Revolutionary technique makes skin transparent

The researchers were able to make the skin on the skulls and stomachs of living mice transparent, using a mixture of water and a common yellow food dye called “tartrazine” (the food dye known as FD&C Yellow 5), which is commonly found in corn flakes, candy, soft drinks, chicken broth and potato chips.

The technique has not yet been tested in humans, as food dyes can be harmful.

In the study, the researchers developed a way to predict how light will interact with dyed biological tissues. The prediction process requires a deep understanding of light scattering and refraction, especially since light changes rapidly and bends as it travels from one material to another.

The research team explained that light scattering is the reason why we cannot see through the body, as fats, fluids inside cells, proteins and other materials “each have a different refractive index,” a property that affects how much an incoming light wave bends.

In most tissues, these materials are tightly packed together, so the different refractive indices cause light to scatter as it passes through.

So the researchers sought to find a way to match the different refractive indices so that light can pass through unhindered, with the goal of making biological materials transparent.

They found that dyes that are most effective at absorbing light “can be ‘very effective’ at guiding light uniformly across a wide range of refractive indices.”

Researchers came up with the food dye tartrazine, whose molecules (when dissolved in water and absorbed by tissue) were found to be perfectly structured to match refractive indices and prevent light from scattering, resulting in transparency.

The research team first tested the technique on thin slices of chicken breast. As the concentrations of tartrazine increased, the refractive index of the fluid inside the muscle cells increased until it matched the refractive index of muscle proteins, making the slice transparent.

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The researchers then gently rubbed the mice with a temporary solution of tartrazine. First, they applied the solution to the scalp, which made the skin transparent to reveal the crisscrossing blood vessels in the brain. Then they applied the solution to the abdomen, showing the contractions of the intestines and movements caused by heartbeats and breathing.

When the dye was rinsed off, the tissue quickly returned to normal.

Dr Guosung Hong, from Stanford University in the US, who helped lead the study, said: "This technology could make veins more visible for blood draws, make laser tattoo removal easier, or aid in early cancer detection and treatment. For example, some treatments use lasers to kill cancerous and pre-cancerous cells, but they are limited to areas close to the surface of the skin. This technology may be able to improve the penetration of light into the body."

The pioneering technology, described in the journal Science, offers doctors a new way to see organs inside the body by making surrounding tissue transparent to visible light, and could eventually be applied to a range of medical uses, including identifying injuries and cancers and monitoring digestive disorders, the study said.

Source: Daily Mail - https://ar.rt.com/y92m