Scientists claim injecting tiny particles into people’s eyeballs could help them see infrared light
Soldiers could soon be able to see in the dark – just like superheroes – thanks to built-in night vision, a new study suggests.
Scientists have enabled mice to see in the infrared spectrum by injecting tiny particles into their eyeballs.
The US research team likened it to comic book movie heroes such as Wolverine, Captain America and Superman – who has X-ray vision.
It would enable the SAS and other elite forces to take on dangerous missions in the dark without the need for special night-time goggles.
“Movies featuring heroes with superpowers such as flight, X-ray vision or extraordinary strength, are all the rage,” said Principal investigator Professor Gang Han
“But while these popular characters are mere flights of fancy, we have used nanoparticles to confer a real superpower on ordinary mice – the ability to see near-infrared light.”
Essentially this allows an animal, or person, to see sources of heat. All objects emit infrared light.
But it is invisible to the human eye – so we use infrared cameras to detect it. Known as “thermal imaging”, it is useful for detecting people, including an enemy, in the dark.
“When we look at the universe, we see only visible light,” said Prof Han.
“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.”
In the study, a special nanomaterial called UCNPs (upconversion nanoparticles) was injected into the lab rodents’ eyes around the photoreceptor cells.
UCNPs contain rare earth minerals called erbium and ytterbium, prof Han told an American Chemical Society meeting in San Diego.
These convert low-energy photons from near-infrared (NIR) light into more intense green light – that mammalian eyes can see.
Biochemist Prof Han, of the University of Massachusetts, said it could one day give built-in night vision to humans – and man’s best friend.
“If we had a super dog that could see NIR light, we could project a pattern onto a lawbreakers’ body from a distance, and the dog could catch them without disturbing other people,” he said.
Superhero style powers aside, the technology also has potentially important medical applications, such as treating diseases of the eye.
“We are actually looking at how to use NIR light to release a drug from the UNCPs specifically at the photoreceptors,” said Prof Han.
The eyes of humans and other mammals can detect light between the wavelengths of 400 and 700 nanometers (nm). NIR wavelengths are longer – between 750 nm and 1.4 micrometres.
Thermal imaging cameras can help people see in the dark by detecting NIR radiation given off by organisms or objects, but they are typically big and inconvenient.
Prof Han and colleagues got the UCNPs to the back of the mouse retina, which converts light into images, by attaching a protein that binds to photoreceptors.
Several physiological and behavioural tests then showed the animals could see and mentally process NIR light.
In one, the researchers placed them in a Y-shaped tank where one branch had a platform they could climb on to escape the water.
They trained them to swim toward triangular visible light which marked the route – which was later replaced with NIR light. A similarly lit circle marked the branch without a platform.
Prof Han said: “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.”
But Prof Han wants to improve the safety and sensitivity of the nanomaterials before trying them out in humans.
He said: “The UCNPs in our published paper are inorganic, and there are some drawbacks there.
“The biocompatibility is not completely clear, and we need to improve the brightness of the nanoparticles for human use.”
Prof Han added: “We have shown we can make organic UCNPs with much improved brightness compared with the inorganic ones.”
These organic nanoparticles can emit either green or blue light. In addition to having improved properties, the organic dyes could also have fewer regulatory hurdles.