Rubbing a common yellow food dye onto a mouse’s skin turns it temporarily transparent, so we can monitor its insides without harming the animal
By Chris Simms
5 September 2024
The yellow food coloring tartrazine changes the speed at which light travels through tissues
University of Texas at Dallas
Massaging a common food dye onto the skin of living mice turned their tissues transparent, allowing us to see their blood vessels and organs at work. The technique could one day help doctors look deeper into our bodies to diagnose conditions.
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Monitoring the internal environment of a living animal isn’t easy. When it is dead, we can take slices of its tissues or use chemicals to remove proteins and fats from them to get a better view. With live animals, some things can be viewed via scans and endoscopies, but to monitor living tissue, it often has to be cut out.
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Now, Zihao Ou at the University of Texas at Dallas and his colleagues have turned tissues transparent in living mice by rubbing the food dye tartrazine, also known as E102 or Yellow 5, onto their skin. When the skin absorbs the dye molecules, this modifies the tissue’s refractive index – the speed at which light travels through it.
The dye made organs visible in living mice Zihao Ou et al. 2024
The mice then became transparent, which enabled the researchers to see peristalsis, the muscle contractions that move food through the digestive tract, and to look into the blood vessels on the surface of their brains.