To examine a neuron's health, activity and response to drugs, scientists record its electrical activity. Current methods of recording are destructive, so they can only be used to study a neuron for a brief period, and can only measure the activity of one cell at a time. But neurons don’t function individually – they act in networks, and commonly used systems for detecting the electrical activity of complex groups of neurons aren’t as sensitive as they could be.

A new technology developed through a collaboration between Anne Bang, PhD, director of Cell Biology in the Conrad Prebys Center for Chemical Genomics at the Sanford Burnham Medical Research Institute, and Shadi Dayeh, PhD, associate professor at UC San Diego, makes high–sensitivity recording possible in neuronal networks. Publishing in the journal Nano Letters, the team describes nanowire arrays that could accelerate drug development for neurological and neuropsychiatric diseases.

"We envision that this nanowire technology could be used on stem–cell–derived brain models to identify the most effective drugs for disorders like bipolar disorder and Alzheimer’s," says Bang.

The nanowire technology developed in Dayeh's laboratory is nondestructive and can simultaneously measure potential changes in multiple neurons – with the high sensitivity and resolution achieved by the current state of the art.

The device consists of an array of silicon nanowires densely packed on a small chip patterned with nickel electrode leads that are coated with silica. The nanowires poke inside cells without damaging them and are sensitive enough to measure small potential changes that are a fraction of or a few millivolts in magnitude. Neurons interfaced with the nanowire array survived and continued functioning for at least six weeks.

Another innovative feature of this technology is it can isolate the electrical signal measured by each individual nanowire. "This is different from existing nanowire technologies, where several wires are electrically shorted together and you cannot differentiate the signal from every single wire," Dayeh says.

Dayeh noted that the technology needs further optimization for brain–on–chip drug screening. His team is working to adapt the arrays for heart–on–chip drug screening for cardiac diseases and in vivo brain mapping, which is still several years away. "Our ultimate goal is to translate this technology to a device that can be implanted in the brain."