Biology Reference
In-Depth Information
Figure 14.10.
(A) SEM image of vertically aligned conducting diamond
nanowires.ExamplesofdetectionofDNAhybridizationby(B)cyclicvoltam-
metry, and (C) differential pulse voltammetry. Target DNA concentration
was 10 nM.
ionetchingusingdiamondnanoparticlesashardetchmaskstoform
nanowires, as shown in Fig. 14.10A. The tips of the wires were
functionalized with aminophenyl groups by electrodeposition of
nitrophenyl diazonium followed by electroreduction of nitro groups
to amines. A heterobifunctional crosslinker was used to covalently
link the free amine groups on the diamond nanowires to thiol-
modified DNA probes. [Fe(CN)
6
]
3
−
was used as a redox probe in
which peak currents would decrease upon hybridization of target
DNA yielding an
∼
2 pM detection limit (see Fig. 14.10B, C). This
conducting diamond nanowire sensor proved 100 to 1000 times
more sensitive than sensors composed of smooth gold or diamond
surfaces.
14.3.3
Nanowire Conductance Based DNA Detection
Nanowires have been used to bridge two closely spaced electrodes
for DNA detection by monitoring the conductance of the nanowire
during hybridization. Binding of the negatively charged DNA strand
to the nanowire increases the net negative surface charge density
leading to an increase in conductance between the two electrodes.
This method is analogous to field-effect transistor (FET) switches
used in microelectronics in which the electrodes serve as the
electron source and drain while the nanowire serves as the
modulatinggate[39].Inadditiontobeinglabel-freeandreagentless,
