Common food dye lets scientists see through skin
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Time-lapse images of blood vessels in the brain of a sedated mouse revealed by reversibly dyeing the tissues with FD & C Yellow 5 and using a technique called laser speckle contrast imaging. Credit: Stanford University/Gail Rupert/NSF
A common food dye can temporarily make the skin, tissues and muscles of a mouse transparent, revealing the blood vessels, nerves and organs inside, scientists reported Thursday.
Why it matters: The process hasn't been replicated in people but could point to new ways to detect and treat cancers, image back injuries and monitor diseases, along with a range of other medical applications.
What they found: Stanford University researchers discovered that applying a topical solution of tartrazine — the dye found in FD&C Yellow 5 — dissolved in water transforms opaque tissue into a transparent window into the inner workings of a living animal.
- When they applied the dye to the abdomen of a mouse, the scientists could see its liver, small intestine, bladder and other organs down to the resolution of microns, they reported in the journal Science.
- The blood vessels in the brain could be seen when the dye was put on a mouse's scalp and viewed with a technique called laser speckle contrast imaging.
- Rinsing off the dye with water reverses the process, they reported.
How it works: Most of the light that hits the body's tissue is scattered because the fluids and structures inside (the plasma membrane, mitochondria and others), have different refractive indices (RI) — a measure of how much light will bend when it moves through a material.
- Light scatters as it moves through these different components of the cell and the tissue appears opaque.
- The researchers' hypothesis was that dyes that strongly absorb certain wavelengths of light can shift the RI of fluids within cells.
- That could then be leveraged to reduce the contrast between the fluid and fats, proteins and other materials that make up cell structures. The process minimized unwanted light scattering and allowed the light to penetrate further into the body.
What's next: ″Looking forward, this technology could make veins more visible for the drawing of blood, make laser-based tattoo removal more straightforward, or assist in the early detection and treatment of cancers,″ Guosong Hong, a study co-author and Stanford University assistant professor of materials science and engineering, said in a press release.
