Scientists Injected Nanoparticles Into Mice’s Eyes to Give Them Infrared Vision

By Nathaniel Scharping | February 28, 2019 10:00 am
mouse in infrared

(Credit: Shutterstock/Alison Mackey/Discover)

It’s easy to forget it, but much of the world is invisible to us. I don’t mean that in the sense of things being really tiny, or in any metaphorical way. No, most of the world is literally invisible.

That’s because what we call visible light is actually a tiny sliver of the much greater electromagnetic spectrum. The rainbow we see sits in the middle of a vast continuum of wavelengths, including everything from high energy gamma and ultraviolet radiation to much lower infrared and radio waves.

There’s a lot out there we’re missing out on. But, a group of researchers from the U.S. and China have figured out a way to let eyes see these otherwise invisible near-infrared wavelengths of light, no goggles or bulky equipment necessary. Using nanoparticles injected into their eyes that translate infrared photons to visible ones, they say they’ve given mice the ability to see beyond the visible spectrum the rest of us are confined to.

Beyond the Rainbow

The concept is fairly simple. The scientists used nanoparticles engineered to combine two photons of infrared light into a single photon that mammalian eyes could pick up. The result is that incoming infrared photons with wavelengths (read, energies) of 980 nanometers get translated into photons with wavelengths of 535 nanometers, which sits right around the green part of the visible spectrum. It effectively turned infrared light into visible light inside their eyes. Greening the planet, indeed.

The nanoparticles were coated with a protein that helps them bind to photoreceptors and injected beneath the retinas of mice, where they  grabbed onto the rods and cones that turn photons into neural messages in our eyes.

Once the mice had been upgraded, the researchers put them through a series of tests to see how they would react to their new and expanded perspective on the world. The first test was simply to monitor their pupil contractions in the presence of infrared light, which confirmed that their photoreceptors were indeed picking up on signals from the nanoparticles.

Then, they put them in a simple setup of two boxes connected by a doorway. One box was dark, the other was illuminated by infrared light. As is a mouse’s normal preference, mice with the nanoparticles consistently chose the dark box. But, mice without the nanoparticles didn’t care which box they stayed in — as infrared was the only light available, both boxes looked dark to them.

Further tests found that not only could the mice see infrared light, their perception of it was good enough that they could tell infrared-illuminated shapes apart. For this, the researchers relied on a simple water maze test that challenged the mice to find a hidden platform to stand on. The platform’s location was given by either a circle or a triangle lit up in infrared, and the mice proved themselves capable of discerning specific shapes to find it.

They also confirmed that the nanoparticles didn’t interfere with the mice’s ability to see normal light, and that they could see infrared alongside normal lighting conditions. What’s more, the researchers found no unpleasant side effects to the nanoparticle injections. The mice’s vision was undisturbed, inflammation was negligible, and the nanoparticles eventually washed out of their eyes after a period of weeks.

The researchers report their results in the journal Cell.

Infrarose-colored Glasses

So, we’re probably all thinking the same thing right about now. They made Predator mice!

The titular aliens have heat vision, and heat vision is infrared, right? Well, kind of. While paper co-author Gang Han, of the University of Massachusetts Medical School, says that the comparison is accurate, there’s a functional problem. Actually, two of them. One, the nanoparticles the researchers injected only picked up infrared photons of a specific wavelength, in the very near infrared. Heat signatures give off photons of much lower energies, far too low for the nanoparticles to pick up on. Han says that nanoparticles that can pick up heat signatures are technically possible, but they haven’t developed them yet.

The other problem with heat vision is that we’re warm-blooded mammals. Even if we did have the ability to pick up infrared photons at those wavelengths, our eyes would be inundated with photons from our own body heat. The resulting noise means that we might end up not seeing anything at all through the infrared static. Sorry about that, bodyhackers.

Science-fiction dreams aside, there are actually some real applications for technology like this, Han says. Nanoparticles that glue themselves to our photoreceptors could one day be used to help treat vision problems, he says, as well as to deliver drugs inside our eyes. He thinks that a similar technique might also be applied to photons of higher energies than we could see, granting the ability to see light in the ultraviolet spectrum as well.

