Green alchemy

Ayurvedic drugs will cost less with microorganisms yielding gold

Published: Tuesday 15 July 2003

gold can now be made inside the cells of a microorganism, thanks to the ecofriendly work of researchers from the National Chemical Laboratory and the Armed Forces Medical College, Pune.

They took microorganisms called Rhodococcus from a fig tree and exposed them to a liquid containing gold ions (electrically charged gold particles). When exposed to the ions, the microorganisms were induced to produce enzymes that acted as a catalyst for the formation of gold nanoparticles in the microorganisms' cells. Following the biosynthesis, the cells of Rhodococcus multiplied normally, as the ions used were not toxic to the cells -- this is important as more gold would be formed as the cells multiply.

The nanoparticles are more concentrated and uniform in size than the ones biosynthesised by previous methods using a fungus. "They are about nine to twelve nanometres in diameter. That's about eight thousand times smaller than a human hair," says Murali Sastry, one of the researchers. Although the exact reaction that causes the gold to form uniformly is not yet fully known, the group believes that the Rhodococcus species gives better results because it is an actinomycete -- a microorganism that is both bacteria and fungi.

Gold particles are already used for making ayurvedic drugs. But since their refining process is quite expensive, and not well characterised, the prices of the drugs are exorbitantly high. The new nanoparticles would overcome this drawback due to its simple biosynthesising process. Furthermore, they can be used to detect disease-causing agents, as they are extremely sensitive to the smallest chemical change and can reach the nucleus of any cell. They can also aid the development of nanomaterials and nanoelectronics.

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