How nanosized particles may affect skin care products

Speaking March 1 at the 68th Annual Meeting of the American Academy of Dermatology (Academy), dermatologist Adnan Nasir, MD, PhD, FAAD, clinical assistant professor in the department of dermatology at the University of North Carolina in Chapel Hill, presented an overview of nanotechnology and how nanoparticles may eventually be used in cosmetic products.

"Research in the area of nanotechnology has increased significantly over the years, and I think there will be considerable growth in this area in the near future," said Dr. Nasir. "The challenge is that a standard has not been set yet to evaluate the safety and efficacy of topical products that contain nanosized particles."

Nanotechnology: On the Plus Side

Products incorporating nanotechnology are being developed and manufactured at an ever-growing rate, especially among clothing manufacturers that incorporate nanomaterials into fabrics to enhance stain and wrinkle resistance, and water repellence. However, Dr. Nasir explained that a substantial proportion of patents issued for nanotechnology-based discoveries are currently in the realm of cosmetic and consumer skin care products. In fact, the cosmetic industry leads all other industries in the number of patents for nanoparticles, which have the potential to enhance sunscreens, shampoos and conditioners, lipsticks, eye shadows, moisturizers, deodorants, after-shave products and perfumes.

One example of how nanoparticles are being considered for use is to improve some of the undesirable properties of skin care products. Dr. Nasir explained that when certain ingredients are included in micrometer-sized particles, which are considerably larger than nanosized particles, the result is a product than can be cosmetically unappealing.

For example, one common ingredient in broad-spectrum sunscreens, which protect the skin from both UVA and UVB rays, is avobenzone, which can make a sunscreen greasy and very noticeable when applied to the skin. Since titanium, another common sunscreen ingredient, requires an oily mixture to dissolve, a white residue can be apparent on the skin upon application. However, when these active ingredients in sunscreens are converted into nanoparticles, they can be suspended in less greasy formulations -- which seem to vanish on the skin and do not leave a residue -- while retaining their ability to block UVA and UVB light.

"While widespread use of this technology is currently under evaluation, I think one of the main benefits of nanoparticles used in sunscreens will be that the particles can fit into all the nooks and crannies of the skin, packing more protection and more even coverage on the skin's surface than microsized particles," said Dr. Nasir. "Since sunscreen formulations using nanoparticles may be more cosmetically appealing and seem to vanish when applied, consumers may be more inclined to use them on a regular basis."

Nanotechnology also is generating excitement for its potential use in anti-aging products. When properly engineered, nanomaterials may be able to topically deliver retinoids, antioxidants and drugs such as botulinum toxin or growth factors for rejuvenation of the skin in the future.

In anti-aging products, Dr. Nasir added that nanotechnology may allow active ingredients that would not normally penetrate the skin to be delivered to it. For example, vitamin C is an antioxidant that helps fight age-related skin damage which works best below the top layer of skin. In bulk form, vitamin C is not very stable and is difficult to penetrate the skin. However, in future formulations, nanotechnology may increase the stability of vitamin C and enhance its ability to penetrate the skin.

"Since anti-aging products that contain nanoparticles of antioxidants will be harder to make, we expect that these products will cost more than products using traditional formulations," said Dr. Nasir. "Once these products are determined to be safe, the consumer will have to decide if the increased costs are worth the added benefits."

Nanotechnology: Future Melanoma Treatment?

Researchers also are reviewing the use of nanomaterials for the treatment of melanoma. In particular, gold, when turned into a nanomaterial called nanoshells, has been shown to be a useful treatment for melanoma in animal studies.

According to Dr. Nasir, gold nanoshells can be engineered to absorb specific wavelengths of light. If the wavelength of light unique to a particular type of gold nanoshell is used on it, the particle generates heat. In one animal study done at MD Anderson Cancer Center in Houston, investigators joined gold nanoshells with a molecule which homes to melanoma. When these gold nanoshells are injected into mice harboring melanoma, the nanoshells accumulate in the cancerous tissue. When mice are illuminated with the proper wavelength of light, their tumors, laden with gold nanoshells, heat up and are effectively killed. The surrounding tissue, which lacks targeted gold nanoshells, is unharmed.

"Nanotechnology holds promise for new non-invasive treatment methods, particularly for challenging dermatologic conditions, such as atopic dermatitis and ichthyosis," said Dr. Nasir.

Nanotechnology: More Consumer Information Needed

Because the skin is the first point of contact and the first line of defense for newly manufactured nanomaterials, Dr. Nasir noted that many dermatologists have concerns about the potential health risks posed by nanotechnology. "Although nanotechnology is an exciting area that holds enormous potential," said Dr. Nasir, "we anxiously await the FDA's review of the safety of nanoparticles which will determine their future role in skin cancer products."