Posted: April 3, 2008

Metallic nanoshells shine light on cancer

(Nanowerk News) Clinicians may soon be able to add metallic nanoshells to the arsenal of weapons that they can use to preserve and protect human health. Metallic nanoshells— super tiny spheres composed of layers of differing materials—allow light to safely penetrate deep within tissues to help diagnose or treat disease, says bioengineer Jennifer West. West will discuss her current work with nanoshells at the second annual Johns Hopkins 2008 NanoBio Symposium, hosted by the Institute for NanoBioTechnology, on May 1 -2 at the School of Medicine.
West is the Isabel C. Cameron Professor of Bioengineering at Rice University in Houston, Texas. She was previously named one of the world’s 100 Top Young Innovators by Technology Review, the innovation magazine of the Massachusetts Institute of Technology, where she earned her undergraduate degree.
Nanoshells have the ability to be “optically tuned,” West says. “Depending on their size and composition, we can make them either absorb or scatter light anywhere in the electromagnetic spectrum.”
This property of optical tuning means nanoshells can either heat up locally to destroy tumor tissue or reflect light back to improve imaging—or both—over a range of light wavelengths. The materials used for each layer of the nanoshell determine the wavelengths over which the device can be tuned. A typical nanoshell can be fabricated by fusing an outer layer of a biocompatible metal, such as gold, over an inner core of silica, West says, though other materials also are used.
Since the nanoshells typically “tune” over a very narrow range of near infrared light (from 700-900 nanometers in the spectrum), they will neither heat up the water in tissues nor will they be absorbed by hemoglobin in blood or melanin in the skin, West explains, This property prevents the nanoshells from causing collateral damage to the surrounding tissues.
“A light shone from outside the body can pass harmlessly through tissue,” West says. “There is such deep penetration of light that this technology can be used for whole breast biopsy and whole brain imaging.”
The property of optical tunability also makes nanoshells an excellent tool for detecting viruses and bacteria in whole blood, West adds. Nanoshells with antibodies attached to their surfaces interact with the antigen in question and form clumps. The clumps diffuse the light reflected by the nanoshells, West explains, and one can determine the concentration of whatever is being studied by the degree of diffusion.
West says that she and the inventor of the nanoshell—Naomi Halas, the Stanley C. Moore Professor of Electrical and Computer Engineering and Professor of Chemistry at Rice—are currently working with a Texas firm to commercialize the use of a nanoshell-based medical device for clinical use.
Source: Johns Hopkins University
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