Spider Silk Flashcards
(21 cards)
Intro (Ana)
Hello everyone! today we will introduce to you an innovative yet very old technology
But, before we start, could I have a show of hands from all people who hate or are afraid of spiders?
Show of hands from people hating spiders
(Me) Now tell me who, among you, has had stitches at least once in their life?
Show of hands stitches
(Ana) Don’t see what this has to do with spiders?
Well, you’d be surprised to find out that ever since the time of ancient Greece, spider webs were used to stop the bleeding caused by battle wounds.
And they are still used nowadays to make stitches.
spider webs were used to stop the bleeding caused by battle wounds.
(Me) But why are they used in such ways? And what other uses are there? Is it easy to produce spider silk ?
We are Ariane’s Thread, a company based in Leipzig, Germany and we are working to put on the market a commercially viable solution to produce spider silk. And together we will explore the intricacies of the production of spider silk.
Presentation of ourselves
(Ana) Spider silk has very interesting mechanical properties as a fiber.
But what do I mean by that?
What are interesting mechanical properties for a fiber ?
Well there are mainly three: Density, Tensile strength or Elastic modulus.
3 mechanical properties
(Me) Tensile strength is the maximum load that a material can support without fracture when being stretched.
When stresses less than the tensile strength are removed, a material returns either completely or partially to its original shape and size.
As the stress reaches the value of the tensile strength, the material will begin to tear and then fracture.
An elastic modulus is a quantity that describes an object’s or substance’s resistance to being deformed elastically when a stress is applied to it.
Finally density is simply the ratio between an object’s volumetric mass (its mass divided by its volume) and a reference volumetric mass (usually water) for the sake of comparison
density is the ratio
(Ana) To make it simpler, just remember that the elastic modulus is: how easy is it to stretch a material; while tensile strength is: how easy is it to tear? (### Demonstrate with an elastic and metal ###)
Spider silk does great in both categories. It has a high tensile strength, comparable to kevlar or steel, while having a low elastic modulus which makes it elastic, like kevlar but unlike steel.
Spider silk does great in both category
(Me) Then, there is density. Since silks are mostly composed of proteins, they are about ⅙ of the density of steel and 10% lighter than kevlar.
Now comes the advantages of spider silk over its competitors
First, spider silk just like normal silk is a biological compound composed of proteins and coated in a layer of glycoproteins. As such, it is entirely biodegradable, unlike kevlar and steel which needs recycling.
spider silk is biodegradable
(Ana) Moreover, kevlar is a plastic polymer and is thus subject to the concerns over the creation of microplastics when eroded.
Finally, kevlar needs a highly concentrated acidic environment for its production, which can be damaging for the environment if there is a leakage.
Uses of Spider Silk
Due to its mechanical and biocompatible properties, many uses have been found for spider silk, in various domains
Uses of spider silk
Me Let’s begin with the biomedical field
As we stated earlier, there have been medical uses of spider webs for a long time. At first used as bandages, spider silk has been spotted as an interesting material for numerous additional purposes in the biomedical domain. Most of these uses are still in a research phase, however, the results seem promising.
The results are promising
(Ana) Some of these purposes include tendon sutures, bone and cartilage regeneration, as spider silk is much more resistant than other materials already used and they have a higher longevity.
Spider silk based films have also been considered for bladder and heart muscle reconstruction. Silk seemed to attach pretty well to the cells composing these organs, and they showed no toxicity towards them, which is very encouraging for further research.
No toxicity towards heart’s and bladder cells
(Me) Another use for spider silk is skin regeneration and wound healing. Spider silk would be used to help regenerate skin in plastic reconstructive surgeries. Moreover, spider silk is already used in sutures for soft tissues such as ocular, neural or cardiovascular.
Other non medical uses of spider silk are also researched.
(Ana) Other non medical uses of spider silk are also researched.
Some of those are for nets, ropes or even seat-belts, but also tear resistant clothes of bullet-proof vests thanks to its high resistance and low density.
Spider silk may also be used to make biodegradable bottles as it is biodegradable.
Problems traditionally encountered when trying to produce spider silk
(Me) For a very long time, lots and lots of people have tried to rear spiders to harness their silk.
However, none have ever been commercially successful due to a quirk spiders have which is that they do not do very well in communities and tend to become cannibal when kept in captivity.
As such, the only solution so far to rear spiders for scientific studies has been to confine each individual in a different container of some sort.
Cannibalistic spiders
(Ana) Then there is the problem of the silk. To obtain natural spider silk, a researcher must anaesthetize a spider, attach the end of one of its fibres to a variable-speed motor from an electric drill, then gently pull the thread out of one of the spider’s glands. Depending on the species of spider, this technique can yield up to 100 metres of silk. This painstaking process is easier than picking apart the threads from spiderwebs, but it is not scalable.
put spider to sleep
(Me) Therefore, researchers started looking in other directions to produce spider silk. Some have taken the route of artificial synthesis. They chose to copy the methods used for artificial fibers synthesis. They use various organisms to replicate the necessary protein components before extracting and purifying the proteins of the silk into a mixture called the feedstock. To form the fibers, the feedstock is then forced through a hollow needle using a syringe.
syringe
(Ana) Although cheap and easy to produce, gland shape and conditions are loosely approximated. As such, the silk spun is of low quality and will need a chemical treatment and maybe even a mechanical treatment (through stretching) to achieve desirable properties, and even then the result is of lower quality than wild spider silk.
How did we solve these problems ?
(Me) To replicate the proteins, some used gene editing to make organisms express it such as the bacterium E. Coli or even goats in their milk.
When considering producing spider silk, a tradeoff must be made. A general rule of fibre-spinning, whether the materials are proteins or plastics, is that the larger the molecules, the stronger the fibre. But this trend bumps up against an axiom of bioengineering: the bigger the protein, the more difficult it is to produce in a genetically modified organism.
tradeoff
(Ana) We chose to use gene editing to modify silkworm silk into spider silk. The first reason is that it is easier, it takes less gene editing to modify something that already exists to make it suit your needs than to try to recreate it from scratch. The second reason is that due to its long history, silkworm rearing techniques are well established and date back thousands of years (the oldest silk fragment ever discovered dates back to 2570 BC or 4600 years ago). The industry already exist, you just have to modify the silkworm and it can be implemented
To do so we introduced spider silk specific genes in fertilized silkworm eggs. It took us 8-years to do so because we had to consider how the proteins we added interacted with and affected the frame that was the proteins of the silkworm silk.
the industry already exists
(Me) Choosing to use modified silkworm silk also resolved one of the biggest problems other techniques had when producing artificial spider silk.In nature, spiders coat their webs with a layer of glycoproteins and lipids which helps it resist humidity and exposure to sunlight. Without this layer, spider silk hardens gradually over time and thus turns brittle, which defeats its whole purpose of being tear resistant.
Why should you invest
Other techniques have not yet managed to solve this problem. In our case, the problem resolved itself because silkworms also coat their own silk with a similar protective layer of glycoproteins and lipids.
Why should you invest in our project?
As we have pointed out during our presentation, Spider silk has many potential uses. However, our product is still confined to the lab. This is why we need investment, to be able to scale up to the industrial and commercial scale with a pilot plant. Invest in our company. Invest in Ariane’s Thread.
