Researchers at Stanford University have achieved a feat straight out of science fiction: They’ve developed a method to make living skin temporarily transparent using a common food dye.
In an experiment reminiscent of H.G. Wells’s “The Invisible Man,” scientists used a common food dye to make the scalps and abdomens of live mice transparent. This innovative technique allowed them to see internal organs without the need for invasive surgery.
“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,” Zihao Ou, one of the study’s lead authors, said in a statement. Ou conducted the study while a postdoctoral researcher at Stanford, before joining the University of Texas faculty.
Traditional imaging methods such as X-rays, MRIs, and CT scans either involve radiation or can lead to side effects. This new approach offers a safer alternative by making tissues transparent, revealing internal details without these drawbacks, according to the statement. However, the researchers note that these findings are still preliminary.
The Science Behind the Magic
In Wells’s novel, the protagonist becomes invisible by altering his body’s interaction with light. The researchers achieved a similar effect using tartrazine, a common food dye used in candies and drinks, according to the study, which was published in the journal Science.
The researchers combined the food dye, also known as FD&C Yellow 5, with skin, and both “block most light from getting through them,” Ou said. “When we put them together, we were able to achieve transparency.”
The scientists used light-bending science to achieve this result. Consider a pencil in a glass of water. The pencil appears bent at the water’s surface because light bends differently in air and water.
A similar phenomenon occurs in tissues. Skin looks opaque because the water, fats, and proteins inside the skin each bend light differently, causing the light to scatter. Tartrazine changes how light interacts with skin, making it appear transparent under red light.
The researchers used this method to see fluorescently labeled cells and various organs such as the liver, small intestine, and bladder. They were also able to track blood flow in the brain, monitor muscle activity in the limbs, and observe the mouse’s heartbeat and breathing in real-time. They also examined the movement of neurons in the gut, gaining new insights into digestive processes.
Quick and Reversible Process
The process is reversible, according to the researchers. “It takes a few minutes for the transparency to appear,” Ou stated.
“As soon as we rinsed and massaged the skin with water, the effect was reversed within minutes,” Guosong Hong, assistant professor of materials science and engineering at Stanford University and lead author of the study, said in a statement.
A related perspective, also published on Sept. 5 in Science, explores how this method represents a major improvement over older techniques used to make tissues clear in order to see inside the body for medical purposes.
Traditional methods often use large amounts of clearing agents such as glycerol or acetic acids, which can dry out the tissue, optics researchers and authors of the perspective Christopher Rowlands and Jon Gorecki wrote. In contrast, the tartrazine method works with much smaller amounts of dye and can be easily reversed, they noted.
Potential Benefits and Applications
The new technology may also serve as a safer alternative to painful biopsies and blood draws, researchers say.
According to Rowlands and Gorecki, this method offers clearer views of tissues, which could improve diagnostic accuracy.
“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 we could just look at what’s going on under the skin instead of cutting into it, or using radiation to get a less than clear look, we could change the way we see the human body,” Hong said.
Rowlands and Gorecki also suggest that transparent tissue could improve our understanding of the brain and enhance tumor detection. They wrote that the new approach could allow deeper imaging into tissues, potentially up to 10 times more effectively than traditional methods, making it possible to study the entire mouse brain, with exciting implications for human health care treatment. This improved visibility could help locate tumors near blood vessels, even through thick layers of tissue, they said.
Challenges and Future Directions
While the results make scientists hopeful, the technique has been tested only on animals, and further tests are needed to see if it would work on thicker human skin.
Nevertheless, researchers are optimistic about the potential of this technology to transform medical imaging and diagnostics, offering a safer and more accessible alternative to traditional methods.
