LONDON (Reuters) - Nanoparticles can damage the DNA of cells from a distance, even without crossing the cellular barriers that protect certain parts of the body, British researchers said on Thursday.

The surprising discovery raises fresh questions about the safety of nanotechnology, which involves manipulating particles that are tens of thousands of times smaller than the width of a human hair.

But it may also help scientists create more effective medicines and diagnostic tools that can work across specialized cell walls, such as the blood-brain barrier.

Scientists from the University of Bristol tested the impact of high concentrations of metal nanoparticles on DNA in a laboratory experiment, which they stressed was not designed to accurately replicate conditions in the body.

“To our great surprise, not only did we see damage on the other side of the barrier but we saw as much damage on the other side of the barrier as if we’d actually not had it there at all,” researcher Patrick Case told reporters.

Case and colleagues found the nanoparticles didn’t pass through the multi-layer cell wall to cause the damage, but in fact generated signaling molecules that were then transmitted to cells on the other side.

The scientists, who reported their work in the journal Nature Nanotechnology, said the findings suggested that direct and indirect effects of nanoparticles on cells were equally important when considering their use in medicine.

Nanoparticles -- with a diameter measured in billionths of meters -- are being studied increasingly in medicine, where they may help in the delivery of drugs against cancer and other diseases. They are also used in cosmetics and electronics.

But their use has raised concerns about dangers.

Chinese researchers reported in August that seven young Chinese women suffered permanent lung damage and two of them died after working without proper protection in a paint factory using nanoparticles.