Nanoshells exhibit cancer-fighting potency
which uses nanoscale particles that can detect and destroy
cancerous cells. This ability differentiates it from current
molecular imaging approaches, which only detect the cancer but
don't offer a method of treatment.
"We don't want to simply find the cancerous cells. We would like to locate the cells, be able to make a rational choice about whether they need to be destroyed and, if so, proceed immediately to treatment," said Rebekah Drezek, professor in the Department of Bioengineering at Rice University.
"You can look for a molecular marker that may indicate a significant clinical problem, but you can't do anything about it [just through imaging]," she added.
Drezek and fellow professor Jennifer West, also from Rice University, developed a new method in which "nanoshells" - tiny spheres of silica coated with a thin layer of gold are used. These spheres are constructed on the nanometer scale and so they exhibit behaviour such as tunable optical properties. This allows researchers to design particles that scatter and absorb light at particular wavelengths.
The scattering of light provides the optical signal used to detect the cancer cells, which "light up" when come into nanoshell contact. The researchers designed the nanoshells to look for breast cancer biomarkers on the surface of the cancer cells. The additional ability of the particles to absorb light is used to generate heat, which then destroys the cancer cells.
The technique can be readily extended to target other types of cancer or disease processes that have known surface markers.
Nanoshells are unique in that particles can be engineered so that both the optical scattering and absorption peaks occur in the near-infrared (NIR) spectral region where light penetration through tissue is highest.
The NIR absorption also makes destruction of the targeted cells less invasive for patients because it uses a light source from outside the body that passes harmlessly through normal tissue and only heats the tissue containing nanoshells.
According to Drezek, the new approach has some advantage over other alternatives that are under development. Optical imaging is much faster and less expensive than other medical imaging techniques. Gold nanoparticles are also more biocompatible than other types of optically active nanoparticles, such as quantum dots.
Gold is a chemically inert material that is well-known for its biocompatibility, which is why it has found use in a variety of medical applications in the past.
"There is a prior history of the use of gold inside the body that makes the safety issues easier to address," Drezek said.
"Of course, any new technology requires extensive safety assessment before coming to market, but initial results from nanoshells testing are promising," she said.
Drezek and West have successfully tested the separate imaging and therapy aspects of the nanoshells in animals and are now evaluating the combined imaging/therapy nanoshells in a mouse tumour model, which they expect to complete within the next six months.
