy silk fiber itself. And this is where it gets even crazier, because most spiders have multiple silk glands in their body, which secrete different types of silk material

optimized for different purposes. By winding different silk varieties together in varying proportions, uh, spiders can form a wide range of fiber material. So it's not just one type of ciders a spider silk that's coming out. There are varying spider silks depending on what their purposes. They can vary fiber consistency by adjusting the spigots from smaller to larger strands, and sometimes they'll create a silk strand consisting of an

inner core with an outer tube around it. Uh, And they might apply various coatings such as a waterproof coating or a sticky layer, depending on what the use is. So so again, when it comes to spider silk, when they're creating it, that the purpose of the silk is reflected in the actual construction of the silk thread itself, which is amazing, especially if you bump this up against

the silkworm and nothing against the silkworm. They're doing a pretty cool job there with making their cocoon, right, But that's sort of like, here's this one thing I can do, whereas a spider is more like its own three D printer exactly. I think that's a fabulous comparison. Yeah, I mean, it's varying the type of product that it's creating. And the best way to really examine this is to look at the anatomy of a web, because I remember, above all else, spiders are predators, and so they've come up

with this elaborate way to catch their dinners. Now, they will initially just cast a silk line out into the wind, and when it senses that it's caught upon something, it will cinch a starting point and use that connection as a bridge, walking across it as it creates a loose silk hanging from the starting and ending points of this bridge is created, so at that point it pulls pulls down the silk time. It creates a kind of y configuration.

It then creates anchor points and structural threads, laying out radius points from the center of the web of the threads. So then you have the various different types of thread being spun. Here, you have a non stick auxiliary spiral that's created as well as a second stick auxiliary one, so the spider has its own smooth path to tread upon while ensuring that the web is good and sticky elsewhere. And there are various I mean, there are tons of

different types of webs and dizzying and their complexity. Right, they're beautiful to look at. But one that I wanted to point out is not even functioning as a true web, and this is via trapdoor spiders who use their webs in a really ingenious way. First they dig a tunnel, which they smooth out with a mixture of saliva and earth.

Then they fit the opening to the tunnel with a trap door, and it's made out of spider silk, and it can be fitted exactly to the dimensions with a beveled edge like that's craftsmanship, or it can just have a sheet of silk and dirt, and then the top of the trapdoors tricked out with debris so that it easily blends in. So this tunnel gives the spider refuge.

It also gives them a place to raise their young end and also in the background, serves as this device to let the spider know that, you know, there's prey around. And it does this that trapdoor by vibrating, and once the spider detects that, it can easily rush out, pull in that prey into its hole and then chomp on it. And it's kind of we were talking about it earlier.

I was like, Hey, I'm a little bit I kind of don't want to necessarily put this upon the spiders trapped or spider, but it feels a little bit serial killer to me. Yeah, I mean that that's kind of the vibe of the spider right now. As you mentioned, their various uses for the silk material, various structures that are created by the spiders, and we discussed some of those in our episode It's a Trap, which will include a link to on the landing page for this episode.

But these structures are amazing, and the level of engineering is is evident not only in the structure of the that they create out of the webbing, it again in the uh, the minute structure of the strands themselves. Uh. Spider silk is is is particularly great engineering substance because it's incredibly strong, but it's also incredibly flexible. Uh. There's some varieties that are reportedly five times as strong as an equal mass of steel and twice as strong as

an equal mass of kevlar. So again, it rivals some of our key tough materials that we as humans wield in the world around us. Now, to understand, you know, why it's so strong, we have to look at the molecular construction of spider silk itself. According to a two thousand eight study from M I. T. The strength lies in the specific geometric configuration of structural proteins, which have small clusters of weak hydrogen bonds that work cooperatively to

resist force and dissipate energy. Two twelve University of California Riverside study identified the genes and determine the DNA sequence for two key proteins in the drag line silk of the black widow spider. And and you often see the drag line silk is a focused point UH in the various studies because of the services the bridge, it has to be really strong. So this is the primo material

when it comes to spider silk UH. And it turns out the straight drag line silk is a composite material comprised of two different proteins, each containing three regions with distinct properties. So you have an amorphous non crystalline matrix that's stretchable, giving the silk elasticity. And then embedded in the amorphous portions of both proteins are two kinds of crystalline regions that toughen the silk. So the resulting composite

