Food dye makes mice skin transparent, aiding medical research

A revolutionary technique employs food dye to make skin transparent, providing a ‘window’ into the body. Researchers applied a mixture of water and Tartrazine, a common yellow food dye found in products like cornflakes, sweets, energy drinks, and chicken stock, to the skulls and abdomens of live mice, making their skin see-through.

This groundbreaking method, detailed in the journal Science, allows medics to view internal organs by making overlying tissues transparent to visible light. Although not yet tested on humans due to potential harmful effects of food dyes, the process proved reversible in animal tests. Scientists believe it could eventually help locate injuries, monitor digestive disorders, and identify cancers.

Dr Guosong Hong from Stanford University, who co-led the research, highlighted potential future applications such as making veins more visible for blood draws, simplifying laser-based tattoo removal, and aiding early cancer detection and treatment. He explained that current laser therapies are limited to areas near the skin’s surface, but this technique could enhance light penetration.

Read about really creative and innovative research from my colleagues @HongNeuroTech and @BrongersmaMark : a common food dye can make your skin transparent!https://t.co/aizYD8Xnv0

— Alberto Salleo (@asalleo) September 5, 2024

Researchers developed a method to predict light interactions with dyed biological tissues, requiring a deep understanding of light scattering and refraction. Scattering prevents visibility through the body, as fats, fluids, proteins, and other materials have different refractive indices, causing light to scatter.

To achieve transparency, the team aimed to match these refractive indices, allowing light to pass through uninterrupted. They found that effective light-absorbing dyes, like Tartrazine, could direct light uniformly through various refractive indices.

Tartrazine, also known as FD & C Yellow 5, dissolved in water and absorbed into tissues, matched refractive indices and prevented light scattering, resulting in transparency.

The technique was first tested on thin chicken breast slices. As Tartrazine concentrations increased, the fluid’s refractive index within muscle cells matched that of muscle proteins, making the slice transparent.

Researchers then applied the solution to mice. They applied it to the scalp, revealing blood vessels in the brain, and to the abdomen, showing intestinal contractions and heartbeats. The dye was rinsed off, and tissues returned to normal without long-term effects, as excess dye was excreted within 48 hours.

They suspect injecting the dye could provide even deeper views within organisms, impacting biology and medicine.

Dr Zihao Ou, Assistant Professor of physics at The University of Texas, Dallas, led the study. He explained that combining the light-absorbing yellow dye with skin, a scattering medium, achieved transparency. The process is similar to a facial cream or mask, requiring time for molecules to diffuse into the skin.

The dye’s biocompatibility, cost-effectiveness, and efficiency are significant advantages. However, human skin, being much thicker than a mouse’s, requires further testing to determine the necessary dosage and delivery method.

Dr Ou noted that current medical imaging technologies like ultrasound are expensive and inaccessible to many. This new technique could offer a more affordable and accessible platform for medical diagnostics and biomedical research.

He emphasized that making tissue transparent could revolutionize optical research in biology, allowing for more detailed observations of living organisms.