Membrane-Encased Nanowires Act Like Nerve Cells

Scientists at the Lawrence Livermore National Laboratory (Livermore, CA) have developed a technique for encasing silicon nanowire transistors in a membrane that resembles those surrounding cells. Functioning like nerve cells, these hybrid devices might find their way into a range of future medical device applications.Aleksandr Noy, a chemist at the lab, developed the membrane-sealed nanowire to make better bioelectronic devices. His device consists of arrays of silicon nanowire transistors--rows of 30-nm-diameter wires bounded at either end by electrical contacts--that are placed in a microfluidic device. The microfluidics deliver hollow spheres of fatty membrane molecules, which are attracted to the negatively charged surfaces of the nanowires. As they accumulate, the fatty molecules fuse together to form a continuous membrane that seals the wires, just as a biological membrane seals the contents of a cell.In contrast to bare nanowire transistors, which exhibit a measurable change in their electrical properties when exposed to acidic or basic solutions, the membrane-sealed nanowires do not react because the fatty layer protects them, just like a biological cell membrane.To make the nanowires responsive to the surrounding chemical environment, Noy added proteins to form ion channels, which control the flow of charged atoms and molecules across cell membranes. When put into solution with the nanowires, these proteins insert themselves into the membrane, where they can mimic nerve-cell electrical signals. By using the nanowires to create a voltage difference across the membrane, the voltage-responsive protein can be opened and closed, allowing the nanowires to turn their chemical-sensing ability on or off.Noy's work may eventually be used to make better interfaces for prosthetic limbs and cochlear implants. "If you can make modern microelectronics talk to living organisms, you can make more-efficient prosthetics or new types of biosensors for medical diagnostics," he remarks.