Mice injected with specially designed nanoparticles were shown to detect infrared light.

The ability to detect infrared radiation would vastly improve the night vision of humans, who are limited to perceiving the world in terms of visible light –– at least without wearing exterior devices designed to expand our capabilities.

Scientists in China are looking for a way to enable infrared vision without the need to wear special technology. Tian Xue, from the University of Science and Technology of China, and his colleagues have discovered that injecting mice with specially designed nanoparticles does the trick.

The nanoparticles are designed to stick to light-detecting cells within the retina. Once attached, the nanoparticles absorb incoming infrared light and emit it as green light, which can be detected and responded to. These nanoparticles were developed by Gang Han of the University of Massachusetts Medical School. He originally developed a version of the nanoparticles for use in optogenetics, the control of the behavior of neurons with light, which has significant promise for treating various brain diseases.

Han was intrigued by the idea of using the particles to affect the vision of mice, so he bound the protein ConA to the nanoparticles to allow them to adhere to light-detecting cells of the retina. The nanoparticles formed an even and durable layer over the cells once injected. Mice with the injected particles exhibited a subconscious reaction when an infrared beam was shone in their eyes. In addition, treated mice given the option to stay in a dark room or one bathed in infrared light preferred the dark room, indicating that the other room was too bright.

There are questions about whether this technology would work in humans. First, a large quantity of infrared light is needed for the nanoparticles to generate detectable amounts of green light –– perhaps unreasonable levels for human eyes. The researchers must also establish how long the particles remain in the eye, where they end up (especially other organs) when they become unattached and whether they cause any undesirable side effects.