Scientists Give Mice Infrared Night Vision With Nanoparticles

Like us, mice can’t see in the infrared. Well, most mice can’t. There are a few rodents in a laboratory that can see infrared light after being enhanced with special nanoparticles. The team thinks a similar procedure could work on humans, giving you night vision without any bulky goggles. You just need to be willing to get nanoparticles injected into your eye.

Mice see approximately the same small slice of the electromagnetic spectrum as visible light that we do — about 380 to 740 nanometers. By injecting the nanoparticles into mice, the team led by Tian Xue from the University of Science and Technology of China and Gang Han from the University of Massachusetts Medical School added the near-infrared (800 to 1,000nm) to the mouse’s visible spectrum. Experiments confirmed the animals could see infrared light for about ten weeks after the injection, and there were no ill effects.

The key to giving these mice visual superpowers was designing a nanoparticle that could operate with the animal’s existing biology. The particles don’t replace any functionality in the eye; they simply translate near-infrared (NIR) wavelengths into something the eye can understand: light between roughly 380 and 740nm.

Tian and Gang call the material “upconverting” nanoparticles. Rodent eyes, like ours, have photoreceptor cells called rods and cones. These cells absorb light and send signals to the brain that the mouse processes as vision. The nanoparticles have tiny molecular anchors that latch onto the photoreceptors. It’s the nanoparticles that absorb the NIR wavelengths, but they convert the longer wavelengths into the visible spectrum. The mice should see NIR radiation as a green glow. So, the particles take NIR around 980nm and turn it into green light at 535nm.

Ocular cells with nanoparticles attached (white specs).

To confirm the mice were able to see NIR, the team devised a number of experiments. Following the injections, the pupil of enhanced mice would dilate when exposed to NIR light. Those without the nanoparticles had no physiological response to those wavelengths. The animals were also able to detect and respond to NIR-illuminated signs in mazes, whereas those with normal vision were left in the dark.

The study says the mice suffered no significant side effects from the nanoparticle injections. The particles separated from the photoreceptors after ten weeks, and the rodents’ normal vision was intact. Some animals did experience minor corneal clouding following the injections, but that cleared up on its own. It’s a fascinating experiment, but people probably won’t line up around the block to get nanoparticles injected in their eyes just yet. Maybe someday.

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