10-09 :: September 2010

nanotimes News in Brief

Nanoparticles // English Ivy May Give Sunblock a Makeover

M

ingjun Zhang, an associate professor of biomedical engineering at the University of

Tennessee, Knoxville, USA, along with his research team and collaborators, has found that ivy nanoparti- cles may protect skin from UV radiation at least four times better than the metal-based sunblocks found on store shelves today.

“The discovery of ivy nanoparticles‘ application to sunscreen was triggered by a real need. While hea- ring a talk at a conference about toxicity concerns in the use of metal-based nanoparticles in sunscreen, I was wondering, ‚Why not try naturally occurring organic nanoparticles?‘” Zhang said.

Zhang speculated the greenery‘s hidden power lay within a yellowish material secreted by the ivy for surface climbing. He placed this material onto a silicon wafer and examined it under an atomic force microscope and was surprised by what they found – lots of nanoparticles. The properties of these tiny bits create the ability for the vine leaves to hold almost 2 million more times than its weight. It also has the ability to soak up and disperse light which is integral to sunscreens.

“Nanoparticles exhibit unique physical and chemical properties due to large surface-to-volume ratio which allows them to absorb and scatter light,“ Zhang said. “Titanium dioxide and zinc oxide are currently used for sunscreen for the same reason, but the ivy na-

noparticles are more uniform than the metal-based nanoparticles, and have unique material properties, which may help to enhance the absorption and scat- tering of light, and serve better as a sun-blocker.”

The team’s study indicates that ivy nanoparticles can improve the extinction of ultraviolet light at least four times better than its metal counterparts. Further- more, the metal-based sunscreens used today can pose health hazards. Zhang notes some studies have shown that the small-scale metal oxides in sunscreen can wind up in organs such as the liver or brain. The team’s studies indicate that the ivy nanoparticles were less toxic to mammalian cells, have a limited potential to penetrate through human skin, and are easily biodegradable.

“In general, it is not a good idea to have more metal- based nanoparticles for cosmetic applications. They are a significant concern for the environment. Natu- rally occurring nanoparticles originated from plants seem to be a better choice, especially since they have been demonstrated to be less toxic and easily biodegradable,” Zhang said.

http://www.tennessee.edu http://web.utk.edu/~mjzhang/about_pi.html

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