Upconversion nanoparticles improve optogenetic study of neural activities

The approach offers a simpler, less-invasive alternative to fiber-optic implantation for deep brain stimulation.

Scientists from the National University of Singapore (NUS) and colleagues have developed a novel approach for deep brain stimulation. The new method uses upconversion nanoparticles developed by Professor Liu Xiaogang from the Department of Chemistry at NUS Faculty of Science to allow delivery of visible light deep into the brain to stimulate neural activities in a less-invasive manner—a method known as optogenetics.

Related: Neuronal targets for optogenetics shown to restore movement in Parkinson's disease model

Optogenetics is a widely adopted research technique in the field of neuroscience that makes use of visible light to activate or inhibit neurons in the brain, enabling researchers to examine the brain's functions. The inability of visible light to penetrate into deep brain structures, however, remains a major experimental challenge for this technique, and current deep brain stimulation still requires the insertion of an optical fiber directly into the brain.

To make deep brain stimulation less invasive, Liu and his colleagues began exploring with near-infrared (near-IR) light, known to possess significantly higher tissue penetration capability and also relatively safe for biological samples. Using a two-step process, upconversion nanoparticles are first introduced into the brain by transcranial injection. Upon reaching deep brain, the implanted upconversion nanoparticles, a unique group of luminescent nanomaterials capable of converting near-IR light into visible light, then generates visible light to stimulate the neurons. The strategy has shown to be effective in triggering memory recall and dopamine release in the team's experiments.

This novel approach offers a simpler, less-invasive alternative to fiber-optic implantation for deep brain stimulation, and holds immense potential in facilitating advancement in neuroscience.

"We have addressed a long-standing experimental challenge faced by neuroscientists with the latest nanotechnology, and it has proven to be an effective strategy for delivering excellent deep brain stimulation with once-unimaginable precision," Liu says. "Neuroscientists can therefore leverage this method to visualize the brain state and uncover new clues that will pave the way for novel therapeutic strategies against neurological disorders such as Parkinson's disease."

Full details of the work appear in the journal Science.

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