Abstract
We report the detection of DNA PCR amplicons using an ultrasensitive label-free electronic
technique based on multiwalled carbon nanotube (MWNT) nanoelectrode arrays embedded in an
SiO2
matrix. Specific PCR amplicons are reliably detected using electrochemical (EC) methods
through allele-specific oligonucleotide hybridization. The inherent guanine bases in the
DNA amplicon target of 
bases serve as signal moieties with the aid of
Ru(bpy)32+
mediators, providing an amplified anodic current associated with the oxidation of guanine
groups at the nanoelectrode surface. The reduced size and density of the nanoelectrode
array provided by MWNTs dramatically improves the sensitivity of EC detection. In
addition, the abundant guanine bases in target DNA produce a large signal. Less than
target amplicons can be detected on a microspot, approaching the sensitivity limit of
conventional laser-based fluorescence techniques. This method also eliminates the labelling
requirement and makes the measurements much simpler. This platform can be employed
for developing highly automated electronic chips with multiplex nanoelectrode arrays for
quick DNA analysis.
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