The Holy Grail for just about any medical device is the ability to seamlessly interact with human biology. Scientists have yet to duplicate the sophistication of living organisms. But combine electronic circuits with biological components and the sky is the limit in terms of potential medical applications for devices that yield drastically increased efficiency.

Researchers at the Lawrence Livermore National Laboratory (LLNL; Livermore, California) have just reported a breakthrough in this area with the invention of a versatile hybrid platform that uses lipid-coated nanowires to build prototype bionanoelectronic devices.

"The idea came from looking at all the sophisticated structures of biological proteins. These machines can do things that rival or exceed the best we can do with the macroscopic devices," Aleksandr Noy, PhD, the LLNL lead scientist on the project, told Medical Device Daily. "The immediate task was to see if we can make them work in electronic circuits. The longer-term goal would be to use a combination of electronic and biological components to create structures that can act as very efficient electronic cellular interfaces, almost as a universal translator between the cellular signaling and electronic signaling."

Noy, who is also Theme Leader for the LLNL Physical and Life Sciences Directorate, reported his complex findings in the Proceedings of the National Academy of Sciences.

"Obviously the work is an early stage demonstration, so I can only speculate about practical use, but I would like to see it used in smart prosthetics that could be controlled directly by the nerve impulses from the brain," he said.

Other applications resulting from the mingling of biological components with electronic circuits run the gamut from enhanced biosensing and diagnostic tools to advanced neural prosthetics such as cochlear implants. The platform could even increase the efficiency of computers.

Noy chose to work at the nanoscale to accomplish this feat because "Nanoscale gives me the ability to use electronic components that have the same size and scale as biological molecules," he said. "It makes the interface more efficient and a lot less cumbersome."

Many researchers have previously attempted to integrate biological systems with microelectronics, but none got to this point of seamless material-level incorporation.

"But with the creation of even smaller nanomaterials that are comparable to the size of biological molecules, we can integrate the systems at an even more localized level," Noy said.

The new hybrid platform uses shielded nanowires that are coated with a continuous lipid bilayer.

"We made silicon nanowire transistors on a chip, then assembled a lipid membrane on the nanowire – essentially mimicking the cell wall – and then we put the membrane protein into the lipid bilayer to complete the device," he said.

The advantages of this technology platform over existing electronic devices include reduced size, better sensitivity as well as the potential to make much more sophisticated circuitry in the future.

The LLNL team used lipid membranes, which are widespread in biological cells. The membranes form a stable, self-healing and almost impenetrable barrier to ions and small molecules.

"These lipid membranes also can house an unlimited number of protein machines that perform a large number of critical recognition, transport and signal transduction functions in the cell," said Nipun Misra, a University of California Berkeley graduate student and a co-author on the paper.

What results is a shielded-wire configuration, which allowed the researchers to use membrane pores as the only pathway for the ions to reach the nanowires.

"This is how we can use the nanowire device to monitor specific transport and also to control the membrane protein," Noy said.

By changing the gate voltage of the device, the team showed that they can open and close the membrane pore electronically.

Going forward, Noy said his group is worked to develop various applications for the platform.

"I am thinking about this structure more as a platform technology. We can put other membrane proteins in the bilayer and make them perform other tasks," he said. "The long-term goal would be to develop viable bionanoelectronic devices that perform functions that are robust enough and complex enough to merit use in real applications; obviously biomedical device use is a prime target." n

Editor's note: For more information about the impact of nanotechnology in the development of medical devices, check out Medical Device Daily's Nanotechnology R&D Report 2009 by visiting www.medicaldevicedaily.com or calling 800-688-2421.

Lynn Yoffee, 770-361-4789; lynn.yoffee@ahcmedia.com

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