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Cornell tests dots that light cancer cells

FDA approves the first human clinical trial using inorganic material in the same way as a drug, and it will determine whether the "C dots" are safe and effective in five melanoma patients.

Ulrich B. Wiesner, left, works with graduate students Jennifer Drewes and Kai Ma to characterize the size and brightness of C dots. Jason Koski/Cornell University

Five melanoma patients at Memorial Sloan-Kettering Cancer Center in New York are about to become subjects in the first human clinical trial approved by the Food and Drug Administration that uses inorganic material in the same way as a drug.

Dubbed Cornell dots (or "C dots" for short), the brightly glowing nanoparticles are silica spheres less than 8 nanometers (one-billionth of a meter) in diameter that hold dye molecules. Those spheres are basically glass, chemically inert and small enough to pass through the body and out in a urine stream, and for clinical use are coated with polyethylene glycol so the body will not reject them as foreign substances.

The researchers first unveiled their Cornell dots in 2005, as they explored possible uses for the nanoparticles in biological imaging, optical computing, sensors, microarrays, and more. This human clinical trial is to determine that they are safe and effective in humans.

The researchers attached organic molecules that bind to specific regions of a tumor so that they could get those dots to stick to tumor cells; once exposed to near-infrared light, those dots glow, pointing to where the tumor cells are living, the extent of a tumor's blood vessels, nearby cellular death, and the extent to which those tumors have spread to lymph nodes and/or other organs.

C dots fluoresce brightly enough to be seen through the skin of a mouse in a 2009 study. Memorial Sloan Kettering Cancer Center

In January 2009 the team confirmed that the C dots were safely and effectively cleared by kidneys in mice, and they'll be watching closely for the same results in humans. The dots will be labeled with radioactive iodine so that they are visible in PET scans and can reveal how many dots attach to tumors and how many go elsewhere in the body and for how long.

The radioactive iodine won't be necessary beyond clinical trials, as surgeons don't need to see where the dots go throughout the body, but rather simply where they have attached to target tumor cells. One of the main pros of the dots is that they stay in the body long enough for surgery to take place while they still light the way.

"The FDA approval finally puts a federal approval stamp on all the assumptions we have been working under for years," says Ulrich B. Wiesner, a Cornell professor of Materials Science and Engineering who has devoted eight years of research to developing the dots. "Cancer is a terrible disease, and my family has a long history of it. I, thus, have a particular personal motivation to work in this area."