Nanoparticles used in medical applications can indirectly damage DNA inside cells by transmitting signals through a protective barrier of human tissue, says UK researchers.
The stunning discovery adds to a growing body of research highlighting proven and potential health hazards from the rapidly expanding universe of engineered objects measured in billionths of a metre.
There are already a number of products containing nanoparticles available, ranging from cosmetics to household cleaning products and sporting goods. But the new findings, reported in the journal Nature Nanotechnology, could also point to new ways in which nanotherapies might zero in on disease-causing tumours, say researchers.
They could even shed light on how poorly-understood pathogens penetrate into human organs. In laboratory experiments, scientists led by Dr Charles Case of Southmead Hospital in Bristol, grew a multi-layer 'barrier' of human cells to mimic specialised protective tissues found in the body.
One such barrier, for example, separates blood from the brain.
Underneath this layer three-to-four cells thick, they placed human fibroblast cells, which play a key role in the formation of connective and scar tissue. And on top they put nanoscale particles of cobalt-chromium, an alloy that has long been used in the making of hip- and knee-replacement joints, and more recently in drug-delivery mechanisms used inside arteries.
As if it wasn't there
Earlier studies had shown that direct exposure to large quantities of the alloy could severely damage DNA in some cells, and the researchers wanted to find out how well the laboratory-grown barrier would protect the fibroblast cells below.
"We never imagined that it wouldn't [protect]," says Case. "But to our great surprise, not only did we see damage on the other side of the barrier, we saw as much damage as if we had not had a barrier at all."
At first, the researchers speculated that the tiny particles, barely 30 billionth of a metre in diameter, had slipped through microscopic cracks in the cellular blockade. But there was no sign of the alloy on the other side, and when the experiment was repeated with far larger particles, the result was essentially the same.
"We could only conclude that the DNA damage occurred after indirect exposure depending on a process of signalling between cells rather than the passage of metal through the barrier," says Dr Gevdeep Bhabra, a surgeon at Southmead and co-author of the study.
Professor Thomas Faunce of the Australian National University in Canberra says the study is significant.
"Nano-toxicological research has focused on looking at what happens if we put nanoparticles inside these type of cells," says Faunce.
"What [this latest research is] saying is once nanoparticles are in the body they have a capacity to cause toxocological effects at a distance."
Previously, Faunce has expressed concern regarding the over use of nanoparticles in products such as nano-silver bandages and undergarments.
He says in light of this recent report any future investigation into the use of nanoparticles and their associated levels of toxicity may need to be rethought.
His views were echoed by the researchers themselves and experts not involved in the study.
"What it tells me is that the precaution with which some scientists and regulators say we should proceed is the right way to go," says Professor Vyvyan Howard, a pathologist at the University of Ulster who founded the Journal of Nanotoxicology.
Source: ABC Australia Article
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