Gold nanoparticles made using chemicals found in tea leaves could be used to combat cancer say US scientists. 

Kattesh Katti, Raghuraman Kannan and colleagues at the University of Missouri, Columbia, used phytochemicals (bioactive compounds) from Darjeeling tea to reduce gold salts to gold nanoparticles. The phytochemicals also stabilised the nanoparticles and covered them in a robust and non-toxic coating. Since only natural chemicals are used in this reaction, no toxic waste products are produced, making it a 100 per cent green process, says Katti. 

Tea has been known for its health benefits for centuries and compounds found in tea have been used as dietary supplements and natural pharmaceuticals. The compounds scavenge disease-causing free radicals in the body. They are powerful reducing agents too, but research into these reactions is still in its infancy. Discovering that phytochemicals in tea can initiate gold nanoparticle formation under non-toxic conditions is of paramount importance for medical and technological applications, says Katti. 

Typical reactions for forming gold nanoparticles use toxic chemicals, making them unsuitable as medicines. Also, thiols are used to stabilise and prevent merging of the nanoparticles, but this means that the particles can't bind to drug moieties that target disease sites. Katti's method gets around this problem, as the coating formed by the phytochemicals stops the nanoparticles merging but still allows them to bond with the drug moieties. 

Katti's team tested their nanoparticles against prostate and breast cancer cells. They found that the particles had excellent affinity for the cancer cells' receptors, which means that they could be used in anticancer drugs.

'Green nanotechnology is an emerging area interfacing nanotechnology and natural sciences,' says Katti. 'Our process is feasible on larger scales and thus allows the discovery of more medical and technological applications of gold nanoparticles.'

Philippa Ross

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