Deep-brain light penetration goes wireless
6 Mar 2018 by Evoluted New Media
A team from a Japanese research institute have found a way to penetrate deep brain structures with light – an important step for the development of optogenetics.
Thomas McHugh, research group leader at the RIKEN Brain Science, has found that upconversion nanoparticles (UCNPs) can act as a conduit for laser light delivered from outside the skull. These nanoparticles absorb near-infrared laser light and in turn emit visible photons to areas that are inaccessible to standard optogenetics.
The method was used to turn on neurons in various brain areas as well as silence seizure activity and evoke memory cells. “Nanoparticles effectively extend the reach of our lasers, enabling the ‘remote’ delivery of light and potentially leading to non-invasive therapies,” said McHugh.
In optogenetics, blue-green light is used to turn neurons on or off via light-responsive ion channels. Light at these wavelengths, however, scatters strongly and is at the other end of the spectrum from the near-infrared light that can penetrate deeper into brain tissue.
“Optogenetics has been a revolutionary tool for controlling neurons in the lab, and hopefully someday in the clinic,” said McHugh. “Unfortunately, delivering light within brain tissue requires invasive optical fibers.”
UCNPs composed of elements from the lanthanide family can act as a bridge. They can be used to turn low-energy near-infrared laser light into blue or green wavelengths for control of specifically labeled cells. Though such bursts of light deliver considerable energy to a small area, temperature increases or cellular damage were not observed. “The nanoparticles appear to be quite stable and biocompatible, making them viable for long-term use. Plus, the low dispersion means we can target neurons very specifically,” says McHugh.
The team found that the nanoparticles are compatible with the various light-activated channels currently in use in the optogenetics field and can be employed for neural activation or inhibition in many deep brain structures. Nanoparticles could become a minimally invasive alternative to optical fibers for brain stimulation, and their chronic interaction with brain tissue is part of ongoing research.
The work was published in Science.
