Monthly Tip Sheet Research Highlights from Biomedical Optics Express - November 2011


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Contact:
Lyndsay Meyer
The Optical Society
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lmeyer@osa.org

Monthly Tip Sheet: Research Highlights from Biomedical Optics Express - November 2011

WASHINGTON, Oct. 31—The following highlights summarize key research recently published in Biomedical Optics Express, the Optical Society's (OSA) principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in the life sciences. The journal scope encompasses theoretical modeling and simulations, technology development, and biomedical studies and clinical applications.

In this issue:

  1. Scientists Use Laser Imaging to Assess Safety of Zinc Oxide Nanoparticles in Sunscreen
  2. Researchers' New Recipe Cooks-up Better Tissue 'Phantoms'


Overlay of the confocal/multiphoton image of the excised human skin

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.

Zinc oxide (ZnO) nanoparticle distribution in excised human skin

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.

1. Scientists Use Laser Imaging to Assess Safety of Zinc Oxide Nanoparticles in Sunscreen

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. 

The high optical absorption 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 optical microscopy, 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 skin patches 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. 

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

EDITOR'S NOTE: Images of ZnO particles in excised skin are available to members of the media. Contact Lyndsay Meyer, lmeyer@osa.org.

2. Researchers' New Recipe Cooks-up Better Tissue ‘Phantoms'

Synthetic human tissue aids in testing photoacoustic and ultrasonic imaging technologies

The precise blending of tiny particles and multicolor dyes transforms gelatin into a realistic surrogate for human tissue. These tissue mimics, known as "phantoms," provide an accurate proving ground for new photoacoustic and ultrasonic imaging technologies. "The ability to provide phantoms that are capable of mimicking desired properties of soft tissue is critical to advance the development of new, more-accurate imaging technologies," said Stanislav Emelianov of the University of Texas at Austin and co-author of a paper appearing in the Optical Society's (OSA) open-access journal Biomedical Optics Express that describes an improved method for fabricating tissue phantoms.

Ultrasonic imaging uses high-frequency acoustic pulses to probe the structure of tissues. Another technique, photoacoustic imaging, uses low-energy laser pulses to create tiny acoustic waves that propagate through tissues. Certain tissues and materials (e.g. blood, nanoparticles used in certain tests, and fluorescent dyes), however, readily absorb the optical wavelengths typically used in photoacoustic imaging. By combining acoustic and photoacoustic imaging techniques, it's possible to create a more comprehensive picture of soft tissues. Designing effective imaging devices that can concurrently harness these two technologies, however, requires true-to-life phantoms. Emelianov and his colleagues have met this need by designing and testing a novel combination of additives that enable gelatin to acquire acoustical and optical properties that accurately match soft tissue in humans.

To match the acoustical properties, the researchers added 40-micron silica spheres to the gelatin. These particles help scatter the acoustical signal, matching the behavior of normal tissue. An emulsion of fat was also used to attenuate, or absorb, the acoustical signal. The fat additive also enhanced optical scattering of the mixture. The final ingredients were commercial dyes – India ink, Direct Red 81, and Evans blue – which provided similar optical absorption to natural tissues.

"These combined characteristics are of particular value because of the growing use of combined ultrasonic and photoacoustic imaging in clinical and preclinical research," says Emelianov. "Furthermore, there has been increased interest in utilizing these combined technologies in clinical applications, such as vascular imaging, lymph node assessment, and atherosclerotic plaque characterization."

Paper: "Tissue-Mimicking Phantoms for Photoacoustic and Ultrasonic Imaging," Biomedical Optics Express, Volume Vol. 2, Issue 11, pp. 3193-3206 (2011).

EDITOR'S NOTE: For interviews with authors of the papers listed above, please contact Lyndsay Meyer, lmeyer@osa.org or 202.416.1435. To get the monthly Biomedical Optics Express tip sheet, email lmeyer@osa.org or follow @OpticalSociety on Twitter.

About Biomedical Optics Express

Biomedical Optics Express is OSA's principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in the life sciences. The journal scope encompasses theoretical modeling and simulations, technology development, and biomedical studies and clinical applications. It is published by the Optical Society and edited by Joseph A. Izatt of Duke University. Biomedical Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/BOE.

About OSA

Uniting more than 130,000 professionals from 175 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.

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