To Nano or Not to Nano

Nanotechonology is the latest industrial leap into the future. In the 1970s the rise of the microchip dramatically shrunk the machines around us and embodied the age of portable technology.  In 2010 however ‘micro’ is a large and lumbering beast compared to the diminutive ‘nano’. Today’s consumer is faced with a new range of products emblazoned with the word nanotechnology. Although the benefits of this new technology are being reaped worldwide, its potential for harm is not yet known. This has spurred the development of a new scientific field – nanotoxicology.

Nano Basics

Nanotechnology is essentially the production of tiny, engineered particles for a specific function. These particles are so small they are measured on the nanoscale. A nanoparticle measures anywhere between one and 10,000 nanometers in at least one dimension - one nanometer being equivalent to just one millionth of a millimeter! These unfathomably small particles are able to easily pass through cells, whether they be human, bacterial or viral. This is by far one of their greatest talents. Man-made nanoparticles come in many forms, with silver, carbon and titanium dominating the field.

These elements are nothing new, just the average Joes of Mendeleevs periodic table. However if you grind them down hard enough (attrition) or apply enough pressure and heat (pyrolysis), their hidden superpowers are revealed. For example, in the case of silver its power lies in anti-microbial activity. When these substances are engineered to such a tiny scale their physical, chemical and optical properties change quite strikingly – we are now observing behaviours we have not seen before. These revelations have already trickled down from lofty research laboratories and into our local stores. 

Everyday Nano

Clothing just got hi-tech. Fancy some silver nano socks? This new weave purports superior anti-odour properties due to the anti-bacterial activity of silver nano ions. Going on a beach holiday? Well best not forget your nano sun block, with greater penetration into the skin it provides more comprehensive UV protection through titanium dioxide nanospheres. Stain-resistant nano trousers anyone? Cotton nanofibers are constructed in such a way that water is not absorbed, so the next time a glass of wine is inadvertently spilt on you, it will simply run off.

Beyond the frivolity of anti-wrinkle shirts, bouncier tennis balls and lighter golf clubs (thanks to cotton nanofibers, clay nanocoatings and carbon nanotubes, respectively), nanotechnology is also changing the face of modern medicine. The ease with which nanoparticles can enter cells is being exploited for more efficient drug delivery, such as with the anti-cancer drug Doxil [ALZA Corporation]. Nanocrystals are also making their mark, both in anti-nausea treatment (Emend, Merck & Co., Inc.) and in immunosuppression for organ transplantation (Rapamune, Wyeth).

Nanotechnology has also been adopted in treating everyday scrapes and gashes. Silver nanoparticle wound dressings provide additional anti-microbial protection. Aluminosilicate nanoparticle dressings [QuikClot, Z-Medica Corporation] speed up blood clotting by sifting out small molecules such as water from the blood, leaving behind a more concentrated mix of clotting factors.

The number of nanoparticle based products is rapidly growing, both in the commercial and medical industries. Since 2006 the number of products available has increased by almost 380% [Figure 2] and has spread worldwide. Nanoparticle products are now available in the USA, UK, Japan, Israel, Malaysia and the list goes on.

Nanotoxicology Emerges

The hype around nanotechnology continues to grow, but as it does, questions regarding its safety are being raised more vociferously. As with any new technology, legislation needs to be implemented to protect the safety of those making the products and those buying them. But what are the safety limits?

Research is now underway to answer this question, using the well established animal models of mice and zebrafish. Studies in mice have shown nanoparticles can accumulate in major organs such as the lungs and liver [Xie G et al Arch Toxicol 2009]. It is still uncertain whether these accumulations can trigger the development of cancer or whether they simply remain inert. However a clearer image is materialising from studies in zebrafish and human cell lines.

In zebrafish embryos metal nanoparticles were shown to accumulate in the brain and heart and resulted in cardiac abnormalities as well as developmental defects [Asharani PV Nanotechnology 2008]. Studies in human cells have shown metal nanoparticles can induce the production of reactive oxygen species (ROS) – a sign of oxidative stress [Li Y J Nanosci Nanotechnol 2010]. This stress may be the cause or consequence of other defects observed in these nanoparticle-exposed cells. Defects including DNA damage and metabolic imbalances [Asharani PV ACS Nano 2009].

Although data is accumulating suggesting nanoparticles have the potential for harm, thankfully there are no known cases of nanotoxicity in humans. The history of technological advancement sadly goes hand in hand with stories of ill health; from the tales of coal miners at the turn of the twentieth century to asbestos factory workers. However health science has moved on from those days and we are better equipped than ever to investigate the effects of burgeoning technologies. So to nano or not to nano? The jury is still out on that one, so the choice is down to you.