Artificial cells power on

Batteries have become a bit more natural.

University researchers have created a model for an artificial cell that mimics the electricity-generation of cells in electric eel – but the mimic is more powerful than anything occurring in nature. The artificial cells could one day be used to power tiny medical devices, such as glucose sensors or retinal implants.

In animal cells, the sodium-ion concentration is significantly lower inside the cell than outside and creates a gradient, said Jian Xu, a postdoctoral associate in the Department of Chemical Engineering. This gradient produces electricity, even in some human cells. But because the electric eel is known to have the highest level of bioelectricity generation out of all animals, scientists chose to base their research on an electric eel cell.

Though these eels have been studied for their electrical properties since the late 1700s, research on the exact mechanism of the eel’s electricity generation was not systematic, Xu said. Usually cell models only depict those with a single membrane, he said, but the eel has two different membranes, both crucial to electricity-generation.

“It’s just like a battery,” he said. “If you only have one end, no matter how much you change the components, you still cannot get a voltage difference.”

When Xu was a studying under David LaVan, a former University professor of mechanical engineering who now works for the Institutes of Standards and Technology, he created the first blueprint for such a cell. They the went one step further.

“We’re the first people who dared to take the first leap from a model that explains a biological system to designing a model that performs better,” LaVan said.

The two questioned whether the eel cell generated optimal energy output – and decided it did not. Xu said they tried to reconfigure the ion channel and the ion pumps in the cell membrane, experimenting with different ion concentrations.

In the end, they found their design worked better than that of the electric eel. The cell they modeled can theoretically produce 28 percent more electricity than an eel cell and is 31 percent more efficient in converting chemical energy into electricity. LaVan and Xu showed they could use only several dozen artificial cells to create a tiny battery, which would only be about one-quarter-inch thick.

“We showed that you can actually do better than nature,” Xu said. “[We have] an electricity-generation mechanism that can be used to provide power to medical devices like prostheses, and it’s made of totally biocompatible materials.”

LaVan said a cell genetically engineered from proteins would be simple enough to construct, but making it out of a nontoxic synthetic material like silicon – which is how the cell was designed – is more difficult.

He said multiple molecular components are still missing, including a good synthetic ion pump. The only options that currently exist are natural protein-based ones, he said, though Xu is currently in the process of trying to publish a similar design for a system that is less efficient but easier to fabricate.

“This is just the first step,” Xu said, predicting that it would be five to 10 years before the technology is viable. “We still have to find a way to quantitatively control insertion of those ion pumps.”

When they do, though, the technology could have numerous applications in biomedical engineering. Though the two researchers have not tested their model to see if it could generate enough power for larger devices, such as pacemakers, they are confident it would work for smaller implantable sensors and similar devices.

LaVan said the artificial cell is ideal for smaller applications because it uses the body’s natural energy sources for power, allowing it to be much smaller and toxin-free, and therefore easier and less dangerous to implant.

“It’s a very clever idea,” said Mark Saltzman, chair of the Department of Biomedical Engineering. “Lots of devices, like pacemakers, require power to work, and we have to put batteries in, which we have to change. But if we had some sort of renewable source, it could be very useful.”