Nanoparticles can damage the DNA of cells some distance away, even when the cells seem safe behind an impassable barrier of tissue, new research has found.

But what does this curious finding, revealed yesterday by researchers at the University of Bristol, UK, mean about the safety of nanoparticles and medical treatments based on them? New Scientist puts the news in context.

Did the experiment represent something that could happen in my body?

The experimental set-up was entirely artificial, and nothing like it occurs naturally in humans or animals. Nor are the nanoparticles in question used in any current treatments, experimental or otherwise.


The tissue barrier, about four cells deep, was made from “BeWo” human cancer cells. They are a standard cell line that has become well adapted to lab work, making them very different to any cells found in the body.

The nanoparticles were 30-nanometre-wide beads of surgical cobalt-chromium alloy, a material used in much larger pieces to make surgical implants such as hip prostheses.

The “target” cells on the other side of the BeWo barrier to the nanoparticles were human fibroblast cells, found in skin and connective tissue.

What exactly were the results?

After a day in a lab dish, DNA damage was discovered in the fibroblasts. It wasn’t extensive, but included single and double-strand breaks in DNA, and abnormal chromosome doubling in some cells. Careful checking found no leaks in the barrier, and no cobalt-chromium beads on the wrong side of it.

How could that happen?

The nanoparticles directly influenced the nearest layer of barrier cells and disrupted their mitochondria – chambers where energy is generated and stored.

That released signalling molecules – mainly the energy-transport molecule adenosine triphosphate (ATP) – which in turn triggered a cascade of biochemical messages inside the cell. That signalling storm eventually reached the other side of the barrier cell, opening channels that spread the message to the next layer of barrier cells.

This Chinese-whispers process continued until signalling molecules reached the fibroblasts, somehow damaging their DNA – the researchers don’t yet know how this happened.

How do we know that’s what happened?

When compounds that block the “message” channels in cell membranes were added to the dish, there was no damage to fibroblasts.

What is special about these nanoparticles that lets them do this?

Nothing, really. Further experiments showed that there are ways to transmit the ghostly messages without using nanoparticles.

Solutions containing cobalt or chromium ions caused the same damage to fibroblasts. So did using much larger particles of cobalt-chromium in place of the nanoparticles.

Might other kinds of chemicals, drugs and nanoparticles perform this trick too?

Possibly, but the only way of finding out is to test a wider range of substances using the same experimental set-up.

Hundreds of thousands of people receive cobalt-chromium implants every year, and there has been no evidence of ill effects reported.

Could the same effect occur naturally?

Possibly, but we don’t know yet. “Maybe small particles like viruses or prions act through these processes too,” says Patrick Case, who led the research.

Does this suggest that all nanoparticles may be unsafe?

No. There are hundreds of nanostructures under development and being tested as possible medical treatments and for other uses. It would be ridiculous to suppose that they would or could all cause this phenomenon.

What about skin creams like sunblocks that contain nanoparticles? Might they cause unknown effects below the skin?

Possibly. But again, this is such a newly discovered phenomenon that it’s too soon to say. The researchers are adamant that their set-up can’t and shouldn’t be extrapolated to any structures in the human body.

Is more research into the new phenomenon planned?

Yes. Experiments are planned to see if other nanoparticles or chemicals can perform the same trick.

It will also be fascinating to see if signalling is possible across the body’s natural barriers, such as the skin, placenta or blood brain barrier.

Much research is trying to design drug molecules able to cross such barriers, which can act as very specific filters. But it may be possible to exploit this newly discovered effect to avoid having to cross them altogether.

Journal reference: Nature Nanotechnology, DOI: 10.1038/nnano.2009.313