Scientists have discovered a way to 'see' through mice – could humans be next?

Imagine being able to see muscles and organs in action through your skin. It sounds like science fiction, but it's the work of a group of scientists at Stanford University. I was able to do it recently It makes the skin of live mice appear transparent, at least under certain light conditions.

There is no doubt that this breakthrough opens up new possibilities in biological research and medical imaging. So how did they do it, and could it potentially make humans invisible?

When we look at an object, light reflects off the object and our eyes can see shapes and colors. However, living tissues such as skin are composed of water, proteins, lipids (fats), etc., all of which bend light at different angles and therefore behave differently. This means that light is scattered by the skin, limiting how deep you can see inside the body without invasive surgery.

To get around this problem, scientists have developed more sophisticated imaging techniques over the years, including: two-photon microscopy and near infrared fluorescence. However, they often require harmful chemicals or only work on dead tissue. Instead, the goal has been to find ways to safely and reversibly achieve biological transparency.

In a Stanford University study, researchers focused on a surprising tool: food dye. Tartrazine (also known as E102) is a common yellow food coloring found in potato chips and soft drinks that has unique properties. When dissolved in water and applied to skin tissue, it changes how light interacts with biological substances.

Imaging of mouse internal organs

The key to this lies in the physics of light absorption and refraction, specifically something called “light absorption.” “The relationship between Kramers and Kroenig”explains how materials interact with light across a variety of wavelengths. Tartrazine has been used for many years in microscopy as a way to stain specific parts of anatomical structures to make them easier to see, but it has never been used on whole tissues in living animals.

By adding tartrazine to water and applying it to the tissue of living, anesthetized mice, the researchers were able to change the refractive index of the water in the tissue, and thus the degree to which it bends light. This brought its refractive index closer to that of lipids, allowing light to pass through the mouse's skin more easily, making the mouse appear transparent.

Remarkably, the researchers were able to observe deep structures inside the mice, such as blood vessels and muscle fibers, in unprecedented detail. In one example, we were able to see the movement of the intestines in real time through a transparent abdomen. This level of visibility was achieved without any obvious deleterious effects on the mice, such as the skin being able to return to its normal opaque state once the dye was washed away.

This discovery could be revolutionary. Imagine being able to monitor organ function or see exactly where veins draw blood without invasive procedures. It could also pave the way for breakthroughs in understanding how diseases affect the body at a microscopic level.

Is invisibility your next destination?

Although this is very interesting, making humans completely transparent remains unlikely for several reasons.

First, the transparency achieved in the Stanford study is clearly not completely invisible. Tartrazine also allows light to pass through tissue, but it works best with certain wavelengths of light, primarily in the red and infrared regions of the spectrum. This means that under normal lighting conditions, mice are practically invisible to the naked eye. Instead, it becomes transparent under specific imaging equipment designed to capture this phenomenon.

Second, this transparency only affects the tissue to which the dye is applied and is still limited by how deeply the dye can penetrate. Human bodies are much more complex than mice, and our skin is much thicker. Making the whole person transparent requires a different level of applications and technology.

For one thing, light behaves differently when passing through larger volumes of tissue. And even if the technology could be scaled up, achieving whole-body transparency would pose major challenges, such as getting the dye to reach all parts of the body uniformly without causing harm. Although tartrazine is safe to consume within daily limits, there is conflicting data that it can cause side effects and allergic reactions, and that in large doses it can be toxic to cells and cause genetic mutations. there is.

Additionally, transparency effects work by changing the way light interacts with living tissue, but do not address the issue of light absorption by other components of the body, such as bones. Bone is dense and may require other methods to become transparent. .

So, is it possible to make humans invisible? Not the way we see it in movies. However, the future may see further developments that push the boundaries of what is possible with biological transparency.