Mouse and human eyes are quite similar, too, so the nanoparticles would likely work in humans with no modifications, he says. The procedure hasn’t been approved by the FDA, of course, but the kind of injection they used is already common, and the nanoparticles themselves seem to cause no harm in the mice. (Han himself says he’d do it “if my spouse says yes…”)

Vision augmented with near-infrared capabilities wouldn’t let us stalk prey through the woods, but it could potentially open up our world in other ways. Seeing new wavelengths of light might add nuance to common vistas, for example, or it might reveal things that previously cloaked themselves in invisible wavelengths.

Stargazing, for one, would never be the same. There are infrared photons streaming down to us from the stars all of the time — astronomers, in fact, often use infrared light to observe the universe.

Turning our eyes to night sky would be an entirely new experience. Stars and galaxies previously invisible would gleam, their electromagnetic transmissions revealed to our naked eyes. It would be a new perspective on the universe, a step, however small, beyond the limitations of our biological senses.

MORE ABOUT: animals, Senses, stargazing
  • Uncle Al

    1) “nanoparticles engineered to combine two photons of infrared light into a single photon” Output will vary as the square of illumination. A little bit won’t give you anything. A lot, enabling non-linear frequency doubling, may bother (e.g. cook) your retina. Pre-charging the nanoparticles (e.g, emission-metastable copper- or silver-doped zinc sulfide) is sum-limited response.

    2) “nanoparticles eventually washed out of their eyes after a period of weeks” Don’t try it through my trabecular mesh! Acute open angle glaucoma from clogging (e.g., displaced pigment granules from the rear of a dark iris rubbing against the can opener exposure of an implanted intraocular lens) might leave you seven hours of vision before your optic nerve blows out.

    3) “Han himself says he’d do” but he didn’t, did he? RFP some army privates prisoners. China chops ’em up anyway.

    • 7eggert

      Incidentally I read (or saw in a documentary) that looking into IR laser, you may see green flashes (caused by two IR photons accidentally combining their energy on the receptor molecule).The people didn’t complain about blindness, so seeing IR is possible without losing sight even without these nanoparticles.

      Fortunately it’s nanoparticles and not microplastics.

      I can imagine it’s annoying to see IR. OTOH I’m curious. OTOH, I’m not intending to be stupid.

      • Uncle Al


        Point of fact, the nanoparticles are bound to retinal cells via an intermediate adsorbed protein. Rods and cones are single photon receptors. The performance claim is then plausible.

        • 7eggert

          I’m not sure weather I made myself clear or maybe you’re referring to something else. I’ll rephrase just in case:

          According to my information, if two photons happen to hit the same molecule at the same time (which is quite unlikely), the two photons can behave like one photon with double energy / frequency. (Alternatively IR lasers would sometimes emit double-frequency photons, which also would be interesting).

          These nanoparticles have the ability to store one photon and release one green photon per two IR photons, also triggering the green receptor but much more likely.

          If the human eye can survive looking into IR laser and seeing occasional green flashes, it therefore would survive looking into the same laser while having the nanoparticles.

          • Uncle Al

            Before you post, look it up. Two-photon photoresist chemistry suppresses diffraction fringes in semiconductor fabs. Read the original paper on the nanoparticle emitters.

            Green laser pointers are frequency-doubled IR lasers. A NIR laser diode emits 808 nm. A neodymium crystal down-converter obtains 1064nm. A KTiOPO4 frequency doubling crystal emits 532 nm. Remove the front end. What was a 10 mW green laser pointer is now a 1 watt 808 nm (invisible) laser weapon, arXiv:1008.1452

  • mzsquare2

    That’s bad news for snakes, they’d go hungry…

    • The Ropo Man

      Good news for snakes, as they are cold-blooded AND they already have infrared vision!

      • mzsquare2

        My point was the opposite: mice will have the ability to see snakes at night.

        • 7eggert

          No, they see mice at night.

  • Mike Richardson

    I don’t like needles, and I really don’t like things touching my eyes, so I’ll pass on injecting nanoparticles into my eyes. But it’s a pretty interesting way of achieving enhanced vision like a metahuman, if anyone is so inclined. So much of what seemed to be only science fiction in the past is steadily becoming our reality.

  • DickFTN

    can the mice see noises too ?

  • OWilson

    Actually, we are already there with advanced EMW observation.

    The plethora of military and scientific instruments, like night glasses and telescopes can reveal all.

    Maybe just technologically advanced lenses can do a better job than invasive surgery?

  • Ralph Rivenburg

    I would love to try this.sing me up for human trials lol


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