Credit: © 2009 AIP

Research on the neural networks of animals relies on glass micropipettes and microelectrode arrays to probe the response of cells to electrical stimulation. However, micropipettes and electrode arrays have limitations, including the need for high voltages to induce a measureable response, and low spatial resolution. Cattien Nguyen and colleagues at Santa Clara University and the NASA Ames Research Center have now used a single multiwalled carbon nanotube electrode for stimulating, recording and 'clamping' frog muscle fibres1.

The nanoprobes were produced by mechanically attaching a 30-nm-diameter, 5-μm-long multiwalled carbon nanotube to a nickel coated support, passing a d.c. current through the nickel–nanotube interface to weld the carbon nanotube to the nickel layer. Typically, the nanotube probes stimulated localized twitching of frog sartorius muscles at ∼6.6 V, compared with the ∼63 V required when using pulled glass micropipettes. The order of magnitude difference in these voltages was attributed to the low 500 kΩ access resistance of the nanoprobes, compared with ∼5 MΩ for the pipettes. The researchers also examined the efficiency of the nanotube electrodes in intracellular stimulation of a single cell, finding that the lower access resistance provided higher stimulus efficiency compared with glass micropipettes.

Furthermore, the nanotube probes were used to record extracellular and intracellular bioelectrical potentials, and to perform whole-cell voltage clamping of single fibres.