Originally Published MDDI June 2005

R&D DIGEST

Maria Fontanazza

Researchers at Sandia National Laboratories (Albuquerque) are refining a vertical-cavity surface-emitting laser for use in early cancer detection and stem-cell research. The research could lead to advancements in diagnostics for cell diseases.

“One of the key aspects of this technology is the very high speed at which it works, using light alone to differentiate cells,” says Paul Gourley, PhD, a senior technical staff member at Sandia and the project's manager. “It doesn't use any chemicals, reagents, or fluorescent probes, so there's no need to modify the cell or incubate it with a dye. We take the cell in its physiological condition and make the light measurement in a very short period of time.”

With electrical-to-optical conversion efficiencies of about 60%, vertical-cavity surface-emitting lasers are one of the most efficient lasers yet. A bioactive laser is being designed to detect differences between normal cells and those that have transformed into cancer cells. Although the team's device was originally about as small as a cell, it needed to be smaller. They shrunk it to nearly the size of an isolated mitochondrion, about 600 nm.

“We're working on making the laser even smaller, including the auxiliary equipment that goes along with it,” Gourley explains. “Technological advances in the last several years have made the equipment smaller and less expensive. All of those things will make this a more affordable and compact unit.”

Other adjustments to the technology include making the laser that energizes the bioactive laser smaller, and speeding up the analytical software that examines the light coming out of the laser.

Gourley explains that the cells are taken into the laser and generate the laser beam. The process occurs at the speed of light. Then, he says, “the imaging device sends the information to the computer, which analyzes it very quickly. Within a couple of minutes, you can get information about whether these cells are normal or cancerous.”

When a cell turns cancerous, the mitochondrial network changes and becomes more disorganized. “In fact, it seems like the cancer cell reverts to a more primitive way of getting energy for the cell and doesn't use the mitochondrial machinery for respiration of normal cells,” says Gourley.
Using liver cells, researchers showed that the laser is sensitive to how the mitochondria are distributed in the cell. The mitochondria, which supply energy to a cell, strongly interact with light and are just about equal in size to the wavelength of the laser-emitted light.

“Once we understood how light interacted with the mitochondria, we started putting the cells that had a lot of mitochondria, like the liver cell, into the laser,” says Gourley. They were able to distinguish between the normal and cancerous cells based on the light interaction differences with the mitochondrial matrix.

Researchers are also collaborating with the University of California's Mitochondrial and Metabolic Disease Center (San Diego). The bioactive laser could be applied to study stem cells and examine the relationship between cancer and stem cells.

“There have been a lot of exciting breakthroughs recently in using adult stem cells,” says Gourley. “You want to be able to find them in the body noninvasively, so that you're not altering anything. Using light alone may be a way to do that.”

Copyright ©2005 Medical Device & Diagnostic Industry