Killer Paper Introduces Another Application for Silver Nanoparticles

Could killer paper preserve vegetables? photo

Image: Young in Panama

The ACS' science journal Langmuir has published a paper describing a breakthrough in sonochemical coating of paper by microbiocidal silver nanoparticles. We picked up on the dramatic moniker "killer paper" over at Fast Company. The description is accurate; the scientific team of Gottesman, et. al. not only demonstrates a method for building a stable layer of silver nanoparticles on paper, they have proven that the coated paper kills E. coli and S. aureus. The antibacterial activity of the paper could make it useful as a food packaging which could extend shelf life by killing the bacteria that accelerate deterioration. But are the benefits of less food waste worth the risks of yet more nanoparticles in the products we buy? Tell the investors not to line up yet.A review of the current state of nanotechnology risk assessment done by the Scientific Committee of the European Food Safety Authority paints a picture of a field in which product technology is outstripping the advances in risk analysis methods necessary to even understand and assess the risks. In the case of silver nanoparticles, for example, there are many chemical methods to measure the amount of silver exposure. But figuring out how much of that silver is normal and how much is nano is much harder: it requires imaging technologies rather than mere chemical identification. And whereas chemical methods typically allow us to measure chemical exposures down to parts per million and even parts per billion levels quite reliably, looking for one nanoparticle part per million is like looking for a needle in a haystack.

There are also well-established toxicological methods for assessing the short-term and long-term toxicity and health risks from chemicals. But we know from a growing body of evidence that nanoparticles do not behave like normal materials, and the test methods to predict which nano-technologies might be safe and which could be harmful are in their infancy.

For example, normal toxins have what is known as a dose-response relationship in which the more of a chemical gets in your body, the more effects would be seen. This is not true for nanoparticles. It is more complex, depending not only on the total quantity of exposure but also on the particle size and surface area relative to volume. In particular, it has been observed that nanoparticles can be toxic at a much lower dose than macro-particles. It is also known that nanoparticles can cross the air-blood-barrier when inhaled, from whence they can move into the internal organs, and that some nanoparticles can cross the placental barrier.

Unfortunately, although the science is not yet advanced enough to make good risk assessments, there are already enough products in everyday use that studies are finding silver nanoparticles in waste water sludge. If killer paper does join the crowd, it will be just one more cat out of the bag.

There are some good people working hard to advance the toxicology and analytical science to support risk assessment of nano materials, many of whom know that we need to keep the cats in the bag until we know what we are doing because one or two high-profile cases of illnesses arising due to nanotechnology will cause the public to lose faith in what is a very promising technology. What this field needs now is a lot of great science like that done by Gottesman's team, extending the utility and comprehension of nano-technology, combined with strict regulations that allow only those nano-products which are truly justified by the benefits even though the risks are not fully understood.

For example, agencies might permit medical nano-technologies while putting a hold order on nano-silver socks and killer paper. Government funding should be focused predominantly on the science of nano-risk characterization, because private money for these promising technologies will tend more towards the product innovation side of the equation.

More on Nano-Technology:
Nanoparticles or No-No particles?
Report Links Nanotechnology to Fight Against Climate Change
Beware The Silver Lining: A Risk Management Review Of Commercial Nanotechnology
The Debate over Nanotechnology

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