Researchers say they've developed a smart beacon hundreds of times smaller than human cells that lights only when encountering a specific disease.

The scientists at Rice University's Center for Biological and Environmental Nanotechnology say the beacon lights only when activated by particular proteases, or enzymes. Altered expression of proteases is a common hallmark of cancer, atherosclerosis, and many other diseases.

Other groups have used targeted nanostructures, including quantum dots, for molecular imaging, but they have never been able to adequately solve the problem of clearly distinguishing between the 'cancer is here' signal and the background light which arises from nanostructures not specifically bound to their molecular targets, said co-lead author Jennifer West, director of CBEN's biological research program.

The new technology solves that problem by using emissive nanoparticles emitting light in the near-infrared, a rare portion of the spectrum that has no background component in biomedical imaging.

Near-infrared light also passes harmlessly through skin, muscle and cartilage, so the probes could alert doctors to tumors and other diseases sites deep in the body without need for biopsy or invasive surgery.

The study is detailed in the September issue of Biochemical and Biophysical Research Communications.