Spider silk is well known for its extraordinary mechanical properties. Spiders can produce several types of silk and the strongest of these - the dragline silk - is one of the toughest materials known to man (Gosline et al., 1999). Already at the beginning of the 18th century, techniques for manufacturing stockings and gloves from spider cocoon silk were described (Bon, 1710-1712). In folklore, spider silk also has medical implications, e.g. to stop haemorrhaging and for wound healing.
Recently, native spider silk was successfully used to regenerate peripheral nerves in rats (Almelling, et al 2008). Furthermore, old abandoned spider webs seem to have an inherent resistance to microorganisms (Foelix, 1996). Thus, spider silk is an attractive material for a large variety of applications.
Until recently, however, producing spider silk has been a major obstacle for industrial applications. Despite being in the focus of biologists and material scientists for centuries, it is only now that synthetic spider silk can be produced using methods suitable for industrial scale use. Moreover, in contrast to other man-made high-performance materials, spider silk is produced at ambient temperature and pressure using renewable resources and a benign solvent.
Spiber Technologies has succeeded in mimicking nature’s way of producing spider silk, by letting bacteria produce the miniature spider silk protein. The result is called Spiber™.
Spiders can produce up to seven different types of silk fiber. The strongest of them is dragline silk, which is used as a lifeline and for constructing the framework of the web. This is the toughest material ever described. Most of the research in labs around the world has been done on this type of silk.
Dragline silk is mainly composed of proteins called spidroins. These are very long proteins with a specific architecture that so far have been found only in spiders.
Spidroins are stored as a viscous fluid in specific glands. When the spider is about to spin a thread, the fluid containing these silk proteins is passed through a channel. There, the conditions are changed; pH is lowered and the ionic composition altered, for example. When these changes occur, the spidroins rearrange to form solid threads.
To ensure that the silk proteins are stored as a viscous liquid yet maintain their ability to transform to solid fibers, spidroins have three distinct regions: