stoking fears. A new study has raised new concerns about nanoparticles, but may be unfounded.
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Titles are laced with fear. "Nanoparticles" can damage DNA. "" Security Nanoparticles Watch more complicated. "" Nanoparticles indirect threat to the DNA. "All seem to suggest that a new study, published yesterday, found that nanoscale materials, used in everything from medical imaging for cancer treatment, can damage the genetic material in our bodies, fueling public fears. But this study has little relevance to the risk of human exposure, experts say, and it is deeply flawed in other ways. "I think it is a study of meaning, to be frank, "said Günter Oberdörster a nanotoxicologist at the University of Rochester in New York.
Oberdörster and others agree that some concerns over nanoparticles are valid. These particles, 1 to 100 nanometers, are made from a wide variety and a combination of elements. Their small size gives them optical, electrical and unique chemical, raising concerns they might have unforeseen effects in the body. And a variety of studies in animal models have shown that nanoparticles can trigger damage in living tissue ( Science , 18 June 04, p. 1732).
But the new work was narrower. Charles Patrick Case, an orthopedic specialist at the University of Bristol in the UK, and a number of colleagues reported yesterday online Nature Nanotechnology that particles of cobalt-chromium - a smaller version of the metal alloy which is widely used in replacement joints -. can damage the distant cells in a specially designed cell culture
teamcase exposed a "barrier" thin four layers of cancer cells to ions, or particles of cobalt-chromium. Relatives cells nanoparticles have experienced signs of mitochondrial damage. But even the cells on the other side of the fence was damaged DNA, the team found, despite the fact that there was no evidence that the metals themselves moved across the cells on the other side of the barrier. Other studies have suggested that damage to cells of the barrier set off a chemical cascade that has affected neighboring cells, says Case.
In the document, the case and colleagues suggest that, according to the results, the nanoparticles used in a clinical setting may need to be evaluated for these unforeseen effects. "The potential damage to the tissues located behind cell barriers should be considered when using nanoparticles to target disease states," the team writes. The point was also stressed in a press release issued by Nature Nanotechnology this week: "These results suggest that the direct and indirect effects of nanoparticles on cells were equally important when considering the risks potential use in nanomedicine. "
is the kind of language that scares and confuses the public, says toxicologist Andre Nel of the University of California, Los Angeles. Above all, he and others say, when there is no evidence that the results are reflected in people.
In addition, there are other reasons why the study is not applicable to human health, said Andrew Maynard, scientific director for the Woodrow Wilson International Center for Scholars Project on Emerging Nanotechnologies at Washington, DC to start, Maynard and others point out that the case team in cells exposed metal particles at a concentration of thousands of times higher than could be expected to occur in the body. "They completely forget that it is the dose that makes a poison and a mechanism of action," said Oberdörster. Although the group found that metal particles of micron size and metal ions also damage DNA, they focused mainly on nanoparticles. "The effects appear to be specific nanoparticle," says Maynard.
In a press conference yesterday to discuss the results of the paper, the case has said his team does not aim to draw conclusions about the effects the metals can have in the body. Instead, he said, the study was designed to ask the more fundamental question of whether a physical barrier cells would indeed act as a barrier to avoid damage to the cells on the other side.
These conservative interpretations are often lost in news coverage and efforts by journals to promote the coverage of particular documents, however. Nature Nanotechnology not only highlighted paper in a news release, but also organized the press conference, drawing extra attention to the study. "the danger is that they have created controversy by giving this attention "says Maynard. Nel points out that this is a regular event in the field of nanotechnology, because the field is hot and plays into the fears of the people about the new technology. "We must be much more careful in interpreting these results," said Oberdörster.
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