New Medical Research: A common food dye used to make skin and muscle temporarily transparent

New research has revealed that a common yellow-coloured food dye can temporarily make skin, connective tissues, and muscle transparent. The research was conducted on a mouse, and got some unbelievable findings, allowing for an innovative visualisation of the internal structure of the mousewithout any passive procedures.

All you should know about the research

By applying the dye to the belly of the mouse, the researchers saw its liver, intestines, and bladder clearly through the skin. When the dye was applied to the rodent’s scalp, it enabled the visualisation of blood vessels in the animal’s brain. The treated skin became normal to its natural colour after the dye was removed.

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The team then applied the yellow food dye on the mouse's underbelly, which made the abdominal skin transparent and revealed the rodent's organs and intestines. The team also experimented on the mouse’s shaved hair through laser speckle contrast imaging, leading to the transparent and clear visualisation of blood vessels in the brain.

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What are the researchers saying?

The researchers at Stanford University believethat the technique would have many potential applications in humans, from finding veins for drawing blood to locating injuries and spotting tumours.

Dr Guosong Hong, a senior researcher, said, “Instead of relying on invasive biopsies, doctors might be able to diagnose deep-seated tumours by simply examining a person’s tissue without the need for invasive surgical removal.” He added, “This technique could make blood draws less painful by helping phlebotomists easily locate veins under the skin.”

This technique is very similar to Griffin’s technique in The Invisible Man(1897), in which the scientist said that the secret to invisibility lies in matching an object’s refractive index and the ability to bend light.

For example, when light passes through our tissues, it gets scattered because of the different refractive indices of fatty membranes and cell nuclei. However, as light moves from one refractive index to another, it tends to bend, making tissue non-transparent.

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Dr Guosong Hong said, “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 in water, the more ink you add, the less light can pass through the water,” He added, “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 what we typically expect with dyes.”

The researchers have tagged the procedure as “reversible and repeatable”, with skin becoming normal once the dye is washed. At the moment, transparency is subject to the depth the dye penetrates, but Hong suggested that injections or microneedle patches could let the dye penetrate more deeply.

The procedure is yet to be tested on humans. The researchers need to ensure that the dye is safe for humans, especially, through micro-needling or injections.

Many scientists stand to benefit from this breakthrough discovery, especially those who study naturally transparent animals like zebrafish. The technique of transparency dyes will offer a much wider range of animals to be studied in this way.

(with inputs from agencies)