Nanoparticles injected in eyes might give us ‘superhuman’ night vision

27 Aug 2019

Organic nanoparticles in a vial convert invisible near-infrared light to intense blue light, which can easily be seen by human eyes. Image: Gang Han

Night-vision goggles are used by the military to see clearly in the dark, but nanoparticles could alter our eyes to make the devices unnecessary.

A team of researchers from the University of Massachusetts Medical School is set to present findings at an American Chemical Society meeting, which show that the cyborg vision for humanity could include in-built night vision.

While bulky night-vision goggles can help soldiers see in the dark as clearly as the daytime, nanoparticles could be inserted into the eye that would give us the same power using our eyes alone.

The team reported that in testing in mice, the animals’ ability to see near-infrared light was enhanced once the nanoparticles were applied.

“When we look at the universe, we see only visible light,” said Gang Han, the project’s principal investigator. “But if we had near-infrared vision, we could see the universe in a whole new way. We might be able to do infrared astronomy with the naked eye, or have night vision without bulky equipment.”

The eyes of humans and other mammals can detect light between wavelengths of 400 and 700 nanometres. However, at near-infrared light, this increases to between 750 nanometres and 1.4 micrometres. Devices that use thermal imaging work by detecting near-infrared light radiation given off by organisms or objects, but the bulkiness of these devices make them inconvenient for everyday use.

However, the team’s work looked at the potential of injecting a special nanomaterial – called upconversion nanoparticles (UCNPs) – into the eyes of the mice. These nanoparticles, which contain the rare-earth elements erbium and ytterbium, can convert low-energy photons from near-infrared light into higher-energy green light that mammalian eyes can see.

Creating super dogs

In testing earlier this year, the UCNPs were targeted at photoreceptors in mouse eyes by attaching a protein that binds to a sugar molecule on the photoreceptor surface. Then, researchers injected the photoreceptor-binding UCNPs behind the retinas of the mice.

To determine whether the mice could see in the dark, the team did a number of tests including placing them into a Y-shaped tank of water that included one branch with a platform for the creatures to escape the water. The mice were trained to swim toward visible light in the shape of a triangle that marked the escape route, but only the mice with the injection could tell the difference between the two shapes.

The UCNPs persisted in the mice for at least 10 weeks and no noticeable side effects were seen, but the team wants to continue testing before putting these particles into the eyes of humans, potentially with organic nanoparticles instead of rare-earth elements.

Discussing the next steps, Han said that the technology could be tested in service dogs. “If we had a super dog that could see near-infrared light, we could project a pattern onto a lawbreaker’s’ body from a distance, and the dog could catch them without disturbing other people.”

Colm Gorey was a senior journalist with Silicon Republic