Tiny and useful – but is it also safe?

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Antibacterial coatings comprising silver nanoparticles on textiles or in refrigerators, self-cleaning surfaces or scratch-proof paints thanks to minute titanium and silicon dioxide particles, light-reflecting particles in sun creams – nanotechnology has long been part of our everyday lives.

Nanoparticles also in food

Food can also contain nanoparticles. "Tomato ketchup would not come out of the bottle if manufacturers did not add some silicon dioxide powder to help it flow", says Thomas Schneider from the Department of Nutritional Toxicology at Friedrich Schiller University Jena (only in German). A biologist, Dr Schneider also explains that chocolate buttons are treated with titanium dioxide nanoparticles to make them shinier. Like silicon dioxide and magnesium oxide, titanium dioxide is approved as a food additive in the European Union (EU). Where it is added in the form of nanoparticles, manufacturers have to state this on the packaging.

Small enough to overcome barriers in the body

However, the aspect that gives the products their desired properties in the first place – namely the tiny dimensions of the nanoparticles – can also cause people problems. "The wall of the intestine acts as a natural barrier, preventing toxins or pathogens from entering the bloodstream", explains Dr Schneider. "Yet nanoparticles can overcome this barrier, move around the body in the blood and accumulate in all of our organs."

Studies into the potential health risks have been conducted for roughly ten years. From studies of cell samples, it is already known that particularly small particles of up to two or three nanometres in size can penetrate right to the nucleus of the cell and bring about changes in our genetic make-up. The degree of toxicity has yet to be systematically researched, however.

High reactivity causes problems

Thomas Schneider hopes to make good progress in this area over the next two years – by collaborating with Analytik Jena AG, a company specialising in analytical technology. Their joint research, which began this year, aims essentially to create an analysis platform for nanoparticles in foodstuffs. The idea is that it will be possible in future to analyse samples so precisely that the type and size of the nanoparticles they contain can be characterised. Though this may sound simple, it is in fact highly complicated because the particles occur in their pure form only in water, if at all. In foodstuffs, they quickly combine with other molecules, such as proteins. As yet it is not always clear then which constituents a nanoparticle precisely has and which forms are toxic or less toxic. The scientists in Jena plan to use an extended version of mass spectrometry for the analysis. This will identify the chemical elements that constitute the nanoparticles, measure their size and determine the concentrations in which they are present in a sample.

In a parallel step, Dr Schneider intends to investigate the impact of nanoparticles of different sizes and compositions in the lab. Using cultures made from epithelial cells that coat the wall of the intestine, he observes whether and how the particles enter the cells and whether this causes them to degenerate or die.

Threshold values still a long way off

"Our goal is to create an analysis platform that will allow us to study a sample and directly ascertain the concentration of nanoparticles", explains Dr Schneider. "However, this does not yet mean that we will be able to say which concentrations are toxic and which are safe." Nano risk research is still a long way from being able to identify the kind of threshold values that have applied for example to heavy metals and dioxins in fish, meat, milk and eggs in the EU since 2002.

DaNa2.0 – Knowledge platform for nano risk research

Germany's Federal Ministry of Education and Research (BMBF) funds scientific studies of the risks nanotechnology poses to humans and the environment. Specialist publications and reports on these research projects are documented on the public knowledge platform DaNa2.0. Furthermore, users can find specific information about individual nano materials –  which products they are used for and what is already known about their toxicological effects.