Nexia Biotechnologies Inc. and the US Army Soldier Biological Chemical Command (SBCCOM) have reported in this week’s journal of Science that they have made the world’s first spider silk fibres from man-made materials with properties similar to natural spider silk.
Spider silk has long been admired by material scientists for its unique combination of high-performance properties including toughness, strength, lightness and biodegradability. Nexia is developing recombinant spider silk, dubbed BioSteel, for applications in the medical, military and industrial performance fibre markets.
The Science paper, titled ‘Spider Silk Fibres Spun from Soluble Recombinant Silk Produced in Mammalian Cells’ describes the production of a number of different dragline spider silk proteins via cell culture techniques using silk genes derived from two different species of orb-weaving spiders.
The monomer silk proteins from one of these species were spun from an aqueous solution to produce water-insoluble BioSteel fibres. These fibres were tested for a number of mechanical properties and compared to natural spider silk.
The researchers found that the spinning conditions used were adequate to produce fibres with mechanical properties similar to natural dragline spider silk including toughness and modulus, but had lower strength (tenacity) than natural spider silk. Toughness measures the amount of energy that the fibres can absorb before breaking and spider silks are among the toughest materials in the world.
Initial fibres of BioSteel were reportedly able to absorb similar amounts of energy as natural spider silk by stretching farther. The fibres also had good water stability, orientation and were uniform in diameter.
Dragline silk, which comprises the radiating spokes of a spider web, exhibits a combination of strength and toughness unmatched by high-performance synthetic fibres. Dragline silk is three times tougher than aramid fibres and five times as strong, by weight, as steel. Dragline silk is composed of proteins with multiple repetitive sequence blocks that impart its mechanical properties. Spiders can be coaxed to make silk, but attempts to create ‘spider farms’ have failed because of the territorial nature of spiders.
BioSteel is said to be eco-friendly both in terms of its composition and its production process. As opposed to most other synthetic fibres, BioSteel is expected to be biodegradable over time in the presence of water making it a promising material for such applications as medical sutures and fishing lines. Additionally, the aqueous production process has the potential to be non-polluting and environmentally friendly in contrast to the manufacturing of other synthetic fibres.
‘It’s incredible that a tiny animal found literally in your backyard can create such an amazing material by using only amino acids, the same building blocks that are used to make skin and hair,’ said Dr Jeffrey Turner, president and CEO of Nexia. ‘Spider silk is a material science wonder – a self-assembling, biodegradable, high-performance, nanofibre structure one-tenth the width of a human hair that can stop a bee travelling at 20 miles per hour without breaking. Spider silk has dwarfed man’s achievements in material science to date.’