Nanomedicine Boosters Cautioned On Unknowns

(NHI Nanoblog) POTOMAC, Md.—After a whirlwind string of presentations highlighting some of the most mind-blowing research in nanomedicine, two toxicology experts stepped forward with a sobering message: a new frontier comes with new, and often unknown, risks.

Closing out the American Society of Nanomedicine’s second annual conference here, Gunter Oberdorster and Paul Howard tried to avoid being too dark a cloud over the generally optimistic meeting.

Both said that while there are reasons to be concerned about the human and environmental impact of nanomedicine—cures developed for super-small “nano” particles that acquire new super-properties— the most immediate issue is a simple lack of knowledge about exactly what these new materials will do.

Oberdorster, a professor of environmental medicine at the University of Rochester, said the common thinking about all nanomaterials is that they’re small and move freely around the body, and that humans have few defenses against them. In short, he said, people think these substances are “cute little assassins.”

But, he asked, how true is that notion? It seems clear that some nanoparticles, such as carbon nanotubes, can do harm to the body. It’s still murky, though, how other substances, especially those being used in medical applications, will fare, he said.

Many studies that are being done to evaluate nanomaterials, Oberdorster said, are using extremely high doses of the material, which calls their relevance into question. Risk, he reminded the audience, is a combination of the hazard posed by a material and the amount of exposure.

“If a particle is low hazard, it doesn’t matter what the exposure is. It will still be low-risk,” Oberdorster said. And the converse is also true.

Howard, an official with the Food and Drug Administration’s National Center for Toxicology Research, said his agency’s biggest problem is the difficulty of detecting problematic materials, since many traditional testing methods are inconsistent or completely unreliable when nanomaterials are involved. That’s caused some hesitancy in the regulatory field, as researchers struggle to find a standardized test in order to set benchmarks for drug developers.

There have been successes, he said. For example, FDA researchers found that nano-sized titanium dioxide particles used in sunscreens didn’t penetrate much beyond the surface of the skin of pigs used in the testing. Fear of the nanoparticles accumulating inside the human body has been a top criticism of nano sunscreens.

But just as experts in the occupational health field have said, Oberdorster and Howard emphasized that a lot more investigation is needed to understand exactly what’s scary—and what’s not—when it comes to nanomedicine.

Many medical researchers working in the nano field tout the biodegradable nature of their materials, but Oberdorster said it’s important to know what happens to nanoparticles when they break down, accumulate in the body, or otherwise change. Scientists also need to find out what happens to the materials after they come out of the body, and if they could accumulate in wastewater like traces of prescription drugs

“The question I would ask is, where does it go? How is it metabolized?” Oberdorster said. “That’s the key issue, to follow the life cycle of a nanomaterial, from cradle to grave.”

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