Source-edition.cnn.com
Scientists have made a surprising discovery that could revolutionize medical and scientific imaging. A common food dye, Tartrazine (also known as Yellow 5), which gives certain sodas and snacks their characteristic orange hue, can temporarily turn biological tissue transparent. According to a study published on September 5 in the journal Science, this discovery allows researchers to see through mouse skin and observe organs, blood vessels, and muscle tissue with exceptional clarity. This innovative method has the potential to advance microscopy and improve medical diagnostics and treatments significantly.
Christopher Rowlands, a senior lecturer and biophotonics researcher at Imperial College London, was amazed by the discovery, stating, “In optics, we spend an awful lot of time trying to increase [how well we can see into tissue] by 20 percent or 50 percent. These guys come along and they annihilate the boundary by a factor of 10.” Rowlands, who was not involved in the study but reviewed the research, emphasized the potential impact of this technique on optical imaging, which could make details more than a centimeter deep visible to the naked eye.
The Simple Science Behind the Method
The process is surprisingly simple. By massaging a solution of Tartrazine into hairless mouse skin or using microneedling, researchers achieved “complete optical transparency in the red region of the visible spectrum.” After washing off the dye, the mouse skin returns to its natural, opaque state. Guosong Hong, co-senior author of the study and a bioengineer at Stanford University, explained that biological tissues like skin are typically not see-through because light scatters as it passes through them. This scattering occurs due to the different refractive properties of water and fats in tissue.
However, Tartrazine changes the refractive index of water to closely match that of fat, allowing light to pass through the skin more directly. This effect is due to a fundamental physics principle known as the Kramers-Kronig relations, which governs how waves, such as light, behave. As a result, light can pass through the tissue almost as if it were homogeneous, providing a clear view of the inside of a mouse.
Potential for Medical and Scientific Advancements
The implications of this discovery are vast. Hong and his team arrived at this method by modeling how different dyes could alter the way light travels through tissue. After identifying Yellow 5 as a strong candidate, they tested it on various materials, including live mice and other tissue samples. Their experiments demonstrated that Tartrazine could enhance existing optical microscopy techniques, making it a valuable tool for future research.
The team also conducted an initial toxicity analysis, finding that Yellow 5 passes through the body within 24 hours with minimal inflammation, irritation, or systemic toxicity. This finding suggests that the method could be safe for broader medical applications. As Rowlands noted, the discovery is a “triumph of fundamental understanding” that could lead to new scientific insights and improved diagnostic and treatment strategies.
