Biomimetic engineering of spider silk

29 Mar 2016 NUS biologists discovered the mechanistic understanding of silk formation, the spinning process, and property-structure relationship as the key to mass-produce man-made spider silk.

Spider silk is one of the most extraordinary natural fibres, which is assembled from one or more large silk proteins, each comprising multiple modular units. Nevertheless, spider silk is still not widely used due to the difficulty in large-scale farming. To make use of “nature’s super fibres”, biomimetic production of spider silk is a good option. A team led by Prof YANG Daiwen from the Department of Biological Sciences in NUS found the structures of individual protein units and their roles in conferring silk formation and silk property [1,3,4] which enabled his group to design and produce artificial silk fibres that have higher tensile strength but lower elasticity and toughness, compared to their natural counterparts [2]. Prof Yang’s group also discovered a novel silk protein unit that can be produced in high yield using an E. coli expression system. Different from other silk protein units, this unit alone can form silk-like fibres. With the availability of this small unit, one will be able to produce artificial silk in a large amount.

The artificial silk with exceptional mechanical properties can be used in defense and other areas in which light weight, toughness, strength, hardness and elasticity are required, provided it can be mass-manufactured. In addition, the strong silk can be used to repair damaged ligaments in patients. The strategy developed for silk design can be applied to the incorporation of functional modules into silk proteins for the production of silk fibres with desired biochemical or biophysical functions.

To mass-produce artificial silk with properties comparable or superior to those of natural silk, Prof Yang’s group will study the molecular mechanism of silk formation, the silk property-structure relationship, and the silk spinning process using native-like silk proteins in the next few years. At the same time, they will optimise protocols for generating silk proteins in a cost-effective way and develop new devices for spinning the proteins into silk fibres.

Spider web silk proteins have been a major focus in other research groups. Spider prey-wrapping silk has the highest toughness and its repetitive units are stable and easily obtained. So, it has been chosen by Prof Yang to unravel the secrets of spider silk. Since native silk proteins function differently from their individual units, the use of native-like silk proteins for understanding silk formation and production has become the major focus of Prof Yang’s laboratory.

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Figure shows a new silk protein was designed on the basis of silk genes identified from a local golden web spider and structures of individual silk protein units. The designed protein was purified from an E.coli expression system. In the presence of shear force, the protein self-assembled to form ball-like structures and then further to become silk fibres. The fibres produced from an egg case-like protein were stronger than the natural egg case silk fibres. [Image credit: Yang Daiwen]

 

References

1. Wang S, Huang W, Yang D. “Structure and function of C-terminal domain of aciniform Spidroin” Biomacromolecules, 15 (2014) 468.

2. Lin Z, Deng Q, Liu X, Yang D. “Engineered large spider eggcase silk protein for strong artificial fibers” 25 (2013)1216.

3. Wang S, Huang W, Yang D. “NMR structure note: repetitive domain of aciniform spidroin 1 from nephila antipodiana” 54 (2012) 415.

4. Lin Z, Huang W, Zhang J, Yang D. “Solution structure of eggcase silk protein and its implications for silk fiber formation" Proc. Natl. Acad. Sci. USA 106 (2009) 8906.