The 2011 annual meeting of the American Academy of Dermatology (AAD) in New Orleans featured coverage of nanoparticles, tiny particles that received a huge amount of interest.

Zoe Draelos, MD, consulting professor in the department of dermatology at Duke University School of Medicine, presented "Nanotechnology: Rationale and Implications" during the AAD’s "Hot Topics" symposium.

While nanotechnology was first developed in ninth-century Mesopotamia for clay pot glitter, it today holds biomedical, optical, and electronic promise.

Nanoparticles are smaller than bacteria and overlap in size with viruses, smog, fumes, and smoke. "That is how you all got your nanoparticle dose today, walking to the convention center by breathing in smog and fumes. Combustion is the most important source of nanoparticles in the environment today," Draelos says.

Nanoparticles have interesting properties that change at the nanoscale in unexpected ways. "The material properties change in nanoparticles as the percentage of atoms at the surface increases in relation to the bulk of the material. This means that nanoparticle substances have a different magnetic potential and electrical conductivity," she says. "All of this is important to us in medicine."

This is because nanoparticles may revolutionize imaging of the body and potentially the skin. "Superparamagnetism is possible in magnetic materials. The ferromagnetic materials of particles smaller than 10 nm, something like a quantum dot, actually can change their magnetization direction with room temperature thermal energy," she says. "This means they are highly unstable, but have potential medical uses."

Nanoparticles can further be injected in the form of quantum dots, which can change their magnetism with room-temperature energy or very mild magnetic fields. Because the polarity of these nanoparticles can be changed at room temperature, it might be possible to image the skin in physician’s offices, she adds.

There are other types of nanoparticles. Nanoemulsions are nanoparticles dispersed in oil water emulsion. Polymeric nanoparticles are nanoparticles coated with polyester or nylon to form smooth sphere. Liposomes the size of 25 nm can fuse to the surface of cells and deliver targeted drug-delivery systems. Quantum dots of less than 10 nm are used for electrical purposes, such as personal computing and imaging.

According to Draelos, nanoparticles are here to stay in dermatology. While there were 54 nanoparticle products worldwide by 2005, there were 1,015 nanoparticle products on the market in 2009.

"The high surface area-to-volume ratio of these very, very small particles provides an increased driving force for diffusion," she says. "What does this mean? Nanoparticles offer unique opportunities for drug delivery in and through the skin. Their very small size makes them invisible."

Nanoparticles are four to seven times smaller than a wavelength of light, which renders them invisible. Furthermore, you can take nanoparticle-size pigments that absorb visible light at one wavelength and emit it at another wavelength, producing unusual colors on the face, she says. For example, for wrinkle camouflaging purposes nanoparticles may be the future of color cosmetics.

The most abundant and most conclusive area for dermatologists is in sunscreens. Nanoparticles ZnO and TiO2 are very effective inorganic sunscreens to reflect UV radiation. But a downside is they appear white when placed on the skin surface in large particle size, larger particle size yields higher SPF.

[Source: AAD]