X-rays, ultrasounds, and other forms of medical imaging can help us peer inside the human body without actually cutting it open. But Zihao Ou, 32, is taking a more radical approach: making skin, muscle, and connective tissue transparent, allowing scientists to see the mouse organs within.
Early in his research, Ou, a biophysicist, was interested in how electromagnetic waves—such as visible light and ultraviolet—interact with nanoparticles and molecules in the body.
When light waves hit a surface, there’s a scattering effect. Light bounces off the bubbles in a glass of fizzy water to give the water a milky, opaque appearance. Similarly, light hits lipids, proteins, and fats inside the body, making us opaque.
Ou realized there might be a way to reduce this scattering effect. If he introduced a molecule that could absorb the specific wavelength of light being used, the light could make a straight path without being deflected in other directions.
With the theory in place, Ou and his colleagues tried to find such a molecule. It had to be efficient, so that a small amount of it would allow for strong light absorption (which would look like a strong color), and it also had to be safe.
Ou shot off an email to a company that makes food dyes and flavorings, asking for a range of samples to test out on pieces of chicken breast. One of the samples, a yellow often added to chips, cereals, and soft drinks, worked: It absorbed light, reducing scattering. Within minutes of being applied, it appeared to turn the chicken breast see-through. The team placed the logo of Stanford University (where the research took place) underneath the chicken, and watched as it gradually became more visible.
A living mouse was next. When Ou and his colleagues rubbed a cream containing the dye onto the belly of a mouse, the animal’s internal organs started to become visible within “a few minutes,” he says. “You can see the intestines, the liver, and sometimes the bladder as well,” he adds.
After Ou and his colleagues published their finding in Science, the jokes started coming. Other scientists asked Ou if he’d made his discovery by accidentally forgetting to wash his hands after eating a bag of Doritos or some other snack, he says. His response: “I wish!”
His next challenge is to find a way to make human skin (which is much thicker than mouse skin) transparent. For that, he’ll need molecules that are able to absorb even more light. Ou and his colleagues are also exploring ways to improve medical imaging. “We really hope that within the next five or 10 years, we’ll be able to [demonstrate the use of] this technology for patients,” he says.
