Bottom line: Researchers have created an injection that allows mice to see in the dark. The solution is comprised of nanoparticles and may eventually be used in humans for various applications.
Scientists from the University of Science and Technology of China and the University of Massachusetts have developed nanoparticles that when injected into the eyes, gave mice near-infrared (NIR) vision allowing them to see in the dark.
"Mammals cannot see light over 700 nm in wavelength. This limitation is due to the physical thermodynamic properties of the photon-detecting opsins," the study published in Cell reads. "To break this limitation, we developed ocular injectable photoreceptor-binding upconversion nanoparticles (pbUCNPs)."
The pbUCNPs, also called "nanoantennae," attach themselves to retinal photoreceptors and act "as miniature NIR light transducers." In other words, the particles convert infrared light into green light. This allows the retinas to register images in NIR the same way infrared goggles do.
The scientists confirmed this by studying the behavior and physiological reactions of mice treated with the particles. Examination of the pupils showed them constrict when exposed to near-infrared light, even from a very low power source. The control mice pupils did not react at all to the NIR light.
They also used single-photoreceptor recordings, electroretinograms, cortical recordings, and visual behavioral tests to confirm that the mice saw in the dark.
"We demonstrated that mice with these nanoantennae could not only perceive NIR light but also see NIR light patterns," the team explained. "Excitingly, the injected mice were also able to differentiate sophisticated NIR shape patterns."
Even more impressive was the discovery that the particles did not interfere with normal daylight vision. The mice were able to see NIR light and visible light simultaneously.
The scientists said the injections lasted about 10 weeks and showed no signs of any adverse side effects. They see a variety of applications in humans, including correcting color blindness and military use in nighttime combat.
"This new method will provide unmatched opportunities for a wide variety of emerging bio-integrated nanodevice designs and applications," they concluded.
The team did not mention whether it was pursuing approval for trials on humans.