Graphene "CAGE Sensor" Lets You Turn Electrical Activity in Cells Into a Shifting Light Show

Researchers at the University of California at Berkeley and Stanford University have succeeded in "filming" a beating heart using a "camera" made from a sheet of graphene.

Hailed as a wonder-material, graphene is simple - it's no more than a single-atom-thick layer of carbon arranged in a honeycomb pattern, and can be produced using a pencil and Scotch tape — but its unusual properties show promise in a range of fields. Including, apparently, capturing real-time electrical activity in cells.

An entirely new form of sensor, the graphene "camera" developed by the team is designed to replace electrodes and chemical dyes, which can only record voltages at a single measurement point, with a sheet capable of measuring the voltage over an entire surface at once.

"Because we are imaging all cells simultaneously onto a camera, we don’t have to scan, and we don’t have just a point measurement," paper co-first author Halleh Balch, Ph.D., explains. "We can image the entire network of cells at the same time."

"The ease with which you can image an entire region of a sample could be especially useful in the study of neural networks that have all sorts of cell types involved," adds fellow first author Allister McGuire, Ph.D. "If you have a fluorescently labeled cell system, you might only be targeting a certain type of neuron."

"Our system would allow you to capture electrical activity in all neurons and their support cells with very high integrity, which could really impact the way that people do these network level studies."

The device, which was tested on a chicken heart, is known as a critically coupled waveguide-amplified graphene electric field sensor, or CAGE sensor. The sample to be measured is placed on top of the graphene sheet, which sits on a waveguide. Laser light is beamed into the waveguide through a prism, reflects off the graphene, and is recorded by a camera — making the electric field visible in real-time.

"One of the things that is amazing to me about this project is that electric fields mediate chemical interactions, mediate biophysical interactions — they mediate all sorts of processes in the natural world — but we never measure them," says Balch. "We measure current, and we measure voltage,” Balch said. “The ability to actually image electric fields gives you a look at a modality that you previously had little insight into."

The work has been published under closed-access terms in the journal ACS Nano Letters.