Superheroes are a source of inspiration for many scientists, and if there is one character that fascinates them, because of his ties to the animal kingdom, it is Spiderman. A team of researchers from the United States has unravelled the genome of a spider that produces an ultra-resistant material, such as the one used by the web slinger to swing between skyscrapers. By understanding the information that is stored in the DNA, they can design new materials that are stronger and more flexible.
Other scientists, also copying spider silk, have designed a technology that immobilizes cars. Even some shampoos now incorporate their silky proteins. Here we review the latest in a myriad of arachnoid applications that the scriptwriters at Marvel—the comic book publisher of Spiderman—could never have imagined.
The ‘secret’ genes of spiders
The golden silk orb-weaver spider (Nephila clavipes) manufactures a silk of a golden hue that has given this arachnid its name. Leaving aside the beauty of the material, what intrigued scientists was its enormous strength, even stronger than steel in a smaller weight fraction. To find out where its properties come from, researchers at the University of Pennsylvania (USA) have sequenced its genome.
In total, they identified 14,000 genes that could be related to silk and, among them, 28 appeared to encode the proteins responsible for the strength, traction, flexibility and stickiness of the material.
“It is perhaps the resilience, the combination of strength and flexibility before a thread breaks, which is of greatest interest to the scientific community in general,” says Professor Benjamin F. Voight, one of the authors of the work published in Nature Genetics.
The researchers did not expect so much complexity in the process of making the silk. Understanding it in minute detail is essential to imitate it in the laboratory. Its properties open up a range of possibilities in the industrial and biomedical area, although Voight suggests caution since there is still much to investigate.
“We must learn what sequences generate diversity in the biophysical properties of silk: tensile strength, stiffness, stretchability, durability or adhesion,” he says. Once you figure this out, the next step will be to study how to scale the new materials to make them profitable.
From shampoos to microsutures
At the same time, a few laboratories are producing the silk proteins in culture flasks to convert the liquid protein into fibres of solid silk. Although their properties are inferior to those of the natural material, it is a first step.
“Private companies have techniques to do this and are looking for sequences and materials with optimal properties for their production on an industrial scale,” says Voight. In his case, he and his team are sequencing the genome of another type of spider, the Darwin’s bark (Caerostris darwini), which produces even larger and stronger webs.
Once they have its genetic information, they want to collaborate with material science experts to test how silk DNA sequences relate to the biophysical properties of the new fabric they develop.
For now, some of its features are already being used in the cosmetic area to make shampoos that leave hair silkier. The proteins are obtained with a genetic modification of the E. coli bacterium, which expresses them through a fermentation process.
“There are several companies that claim to produce spider silk but in all cases the fibres they are producing are not real proteins but rather computer-designed simulations,” explains Randy Lewis to OpenMind. Lewis, a professor of biology at Utah State University (USA), has been trying to synthesize spider web in the laboratory for 25 years.
Among their potential applications, Lewis emphasizes that the fibres can be used for microstructures, ligaments and artificial tendons. High-tech clothing and sports equipment that is flexible and sturdy could also be designed. Their proteins are being studied in gels that regenerate tissues, in adhesives and in drugs.
In the purest Spiderman style, the US Department of Homeland Security has designed SQUID, a device that, by unfolding its tentacles, immobilizes suspicious vehicles.
According to John S. Verrico, head of media relations in the Department’s Science and Technology Directorate, SQUID was acquired for use on the borders. When closed, it looks like a wheel, but when it opens it unfolds a net that entangles the axle of the vehicle that passes over.
“It’s a very strong bond. If you’ve read comics or seen Spiderman movies, it acts like spiders do, firing its weapon and entangling its prey,” Verrico explains to OpenMind.
In his view, comics and science fiction show what is potentially achievable by the human being. “Superheroes are a good source of inspiration because they have skills that we would like to have,” he says.