Researchers at Stanford University in the US recently discovered that a common food dye can make skin and muscles temporarily transparent, opening up new perspectives for viewing the inside of the human body.
Researchers have discovered a method to make skin transparent – Photo Archive
Scientists at Stanford University have observed that a common food dye can temporarily transform the skin, muscles and connective tissues of living animals into semi-transparent materials, according to The Guardian.
In a groundbreaking experiment, the team applied tartrazine, a yellow dye used in products such as Doritos and SunnyD, to the belly of a mouse and was able to make the internal organs visible through the abdominal skin. Applying the dye to the mouse’s scalp allowed the researchers to visualize the blood vessels in the animal’s brain.
The researchers found that dye-treated skin regained its normal color after washing. They believe the method could have valuable clinical applications, including locating wounds, finding veins to draw blood from, monitoring digestive disorders and detecting tumors.
“Instead of relying on invasive biopsies, doctors may be able to diagnose deep-seated tumors simply by examining a person’s tissue, without the need for invasive surgical removal. This technique could make blood draws less painful, helping doctors easily locate veins under the skin.”, said Dr. Guosong Hong, lead researcher on the project.
The Invisible Man Experiment
The method is reminiscent of the novel “The Invisible Man” by HG Wells, where the secret of invisibility lies in aligning the refractive index of an object with that of air. Light scatters in tissues due to different indices of refraction, similar to how a pencil appears bent in a glass of water.
Dr. Zihao Ou and the Stanford team discovered that certain dyes can make light pass through skin and tissues more easily by changing their refractive index. In experiments described in Science, a chicken breast became transparent under red light after being immersed in tartrazine, a yellow food dye. The dye reduced light scattering, allowing deeper penetration.
It’s the yellow food coloring used in Doritos chips, SunnyD drink and other products in the US.
The team then applied the yellow dye to a mouse’s belly, making the abdominal skin transparent and revealing the rodent’s intestines and organs. In another experiment, they applied dye to the shaved head of a mouse and, using a technique called laser speckle contrast imaging, saw the blood vessels in the animal’s brain.
“The most surprising part of this study is that we usually expect dye molecules to make things less transparent. For example, if you mix blue pen ink into water, the more ink you add, the less light can pass through the water. In our experiment, when we dissolve tartrazine in an opaque material like muscle or skin, which normally scatters light, the more tartrazine we add, the clearer the material becomes. But only in the red part of the light spectrum. This goes against our usual expectations with dyes.” explained Dr. Guosong Hong, lead researcher.
The researchers note that the process is “reversible and repeatable,” skin regaining its normal color after washing. For now, transparency is restricted by how deep the dye penetrates, but Dr. Hong suggests that microneedle injections or patches could allow the dye to penetrate deeper.
Although the method has not yet been tested on humans, researchers hope the procedure will allow detailed studies of organs and diseases without requiring major surgery.
According to Christopher Rowlands and Jon Gorecki of Imperial College London, this technique, combined with modern imaging, could provide the visualization of an entire mouse brain or the identification of tumors beneath tissues several centimeters thick. They say there will be “an extremely broad interest” for this procedure.
“HG Wells, who studied biology under TH Huxley, would certainly have approved of this procedure” they conclude.
