Yet another promising use of a much-discussed wonder material: It has allowed researchers to develop a technique that can speed up or slow down human heart cells growing in a dish on command — simply by shining a light on them and varying its intensity.

It’s an advance that could speed the search for more precise, less toxic therapeutic drugs. Research and clinical applications include testing therapeutic drugs in more biologically relevant systems; developing use-specific drugs that are more precise and have fewer systemic effects; and creating better medical devices, such as light-controlled pacemakers.

A paper on the study, performed by researchers at University of California San Diego (UCSD) School of Medicine and their collaborators, appears in Science Advances. According to first author Alex Savchenko, Ph.D., those who first witnessed the experiment in motion didn’t believe what they were seeing. "When we first got this working in our lab, suddenly we had something like 20 people gathering around, shouting things like 'Impossible!' and accusing me of pranking them,” he said. “We'd never seen anything like this before."

The Wonder Material

If you haven’t guessed already, what’s unique about the dish in which those heart cells were growing is that it’s made of graphene. Essentially a thinner version of graphite (“pencil lead”), graphene is a semi-metal made up of a latticework of carbon atoms — the same element that forms the basis of all living organisms. One of the properties that makes it so unique is its ability to convert light into electricity.

By contrast, most petri dishes and plates used to grow cells or cultures for biomedical research are made of plastic or glass — both of which are insulators. Graphene provides a more biologically-accurate environment. "In your body, you don't see many surfaces acting like plastic or glass," said Savchenko. "Instead, we're conductive. Our hearts are extremely good at conducting electricity. In the brain, it's electric conductivity that allows me to think and talk at the same time."

Developing the System

Savchenko said it took the team a while to pin down the optimal graphene-based formulation, followed by more time spent on finding the best light source and an effective method of delivering it to the graphene-cell system. Eventually, however, they found a way to precisely control how much electricity was generated by variations in the intensity of the light. "We were surprised at the degree of flexibility, that graphene allows you to pace cells literally at will," he said. "You want them to beat twice as fast? No problem — you just increase the light intensity. Three times faster? No problem — increase the light or graphene density."

Another surprise was the lack of toxicity: Introducing a new material in biology tends to kill cells in the process, presenting a significant challenge for researchers. But this simply wasn’t the case in the graphene-based experiments — which the researchers also extended to controlling heart activity in a living organism (zebrafish embryos).

Drug Screening Applications

The graphene/light system offers particular promise for drug screening, because of its ability to represent real-world biological conditions. Currently, researchers use robotic technology to test hundreds of thousands of chemical compounds, screening them for their abilities to change cell behavior. When a desired effect is found, a compound can be identified for further study as a potential new therapeutic drug. But because the test cells are grown on plastic, outside of the disease context, it’s possible that many beneficial compounds are being missed.

By contrast, the new system can model conditions that will respond to “use-dependent” drugs — drugs that only have an effect under certain conditions. Savchenko and his team experimented with adding mexiletine, a use-dependent medication used to treat arrhythmias (irregular heartbeats), to the system; they found that the faster they got the heart cells to beat, the better the drug worked to inhibit them.

Next Steps

The team eventually hopes to apply the graphene/light system to search for drugs that specifically kill cancer cells, while leaving healthy cells alone. The researchers also envision using graphene to find opioid alternatives: pain medications that only work when and where a person is in pain, reducing the systemic effects that can lead to misuse and addiction. Savchenko also believes that light-controlled pacemakers made of graphene could be safer and more effective than current models.

While much remains to be done, Savchenko offers an optimistic take: "You can squeeze a half-year of animal experiments into a day of experiments with this graphene-based system.” Stay tuned.