Gold nanowires and nanotubes for high sensitivity detection of pathogen DNA

Gold nanowires with a diameter of 70 ± 20 nm, and gold nanotubes of the same diameter with a wall thicknesses of 20 ± 10 nm, have been electrodeposited within the pores of a track etched polycarbonate membrane filter. These nanowires and nanotubes were then utilised in a DNA detection assay. The top end of the nanowire/nanotube was selectively functionalised with a 20-base oligonucleotide with a C3 spacer thiol (probe strand) that is complementary to a sequence specifically associated with S. Aureus mastitis. Once functionalised with probe strand DNA, the nanowires/nanotubes were released by dissolving the polycarbonate membrane and are capable of biorecognition on the top end of the nanowire and electrocatalytic reduction of hydrogen peroxide along their entire length. A gold disc electrode was modified with a 15-base oligonucleotide with a C3 spacer thiol (capture strand). The target, a 41 base oligonucleotide specific to S. Aureus mastitis, hybridises with both capture and probe oligonucleotides and brings the nanowires close to the electrode surface enabling the electrocatalytic reduction of hydrogen peroxide. Semi-log plots of the pathogen DNA concentration vs. faradaic current are linear from 1 fM to 1 μM and aM concentrations can be detected without the need for molecular, e.g., PCR or NASBA, amplification.