HONG KONG, April 28 (Xinhua) -- Silver nano-particles with an average diameter of 5 to 50 nanometers can rein in the in vitro replication of hepatitis B viruses (HBV) through direct interaction with its DNA and viral particles, researchers said Monday.

    Lei Lu, a Ph.D. candidate at the Hong Kong University, said his team found that the ultra-tiny silver particles could reduce the extra cellular DNA formation of HBVs by over 50 percent, and could check their intracellular 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 carrier to enhance the antiviral efficacy while minimizing the undesirable side effects," Lu told a press conference Monday.

    The young researcher said there are currently only two kinds of drugs approved for treating chronic HBV infection, namely immunomodulators and nucleoside analogues. But their uses are affected 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 certain 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 of the tiny particles.

    The study on silver nano-particles is still in the laboratory stage and any drugs it may lead to are still 3 to 5 years away from clinic use, Lu said.

    The study, conducted jointly by researchers at the Department of Medicine and the Department of Chemistry of the Hong Kong University, has been published in the March issue of Antiviral Therapy, the world's leading antiviral research journal.