is strong, tough, yet elastic. And and again it's it's there and just the minute construction of the thread itself, and we humans see it, we admire it, and we want it. But commercial production of spider silk from spiders is impractical because spiders are jerks right there. They're to cannibalistic and territorial for farming. They're not really jerks, but

you know, they're just not ideal for that purpose. Uh And researchers have looked to other organisms, including bacteria, insects, mammals, and plants, But those proteins require mechanical spinning and this is a task that our friend the silkworm performs naturally

with those nifty spinneretts. So so what's the researcher to do. Well, let's look at Malcolm Fraser Jr. Who in two thousand and twelve with his team created a hybrid silkworm to do their bidding, one with both silkworm and spider silk proteins, and results showed that taking these two proteins um would result any tougher than typical silkworm silk. It would be as tough as drag line silk um and it would be just the right material that you would want to

try to commercially produce. So why would you do this? Why would you mercially produce it um? We'll discuss other instances in which you can use it. But when they were looking at for this purpose, it was for wound dressings, artificial ligments, tendons, tissue scaffolds, micro capsules, cosmetics, and textiles. Okay, Now, while some of you have probably heard of these transgenic silk worms, I bet even more of you remember the transgenic spider goat hybrid, because this really made the rounds,

especially back in two thousand two. Uh, instantly bringing to mind and uh and probably to digital reality. Poorly photoshopped images of a goat with like big spider legs coming out of its side, right, was photoshopped? Yeah, because because

the real transgenic goat spider hybrid just looks like a goat. Um. This again, it's happening back in two thousand two, researchers at Nexia Biotechnologies genetically modified goats using silk producing genes from spiders, which just a headline level back in two thousand two, it of course instantly sounds Frankensteiny, right, like who are these scientists and why are they trying to

make goat spiders? Um. But at this point in the podcast, I think everyone understands what they were going for the idea was that you would have a small number of goats that would be able to produce a large amount of silk material in their milk, which could then be used in various UH then could be utilized for various purposes as we'll discuss. Essentially, they would be the goats

will be creating dragline milk. Now, the strands that they produced were only as strong as natural spider silk, but still it's a start, right UH and and at their height next to as Montreal Flock had nearly fifty spider

goats total. But the company went bankrupt in two thousand nine, So you had a couple of transgendent goats that went to the Canadian Agricultural Museum, while the rest of them went to Utah State University where they're continue to study them to this day and figure out how we can best utilize a spider goat UM for the for the better men of humanity. Now, that's not the only instance of a company either going bankrupt or just pulling out

of the endeavor entirely. And that is because even though you you have UM information being uncovered and you have the transgenic UH, the ability to mess around with this and try to do this in other organisms you still have to understand the relationship between spider silk structure and

its function. And again a lot of companies have tried to do this, but it wasn't until researchers from Dalhousie University in Nova Scotia took a closer look at the mechanism and tried to uncover some piece of information that might get them a little bit closer. Now, the first step is that they created artificial spider silk to replicate the proteins that make up the natural version, in this

case by recombinantly expressing them in the Bacterium E coli. Now, they looked at the key protein and acid informed silk called a c sp one and they said, okay, it's got three parts. And they said, all right. The protein, most of it is repeated sequences of about two hundred amino acids, and there are two tales called the N and C terminal domains that hang off each end of the protein chain. Now, when they took these proteins and they chained them together, they found that the chains weren't

working in unison, but rather as independent units. So that was the first clue of how these are actually working within spiders. And it was the C terminal domain of the protein that was the juncture of the protein that determined the strength of the fiber. So when you're talking about that spider being in the architect and choosing a different type of that type of material, but maybe um consistency or strength, that's the C terminal that is controlling that.

And this was a huge breakthrough, right because it peeled away a layer of mystery, and yet there's still so much to be learned in the evolution of spider silk. Yeah, because then we what do you do with that data? Then it just leads to six other questions regarding the engineering process that's taking place there. I guess what you knew is you look at it in its in its form right now and say, oh, what can we deal

with it? Right? And that's really the the examples we're gonna look to next in the podcast are really looking more at at possible uh ways that we can use the spider silk and the structure of the spider silk and in some cases of the structure of the web itself,

how we can mimic that design in various pursuits. According to a two thousand fourteen paper from the University of Akron UH spider silk could be used as an inspiration to create more efficient and stronger commercial and biomedical adhesives that could, for example, potentially attach tendons to bones, bind fractures, etcetera. Anytime you need to bring to shoot together and hold

