The world's first man-made spider silk fibres - stronger than steel - have been created using genetically engineered mammal cells by Canadian scientists collaborating with the US Army (director-e News, Friday 18 January).
Researchers hope the silk from transgenic goats soon will find use in a number of medical and military applications - anything from artificial tendons to bullet-proof vests.
Nexia Biotechnologies Inc. and the U.S. Army Soldier Biological Chemical Command (SBCCOM) have reported in the journal 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, trade named BioSteel, for applications in the medical, military and industrial performance fibre markets.
"Mimicking spider silk properties has been the Holy Grail of material science for a long time and now we've been able to make useful fibres", said Jeffrey Turner, PhD, president and CEO of Nexia. "Having achieved this proof of principle, Nexia has now moved toward commercial development for multiple applications such as medical sutures, biodegradable fishing lines, soft body armour and unique material composites.
"Our strategy is two-fold: to produce large quantities of BioSteel through our proprietary transgenic goat technology and to optimise spinning processes to create a diversity of spider silks with specific properties".
The Science paper, titled 'Spider Silk Fibres Spun from Soluble Recombinant Silk Produced in Mammalian Cells' (Lazaris et al., 2002-01-18. Science. Vol. 295:472-476), 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 dragline spider silks from these species have been documented to be among the strongest silks reported. 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.
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.
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. In effect, initial fibres of BioSteel were 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.
"We believe the Science paper will be seen as a landmark article in spinning water stable fibres with good mechanical properties using an aqueous process", said Jean Herbert, leader, Materials Science Team at SBCCOM's Natick Soldier Centre.
"We and others have been working on spider silk for considerable time and are thrilled finally to have the opportunity to spin synthetic silks and move the field towards real applications. The availability of Nexia's water-soluble recombinant silk proteins has been a fundamental breakthrough in our ability to spin spider silk fibres".
Dragline silk describes the radiating spokes of the spider's web.
Scientists at the Natick facility are well known for their expertise in high-performance fibre application development and their deployment of superior military, and often civilian, systems. The Natick Soldier Centre has been working with Nexia under a co-operative research and development agreement since May, 1999 and the results are reported jointly in the Science paper.
"These results are remarkable", said Costas N. Karatzas, PhD, vice-president, research & development at Nexia and senior author on the Science publication. "First, we were able to produce monomers and spin fibres in an aqueous environment thereby mimicking the spider's way of spinning silk, a process that has been perfected through 400 million years of evolution.
"Using these water-based BioSteel solutions for large-scale fibre spinning would be considerably more environmentally friendly than using harsh solvents such as those used for most synthetic fibre manufacturing", he added.
"Second, the material from mammalian cells was spun into fibres with significant toughness. Scientists have been successful in producing spider silk proteins in bacteria and yeast in the past, but for a number of reasons, have been unable to spin fibres with appreciable properties.
"Now, with the availability of mammalian-derived BioSteel fibres, we can begin to optimise the spinning process in order to tailor BioSteel properties for a wide range of applications. We are grateful to the US Army team at Natick and our other collaborators for their expert guidance in this project", added Dr. Karatzas.
BioSteel is 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. Turner.
"Spider silk is a material science wonder - a self-assembling, biodegradable, high-performance, nano-fibre 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".
Nexia has exclusive, worldwide rights to broad patents covering spider silk genes and proteins and is in the process of developing commercial quantities of spider silk using its proprietary transgenic goat technology.
Nexia has developed a number of male and female BioSteel founder goats. Males are being used to expand the herd and females will begin producing milk in the second quarter of this year to provide increasing quantities of BioSteel for spinning process optimisation, product development and commercialisation.