We have built supersonic missiles that fly faster than the speed of sound and travelled all the way to the moon; yet the silken threads created by tiny house spiders to catch their prey remains an astonishing marvel of nature’s engineering.
As thin as it seems, a spider web can absorb large amount of energy without breaking or losing its flexibility.
Inspired by nature’s marvel, scientists have now created a synthetic spider silk with properties similar to the spider’s web. In 2010, the National Science Foundation conducted a research to genetically engineer goats and extract spider silk from their milk. There is a record of several researches where scientists have attempted to produce spider silk proteins called spidroins in yeast, bacteria and insect cells. In 2015, the Biomaterials journal reported that a group of researchers had used spidroins produced by transgenic goats to form a scaffolding for growing brain cells.
However, to quote the Journal Nature Chemical Biology: “Small amount of spider silk produced by spiders is not enough for any of its industrial application; it requires production of recombinant spidroins and generation of artificial spider silk fibers.” And when scientists attempted to produce spidroins artificially, they found that the artificial fibres were clumping together and were also not dissoluble in liquids.
This challenge has found several companies entering this space to find the perfect composition to create a near-alike version of natural spidroins. Patents US 8173772 B2, EP 2621957 A2 and WO 1997008315 A1 describe interesting technologies to produce spider silk.
Kraig Biocraft Laboratories is actively focused on developing technologies and commercializing the use of artificial spider silk. On July 12, 2016, the company announced that it received a military contract to produce artificial spider silk-based ballistic shoot packs to help protect soldiers.
Engineering Super Fibers – the science behind it
Spiders have silk-spinning ducts that produce spidroins with a naturally varying pH level. Different spiders have different pH levels at varying points in time, which determines the solubility of the web. Reserachers have tried to observe and replicate these natural conditions inside the spider’s silk duct to create more natural-like artificial fibres.
In one such attempt, researchers used spidroin genes from two different spider species to create a hybrid spider silk gene NT2RepCT. This gene included the best properties from both species i.e. high solubility and high sensitiveness to pH. Later, this gene was inserted in the DNA of bacteria which produced proteins. The result of the process was very similar to the real ones inside the silk glands; it was a highly concentrated solution with a cloudy and viscous appearance. The solution was pumped through a glass capillary and mimicked the way spider silk is produced. This process produced 3,280 feet (1,000 meters) of fiber in a 0.26 gallon (1 liter) flask.
While the resulting silk was very similar to the real, it still lacked its toughness and strength. Hence, researchers are now looking for ways to increase the toughness by spinning the NT2RepCT fibers with diameters closer to that of native dragline silk, as this apparently has an impact on the mechanical properties of silk fibers.
The application of spider silk ranges from ballistic protection to superior strength and toughness including military, industrial and consumer applications. There is an increasing demand for these products in industrial and consumer applications. If successfully engineered, artificial spider silks can soon become an integral aspect of safety management as well.
(Featured image source: https://www.flickr.com/photos/mliu92/2835308212)