Scientists use laser imaging to assess safety of zinc oxide nanoparticles in sunscreen

Nov 30, 2011
Overlay of the confocal/multiphoton image of the excised human skin. Yellow color represents skin autofluorescence excited by 405 nm; Purple color represents zinc oxide nanoparticle distribution in skin (stratum corneum) excited by 770 nm, with collagen-induced faint SHG signals in the dermal layer. Credit: Biomedical Optics Express

Ultra-tiny zinc oxide (ZnO) particles with dimensions less than one-ten-millionth of a meter are among the ingredients list of some commercially available sunscreen products, raising concerns about whether the particles may be absorbed beneath the outer layer of skin.

To help answer these safety questions, an international team of scientists from Australia and Switzerland have developed a way to optically test the concentration of ZnO nanoparticles at different skin depths. They found that the nanoparticles did not penetrate beneath the outermost layer of cells when applied to patches of excised skin. The results, which were published this month in the Optical Society's (OSA) open-access journal Biomedical Optics Express, lay the groundwork for future studies in live patients.

Zinc oxide (ZnO) nanoparticle distribution in excised human skin. The black line represents the surface of the skin (top), blue represents ZnO nanoparticle distribution in the skin (stratum corneum), and pink represents skin. Credit: Timothy Kelf, Macquarie University.

The high of ZnO nanoparticles in the UVA and UVB range, along with their transparency in the visible spectrum when mixed into lotions, makes them appealing candidates for inclusion in sunscreen cosmetics. However, the particles have been shown to be toxic to certain types of cells within the body, making it important to study the nanoparticles' fate after being applied to the skin. By characterizing the optical properties of ZnO nanoparticles, the Australian and Swiss research team found a way to quantitatively assess how far the nanoparticles might migrate into skin.

The team used a technique called nonlinear , which illuminates the sample with short pulses of laser light and measures a return signal. Initial results show that ZnO nanoparticles from a formulation that had been rubbed into for 5 minutes, incubated at body temperature for 8 hours, and then washed off, did not penetrate beneath the stratum corneum, or topmost layer of the skin. The new optical characterization should be a useful tool for future non-invasive in vivo studies, the researchers write.

Explore further: Nanocontainers for nanocargo: Delivering genes and proteins for cellular imaging, genetic medicine and cancer therapy

More information: "Characterization of optical properties of ZnO nanoparticles for quantitative imaging of transdermal transport," Biomedical Optics Express, Vol. 2, Issue 12, pp. 3321-3333 (2011).

add to favorites email to friend print save as pdf

Related Stories

Low-Temperature Growth and Properties of ZnO Nanowires

Jun 01, 2004

Xuan Wang et al. from Peking University, China report in the last issue of Applied Physics Letters about ZnO nanowires grown through evaporation of zinc powders under a low temperature of 400 C. Being about 10 ...

Exposing ZnO nanorods to visible light removes microbes

May 12, 2011

The practical use of visible light and zinc oxide nanorods for destroying bacterial water contamination has been successfully demonstrated by researchers at the Asian Institute of Technology (AIT). Nanorods grown on glass ...

Consumers' close encounters with nanoparticles

Aug 10, 2011

The most personal encounter that many consumers have had so far with the much-heralded field of nanotechnology is the topic of an article in the current edition of Chemical & Engineering News (C&EN), the American Chemical Societ ...

Recommended for you

Twisted graphene chills out

58 minutes ago

(Phys.org) —When two sheets of graphene are stacked in a special way, it is possible to cool down the graphene with a laser instead of heating it up, University of Manchester researchers have shown.

Researchers use liquid inks to create better solar cells

59 minutes ago

(Phys.org) —The basic function of solar cells is to harvest sunlight and turn it into electricity. Thus, it is critically important that the film that collects the light on the surface of the cell is designed ...

User comments : 0