What’s stronger and tougher than steel and more resilient than rubber, weight for weight? Spider silk is, and this incredibly versatile material could transform engineering, materials science, and even medicine – if only we could figure out how to produce it.
Now, a new global study that has cataloged the properties of silk from nearly 1,100 spiders hopes to provide a launching pad for the design of future biomaterials that mimic this wonder of nature.
Read more: Research to determine if “steel-hard” spider silk can be bred for manufacturing
Dr Sean Blamires, an evolutionary ecological biologist from the School of Biological, Environmental and Earth Sciences at UNSW in Sydney, says the new research, which was published recently in the journal Scientists progresslooked at the chemical structure, genetics and the particular way each spider weaves its webs and compared them to the physical properties of silk.
The team of researchers who covered Asia, Oceania, Europe and the United States spent five years collecting spiders from around the world, observing them, extracting silk and sequencing their transcriptomes – the RNA molecules encoded to make silk. They added a massive dataset to the existing knowledge base that was previously limited to 52 spider species in 18 families, with 1098 new species from 76 families.
“So far, there’s been a pretty good literature on the performance of spider silk, and we’ve also seen good genetic analyzes with whole silk transcriptomes mapped across three or four species,” says Dr Blamires.
“But what was missing was a way to generalize across spiders and find out what actually causes specific properties. Is there a connection between genes, protein structures and fibers?
“By combining so many species and so many individual samples, it becomes possible to make complex models using machine learning to help understand what is happening at all levels. Plus, how and why you get specific properties for certain setae that not only vary greatly from species to species, but can even vary from individual to individual.
There are seven types of spider silk and one of them has captured the imagination of scientists for decades for its strength, durability and flexibility: dragline silk.
“We focused on a specific silk called major walking silk or dragline silk,” says Dr. Blamires.
“In a spider’s web, the dragline silk forms the frame and the radials. It is also the silk that the spider uses when it falls from a web. Spiders that do not build a web can use to make retreats or to signal each other, while trapdoor spiders use something very similar.
He says the reason for the interest in dragline silk is that in some spiders like orb-weaving spiders, it is extremely strong and outperforms Kevlar and steel. But in addition to its hardness, it is flexible.
“So it’s rubbery and tough at the same time, whereas most other materials are either one or the other.”
It is the quality that has made it so attractive as a biomaterial to be emulated in technological applications. Suggested uses include a lightweight material for use in body armor, a flexible building material, biodegradable bottles, or as a non-toxic biomaterial in regenerative medicine that can be used as a kind of scaffold to grow and repair nerves or damaged tissues.
But what is it about cobweb silk that makes it so different from most other organic and inorganic materials?
Dr Blamires says this is the question that has fascinated mankind for hundreds of years.
“Spider silk is basically made up of proteins called spidroins. We know that spiders secrete it from a gland, but how that contributes to its tenacity and flexibility, and even how it’s stored in the gland before being secreted, remains a mystery.If we want to produce it, we must understand it.
“And even then, understanding how the spider does it is one step, the next is to replicate something similar, possibly using microfluidic technology in a lab.”
This is where the database of 1100 spider silk transcriptomes will be so useful to biologists, materials scientists and engineers.
“Just as the Human Genome Project has given researchers the ability to identify specific gene sequence mutations that cause specific diseases, this database and the accompanying structure-function analyzes give biologists and scientists material the possibility of deriving direct genetic causes for the properties of spider silk,” says Dr. Blamires.