News from across RSC Publishing.
Nanoparticles in sunscreens made safe
27 September 2007
Polymer-coating the nanoparticles used in sunscreens would protect DNA against any potential UV damage they might cause.
There has been recent controversy over the potentially adverse effects of using nanoparticles such as titania (TiO2) in sunscreens. TiO2 is a major component of photovoltaic cells and it is well-known that it emits a photoelectron when exposed to UV light. It is believed that these electrons go on to catalyse the production of peroxide radicals and other reactive oxygen species (ROS) which are known to react with lipids and DNA, causing damage.
Exactly what kind of titania particles sunscreen manufacturers use in their products isn't clear
The team grafted anti-oxidant molecules, made from a mixture of grape seed extracts, and an anionic polymer onto the titania particles. The multi-component polymer coating absorbs the photoelectron generated when titania nanoparticles are exposed to UV light and blocks the photocatalytic activity that causes DNA damage.
What is not clear, however, is exactly what kind of titania particles sunscreen manufacturers are already using. A spokesperson from cosmetics giant L'Oréal UK confirmed that their suncare products do contain titanium dioxide among other sun filtering ingredients. 'This may be in a microparticle form, sometimes coated, to enhance the light filtering performance,' said the spokesperson. 'We comply with all EU and national laws in ensuring the absolute safety of our products and their ingredients, which are clearly labelled on our products.'
Kerry Hanson, a research scientist at the University of California, Riverside, US, has recently published a report on the enhancement of UV-induced reactive oxygen species (ROS) in the skin due to sunscreen.2 The real question, said Hanson, is whether titania particles actually penetrate skin cells. Researchers have shown that the particles can penetrate the hair shaft, but whether or not they penetrate the surface of the skin or can travel through the nuclear membrane remains to be determined.
Even if the particles do get deep into cells, it's not clear that UV light would actually reach them there. 'If the molecules penetrate the skin, but the UV attenuation at the skin surface is great such that it does not reach the penetrated particles, then ROS will not be sensitised,' added Hanson.
Nevertheless, Hanson remained enthusiastic about the findings. '[These researchers] have come up with a clever way to reduce ROS generated by the sunscreen itself, right at the source of the ROS, which would prevent any subsequent damage that the sunscreen would have otherwise caused.'
1. W. A. Lee, N. Pernodet, B. Li, C. H. Lin, E. Hatchwell and M. H. Rafailovich, Chem. Commun., 2007, DOI: 10.1039/b709449c
2. K. M. Hanson, E. Gratton and C. J. Bardeen, Free Radical Biol. Med., 2006, 41, 1205-1212.
Link to journal article
Multicomponent polymer coating to block photocatalytic activity of TiO2 nanoparticles
Wilson A. Lee, Nadine Pernodet, Bingquan Li, Chien H. Lin, Eli Hatchwell and Miriam H. Rafailovich, Chem. Commun., 2007, 4815
Also of interest
When you apply sunscreen you might not be as well protected from the sun as you think, say researchers in Italy.
Aquatic bacteria are a potential source of natural UVA protective sunscreens, say researchers in Israel.
Australian scientists call for biological and toxicological testing of nanomaterials.