If possessing night-vision sounds like something straight from a comic book or sci-fi novel, then the lines between fiction and reality may have just blurred as scientists at the University of Massachusetts have made an astonishing breakthrough that allows mice to see infrared light.
Image credit: Gang Han/American Chemical Society
The Massachusetts-based team developed a nanoparticle solution – made from rare earth metals, erbium and ytterbium – and then injected this directly into the eyes of the mice, just behind their retinas. Once this process was completed, the scientists put the mice through a series of physiological and behavioral tests, which after careful analysis confirmed the nanoparticles had indeed given the mice night-vision capabilities.
What these nanoparticles do is allow the mice to see infrared light, a part of the electromagnetic spectrum not detected by the human eye. What humans do see on the electromagnetic spectrum is known as the visible spectrum which can be seen as light at wavelengths between 380-700 nanometers. IR wavelengths on the other hand extend from the ‘red edge’ of the visible spectrum above 700 nanometers (frequency 430 THz), to around 1 millimeter (300 GHz).
This is why, in order for humans to see in the dark efficiently, we rely on technology such as specialized cameras or thermal imaging goggles, which convert the near-infrared light into optical wavelengths – such technologies can often be expensive and inconvenient in their size. This research offers the potential for new ways of seeing.
“When we look at the universe, we see only visible light,” states Gang Han, the projects lead investigator and researcher at the University of Massachusetts Medical School, in a recent press release.
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.
During the tests, it was tricky for Hans and his team because while the mice with these newfound capabilities of seeing IR wavelengths, the researchers could not. Developing “ocular injectable photoreceptor-binding upconversion nanoparticles,” the scientists could bind them onto photoreceptors found on the retinas of the mice. The nanoparticles then assist in the conversion of the IR wavelengths into green light which has a higher energy detectable by the eyes of mammals.
The researchers then placed visibly-lit triangular and circular surfaces at the ends of a Y-shaped tank, which had a platform at the end near to the triangular surface that could enable the mice to get out. After properly training the mice to swim towards the surfaces, the team replaced the visible triangular surface with one lit by near-infrared light.
The Mice with the particle injection could see the triangle clearly and swim to it each time, but the mice without the injection could not see or tell the difference between the two shapes.
The effects of the injections lasted for around 10 weeks.
However, while this is certainly an exciting development, the current drawback in that the rare metals used are inorganic and biocompatibility is not entirely clear. Yet, the team have begun testing similar nanoparticles made using organic dyes. “We’ve shown that we can make organic UCNPs with much improved brightness compared with the inorganic ones,” says Han.
In order to overcome the grisly process of an injection straight into the eyeballs, Hans said that the researchers have tried to create a contact lens version, “We’re not sure if contact lenses can do the same thing or not, but it’s definitely something we’re going to try,” he stated. The stalling block could be that during these trials the scientists did find that the particles must be injected into the eye’s photoreceptors which is not the same as simply placing a film onto the eyes surface.
So, will this research be the initiative into creating the next-generation of human with superhero-like abilities and military surveillance techniques, or will it offer other more practical potentialities such as correcting red-color vision defects and triggering drug release with infrared light? Either way, this advancement does declare itself as an exciting step forwards as the team plan on continuing their research and development to find nanoparticles with effective biocompatibility and safety.