A laboratory test has made it possible to obtain make the skin of living mice transparent at the level of the skull and abdomen, using a mixture of water and tartrazinea common food coloring. The researchers, who published their work in the journal Sciencesay it has not yet been tested on humans, but they hope it will help improve diagnostic techniques for diseases and injuries.
“The yellow dye contains molecules that absorb a large part of the light spectrum, in particular blue light and ultraviolet rayswhich would otherwise disperse upon contact with the skin,” explains Zihao Ouassistant professor of physics at the University of Texas at Dallas and lead author of the study. “Individually, they block most of the light that tries to pass through them. But by putting these elements together, we were able to make the skin of mice transparent.”
“The novelty is the substance used and its use in vivo“, he values Maria Victoria Gomez Gaviro, a senior researcher at the Gregorio Marañón Health Research Institute, in statements to Science Media Center. “An initially harmless topical dye is used to transparentize skin and peritoneum, leaving muscles and vasculature visible. This has advantages for preclinical experimentation and surgical models. Invasive procedures such as cut the skin and manipulate muscles, vessels and organs“.
The technique may seem “a magic trick“Or admit. But the key is in dissolve tartrazine in waterwhich allows its refractive index – the extent to which it reflects light – to be changed to match that of organic elements in the skin, such as lipids. In this way, the molecules reduce the ability to dissipate light, allowing it to pass through and illuminate deeper layers of tissue. The dye can then wash to reverse the effect, and its contents will be metabolized and excreted through urine.
They manage to make the skin transparent to observe the organism.
“Transparency takes a few minutes to appear,” the researcher explains. “It works like a mask or a face cream: its effect depends on how quickly the molecules spread through the skin.” Regarding its effect, applying the dye to the skulls of the mice allowed them to observe the blood vessels of the brain. In the abdomen, they came to see the vital organs and peristalsisthe muscle contraction that occurs to move food through the digestive tract.
Tartrazine, also called ‘Yellow number 5′ In the nomenclature of food additives, it is a compound approved by regulatory agencies in both the United States and the European Union. It is often found in processed foods that are orange or golden. “It is important that it is biocompatible“So it’s safe for living organisms,” Ou says. “Plus, it’s very cheap and effective: we only need a small amount for it to work.”
Human skin, next step
Researchers have not yet tested this technique on humans with skin that is about ten times thicker than that of rodents. It is also not known what dose of tartrazine needed to penetrate our dermis, nor what would be the appropriate method to administer it. “Currently, we work with ultrasound to peer deep into the living organism,” Ou reflects. “But many diagnostic methods are expensive and difficult to obtain. Our technology, on the other hand, does not have to be.”
So, this technique could improve the optical methods that exist today. “We work at the academic level and our first impression was that this could help improve biomedical research,” he recalls. “Optical instruments such as the microscope are not directly applied to the study of living beings or human patients because light cannot penetrate the skin. But now that we can make tissues transparent, this will allow us to observe dynamics in more detailand completely revolutionize biological research.