it in place firmly. And and of course one of the advantages here is we'd be using a biosubstance as opposed to something that has to be ejected from the body or taken out at a later date. UH. In particular, with this particular with this study, UH, they were looking at the attachment disks that spiders used to attach their webs to structure. So the spider pins down an underlying thread of silk with additional threads like stitches or staples

on top of it. UM. But the real engineering feed here is that the geometry of the attachment disk, the way that they're actually laying down these strands, it creates a super strong attachment force using very little material. So it's you know, a perfect economic model to try and and mimic. So this this particular team led by you a professor of polymer science, Ali Dinawala, utilized electro spinning

to mimic the efficient staple pin method. Now, electro spinning is a process by which an electrical charge is used to draw very fine fibers from a liquid. And in the case of this, uh, this particular experiment, they were using polyure thing. Okay, So again, the possible uses here include you know binding, uh, you know, tendons back together, binding, tends to bone, binding, fractures, etcetera. And you'd be using material that can degrade and be reabsorbed by the body.

Now that's an example of mending the human body. But spider silk also shows up when you're talking about essentially growing new organs for yourself. And that's because you need when you're talking about growing artificial tissues and organs, you need some kind of structure or substrate for the entity to grow around. And so what could be feather light but formidable enough to provide a framework spiderwebs, of course.

So you have a group of researchers led by Professor Constantine A. Glad Say, who heads the Laboratory of Biophysics of Excitable Systems m I p T, and they work specifically on cardiac tissues. Isolate, a protein used in web

spinning called spiedroying. What they did is they seated isolated neonatal rat cardiac cells on fiber matrices and during the experiment, the researchers monitored the growth of the cells and they tested their contractability right in their ability to conduct electrical impulses, and these are the main features of normal cardiac tissue. They wanted to see if that could be mimicked in

in the protein. And the monitoring, which was carried out with the help of a microscope and fluorescent markers, showed that within three to five days a layer of cells formed on the substrate that we're able to contract synchronously and conduct electrical impulses, just like the tissue of a

living heartwood. And this is pretty big news, right. It doesn't mean that we're around the corner from grow your replacement heart clinics um, but it does mean that it's it's a serious step toward me a beating heart out of a few cells, Like that's going to become an eventual reality. And now you found the material. That's just one more in the link to it. It's sounding more and more like the bodies of the future will just be riddled with spider self and I have another example

of it here. Uh. I mean, this one really kind of blew me away because the example, if we looked at so far that they're they're based in structure, right, We're looking at the structure of the webbing and how it can be used to make attachments, to to create a structure, to grow tissue over, etcetera. But there were a couple of studies that came out in a two thousand twelve edition of Researchers at Frontiers and Optics, a

scientific journal. UH looked at two independent teams, one at TUF University in Boston at one at c n R. S Institute of Physics in France. UH, and they were looking at ways that this natural spider silk could be used as an eco friendly alternative two traditional methods of manipulating light. So we're talking about, um, an alternative to glass or plastic fiber optics and lenses. UM. Why would

you want this again? It comes back to biomedical technology, right, the placement of sensors and tags or any kind of utilized utilization of light within the human body. UM. I mean the revelation for me here that I just did not realize was that as it turns out, in addition to being super sturdy and flexible, silk is a gifted light manipulator, and so so light could travel through silk almost as easily as it flows through through glass fibers.

So the potential here hits two key areas. One implanable biodegradable optics utilized in sensors and tags that are placed inside the body. We've talked about the the importance of real time monitoring um of of our of our body and how that is that can play into better management of our overall health. And another area is that you

can take this on biosensors. You can take a pristine fiber of spider silk and carry light into the body through a very small opening um which would be quite useful for internal imaging or even chemical diagnosis using spectroscopy, which is the analysis of matter based on its interaction with light. So yeah, just it's amazing to think of this, like this tiny little thread of of of spider silk going in through a tiny hole in the body and

aiding in the in diagnosis. That really, to me is like, I think, a game changer and amazing to me that the material is being used that way. Yeah, it just again, it just it just drives home just how impressive this material is. Yeah, and again, just to underscore that uh impressive durability and strength, let's go back to the spider's drag line again. It is the stuff of engineer's streams, the tensile strength of a high grade alloy steel, while

