Silver nano-particles with a diameter of between 5 and 50 nanometers can rein in the in vitro replication of hepatitis B viruses through direct interaction with its DNA and viral particles, researchers said on Monday.

Lei Lu, a Ph.D. candidate at Hong Kong University, said his team found that ultra-tiny silver particles could reduce the extra-cellular DNA formation of HBVs by over 50 percent, and could check their intra-cellular RNA formation, too.

"Silver nano-particles have special properties such as larger active surface and porosity so that they can easily bind with small molecules," Lu said, referring to a hypothetical explanation they had put forward on the new antiviral mechanism.

"The finding provides a new direction for developing new anti-HBV drugs, with nano-particles used as drug carriers to enhance the antiviral efficacy while minimizing undesirable side effects," Lu told a press conference Monday.

The young researcher said there were only two kinds of drugs approved for treating chronic HBV infection, namely immunomodulators and nucleoside analogues. But their use was governed by side effects and drug-resistant mutations.

Hepatitis B is one of the worst killers as it chronically infects over 400 million people worldwide with some developing countries and regions hit hardest.

Lu said silver nano-particles have an additional distinct advantage. It is unlikely that HBV can become resistant to silver nano-particles because the interaction is determined by the physiochemical properties. The study is still in the laboratory stage.

(Shanghai Daily April 29, 2008)