For decades, neuroscientists and engineers have wanted to uncover the secrets of the human brain. Pop culture and science fiction films only serve to play into the understanding of the idea that the human brain can be 'hacked'. But one team of researchers might have actually gotten the world significantly closer to manipulating how our brain functions.
Researchers from the University of Chicago used tiny, light-powered silicon wires to reshape how the brain responds. One day, the process could be used to treat brain disorders.
The findings tap into the technique called optogenetics. The decade-old technique uses light to shape neural activity. However, the problem was that any optogenetic procedure often involved manipulating genes as well. The University of Chicago team went a different route in their study. Rather than genetics, they looked to technology and used nanowiring – originally designed for solar cells. They combined the nanowires with two types of silicon that would create an electrical current whenever exposed to light.
Assistant professor Bozhi Tian led the researchers as they conducted their work on rat neurons growing in a lab.
“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.
More specifically, the team used a p-type core (boron-doped) and an n-type (phosphorous-doped) shell with a surface of atomic gold. Those metals were then hit with light, and the photoexcited carriers travel through the wires where they separate at the core and shell's junction point.
“These electrons then participate in cathodic electrochemical reactions in a surrounding electrolyte solution, generating a cathodic current,” Tian explained to NanoTechWeb. “When we then interface the coaxial nanowires with a target neuronal membrane, this current depolarizes the membrane, mimicking the effect of a nerve impulse and causing the neuron to fire an action potential.”
They discovered they could in fact trigger neurons to fire the signals to their neighboring cells, and all it would take is just a single nanowire to start up this neuron firing.
“The nice thing about it is that both gold and silicon are biologically compatible materials,” said graduate student Ramya Parameswaran, the first author on the study. “Also, after they’re injected into the body, structures of this size would degrade naturally within a couple of months.”
Silicon also played a critical (and relatively cost efficient) role in the process -- especially when compared to other technologies attempting to stimulate the same response.
“This tool could be used for both fundamental single bioelectric studies and clinical therapeutics,” Tian said. “Silicon strongly absorbs light in the near-infrared, a wavelength of light that deeply penetrates biological tissue, which means that the nanowires could be used to stimulate peripheral nerves (lying as far as 1 cm below the skin) if injected into tissue. This could ultimately allow for non-invasive treatment of diseases characterized by severe neuropathic pain, such as diabetic peripheral neuropathy, for example.”
Next steps for this team include testing on animals: by seeing the effect of the nanowires and light on living creatures, it could clue them in on how to potentially treat Parkinson's disease and other brain-based abnormalities.