April 29, 2008

Scientists Putting a New Spin on Spider Silk

A German team of engineers reported developing a device that borrows silk-spinning techniques from spiders to create strong strands with potential uses for lightweight medical equipment materials.

The team said their work shed light on how spiders produce their rugged webs.

"We can observe the initial steps of fiber formation, which was not possible before," said Sebastian Rammensee of the Technical University of Munich and one of the authors of the Proceedings of the National Academy of Science's paper.

"Now we can better understand how the processing conditions affect the quality of the silk."

Previous research has failed to produce anything capable of competing with silk created by spiders.

Spiders make their silk naturally as water-soluble proteins that are secreted from cells. These solutions are forced through tiny holes in their body - known as a spinneret - which extrude the thread.

Rammensee described the process used by his team saying that two genetically-engineered spider silk proteins were created using bacteria, which were fed through a device that consists of three channels etched into glass.

"The protein is introduced from one channel and from the two other channels salt solutions are introduced," said Rammensee.

Different grades of fiber were formed from different combinations of proteins and salts, but none were able to challenge the quality of spider's silk, said Professor Fritz Vollrath of the University of Oxford.

"It's another important small step towards making the material," he said. "It adds a piece to the puzzle but it's a very big puzzle and there are many pieces missing."

Vollrath also filed for a US patent in 2002 for a similar silk-spinning device.

In 2002, a Canadian company called Nexia tried to develop artificial spider silk by using a process that involved implanting a gene from a golden orb-weaving spider into a goat egg to produce animals that would secrete spider silk into milk.

Their attempts were successful, although the fibers produced were not high quality. Nexia decided to discontinue the project.

"We are finding certain wild silks which are stronger when you unravel them than natural spider silks," said Dr David Knight, a colleague of Professor Vollrath and chief scientific officer at Oxford Biomaterials.

Researchers at Oxford Biomaterials have created Spidrex, a new biomaterial based on spider silk, as well as SilkBone, which is a highly porous composite of silk proteins and the natural mineral component of human bone, hydroxyapatite.

"Genetic engineering is completely out for producing high-strength polymers - it's just much too expensive," Knight said.

"You have to have very precise environmental controls, you have to have very pure chemicals, you have to have a single strain genetically engineered bug - all that is just a recipe for capital and energy intensivity."


On the Net:

Prof. Fritz Vollrath

Oxford Biomaterials Limited

Proceedings of the National Academy of Science