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charged complementary DNA molecules. As a practical application,
an allele-specific assay was developed to detect the presence of
singlenucleotidepolymorphisms(SNPs)[91a].Anetworkofcarbon
nanotubes within an FET device was functionalized with either
mutant or wild-type alleles while DNA hybridization to the corre-
sponding allele was measured through a decrease in conductance.
One last example is an amplification method reported in a CNTFET
device.Asnotedearlier,theincorporationofnanoparticleshasbeen
shown to further enhance an electrochemical response of a CNT-
modified electrode [99]. Dong et al. [118] report on the use of a
SWCNTFET to detect target DNAs labeled with Au nanoparticles.
Hybridization events of CNT-DNA probes were detected down to
100 fM due to an increased conductivity through the NPs in close
proximity.
14.5 Conclusion
The integration of nanotechnology with biology and electrochem-
istryhasproducedmanyadvancesfornovelDNAsensingstrategies.
The ability to synthesize many nanomaterials in similar size
ranges to biomolecular markers makes their coupling with DNA
extremely e cacious toward the design of sensors to transduce
DNA hybridization events. Nanoparticles, nanorods, nanowires,
nanotubes, etc. have been used as labels in novel DNA detection
assays that are fast, sensitive, and reliable. Their use as supports
for DNA immobilization, tags that take advantage of their intrinsic
atomic make-up or ability to load and pre-concentrate secondary
labels, and ability to modulate interfacial phenomenon have been
described.Furtheradvancesareexpectedtoleadtonewgenerations
of electrochemical DNA sensors with implications in fields such as
medical diagnostics, drug discovery, detection of biothreats, and
environmentalmonitoring.
References
1. (a) J. Wang, Analyst 130 , 421-426 (2005). (b) X. Mao and G. Liu,
J. Biomed. Nanotechnol. 4 , 419-431 (2008). (c) M. Pumera, S. Sanchez,
I. Ichinose, and J. Tang, Sens. Actuators, B 123 , 1195-1205 (2007). (d)
 
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