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Can High-Speed Tests Sort Out Which Nanomaterials Are Safe?

If you’ve ever marveled at a painter mixing colors on a palette, you have a taste of what nanotechnologists feel when designing materials at the smallest scale. Nanoscientists today mix collections of different atoms to create a multitude of novel pint-sized particles with a vast array of new electronic, optical, catalytic, and chemical properties. Iron oxide particles, for example, are proving exceptional as contrast agents for medical imaging. Bits of titanium dioxide harvest sunlight in solar cells. And on and on. “These are materials with wonderful properties,” says Fanqing Chen, a biomedical scientist at Lawrence Berkeley National Laboratory in California. “Their contribution to science, technology, and the economy is going to be huge.” But the remarkable diversity of nanomaterials is also one of the field’s biggest headaches. With potentially thousands of novel materials under investigation, health and safety regulators are left scratching their heads over which are safe and which are potentially toxic to humans or other species. That uncertainty threatens to undermine public confidence in nanotechnology and stymie the development of what is expected to be a major global economic engine. What’s worse, traditional toxicology studies that test one material at a time appear woefully inadequate to the task of sorting the dangerous from the benign. “If we continue with the classical toxicological assessment [for nanomaterials], we will never catch up with this work,” says Andre Nel, a nanomaterials toxicologist at the University of California, Los Angeles. In hopes of picking up the pace, Nel and a handful of other toxicologists around the world are creating batteries of highspeed assays for testing the toxicity of hundreds and even thousands of different nanomaterials at the same time. The assays involve exposing different types of cells to nanoparticles and monitoring the cells for changes, such as DNA damage, alterations in gene expression, cell death, and impacts on cell growth and proliferation. It’s still too early to say whether these hopes will pan out. But at a minimum, nanotoxicologists hope high-throughput studies will help them prioritize nanomaterials that should undergo conventional toxicology tests. Clearly, there is cause for concern about the toxicity of some nanomaterials. Early studies with soccer-ball–shaped carbon fullerenes revealed, for example, that the particles can damage brain cells in f ish. Conventional toxicology studies also raised yellow flags about the straw-shaped cousins of fullerenes called carbon nanotubes. When the lung tissue of rats was flushed with high levels of nanotubes, researchers found that the tubes clumped together, making it difficult for the animals’ immune systems to clear them from their bodies. Still other studies have raised concerns about particles mostly considered harmless at larger sizes, such as titanium dioxide nanoparticles. Unfortunately, such studies are slow and expensive. A single in vivo animal study can cost $50,000. In addition, it’s often difficult to extrapolate how a material tested in one tissue will affect others. It’s even harder to extend that one study to determine how other nanomaterials will behave. The study that showed fullerenes can damage the brain cells of fish, for example, says little about exposure to particles of iron oxide, silicon dioxide, or carbon nanotubes. Can High-Speed Tests Sort Out Which Nanomaterials Are Safe?