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For years researchers have been trying to create a glowing dye that’s safe to inject inside people. The dye could be viewed by a special camera to produce deeper, sharper images from inside the body.

This fluorescent imaging can help to pinpoint tumor locations near the skin’s surface in a variety of cancers, such as head and neck, melanoma, and breast cancer.

Many of the dyes created so far have safety concerns. Some made from carbon nanotubes or quantum dots can linger in the body for days and months, caught in the liver and spleen, before being excreted slowly.

Now, researchers at Stanford University have created a dye that can be excreted through urine within 24 hours, a development that may at some point make this valuable imaging procedure available for human health care.

“The difficulty is how to make a dye that is both fluorescent in the infrared and water soluble,” says Alex Antaris, a graduate student and the first author on a recent paper in the journal Nature Materials. “A lot of dyes can glow but are not dissolvable in water, so we can’t have them flowing in human blood. Making a dye that is both is really the difficulty. We struggled for about three years or so and finally we succeeded.”

What’s more, the new dye produces images that are sharper and more detailed than before, increasing their potential value to medicine and surgery, Antaris says.

The dye produces light in a portion of the near infrared range known as the second near-infrared window, or NIR-II. Dyes emitting light in that range have long wavelengths that can escape from tissues with little scattering, thus producing better images.

The paper details how NIR-II fluorescence imaging has potential as a surgical guide because it can capture video in real time, a striking contrast to tomographic imaging techniques, which can take minutes to hours to complete one scan.

“This could enable clinical use of fluorescence imaging to reach unprecedented depth for diagnostics or imaging guided surgery,” says study leader Hongjie Dai, a chemistry professor.

Source: Stanford University