In the race to figure out whether super-small particles in food, packaging and other workaday consumer products could hurt us, chicken intestines may be a crucial window into potential dangers.
Most of the research into the safety of these ultra-tiny nanoparticles — found more and more in a wide variety of products — uses test-tube experiments, or small marine organisms, to look at toxic effects. But a group of scientists has developed a method they think is better, based on the intestinal linings of chickens.
Their first results are striking: chickens that swallowed polystyrene nanoparticles experienced changes in how they absorbed and processed iron, an essential nutrient. While the researchers don’t think many people are gobbling mini-versions of a common plastic packaging, they hope the intestinal model will be a good way to test for potential problems with other materials.
The paper based on those results was recently published in the journal Nature Nanotechnology.
Co-author Gretchen Mahler, an assistant professor of bioengineering at Binghamton University, said the point of the experiments was to see whether chronic exposure to a relatively low dose of nanoparticles — what a person might get from taking a drug or a dietary supplement, for example — might have a long-term impact.
“I think the answer, based on our research, is yes,” she said.
Nanotechnology leverages the often-unique properties of super-small particles to create products with amazing qualities. These materials can make better batteries or lighter and stronger bike frames, as well as new medical instruments and medicines that can save lives. They’re increasingly common in consumer products, from “mineral-based” sunscreens to stain-repellent pants to boat paints that resist algae growth.
Nanomaterials are believed to hold great promise for a wide variety of applications. But their ultra-tiny size also gives them different properties, and scientists are struggling to figure out whether that can make them dangerous in the process, and how and why it happens.
It’s unclear exactly how many products are out there that could cause people to ingest nanoparticles. But these materials are turning up in a variety of places, from anti-microbial food packaging to wrinkle-fighting creams.
Mahler and her co-authors ran their study in two ways: using a test-tube culture of human intestinal cells, and using live chickens. They found that short-term exposure changed the way cells and the bloodstream dealt with iron.
After a longer-term exposure, they saw changes in the chicken intestines. The villi — tiny fingers that are crucial to the absorption of nutrients into the bloodstream — broadened their surface area, allowing iron to be absorbed more easily.
If those changes were to happen inside the human body, with other nanoparticles, it could mean that swallowing these tiny materials could change how our bodies interact with an assortment of other nutrients or substances.
Mahler said as the number of nano-enabled products increases, it’s important to know where the small impacts might be happening, rather than just the ones that are immediately obvious.
“That was the idea behind our study, to look at some of the more subtle effects of nanoparticle exposure,” she said. “We just want people to know that there are physiological ramifications to this exposure, whether they’re good or bad … the body of our animal model is remodeling and changing in response to this exposure. That’s something that needs to be considered.”
She said the team chose polystyrene because it’s easy to get, and because the particles show up well in experiments. The group plans to use the same methods to study other nanomaterials, and test how they affect the body’s ability to process other nutrients. Mahler said they’re especially interested in fat-soluble vitamins, such as Vitamins A, D, E and K.
Chickens will definitely be part of those tests, she said. Chickens’ guts resemble those of their human counterparts, Mahler said, much more than those of mice or rats, the most common mammalian test subjects. That means test results are more likely to predict what would happen in people.
The human cellular model also has advantages, she said, because it can potentially be scaled up and used to test a wide variety of particles. That’s key in the area of nano-related safety research, since the sheer number of ultra-tiny materials that need vetting is fairly daunting.
“The idea is that you want to do the best job that you can mimicking this tissue outside of the body, so you can make the best estimate of what’s going to happen inside a human,” Mahler said.
