"It is of great interest for biosensing to reduce the radius of electrodes to 10-100 nm, approaching the size of biomolecules," researcher Jun Li told nanotechweb.org. "Multiwalled nanotubes, with well-defined nanoscale geometry, are attractive nanoelectrode materials. They present a wide electrochemical window, flexible surface chemistry and biocompatibility."

To make the devices, the scientists grew vertical arrays of multiwalled carbon nanotubes on prepatterned microelectrodes by plasma-enhanced chemical vapour deposition (CVD). Then they encapsulated the nanotubes in silica grown by tetraethoxysilane CVD, and used chemical mechanical polishing to flatten the surface and expose the tips of the tubes.

"We have demonstrated the application by measuring small redox species in bulk solution and immobilized at the electrode surface, as well as guanine oxidation signals from hybridized oligonucleotides," said Li. "It can also be employed in enzyme-based biosensors and antibody-antigen-based immunosensors by functionalizing appropriate biomolecules."

According to Li, the team's approach will benefit customers in a range of fields, from clinical molecular diagnostics to pathology and drug discovery. "Our work on DNA detection can be developed into handheld devices for molecular diagnostics requiring quick answers, such as early cancer detection, point-of-care and field uses," he said. "Enzyme-based biosensors (such as glucose sensors) can be used for household healthcare, while pathogen sensors can be used for homeland protection."

NASA spin-off Integrated Nanosystems, which was involved in researching the technology, is now working on product development.

The researchers reported their work in Nano Letters.