Thursday, 15 March 2012

Transgenic silk worm makes strongest silk yet

What does body armour, artificial tendons and ligaments as well as extra fine sutures all have in common? (Handwerk, 2005)


Yes. Spider silk; they can all be made of spider silk. Spider silk is one of the strongest and flexible materials known to man(Science Daily 2010). Thanks to our knowledge of genetic modification, we are now one step closer to turning these products into reality.


For many years people have been trying to mas produce these fibres. However this proved impractical because spiders are very territorial and tend to eat one another(Yong n.d). Scientists have realized this problem and have tried to use genetic engineering methods to try and make mass production a much more plausible concept. They've used everything from goats to bacteria, but the problem with these organisms is that they are not able to make much silk protein at once (Yong n.d) , in addition to that, the extraction and purification process is quite long. The next logical step then was to find an animal that spun silk; the silk worm.

Spider goat, Spider goat does what ever a spider goat does...

The first step in trying to create a transgenic silk worm was to create something called a plasmid vector. This vector is the structure that will carry the desired silk gene into the silk worms DNA. They called this new silk gene the A2S814 Gene which is made up of spidroin-1 and spidroin-2 silk genes from the Golden Orb-Web Spider as well as genes that make the silk stronger (alanine-likner 8) and more elastic [(GPGGA)8] called motifs the final step was to add a fluorescent marker called EGFP which would make the silk give fluoresce under UV light to verify that the gene transfer worked. (Teulé 2011)

Once the Plasmid vector was constructed, they were microinjected into the eggs of the silk worms one hour after they were laid the puncture holes were then sealed up. The eggs were then left in an incubation chamber until they hatched. Once the eggs hatched, the worms were raised on an artificial diet and interbred to form subsequent generations of the genetically modified silk worms. The transgenic worms were identified by their EGFP marker that was expressed and caused their silk to glow. Their cocoons as well as their silk glands were removed and analyzed using gel electrophoresis. The silk proteins were also tested for stress, breaking strain and toughness.(Teulé 2011)

A: Cocoons from the unmodified (left) and modified (right) silk worms
B: Silk glands
C: Silk glands fluorescing dude to expression of EGFP
D: Silk fluorescing dude to expression of EGFP
Taken from:(Teulé 2011)

The researchers found that the new silk was a combination of spider and silk worm silk proteins, and that this new transgenic silk was considerably stronger than the original silk from the unmodified silk worms and was as strong as the natural dragline silk of the spider which is considered to be the strongest form of silk in the natural world. In the best case scenarios, the scientists recorded a strand of transgenic silk that was stronger than the natural drag line.(Teulé 2011)

With this new transgenic silk worm producing one of the strongest silk fibres ever, we are able to dodge the difficulty of spider farming as well as shorten the extraction and purification process because silk worms spin silk anyway. A few more years and we all might be wearing this.

The new style ?

References
Ed Yong – nd., Genetically engineered silkworms with spider genes spin super-strong silk, Discover Magazine, 15th March 2012 http://blogs.discovermagazine.com/notrocketscience/2012/01/03/genetically-engineered-silkworms-with-spider-genes-spin-super-strong-silk/
Florence Teulé , Yun-Gen Miao , Bong-Hee Sohn c , Young-Soo Kim c , J. Joe Hull , Malcolm J. Fraser, Jr. c , Randolph V. Lewis , and Donald L. Jarvis, ‘PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA’, Silkworms transformed with chimeric silkworm/spider silk genes spin composite silk fibers with improved mechanical properties,109,3,923-928.
Leslie Brunetta, Catherine Craig – 2010, How spiders took over the sky, 15th March 2012, http://gizmodo.com/5650464/how-spiders-took-over-the-sky
Brian Handwerk- 2005, Artificial spider silk can be used for amour, More, National Geographic, viewed 15th March 2012, http://news.nationalgeographic.com/news/2005/01/0114_050114_tv_spider.html
Science Daily 2010, Native-Like Spider Silk Produced in Metabolically Engineered Bacteria, viewed 15th March 2012, http://www.sciencedaily.com/releases/2010/07/100727121940.htm
Protocol online 2006, EGFP and GFP – how different are they?¸viewed15th March 2012, http://www.protocol-online.org/biology-forums/posts/19765.html

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