Jul 5, 2007
Vertical nanofibres point towards neural interface
Free-standing carbon nanofibres (CNFs) could improve the functionality and reliability of implantable biomedical devices such as deep brain stimulators for managing Parkinson's disease, epilepsy and depression, say NASA scientists. Neural–electrical interfaces are notoriously difficult to engineer due to the range of mechanical, chemical and electrical properties that need to be accommodated.
"We use vertically aligned CNFs as a stable template for a coating of conformal electroconductive polymer," Jun Li, senior scientist at NASA Ames research centre, told nanotechweb.org. "The free-standing fibres behave as soft needles that can release the mechanical stress by bending."
Carbon nanostructures have been investigated previously, but in a bundled configuration. "They are entangled with each other and have much less freedom to move," said Li. "The stiffer structure is much less compatible with the tissue mechanically."
NASA's brush-like substrate is grown by plasma-enhanced chemical vapour deposition using nickel catalyst deposited on a 200 nm thick chromium film covering a silicon wafer. Fibres have an average diameter of 150 +/– 30 nm and extend up to 7 μm vertically.
The open 3D architecture allows intimate physical contact between neural cells and individual polymer-coated CNFs. Li and his colleagues are upbeat about their chance of success and have already shown that PC12 neuron cells cultured on the free-standing structure can form an extended network.
"Because each electrode site is smaller than the size of a neuron, we should be able to develop a multiplexed system that combines electrical stimulation (with very low current), electrical recording, and electrochemical recording of the release of neurotransmitters," explained Li. "There is a strong need to come up with a closed-loop prototype so that the stimulation of neuroprosthetics can be optimized in real-time."
The researchers reported their work in IEEE Trans. Biomed. Eng..
About the author
James Tyrrell is editor of nanotechweb.org.