New Study Enables Optical Neuron Activation through Nanowires
Optogenetics or optogenetic tools are genetically encoded switches that allow neurons to be turned on or off with bursts of light. Introducing these proteins into cultured cells or the brains of live animals allows investigation of the structure and function of neural networks. These ‘optogenetic’ tools also hold clinical promise, with the potential for modulating activity of brain circuits involved in neurological disorders or restoring vision loss.
But a bump however is, most available methods are either mechanically invasive, require genetic manipulation of target cells or cannot provide subcellular specificity.
Therefore, now, researchers at the University of Chicago have developed a method based on silicon nanowiring that circumvents this need for genetic engineering while still utilizing the precision of light for specific neuron-targeting.
Silicon nanowires are biocompatible, highly conductive, and so thin they are essentially one-dimensional. Inside human cells, they could potentially be used to do a lot of things. They could record the electrical communication between structures inside the cell—signals passed from one organelle to another. They could electrically stimulate those organelles for therapeutic purposes.
Or the nanowires could carry small molecule drugs and deliver them directly to cells, bypassing some of the body’s natural
barriers. The fact that the cells consume the nanowires naturally, without any kind of special treatment, and without damaging themselves, makes it that much more useful.
Ramya Parameswaran, graduate student and first author of the study, said: “We hope that this technology can eventually be used for both fundamental bioelectric studies of not just neuronal circuits but also other cell types that rely on electrical signalling to function. We also hope to use our nanowires for clinical therapeutics to restore cellular function in the context of disease.
“We hope to target any disorders that are characterised by aberrant electrical signalling in cells. In the brain, we can target Parkinson’s disease or psychiatric disorders such as major depressive disorder. Additionally, we hope to target diseases that involve peripheral nerve damage, such as diabetic peripheral neuropathy.”
The team was led by Asst. Prof. Bozhi Tian. They built minuscule wires previously designed for solar cells. These nanowires are so small that hundreds of them could sit side by side on the edge of a sheet of paper—putting them on the same scale as the parts of cells they’re trying to communicate with.
These nanowires combine two types of silicon to create a small electrical current when struck by light. Gold, diffused by a special process onto the surface of the wire, acts as a catalyst to promote electrochemical reactions.
“When the wire is in place and illuminated, the voltage difference between the inside and outside of the cell is slightly reduced. This lowers the barrier for the neuron to fire an electrical signal to its neighboring cells,” Tian said.
The team tested the approach with rat neurons grown in a lab, and saw they could indeed trigger neurons to fire these electrical signals.
“The nice thing about it is that both gold and silicon are biologically compatible materials,” said graduate student Ramya Parameswaran. “Also, after they’re injected into the body, structures of this size would degrade naturally within a couple of months.”
“It’s a fundamental but very promising approach,” Tian said. They plan next to test the system in animals, which could both help researchers further understand how these electrical signals work in the brain as well as suggest ways to address problems like Parkinson’s disease or psychiatric disorders.
