Mice with improved vision through nanotechnology have been able to see infrared light and visible light, reports a study published February 28 in the newspaper Cell. A single injection of nanoparticles into the eyes of the mice allowed infra-red vision for up to 10 weeks with minimal side effects, allowing them to see infrared light even during the day and with enough specificity to distinguish different shapes. These findings could lead to advances in human infrared vision technologies, including potential applications in civil encryption, security and military operations.
Humans and other mammals are limited to viewing a range of wavelengths of light called visible light, which includes the wavelengths of the rainbow. But the infrared radiation, which has a longer wavelength, is all around us. People, animals and objects emit infrared light when they emit heat. Objects can also reflect infrared light.
"The visible light that can be perceived by the natural vision of man occupies only a very small part of the electromagnetic spectrum," said senior author Tian Xue of the company. University of Science and Technology of China. "Electromagnetic waves longer or shorter than visible light contain a lot of information."
A multidisciplinary group of scientists led by Xue and Jin Bao at the China University of Science and Technology, as well as Gang Han at the University of Massachusetts Medical School, have developed nanotechnology to work with the existing structures of the eye.
"When light enters the eye and reaches the retina, rods and cones – or photoreceptor cells – absorb photons with wavelengths of visible light and send corresponding electrical signals to the brain." Han said. "Because infrared wavelengths are too long to be absorbed by photoreceptors, we are not able to perceive them."
In this study, scientists made nanoparticles capable of anchoring tightly to photoreceptor cells and acting as tiny infrared light transducers. When infrared light strikes the retina, the nanoparticles capture the longest infrared wavelengths and emit shorter wavelengths in the visible light range. The nearby rod or cone then absorbs the shorter wavelength and sends a normal signal to the brain, as if visible light had reached the retina.
"In our experiment, the nanoparticles absorbed infrared light at a wavelength of about 980 nm and converted it into light whose peak reached 535 nm, which made light appear. infrared in the form of a green color, "says Bao.
The researchers tested the nanoparticles in mice that, like humans, can not see the infrared naturally. The injected mice showed unconscious physical signs of infrared light detection, such as the constriction of their pupils, whereas mice injected only with the buffer solution did not respond to infrared light.
To test whether the mice could interpret infrared light, the researchers developed a series of labyrinth tasks to show the mouse that she could see the infrared in the light of day, simultaneously with the light visible.
In rare cases, injection-related side effects, such as opaque corneas, have occurred but have disappeared within a week. This may have been caused by the injection process alone, since the mice that received only injections of the buffer solution had a similar rate of side effects. Other tests have revealed no damage to the structure of the retina after subretinal injections.
"In our study, we have shown that rods and cones link these nanoparticles and are activated by near-infrared light," says Xue. "We therefore believe that this technology will also work in the eyes of humans, not only to generate super vision, but also to bring therapeutic solutions to vision deficits in red in humans."
Current infrared technology relies on detectors and cameras often limited by daylight and needing external power sources. Researchers believe that bio-integrated nanoparticles are more desirable for potential infrared applications in civil encryption, security and military operations. "In the future, we believe that it may be possible to improve the technology with a new version of organic-based nanoparticles, made up of FDA-approved compounds, that seem to produce further infrared vision." brighter, "Han said.
The researchers also believe that more work can be done to fine-tune the emission spectrum of nanoparticles to the human eye, which uses more cones than rods for their central vision compared to the eyes of mice. . "It's a fascinating subject because the technology we've made possible here could eventually allow humans to see beyond our natural capabilities," Xue says.
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