being a sixth as dense and incredibly flexible. You can draw it out about five times at some length without compromising it. So how do you get a spider to do better? How do you ask it to just up its game of kevlar strength? Okay, we're still trying to actually steal its secrets, but then we're also saying what can we do to bump it up? Yeah, we're saying, hey, we know you've perfected this over four hundred million years of evolution, but do you think right now you could

do something to increase the durability. Well, of course we're talking about here is some researchers. In this case, we're talking about Nicola Puno at the University of Trento in Italy and his team who took some seller spiders who are also known as fulsit I and the site spider Hugger dot com by the way, describes these spiders as quote looking like something made out of many marshmallows of

pipe cleaners. So the research took these seller spiders and they douse the spiders with either water containing carbon nanotubes or graphine flakes. Now two materials that are both really really strong, right, So this is an attempt to sort of to supersize the strength of the of the spider and sort of make it into it's a little spider superhero.

They checked out the spider's handiwork after they did this for each strand of silk, and they fixed the fiber between two C shaped cardboard holders and placed it in a device that can measure the load on a fiber with a resolution of fifteen nanomutants in any fiber displacement

with a resolution of a point one nanometers. Okay, So, in other words, are very serious about the tin sile strength here, and Pina wrote that the thread is the highest toughness modulus for a fiber, surpassing synthetic polymeric high performance fibers like Kevlar forty nine and even the current toughest knotted fibers. So it was amazing about that is not only it was the thread tougher than before, right, tougher than kevlar, tougher than its own natural tensile strength.

But they could find the actual carbon nanitubes in it. They just weren't sure of how it was happening. At first. They thought, well, maybe they were taking it and spreading it onto the spider silk after it came out of them, but that was discounted. They're just not sure how it was incorporated into their bodies to create it. So again we find out a little more about the mystery of spider silk, and we just end up with more questions.

It is the great mystery. Well you know, um, we have one more study to to mention here, and and this one we feel really really drives home the elegance of the design that we see here again not only in the structure that they build, but the but the material that they build in the varying take some material they build to construct it. The comparison here spy eighter silk and music spidered web and U and you know,

a classically arranged piece of music. Um. In particularly, we're looking at a study from two thousand eleven researches at M. I. T. They created a scientifically rigorous analogy that shows the similarities between the physical structure structure of spider silk and the sonic structure of a melody. Um and taking it down, just stripping it down to the building blocks of either an amino acid in the case of the webbing, and a sound wave in the case of the music. Yeah.

And it's got many different layers of sound in music to it in this analogy, and the study explains that structural patterns are directly related to the functional properties. That's one layer of lightweight strength in the spider silk and in the riff sonic tension that creates an emotional response in the listener. It's interesting to think of actually melody music is spider webs, right, and the tension that's held

within them and the structures, the repeating patterns. Yeah, it just again it drives home just the elegance of the design and just how how nuanced it is. Um. I don't know if I'm going to start thinking of music I like as a spider web exactly, but but but it's it's it's a wonderful analogy that they make and

back up with data. Yeah, it's another way to look at um, not Fibonacci, but symmetry and nature and the patterns held within and only that uh, the communication, right, because if you think about the spider web and the vibrations that it's giving off, that perhaps is a kind of melody to the spider itself telling it something about the pacing, something about the beat of the thing that's making it vibrate. Yeah, the sweet sweet music of of of a creature in agony wrapped up in your web

that you could take. I'll go and uh and wrap up some more and drain the life force from that exactly. That's the song of the spider right there, all right. So there you have it, uh, spider silk. I hope that uh, I hope that that that you guys and guys listening have more respect now for the spider and

what it's doing. It's not just a silly string coming out of a spiders but it's uh, and it's not you know, spiderweb itself is not on par with just you know, doing some cat's cradle stuff with some string and your fingers. That it's an engineering marvel at every level. If you would like to learn more about this topic and others, that'll be sure to head on over stuff

to Blow your Mind dot com. There's where you'll find uh podcast videos, blog post links out of social media accounts, and we'll make sure that we have stuff on the landing page linking out to some wonderful resources, including the how spiders Work article on how stuff works dot com,

which gives you a wonderful overview of spider anatomy. If you have thoughts about the culture or residents of silkworms in China, or if you have thoughts about spider webs and silk used in biomedicine, particularly in your own body, or even what we're talking about with melodies and the patterns of spider webs, please do share those thoughts with us. We'd love to hear from you, and you can email us at blow the Mind House to works dot com

for more on this and thousands of other topics. Is it how staff works dot com