Doritos might be known for spicing up snack time, but Stanford researchers have discovered that a dye in the chips can also turn mice translucent.
The study, published on Sept. 6 in the journal Science, explains how researchers at Stanford University in California used a common food dye called Yellow No. 5 — found in various foods and beauty products — on the skin of live mice.
The dye created a temporary “window” that made their organs, muscles and blood vessels visible, the researchers said.
The technique, called “optical tissue clearing,” which has not yet been tested on humans, could potentially allow the non-invasive observation and monitoring of injuries or diseases, the authors argue.
“Looking forward, this technology could make veins more visible for the drawing of blood, make laser-based tattoo removal more straightforward, or assist in the early detection and treatment of cancers,” co-author and Stanford University assistant professor of materials science and engineering Guosong Hong said.
“For example, certain therapies use lasers to eliminate cancerous and precancerous cells, but are limited to areas near the skin’s surface. This technique may be able to improve that light penetration,” Hong said in a Sept. 6 press release.
The artificial food dye used in the experiment, tartrazine, also known as Yellow No. 5, is approved for use in the United States and Canada. It is commonly used to give yellow colour to a range of products, including Doritos, Mountain Dew, M&Ms, cereals like Cap’n Crunch, and beauty products such as shampoo, conditioner, soap and eyeliner, as well as some vitamins and medicines.
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Although tartrazine is widely used to colour foods and cosmetics, researchers sought to explore whether it could make mice’s skin translucent. So, how did they achieve this surprising effect?
Scattering of light prevents us from seeing through our bodies, the authors explained.
This is because fats, cellular fluids, proteins and other materials each have different refractive indices, which determine how much incoming light waves are bent.
To make bodies transparent, scientists wanted to make all the different parts of the tissues have the same light-bending properties.
The researcher found that tartrazine can do this.
When this dye is added to water and soaked into tissue, tartrazine molecules are structured in a way that aligns with the light-bending ability of the skin. The dye absorbs blue and purple light and allows red and orange light to travel through the tissue, resulting in transparency, the study said.
The method was first tested on thin slices of chicken breast.
As researchers increased the concentration of tartrazine, the light-bending properties of the fluid inside the muscle cells became similar to those of the muscle proteins, making the slice transparent, the researchers said.
The researchers then applied a temporary tartrazine solution to mice. On the scalp, this made the skin transparent, revealing the brain’s blood vessels. When applied to the abdomen, it showed the movements of the intestines, heart and lungs.
“Strongly absorbing dye molecules, when applied topically to biological tissues, can reduce the intrinsic light scattering within these tissues,” the study said. “This effect renders various biological tissues –including the scalp, muscle, and abdomen — transparent.”
After rinsing off the dye, the tissues quickly returned to their normal opacity, the researchers said, adding that tartrazine did not seem to have any lasting effects.
In an editorial article about the study, Christopher J. Rowlands and Jon Gorecki, both researchers of Imperial College London in the United Kingdom, argue these results will create “extremely broad interest” in the procedure.
“This approach offers a new means of visualizing the structure and activity of deep tissues and organs in vivo in a safe, temporary, and noninvasive manner,” they stated.
In a commentary published on Sept. 5, Hong noted that this technique currently only works on mice due to their relatively thin skin layers.
Human skin is much thicker, he said, “so this method isn’t quite ready for practical use on people yet.”
However, Hong and his colleagues are working to improve the technique for human tissues and hope that, eventually, it could aid in the early detection of skin cancer and simplify laser-based tattoo removal.
— with files from Reuters
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