HOUSTON, April 15, 2005 ‹Rice researchers have developed a new approach to fighting cancer that aims to both detect and destroy cancerous cells using the same, targeted nanoparticles. The research is described in the April 13 issue of the American Chemical Society¹s journal Nano Letters.

Current molecular imaging approaches solve only the detection half of the cancer management problem, said lead researchers Jennifer West, the Isabel C. Cameron Professor of Bioengineering, professor of chemical and biomolecular engineering and director of the Institute of Biosciences and Bioengineering, and Rebekah Drezek, the Stanley C. Moore Assistant Professor of Bioengineering and assistant professor of electrical and computer engineering.

³You can look for a molecular marker that may indicate a significant clinical problem, but you can¹t do anything about it,² Drezek said. ³We don¹t 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. Ultimately, we want to provide a comprehensive Œsee and treat¹ approach to cancer care.²

To this end, Drezek and West developed a new optically-based imaging and treatment method based on metal nanoshells ­ spheres measuring just a few nanometers, or billionths of a meter in diameter. Invented by Naomi Halas, the Stanley C. Moore Professor of Electrical and Computer Engineering and professor of chemistry, nanoshells consist of a silica core coated with a thin layer of gold. Because of their size, nanoshells are subject to the strange and counterintuitive forces of quantum mechanics, and as a result, they interact with light in unique ways. They scatter and absorb light of particular colors, and by varying the diameter of the core and the shell, researchers can ³tune² the shells to react to a specific wavelength of light.

In this study, the strong scattering of light by nanoshells provides the optical signal used to detect the cancer cells. West and Drezek¹s research team attached an antibody to the nanohells that binds with a protein that¹s commonly found on the surface of breast carcinoma cells and not on healthy cells. In this way, doctors can shine a harmless, non-visible beam of light through a patient¹s body and ³light up² the location of breast cancer cells The technique can be readily extended to target other types of cancer or disease processes that have known surface markers.

In prior studies, West and Halas have shown that nanoshells can be made to absorb light, convert it to heat and destroy cancer tumors.

³With nanoshells, we have the unique ability to engineer particles in which both the optical scattering and the absorption peaks occur in the near-infrared (NIR) part of the spectrum,² West said. ³That¹s the spectral region where light best penetrates tissue, and because NIR light is also completely harmless to normal tissue, this method opens the door for a non-surgical means of both imaging and treating cancer.²

The new approach has some significant advantages over other alternatives that are under development. For example, optical imaging is much faster and less expensive than other medical imaging modalities. And while nanoparticle contrast agents are being developed for use with such technologies as computed tomography, or CT scans, and magnetic resonance imaging, or MRI, gold nanoparticles are regarded as more biocompatible than other types of optically active nanoparticles, such as quantum dots.

Gold is a chemically inert material well-known for its biocompatibility, which is why it has found use in a variety of medical applications in the past.

³There is a prior history of the use of gold inside the body that makes the safety issues somewhat easier to address,² Drezek said.

Any new technology requires extensive safety assessment before coming to market. Nanospectra Biosciences Inc., a Houston-based company that is commercializing nanoshells technology, has conducted initial evaluations of nanoshells and found no ill effects.

Rice University is consistently ranked one of America¹s best teaching and research universities. It is distinguished by its: size‹2,850 undergraduates and 1,950 graduate students; selectivity‹10 applicants for each place in the freshman class; resources‹an undergraduate student-to-faculty ratio of 6-to-1, and the fifth largest endowment per student among American universities; residential college system, which builds communities that are both close-knit and diverse; and collaborative culture, which crosses disciplines, integrates teaching and research, and intermingles undergraduate and graduate work. Rice¹s wooded campus is located in the nation¹s fourth largest city and on America¹s South Coast.