Researchers develop dye technique to make skin ‘invisible’

(CN) — It isn't quite the superpower of invisibility, but scientists may now be able to make certain tissues in the body transparent to help aid in the biology and medical fields.

“Looking forward, this technology could make veins more visible for drawing blood, simplify laser-based tattoo removal, or assist in the early detection and treatment of cancers,” said Guosong Hong, an assistant professor at Stanford University and one of the lead researchers, in a statement.

Hong and other Stanford University researchers demonstrate how the food-safe dye tartrazine, also known as FD&C Yellow 5, makes light pass through normally opaque tissues in a study published Friday in the journal Science.

“Certain therapies use lasers to target cancerous and precancerous cells but are limited to areas near the skin’s surface,” Hong said. “This technique may improve light penetration.”

The research team focused on how light interacts with biological tissues. Light scatters when it encounters different materials such as fats, fluids, and proteins, which prevents us from seeing through our skin or other tissues.

They found that tartrazine, which absorbs and directs light, reduces this scattering and makes tissues appear transparent.

To test their method, the researchers first applied tartrazine to thin slices of chicken breast. As they increased the dye concentration, the chicken slice became clearer.

They then tested the dye on live mice. Starting with the scalp, the dye made the skin transparent enough to reveal blood vessels in the brain.

When applied to the mice’s abdomens, the dye made the skin fade, allowing researchers to see the movement of the intestines and the beating of the heart. After rinsing, the tissues returned to their normal state with no long-term effects.

The team was also able to make these tissues transparent down to a micron scale, which is a millionth of a meter. They believe that with further testing, injecting the dye directly into tissues could provide even deeper views inside the body.

While the tartrazine dye is commonly used in food, the researchers emphasized that this technique has not been tested on humans yet, and caution should be used when dealing with dyes.

A key aspect of the study involved using an ellipsometer, a tool commonly employed in semiconductor manufacturing. This instrument enabled them to predict the optical properties of the dye and its behavior when applied to biological tissues.

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