Iron-containing nanomaterials can damage skin.

Feb 11, 2009

Murray, AR, E Kisin, SS Leonard, SH Young, C Kommineni, VE Kagan, V Castranova and AA Shvedova. 2009. Oxidative stress and inflammatory response in dermal toxicity of single-walled carbon nanotubes. Toxicology doi:10.1016/j.tox.2008.12.023.

Synopsis by Abby D. Benninghoff, Ph.D.

Iron-containing nanomaterials can cause inflammation and other cell damage if it touches skin, conclude the researchers who tested the particles on engineered skin, human skin cells and mice skin.

The particles may be a health risk for workers who make or use the tiny single-walled carbon nanotubes (SWCNT), as well as consumers of the final products that contain them. Development of new electronic devices, circuits and computers using these particular materials is underway.

Because they are very, very small, nanomaterials have vast potential applications in industry, engineering and medicine. However, their small size -- usually less than 200 nanometers -- also presents unique potentials for toxicity.

The manufacture of carbon-based nanomaterials relies on the use of metals as catalysts. These metals are often still present at high amounts in the finished product. The toxic properties of nanomaterials may be due to either the unique carbon structure or to the residual metal. 

Other carbon materials can cause skin disorders in people. Some metals form free radicals and cause oxidative stress that can damage cells. Although not normally harmful, iron combined with some carbon-based nanomaterials may also cause this type of cell damage.

In this study, researchers compared the toxic effects of two formulations of single-walled carbon nanotubes (SWCNTs): one batch was partially purified so that it had a very low iron content, while the other batch was unpurified and contained 30% iron. 

Using human skin cells grown in a laboratory, they compared the effects of exposure on molecular markers that indicate inflammation and oxidative stress in cells. They found that both formulations of iron-contaning SWCNTs caused free-radical formation and oxidative stress in skin cells, though the nanotubes with high iron content were more toxic. 

The researchers also tested the unpurified form on engineered human skin grown in a laboratory and on the skin of mice.  Direct topical exposure of these nanomaterials  increased the skin thickness and caused inflammation in the skin. 

It is not know if SWCNTs can follow hair follicles or otherwise penetrate to deeper layers of skin, like some other nanoparticles can. Even though, this study presents solid evidence that "unpurified SWCNT, can cause dermal toxicity associated with free radical generation, oxidative stress and inflammation."