840.119:Biosteel

Project Description

The first group of scientists to successfully obtain dragline silk from goat's milk was done by Lazaris, et al, 2002. The project was successful in obtaining spider silk, but not enough to spin into a fiber. In the future, if scientists are successful in obtaining enough with the same strength as a natural spider web, the possibilities for its use would be limitless. In the experiment done by these scientists in 2002, they started out with the spider silk gene, and then placed that gene into the egg of a goat. Once the goat grew to an adult, it was cabable of producing silk within its own milk producing glands. Currently, other methods of producing dragline silk outside of the spider are being persued through transgenesis in potatos, tobacco plants, and bacteria; though problems with these alternative methods exist. Hence, the main focus still remains on the goat production method, though Nexia Biotechnologies has as of late put this new application of biotechnology on hold.

State of the Art

Why is this needed?

This product could potentially be used for artificial tendons, and limbs; tissue repair; sutures for eye or neurosurgery. Using this product could potentially save hundreds of lives through stronger bulletproof vests, and its use as medical suturing. Because spider silk is biodegradable, this product could replace plastic bottles and nylon to make these products safer for the environment. Since silk is lighter than many synthetic fibers, it has the potential to be used for aircraft and cars

Spider Silk

Over 400 million years of evolution has perfected this amazing fiber. The silk has to be both durable and invisible to prey to be successful. First the spider secretes a protein solution, as the silk dries, it becomes taut, forming an insoluble thread.

Objectives

The focus of this website is to inform the public about prior research using recombinant spider silk genes in mammary glands. The following information will describe the details of transgenesis. Background information on the spider and their proteins will also be described.

Advantages of using Biotechnology

Recombinant silk in mammalian cells is far more efficient then obtaining enough spiders to mass produce the amount of silk that would be needed to manufacture items such as bulletproof vests.

Scientific Approach

Canada's Nexia Biotechnologies were the first to discover what would happen when a spider silk gene was inserted into a goat's genome. Because the spider silk producing gland is similiar to the goat mammary glands, they were able to inject the gene into an unfertilized egg. This 'biopolymer' is then produced in the specialized epithelial cells in the goats mammary glands. When the female goat goes through lactation, the spider gene will turn on and subsequently off once the female is done lactating. In one day, the goat can produce 1.5 liters of milk, with a substantial amount of this being the silk proteins. The silk can be harvested from the milk through intense heat; cooking off all other materials except for the silk which is strong enough to resist denaturing.

The arachnid genes used in this process are actually derived from two seperate spider species. These include Nephila clavipes, and Araneus diadematus. The specific genes used from these spiders are the ADF-3 and ADF4, derived from A. diadematus', as well as MaSpI and MaSpII from N. clavipes.

Methods

The following is taken from the Lazaris experiment which successfully obtained spider silk in mammary cells. Two cell lines were chosen for the expression of spider genes: MAC-T (bovine mammary epithelial alveolar cells) and BHK (baby hamster kidney cells). MAC-T cells were picked since they are secretary epithelial cells, which are similar in cell type within the spiders, and the experimental usage of them would help determine if the cells could produce spider silks in the milk of transgenic animals, such as goats.

Experiment

Each of the spider genes (ADF-3His, ADF-3, MaSpI, and MaSpII) had their own vectors designed specifically for them. E coli was the plasmid used in all cases. MAC-T and BHK were transfected, then allowed to sit for 7-8 days. The surviving colonies were expanded further.

Results indicate that BHK cells showed higher amounts of ADF-3 proteins than MAC-T cells. This demonstrates that hamsters have greater capabilities of incorporating the new genes rather than goats.

Alternative Methods

Other methods of obtaining the dragline silk, includes using recombinant DNA technology in plants, specifically the tobacco leaves and potato tubers. Up to 2% of the total soluble protein in these plants endoplasmic reticulum is found to be the dragline silk transgenic product. The silk can be obtained from these plants through extreme heat purification, due to the large stability of the silk products. Problems with this method include producing manufacturable products from the purified silk intermediate.

Attempts with yeast and bacteria were also tried. However, the size of the silk produced was too large for the yeast and bacateria to house, due to their small size. Because of the repetitive nature as well as the unusual mRNA secondary structure, there was inefficient translation, thus limited size of the produced silk proteins.

Impacts

With enough silk fibers, a fabric could be produced that would be five to even 20 times stronger than steel, biodegradable, and extremely lightweight for its strength. The material could be used to produce flak jackets beyond the strength of current kevlar, and biodegradable products including sutures. The use of this product along with the science behind its high tensile strength and low weight, would create huge advancements in cable/rope strength, that would be used for anything from "space-age architecture" to air and space craft.

Associated Risks

Currently there are no known problems with using transgenesis in goats. The goats that are born are like any other healthy goats, except that they produce silk within their milk. However, this application is still in its young stages, and long term effects on these goats are still unknown, if there are in fact complications.

Ethical issues

One problem that may be an issue is the altering of another life. There are more ethical issues with doing this with humans, but there are laws against cruelty to animals. People not familiar with transgenesis may not realize that this is safe for the animal. All that is being done is the introduction of another gene, that does not alter or ruin any other processes in the goat.

References

Scientific articles

Lazaris et al., 2002-01-18. Science. Vol. 295:472-476

Scheller, J. et al., 2001-06. Nature Biotechnology. Vol. 19:573-577

Weblinks

http://www.eurekalert.org/pub_releases/2002-01.nbi-nau011102.php

http://www.howstuffworks.com/news-item38.htm

http://arachnophiliac.co.uk/burrow/news/spinning_steel.htm

http://www.moaa.org/magazine/January2003/f_superwarriors.asp

http://www.spacedaily.com/news/materials-02a.html

http://news.bbc.co.uk/1/hi/sci/tech/889951.stm