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October 29th, 2007

Does coating nanoparticles make them safe(r) for cosmetics?

Abstract:
Our title today poses a loaded question. The cosmetics industry of course would argue that their products are already safe, whether they use nanoparticulate ingredients or not. On the other hand, there are research reports that show that nanoparticles could cause DNA damage and could accumulate in organs (with unknown consequences). It has not conclusively been proven, or disproven, that nanoparticles in cosmetics applied to the (healthy) skin are able to penetrate the skin and get into the body. Sunscreens are a good example for the pro & contra discussion about nanoparticles in cosmetics. Most people use sunscreen for two reasons: to avoid getting sunburn and to avoid getting skin cancer. If applied frequently and thoroughly, sunscreens do prevent sunburn. However, no one has ever determined that sunscreens actually prevent skin cancer. Another, mostly aesthetic, limitation with sunscreens is that they don't rub into the skin very easily. You rub, and rub, and rub, but still your skin has that pasty, white appearance. That's due to the two most common active ingredients in sunscreens - zinc oxide (ZnO) and titanium dioxide (TiO2). These inorganic materials are used in sunscreen in order to reflect UV radiation and reduce the amount of organic materials necessary to achieve a specific SPF (sun protection factor) value, but the drawback is they leave that unsightly white film. To resolve this problem, manufacturers have started using nanoparticles in place of the bulk forms of zinc oxide and titanium dioxide because the smaller particle size reduces the visibility of the cream. This could potentially mean solving one problem by creating another because TiO2 nanoparticles - a major component of photovoltaic cells - emit photoelectrons when exposed to UV light. These electrons, in turn, induce the formation of peroxides, free radicals and other reactive oxygen species (ROS) which interact with lipids and DNA, causing damage which may lead to a host of medical problems. Researchers have now found clear evidence that titanium dioxide nanoparticles catalyze DNA damage. Fortunately, they also came up with a solution - by coating them - that would allow these nanoparticles to be used with less risk in cosmetics.

Source:
nanowerk.com/

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