Yellow food dye found in chips and candy corn turns skin transparent in mice, study says

In H.G. Wells’ 1897 science fiction novel, "The Invisible Man," the protagonist invents a serum that makes the cells in his body transparent by controlling how they bend light.

More than 100 years later, scientists have discovered a real-life version of the substance: A commonly used food coloring found in snack foods and kraken2trfqodidvlh4aa337cpzfrhdlfldhve5nf7njhumwr7instad onion kraken2trfqodidvlh4aa337cpzfrhdlfldhve5nf7njhumwr7instad candies such as tortilla chips and candy corn can make the skin of a mouse temporarily transparent, allowing scientists to see its organs function, according to a new study published Thursday in the journal Science.

The breakthrough could revolutionize biomedical research and, should it be successfully tested in humans, have wide-ranging applications in medicine and health care, such as making veins more visible to draw blood.
Light-absorbing dye molecules
The "magic" uses insights from the field of optics. Light-absorbing dye molecules enhance the transmission of light through the skin by suppressing the tissue’s ability to scatter light.

The dye, when mixed with water, modifies the refractive index — a measure of the way a substance bends light — of the aqueous part of the tissue to better match the index of proteins and fats in the tissue. The process is akin to a dissipating cloud of fog.

"We combined the yellow dye, which is a molecule that absorbs most light, especially blue and ultraviolet light, with skin, which is a scattering medium," said Ou, who conducted the study as a postdoctoral researcher at Stanford University in California.

Researchers made the skin on the skulls and bellies of live mice transparent by applying a mixture of water and a yellow food coloring called tartrazine. Washing away any remaining solution reversed the process, which did not harm the animals. The mice’s fur was removed before the application of the solution.

"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," said the study’s first author, Zihao Ou, assistant professor of physics at the University of Texas at Dallas, in a statement.