I know that everyone dreams of seeing outside the wavelengths attributed to our visual systems. As usual, the mice arrived first, with the help of scientific scientists. By injecting specialized nanoparticles into the light in the retina of a mouse, it is suddenly and clearly able to perceive the light in the near infrared, which may be possible to us, provided that you do not keep a needle in the eyes.
The breakthrough is what researchers at the China University of Science and Technology are calling "uptake-enhancing, injectable ocular nanoparticles that bind photoreceptors." It's actually less complicated than it looks. Well … in fact, it's quite complicated.
The human eye can only see wavelengths of light between about 430 and 770 nanometers; Above, there is ultraviolet and below, infrared. We do not see the infrared, but in sufficient quantity, we can feel the heat it transmits. All objects emit infrared, increasingly hot, which is the basis of goggles.
But if a portion of the infrared far exceeds our detection capability, a band called Near Infrared (NIR) is just below the red ones we can detect. And if you could move this NIR up with some kind of optical trick? We do it all the time, of course – convert one type of light or energy into another.
In fact, it turns out that these researchers had already created the trickery needed for another reason, namely a molecule for optogenetic triggers that would absorb the infrared light (which conveniently penetrates into many tissues) and emit a light to visible spectrum.
Nanoantennae, as the researchers call them, are biocompatible and can be combined with proteins that encourage them to bind to the photoreceptor cells in our retinas. What happens when you wrap a cell that normally detects green light with a molecule that absorbs NIR radiation (900-1000 nm) and emits something 500 nm shorter? This cell can actually consider IRs as a shade and intensity of green.
This is exactly what happened when the team injected these molecules into the eyes of mice (such subretinal injections are already practiced in humans suffering from vision problems); the animals were instantly able to detect NIR in various circumstances. Not only did an IR beam cause their pupils to constrict, but patterns projected in IR indicating a reward were reliably searched for by the mice, indicating that it was not simply a problem. 39, a general awareness, but a detailed perception in the wavelength.
Note that this differs from the colorful "thermal vision" we see in movies: night vision goggles use electronic sensors to amplify and categorize incoming radiation outside the visual range, producing these rainbow images noisy and interesting. It would be more like seeing something hot as slightly brighter (and greener) than a cooler article of the same color. You will also be able to see the clicker of the television flashing its small patterns.
The molecules also did not appear to cause serious problems in the retina, such as cell death or irritation – and the mice were still able to see IR about 10 weeks after the injection.
The team explains the importance of their discoveries:
It is important to note that these injected nanoantennae do not interfere with natural vision by visible light. The ability to simultaneously detect visible light and NIR models suggests improved visual performance in mammals by broadening the native visual spectrum without genetic modification and avoiding the use of large external devices. This approach offers several advantages over currently used optoelectronic devices, such as no use of an external power source, and is compatible with other human activities.
In other words, it could be a simple, safe and reversible way to extend the human vision far beyond our current capabilities – no batteries required. It's not really something you would want to do on a whim, but you'd better think the military would be interested. Of course, there is still a lot of work and testing to do, but this seems to be a particularly promising application of nanotechnology.
The research was published today in the journal Cell.