Common Food Dye Can Make Skin Temporarily Transparent: Report

Wouldn't the doctors have it easier if our skin were transparent and they could see everything beyond or underneath it? Sounds hypothetical, no? Even with advanced technologies and highly sophisticated imaging techniques, doctors get unclear results while peeking inside a living body. However, recent research showed this distant dream may soon be a reality, surprisingly by just applying a common food dye.

Researchers at Stanford University have managed to peer into the bodies of living animals with the help of common food dye, making their skin, muscle and connective tissues temporarily transparent, The Guardian reported.

Published in Science on September 5, the research details how rubbing the FDA-approved dye solution on a mouse's skin allowed the researchers to see through the skin, without making an incision. They were able to do this with the naked eye.

The liver, intestines and bladder of the mouse were visible through the abdominal skin after the dye was applied to the belly. Not just that, the researchers even witnessed the blood vessels in the rodent's brain.

Interestingly, the treated skin regained its normal colour once the researchers washed off the dye.

“As soon as we rinsed and massaged the skin with water, the effect was reversed within minutes. It's a stunning result," said Guosong Hong, assistant professor of materials science and engineering.

How does it work?

The idea behind this echoes the approach of a character in the popular 1897 novel, The Invisible Man. In the science fiction novel, written by HG Wells, a scientist discovers how the secret to invisibility depends on matching the object's refractive index -- or the ability to bend light -- with that of the surrounding air.

When the light waves strike the biological tissue, it scatters them, thus making it appear opaque and non-transparent to the eye. The effects take place due to the difference in the refractive indices of various tissue components, like lipids and water. In the visible spectrum, water generally has a lower refractive index than lipids. This causes visible light to scatter while it passes through tissue containing both.

The researchers massaged a solution of red tartrazine on the sedated mouse's abdomen, scalp, and hindlimb to match the refractive indices of various tissue components.

Soon after, the rodent's skin turned red, indicating that much of the blue light got absorbed due to the light-absorbing molecule's presence, the study states.

The increase in absorption further altered the refractive index of water at different wavelengths -- which was red in this case. As a result, the refractive index of water matched with that of lipids in the red spectrum. Ultimately, this led to reduced scattering and made the mouse's skin appear more transparent at the red wavelength.