By directly labeling tumor cells while they are in the bloodstream, some of the costs and problems associated with testing drawn blood samples can be avoided, He said.

"One sample can require five to 10 test tubes during the course of sampling, processing and analysis such as handling, labeling and washing," He said. "In addition, large hospitals can have more than 300 cancer patients in one day. Such a large influx can cause delays in sample processing and delays can affect the results of analysis."


A paper detailing the technology and detection technique was published in the July 10 Proceedings of the National Academy of Sciences. In addition to Low, He and Cheng, postdoctoral researcher Haifeng Wang and Lynn C. Hartmann, a professor of oncology and associate director for education of the Mayo Clinic Cancer Center, co-authored the paper.

The technique uses a fluorescent tumor-specific probe that labels tumor cells in circulation. When hit by a laser, which scans across the diameter of the blood vessel 1,000 times per second, the tumor cells glow and become visible. The in vivo flow detection was performed on a two-photon fluorescence microscope in Cheng's lab. The researchers compared several methods and found two-photon fluorescence provides the best signal to background ratio. The technology is able to scan every cell that is pumped through the vessel, He said.

Low's team has developed two labeling agents that attach to different forms of cancer. One label targets ovarian, non-small lung, kidney and endometrial cancer, and the other targets prostate cancer.

These labels would be administered through an injection. The first label has already been tested in humans and has no adverse side effects and could potentially be administered weekly, He said.

Computed tomography, or CT, scans and magnetic resonance imaging, or MRI, are the current methods used to track the spread of cancer. These methods have a limited resolution, and a 1 millimeter tumor could go undetected by CT or MRI. The Purdue-developed technology can achieve single-cell resolution and can detect rare cell populations.

"Our method can detect cancer cells early in disease development and the test can be conducted frequently," Low said. "Discovering the cancer early and knowing whether it has metastasized, or spread, greatly improves a patient's chance for successful treatment."

The laser penetrates to a depth of 100 microns and is able to examine shallow blood vessels near the surface of the skin. Advanced optical technology could be incorporated into the technology platform and enable the method to reach deeper vessels that handle larger volumes of blood, Cheng said.

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