Tangled webs: Why scientists want to recreate spider silk
Spider silk is one of nature's wonder materials and scientists are naturally keen to exploit it, but first they have to uncover its secrets.
Stronger than steel, more elastic than rubber, spider silk is tougher than any man-made material, and if made into body armour, would be three times stronger than Kevlar.
Its unique properties have been known or suspected for centuries and it is much sought-after.
Even in the minute quantities in which it can be gathered, it has found a number of uses - as a fishing line, or in the crosshairs of optical instruments,
It has also been used in wound dressings, as it has antibacterial properties. Like hair, it is made of protein.
Spider silk clothes
- This cape was made from the silk of the Madagascar Golden Orb spider
The main challenge to using spider silk is that it has always been difficult to gather.
Spiders are very difficult to farm. They are predatory and will readily resort to cannibalism in the absence of other prey.
Individual spiders have been captured and forcibly silked in laboratory conditions but the quantities recovered are tiny.
Spiders produce only small amounts of silk, spinning only what they need for a web, then consume it to re-use the protein.Bungee cord
Some applications of spider silk are suggested by how the spider uses its own silk, in particular the strongest form known as dragline silk, which can be used as a safety rope or a bungee cord or for making the strong radial strands of its webs.
As well as bungee and parachute cords, strong, elastic fibres could also be used for airbags or tyres.
"So far, no one has been able to artificially spin spider silk fibres with mechanical properties indistinguishable to those made in nature by a spider," says Professor Thomas Scheibel, chair of Biomaterials at the University of Bayreuth.
"But if we could, all these ideas on how to use spider silk in diverse applications could come true."
In nature, spider silk is spun into threads, but in laboratory conditions the same proteins have been recombined into spheres, thin films, capsules and hydrogels - a network of silk protein with high water content.
Being able to construct new shapes out of spider silk protein opens up options for tailor-made materials for specific applications including many in medicine - for delivering drugs to parts of the body or as thin wound dressings.Spinning gland
Making spider silk artificially might be possible if scientists understood how it is made by the spider and could replicate that.
The silk's journey begins in the spinning gland as a random coil in high concentrations before it is passed through ducts in precise conditions of acidity, water content and chemical concentration, before being extruded out a spinning wart. The fibre that emerges is water insoluble, partly crystal and partly coiled.
Although theories have been proposed for exactly how this is done, this complex sequence is not yet fully understood.
End Quote Professor Randy Lewis Utah State University
By any physiological or behavioural measures they are normal goats”
To get round this problem, one team of scientists has tried to make spider silk by genetically modifying goats to produce spider silk protein in their milk. However, the silk does not share the mechanical properties of natural spider silk.
"The protein is the same as the one naturally produced by spiders," says Professor Randy Lewis of Utah State University. "But scientists still haven't worked out how to create the structures and folds of the protein that give it its combination of high strength and high elasticity.
"We can currently produce proteins that are a quarter to a third of the size of natural proteins," added Professor Lewis. "The goal is to match the strength of natural silk."
Will transgenics or artificial synthesis ever allow the recreation of spider silk with all its amazing properties?
"In my opinion both routes are equally feasible and are both likely to lead to novel applications," says Professor Sheibel. For him, it is an exciting time: "In upcoming years we will see the first products made of spider silk entering the market."
Find out about the secrets of insect anatomy on Insect Dissection: How Insects Work which is broadcast on Wednesday 20 March at 21:00 on BBC Four. The programme will be available on the BBC iPlayer afterwards.