Optogenetics is a powerful method developed over the past few years that lets scientists use light to activate specific genetically modified neurons within the brain. This technology still has a lot of time left in the lab before it can help to address human diseases, but that reality may be a bit closer thanks to a team of Japanese scientists. One major limitation of optogenetics is that it requires the use of light in the green to blue color range, but the brain mercilessly scatters light in this frequency range. The scatter prevents light from reaching depths in the brain beyond just a few millimeters. Implants that penetrate and are positioned under the surface of the brain have been tried, but these are extreme measures that may prevent their use in a clinical setting.
Now researchers at the Riken research institute in Japan have demonstrated that so-called “upconversion nanoparticles” can be used as a medium to deliver the correct color light deep into the brain with enough intensity, all the while not frying brain tissue on the way to the target.
The trick is that the team’s lanthanide-based upconversion nanoparticles absorb energy as near-infrared light and emit it in the blue-green range. By seeding these particles near the target to be stimulated in the brain, one can simply shine near-infrared light onto them and activate the specially genetically modified brain cells nearby. Since near-infrared light penetrates not just the brain, but the skull as well, the researchers were able to manipulate the brains of mice completely remotely.
The researchers used a variation of the same technology to calm seizure activity within the brains of lab mice and even to evoke memory cells.
Extending the capabilities of optogenetics deep into the brain and not having to drill a hole into the scalp to use the technology is a major development for this field. We expect research using optogenetic techniques will accelerate, hopefully leading to safe and reliable ways to treat all kinds of brain-related diseases.