Scientists have injected nanoparticles into the eyes of mice to give them infrared vision


infrared mouse

(Credit: Shutterstock / Alison Mackey / Discover)

It's easy to forget, but much of the world is invisible to us. I do not mean that in the sense that things are really tiny, or in a metaphorical way. No, most of the world is literally invisible.

This is because what we call visible light is actually a thin fragment of the much larger electromagnetic spectrum. The rainbow we see is in the middle of a vast continuum of wavelengths, ranging from high energy gamma and ultraviolet rays to much lower infrared and radio waves.

There are many things that we miss. However, a group of researchers from the United States and China found a way to let the eyes see these otherwise invisible infrared light wavelengths without glasses or bulky equipment. Using nanoparticles injected into their eyes that translate infrared photons into visible spectra, they claim to have given mice the ability to see beyond the visible spectrum, the rest of us being confined.

Beyond the rainbow

The concept is quite simple. Scientists have used nanoparticles designed to combine two photons of infrared light into a single photon that mammal eyes could capture. The result is that incoming infrared photons with wavelengths (reading, energies) of 980 nanometers are translated into photons of 535 nanometers wavelength, located all around the green part. visible spectrum. It effectively transformed infrared light into visible light inside their eyes. Green the planet, indeed.

The nanoparticles have been coated with a protein that helps them to bind to photoreceptors and injected under the retina of mice, where they cling to the stems and cones that turn photons into neural messages in our eyes.

Once the mice were improved, the researchers gave them a series of tests to see how they would react to their new, broader perspective on the world. The first test was simply to monitor the contractions of their pupils in the presence of infrared light, which confirmed that their photoreceptors captured the signals of nanoparticles.

Then they put them in a simple configuration of two boxes connected by a door. One box was dark, the other was lit by infrared light. As mice prefer, mice with nanoparticles have always chosen the black box. But mice lacking nanoparticles did not care about the box they were in – infrared being the only source of light available, the two boxes seemed dark.

Other tests revealed that not only could the mice see infrared light, but that their perception was good enough to distinguish infrared illuminated shapes. For this, the researchers used a simple aquatic labyrinth test that challenged the mice to find a hidden platform to stand on. The position of the platform was given by a circle or triangle illuminated in infrared, and the mice were able to discern specific shapes to find it.

They also confirmed that nanoparticles do not interfere with the mouse's ability to see normal light and that they can see infrared in normal lighting conditions. In addition, the researchers found no unpleasant side effects on nanoparticle injections. The vision of the mice was not disturbed, the inflammation was negligible and the nanoparticles were finally washed from their eyes after a period of several weeks.

Researchers report their findings in the journal Cell.

Infrared color glasses

So we are probably all thinking of the same thing now. They made Predator mice!

The extraterrestrial holders have a thermal vision and the thermal vision is infrared, right? Good type of. While the article's co-author, Gang Han, of the University of Massachusetts Medical School says that the comparison is accurate, there is a functional problem. In fact, two of them. The nanoparticles that the researchers injected capture only infrared photons of a specific wavelength, in the very near infrared. Thermal signatures emit much lower energy photons, far too low to be captured by nanoparticles. Han says that nanoparticles capable of capturing thermal signatures are technically possible, but they have not yet developed them.

The other problem with thermal vision is that we are warm-blooded mammals. Even if we had the ability to capture infrared photons at these wavelengths, our eyes would be flooded with photons from our own body heat. The resulting noise means that we may not see anything at all thanks to the infrared static. Sorry for that, bodyhackers.

Aside from science-fiction dreams, there are actually real applications for a technology like this, says Han. Nanoparticles that stick to our photoreceptors could one day be used to treat vision problems, he adds, as well as to deliver drugs into our eyes. He thinks that a similar technique could also be applied to photons of higher energies than we could see, thus allowing light to be seen in the ultraviolet spectrum.

The eyes of the mouse and the human being are also very similar, so the nanoparticles would probably work in humans without modification, he says. Of course, the procedure has not been approved by the FDA, but the type of injection they have used is already commonplace and the nanoparticles themselves do not seem to be harming the mouse. (Han himself says that he would do it "if my wife says yes …")

An improved vision with near infrared capabilities would not let us hunt our prey through the woods, but it could potentially open our world in different ways. Seeing new wavelengths of light could for example add a nuance to current viewpoints or reveal things that were previously hidden in invisible wavelengths.

Star gazing, for example, would never be the same again. There are always infrared photons coming from the stars – astronomers, in fact, often use infrared light to observe the universe.

Watching the night sky would be an entirely new experience. Stars and galaxies previously invisible would shine, their electromagnetic transmissions revealed to our naked eyes. It would be a new perspective of the universe, a step, even minimal, beyond the limits of our biological senses.

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