carbon

Fruit flies killed by nanoparticles

BROWN (US)—The health and environmental effects of carbon nanoparticles, which are widely used in electronics and medicine, are not well understood. A series of experiments with fruit flies could help reveal potential dangers.

Researchers at Brown University have discovered that certain types of carbon nanoparticles can be environmentally toxic to adult fruit flies, although they were found to be benign when added to food for larvae.

The scientists found that larval Drosophila melanogaster showed no physical or reproductive effects from consuming carbon nanoparticles in their food. Yet adult Drosophila experienced a different fate.

Tests showed adults immersed in tiny pits containing two varieties of carbon nanoparticles died within hours. Analyses of the dead flies revealed the carbon nanoparticles stuck to their bodies, covered their breathing holes, and coated their compound eyes. Scientists are unsure whether any of these afflictions led directly to the flies’ death.

A separate experiment showed adult flies transported carbon nanoparticles and then deposited them elsewhere when they groomed themselves.

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The findings, published online in Environmental Science and Technology, help to show the risks of carbon nanoparticles in the environment, says David Rand, professor of biology, who specializes in fruit fly evolution.

“The point is these same compounds that were not toxic to the (fruit fly) larvae were toxic to the adults in some cases, so there may be analogies to other toxic effects from fine particles,” says Rand, a co-corresponding author. “It may be like being in a coal mine. You get sick more from the effects of dust particles than from specific toxins in the dust.”

The scientists immersed adult Drosophila in a control test tube and test tubes containing four different types of carbon nanoparticles corresponding with their commercial uses. Some had few or no difficulties, but other batches of flies could not escape their surroundings and died within six to 10 hours, the scientists report.

The causes of death are unclear, but detailed analyses led by chemistry graduate student and lead author Xinyuan Liu showed the flies were affected physically.

Rand and Robert Hurt, director of Brown’s Institute for Molecular and Nanoscale Innovation and the other corresponding author, says the findings are important, because they show that permutations of the same material—carbon—can have different effects in the environment.

“It’s not the nanoparticle per se (that may be hazardous), but the form the nanoparticle is in,” Rand explains.

Another experiment by the team showed how insects could be vectors for transporting nanomaterials, Rand adds.

David Rand, one of the study’s authors, says the nanoparticles “glom onto the flies.” He adds: “They just can’t move. It’s like a dinosaur falling into a tar pit.”

While two generations of fruit fly larvae showed no ill effects from eating carbon nanoparticles, the Brown scientists noticed that some of the particles ended up being stored in the flies’ tissue. That means the nanoparticles could accumulate as they are passed up the food chain, Rand says.

The researchers have several related experiments in the works. They plan to test fruit flies’ response to nanosilver and other nanomaterials with different chemistries, and they will investigate why the adult Drosophila died from varieties of the carbon nanoparticles.

The research was funded by the National Science Foundation through a Nanoscale Interdisciplinary Research Teams (NIRT) grant, the National Institute of Environmental Health Sciences, the Superfund Research Program Grant, and a Brown University Research Seed Fund Program.

Brown University news: http://news.brown.edu/

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