Engineers fabricate ion channels for commercial use

A team of Yale researchers has taken a fundamental cell biology concept and introduced it to the world of microchips and electronic nanotechnology.

Aiming to mimic the function of ion channels embedded within cell membranes, Yale electrical engineering professor Mark Reed and Weihua Guan GRD ’14 have designed a microscopic semiconductor whose potential applications include small-scale power generation and portable desalination of ocean water. Reed and Guan most recently published their work in the January 2013 issue of Nano Letters.

“The important result is that we mimic the ionic and electrostatic function of certain types of biological ion channels in an abiotic embodiment in the solid state. This could well enable many new types of microelectronic or biological interfaces,” Reed said.

Ion channels are proteins on the outer surfaces of cells that create openings through which ions flow; typically, these ions move from areas of higher concentration to areas of lower concentration. There are, however, ways for ions to move against a concentration gradient, such as active transport, which relies on an energy source like ATP molecules to move ions from low to high concentration regions. Reed and Guan sought to replicate this concept artificially by employing a silicon microchip to establish an electric field, allowing them to dictate the flow of ions across a given barrier.

“What we are trying to mimic is both the structural and the functional properties of a cell, especially these ion channels in cell membranes, and trying to modulate the membrane potential, just like how cells modulate their membrane potential to send out signals,” Guan said.

One of the potential applications for this technology, desalination, would involve coding the artificial channel to electronically pull unwanted salt ions, such as sodium and chloride, through an artificial membrane and out of water, as opposed to the physical filtering of water and salt seen in traditional desalination practices.

Additionally, this technology might be able to serve as a charging source, using the charge generated by the resulting ion movement to generate energy for nano- or micro-level structures.

“There’s power that comes out from the gradient of salt concentration, and if you have this structure or membrane that we have fabricated, place a droplet of saltwater and a droplet of table water, you get power,” Guan said.

Other researchers interviewed said they think very highly of the concept behind Reed and Guan’s work. Yale biomedical engineering professor Fred Sigworth praised the project for doing “something that hasn’t been possible before.” He cited scientists’ inability to work on a scale small enough to influence ions as a prominent obstacle in previous attempts to develop such technology. Similarly, Rong Fan, biomedical engineering assistant professor at the Yale School of Engineering & Applied Science, called this design “the first example that can really mimic biological ion channels” that he has seen.

Yale associate biomedical engineering professor Tarek Fahmy, also of the engineering school, voiced his strong approval of the science behind this design, but believes that more work needs to be done in identifying its applications.

“This is a very successful, very exciting new development, but the applications are poised to come. What you have to keep in mind is that this is not necessarily a breakthrough in technology that has limited us from doing things. For example, ion exchange membranes are used very widely in the water purification industry. Here, you’re doing the same thing except you’re actually plugging it into the wall, turning on a switch and saying, ‘Start the exchange process,’” Fahmy said.

Further experimentation is needed to validate this technology’s potential in other capacities, such as removing pollutants from water or in biotechnology. Despite this success in recreating an important cell process, Reed said he is skeptical of the possibility of creating artificial cells in the near future, calling the premise “just a bit of science fiction.”

In 2009, Reed won the Institute of Electrical and Electronics Engineers Pioneer Award in Nanotechnology.