Using Synthetic Biology to Make Spider Webs

Okay, as a kid everyone’s favourite superhero was Spiderman, even if it wasn’t, it was up there in your top 5. He is an iconic superhero from comics, action figures, lunchboxes, and just merchandise in general, he has his stamp on every section. So when Spiderman Homecoming came out, my excitement was on another level. One scene that caught my attention was when our protagonist Peter Parker decided to make his spider webs in his chemistry class. Watching that gave my 5-year old mind an idea to live his dream of becoming Spiderman.

Breakdown of Spider Silk

Spider-webs, but more specifically spider-silk is what comes out of spiders. So to start, we should know a little bit about spider-silk; how cool they are, and how this is totally not just a fun project.

To start with, a fact I think we all are very familiar with is that spider-silk is stronger than steel, but what does that mean? Well, it means spider silk is stronger than steel by weight. As spider silk is lighter than cotton and up to 1,000 times thinner than human hair!

Another fun fact about spider-silk is surprisingly diverse, but not in the way it was in the movie like a ricochet web. There are seven known types, each with a unique purpose and feature for its given role. Which is quite impressive that a spider can control what type of spider silk it produces. As the silk itself starts as a liquid and then turns into a solid after leaving the spider.

Lastly, the best part about spider silk is that it’s both biodegradable but also recyclable, much easier than plastic. With all its other factors already coming into play, spider silk is one of the best materials we could theoretically use as a material for structures.

Making Our Own

To live out our dreams of becoming the next Spiderman, we need to begin with how spiders get their webs from? Well, it all originates from the specialized abdominal glands on the spider. So to make spider silk we need to take a look at what happens in their environment. Which can be put simply as spidroins, this is a special protein which you can think of it as a spider silk protein.

Spidroins

Now why are Spidroins able to make spider silk? Well, lets take a look at them, typically 250–350 kDa in size and consisting of three regions. A conserved, non-repetitive, and globular N-terminal. With a typical spidroin containing hundreds of repeats of a, which can be 40–200 amino acids and can form up to ∼90% of the total amino acids of the spider silk protein. These repeats are the instructions that make the spider silk. With variables changing the type of spider web. For example, the presence of long polyalanine segments makes the fibers strong, whereas glycine-rich stretches are known to impart flexibility and make the fibers more extendible. Now we need to decide which one to focus on.

Spider Silk Types

There are different types of spider silk…

Achniform: Produces swathing silk, for wrapping and immobilizing prey.

Aggregate: Produces droplets of “glue” for the outer part of sticky silk.

Ampullate (major): Produces non-sticky draglines, the strongest type of spider silk.

Ampullate (minor): Silk from the minor ampullate gland isn’t as strong as the draglines from the major gland, but it’s just as tough due to its higher elasticity.

Cylindriform: Produces the stiffer silk for protective egg sacs.

Flagelliform: Produces the stretchy core fibers of a web’s capturing lines.

Pyriform: Produces attaching threads, which form the attachment disks that anchor a thread of silk to a surface or to another thread.

Step 1: Identifying

The first thing we need to do in creating our own spider silk is identify the spider silk sequence. In this we can use the methods of bioinformatics built to analyze and identify the amino acid repeats in charge of creating the fiber. But even if we find the sequence, we won’t necessarily be able to use it. As that amino acid sequence is used to build a perfect protein built to use least energy, but also only work in a single environment.

Step 2: Recombinant

Now that we have a template for a protein, it’s time to change it up and make sure we can make spider silk. There are multiple ways we can about this. Nevertheless the best method for this is directed evolution techniques. Directed evolution techniques offer opportunities to engineer spider silk proteins for desired properties. This can be done by adding mutations that can edit the characteristics of the spider silk.

Step 3: Host System

Now for us to get the recombinant protein we made in step 2, we need a host to produce it for us. Now there are multiple different types of host we can use to express our recombinant protein. Some common ones are…

• Escherichia Coli (Bacteria)
• Salmonella Typhimurium (Bacteria)
• Pichia Pastoris (Yeast)
• Nicotiana Tabacum (Plant)
• Solanum Tuberosum (Plant)

Step 4: Coagulation

The last step is harvesting whatever host we choose; for example, E.coli. We let the protein get created and ready to be turned into power form by putting it through a bioreactor. After that we need to turn all the proteins we get from a protein into spider silk. The way we do it is through the help of coagulation, which is basically the process in which we change the structure of a protein that can be done in multiple ways. Some common ones are through heat, mechanical action, acids and even enzymes may be used to cause protein coagulation.

After that, you can spool your own, synthetic spider silk and have a chance at living your dream of being Spiderman…