Tuesday, 3 April 2012

Transgenic Spider silk stronger than ever

Spider silk is probably one of the strongest, most versatile and well known biomaterials known to man. It has the amazing ability to support massive weights stretch over 1.5 times its normal length, and as you’ve probably heard, stronger than steel of the same diameter.

So it’s understandable that mankind have been trying to mass produce this material for a while now. However the simplest way turned out to be the most inefficient. Spider farming may sound cool, however, spiders are very territorial as well as cannibalistic (Yong  n.d). Also, scaling up production is not an option either as it proved to be much too expensive(Yong  n.d). Now days, modern scientists have employed modern biotechnology techniques to genetically modify bacteria, goats as well as potatoes to produce silk.

Why choose silk worms then? It’s simple, because they already have the ability to spin silk. This innate behavior of silk spinning is extremely useful for in terms of mass production. Generally with other genetically modified organisms such as goats or bacteria, the silk had to be isolated then purified, this proved to be a quite expensive process and thus it is where the silk worms have the advantage over the other GMO’s.

How did they do it?
They first started off by isolating the spider silk genes from the gland that made the strongest type of silk line; the dragline (Brunetta, Craig 2010), which is produced in the major ampullate  gland of the spider. From this gland they isolated the genes spidroin 1 and spidroin 2 (Teulé 2011). Other components such as amino acid chains that increase elasticity as well as strength and a fluorescent marker called EGFP (Teulé 2011) which glows green under UV light were isolated. They called this new recombinant gene sequence A2S814 and they ligated it into a piggyBAC plasmid vector (Teulé 2011).

An hour after the silk moth had laid its eggs, they were microinjected with the plasmid and incubated at 27°C until hatched (Teulé 2011). After the eggs had hatched, they were fed an artificial diet and were interbred to make sure that the new recombinant gene was passed on to subsequent generations (Teulé 2011).

The silk of the worms was collected, and their silk glands were removed to be analysed using fluorescent microscopy (Teulé 2011). Then the glands and the silk were homogenized and run through a PCR. Some silk was also then taken to be mechanically tested for strain, breaking strain, stretch and toughness (Teulé 2011).

What did they find?
After running the PCR, the researchers found that the silk was not just spider silk, it was a combination of the two silks the spider dragline and the silk worm silk (Teulé 2011). They also reported that in the mechanical testing procedures, the new transgenic silk line was at least two times as strong as the normal silkworm silk and as strong as or in the best case scenario, stronger than the natural spider dragline(Teulé 2011).

So what are the applications?
At the moment, mass produced silk is being marketed as BioSteel. Due to its extreme elasticity and strength it is used in a variety of different industries (Science Daily 2010). Spider silk threads are being used in the medical industry as super fine sutures that are not recognized by the immune system and can dissolve in the human body. They are also thinking of using spider thread to replace Kevlar(Handwerk, 2005)  to fabricate bullet-proof vests as well as high quality, light racing parts and fabrics.

Kelvin Trinh 42890827 

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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