Scientists have transformed ordinary rodents into "super mice" by giving them the ability to see infrared light – a technique they believe could one day be used on humans.
The vision of the mice was enhanced by tiny nanoparticles that were injected into the eyes by two Tian Xue researchers from the China University of Science and Technology and Gang Han from the University of Massachusetts Medical School .
The mice were able to detect near-infrared light (NIR), as well as normal light, for about 10 weeks without any long-term side effects, revealed the study published Thursday in the scientific journal Cell.
Humans and mice can only see about 380 to 740 nanometers in the visible spectrum, which means that longer wavelengths such as near infrared and shorter wavelengths such as ultraviolet are invisible.
"It's a physical limit on our visible spectrum," Xue said.
The mice were injected with "up-conversion" photon nanoparticles that converted low-energy invisible protons, such as near-infrared light, into high-energy visible protons.
The particles clung to the photoreceptor cells of the mouse's eyes, allowing them to turn near-infrared light into visible light.
To prove their findings, the scientists dilated the pupils of modified mice and exposed them to near-infrared light and then measured their cerebral electrical activity. The results showed that their eyes functioned as if they saw visible light.
The mice were also tested in a Y-shaped water labyrinth to see if they could distinguish different patterns of light. They were trained to escape using a hidden platform lit by infrared light.
Modified mice were able to detect the hidden platform, while uninjected mice "made these choices randomly," the study says.
The scientific breakthrough could mean that someday, the human also will be able to detect the near infrared.
"In our study, we have shown that rods and cones link these nanoparticles and are activated by near-infrared light," said Xue. "We therefore believe that this technology will also work in human eyes, not only to generate supervision, but also to bring therapeutic solutions to deficits of red color vision in humans."