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Once again we are reminded that there are scientists out there working on things that the average person would have never even thought of doing, such as making the skin of living mice see-through.
What’s perhaps even crazier is that they did it using nothing more than a common food dye.
That’s right. A food dye that you might have just sitting in your kitchen cupboard, FD&C Yellow #5, made living mice transparent.
“We found that an aqueous solution of a common food color approved by the US Food and Drug Administration, tartrazine, has the effect of reversibly making the skin, muscle, and connective tissues transparent in live rodents,” the study’s authors wrote in their paper published in the journal Science.
The researchers were able to accomplish this on both the skin on the skulls as well as on the abdomens of live mice.
“For those who understand the fundamental physics behind this, it makes sense; but if you aren’t familiar with it, it looks like a magic trick,” Dr. Zihao Ou, assistant professor of physics at The University of Texas at Dallas and lead author of the study, said in a statement.
The “magic” happens because dissolving the light-absorbing molecules in water changes the solution’s refractive index — a measure of the way a substance bends light — in a way that matches the refractive index of tissue components like lipids. In essence, the dye molecules reduce the degree to which light scatters in the skin tissue, like dissipating a fog bank.
In their experiments with mice, the researchers rubbed the water and dye solution onto the skin of the animals’ skulls and abdomens. Once the dye had completely diffused into the skin, the skin became transparent. The process is reversible by washing off any remaining dye. The dye that has diffused into the skin is metabolized and excreted through urine.
“It takes a few minutes for the transparency to appear,” Ou said. “It’s similar to the way a facial cream or mask works: The time needed depends on how fast the molecules diffuse into the skin.”
After applying the dye to the skull, the researchers were able to directly observe blood vessels on the surface of the brain. On the abdomen, they could see the internal organs and the muscle contractions that move contents through the digestive tract.
Their goal is to do the same thing with humans. One of the problems with that, however, is the fact that human skin in 10 times thicker than mice.
“In human medicine, we currently have ultrasound to look deeper inside the living body,” Ou said. “Many medical diagnosis platforms are very expensive and inaccessible to a broad audience, but platforms based on our tech should not be.”
If they can figure out how to perform this same concept on humans, Ou said, “It will completely revolutionize existing optical research in biology.”