In the book “The Invisible Man”, written by HG Wells in 1897, the protagonist creates a serum capable of altering the refraction indices of light and, in this way, making all the cells in his body transparent.
More than 100 years later, scientists discovered a real version of the substance imagined by the science fiction writer: it is a yellow dye commonly used by the food industry in snacks and candies.
Using this substance, researchers were able to make a mouse’s skin temporarily transparent, allowing them to see its internal organs at work. The work was published in the magazine .
The discovery could revolutionize biomedical research, especially if the effect found in mice is also observed in humans. The applications in medicine are countless. Making diagnosis earlier, making it easier, and helping with fluid administration are just a few of them.
In their work, scientists managed to make the skin on the head and belly of living mice transparent by applying a mixture of water with the yellow dye called tartrazine. The hair of the mice was previously removed. After removing the solution from the animals’ skin, the transparency disappeared.
“For those who understand some basic principles of Physics, it makes perfect sense; but to those unfamiliar with it, it actually looks like a magic trick,” said the study’s lead author, Zihao Ou, a physics professor at the University of Texas at Dallas, in a press release.
In fact, there is no magic, just some basic principles of optics, the branch of Physics that studies the interaction of light with objects. The dye molecules absorb more light, causing it to pass through the skin, and suppressing the fabric’s natural ability to reflect light.
The dye, when mixed with water, has its refractive index changed — a measurement that indicates the way in which the substance refracts light.
“We combined yellow paint, which absorbs most light, especially blue and ultraviolet, with skin, which is a reflective medium,” Ou explained. “When we put the two things together, we achieved transparency in the mouse’s skin.”
When the ink is fully spread onto the skin, it becomes transparent. “It takes a few minutes for transparency to appear,” explained the scientist. “It depends on how quickly the skin absorbs the ink molecules.”
The scientists tested the experiment on chicken breasts before conducting it on live animals.
In mice, scientists were able to observe the , through the skin of the head. The mice’s internal organs were also visible in their abdomen, as well as muscle contractions and the path taken by food through the animals’ digestive tract.
The researchers have not yet tested the experiment on humans, and do not yet know what the necessary dosage of dye would be. Human skin is about ten times thicker than that of a mouse.
“Looking forward, this technology could make veins more visible, facilitating the process of drawing blood for examinations or administering fluids, especially in elderly patients, whose veins are often difficult to locate,” said Professor Guosong Hong, from the University from Stanford, co-author of the study, in an interview with CNN.
“More than that, this innovation can help with the early detection of cancer cells, improve the penetration of light into tissues for some treatments, and even make it easier to remove tattoos with a laser.”
There are already methods of making skin tissue transparent, but the solutions used have serious side effects, such as dehydration and swelling, and can even alter the structure of the tissues.
