In the field of medicine, glowing dye injected beneath a patient’s skin can help doctors detect all kinds of dangerous conditions. These dyes can be used to diagnose early-stage cancers and visualize delicate internal systems like the eye. But until now, those dyes have been too harmful for safe use in humans, and they weren’t excreted from the body quickly enough to justify the risks. A team of Stanford researchers has finally developed a fluorescent dye that is completely safe for internal use, and is even more accurate than the unsafe dyes of the past.
After the fluorescent dye is inserted into the bloodstream, doctors can use high-tech imaging devices to view below the surface of a patient’s skin. The dye will glow under spectral imaging technology to identify anything from a burgeoning tumor to damaged blood vessels. Until now, glowing internal dyes have been made mostly from carbon nanotubes or quantum dots. Because these particles remained in the liver and the spleen for days or even months, patients were vulnerable to more internal damage than the diagnostics were worth.
The Stanford team’s new dye solution contains molecular fluorescent particles that emit light within the near-infrared range of light. Technically this range is known as NIR-II, or the second near-infrared window. This specific light range is crucial to the efficacy of the dye because it means the particles produce longer wavelengths that can be viewed through many layers of tissue and skin without scattering. Stanford’s new dye enables imaging so accurate that real-time video capture is now a possibility.
“The difficulty is how to make a dye that is both fluorescent in the infrared and water soluble,” said Alex Antaris, a graduate student on the Stanford team. The most important achievement in this new fluorescent dye is its soluble quality, which allows it to be excreted from the body within 24 hours. That tacks on a whole new level of safety to the initial benefit of vastly more accurate imaging below the skin. The fluorescent dye could spark a major step forward in medical imaging, from basic diagnostics to imaging-guided surgery.