A team at the University of Science and Technology of China injected the eyes of mice with nanoparticles that allowed the mice to respond to infrared light—a skill no mammals have. The injectable photoreceptor-binding nanoparticles were designed to absorb the incoming infrared light and transform it into visible green light. In effect, they “anchored on retinal photoreceptors as miniature NIR [near-infrared] light transducers to create NIR light image vision with negligible side effects,” the study says.

The researchers added a protein, conjugated concanavalin A, to the nanoparticle solution to help it bond with the rods and cones within the retina.

“We observed that, through the glyosidic bond, these [particles] self-anchored and remained tightly bound to the inner and outer segments of both rods and cones, forming a layer of built-in nanoantennae,” the researchers said in the study.

After injection, the researchers used pupillary light reflex experiments and electroretinogram (ERG) to record the rodents’ response to infrared light, noting the ERGs of the treatment mice “resembled that of visible light-induced responses, whereas no such signal could be detected from the non-injected control mice.”

The researcher then used several experimental mazes test the mice’s ability to visually process infrared light. In one experiment, for example, they found the nanoparticle-injected mice could find a hidden platform visible only to those who could see infrared light.

While research has a long way to go before this technology is even plausible for human eyes, the study authors already wonder about its possible future implications. “Combined with a drug delivery system, these photoreceptor-binding nanoparticles could be modified to release small molecules locally upon light stimulation,” they speculate.

The safety of the technique is still debatable, yet the researchers noted the experiment did not cause a higher rate of adverse reactions compared with a control injection, and all common minor or transient side effects such as cataracts and corneal opacity disappeared two weeks after the injections.

Yuqian Ma Y, Bao J, Zhang Y, et al. Mammalian near-infrared image vision through injectable and self-powered retinal nanoantennae. Cell. February 28, 2019. [Epub before print].