Biology Reference
In-Depth Information
13.3.1
Label-Based Electrochemical Nucleic Acid
Biosensors
Label-based electrochemical nucleic acid hybridization biosensors
work on the principle ofthe following groups:
1. Using redox active hybridization indicator which has an a
nity
for ss or ds DNA
2. Using labeled signalingprobes or labeled target DNA
13.3.1.1 Electrochemical genosensing by using hybridization
indicator
This approach is based on the electrochemical response of a redox
active label changes upon DNA hybridization, when the hybridiza-
tion process occurs due to change of the indicator concentration at
theelectrodesurface[38].Theseredoxactivelabelscanbecalledas
“hybridizationindicators”andhavehigha
nityforeitherssDNAor
dsDNA to transduce hybridization.
Hybridization indicators have various interaction properties of
dsDNA and ssDNA. Some metal complexes or dyes are intercalator
molecules which interact with hydrogen bonds of dsDNA [39], and
some indicators have selective binding processes onto DNA bases
such as guanine[40].
Intercalator hybridization labels are complex molecules that
have a planar aromatic group. Several methods for indicator-based
electrochemical sequence specific to DNA detection have been
reported. Wang
et al
. [41] described the hybridization detection
of short DNA sequences related to HIV virus genome due to the
chronopotentiometric transduction of Co(phen) as an hybridization
label. Electrochemiluminescense assays have also been reported by
Carter
et al.
[42] forspecific DNA sequencedetection.
Early studies on electrochemical nucleic acid biosensors were
based on electrochemical transduction of redox labels (indicators)
thathavesignificantdifferentbehaviorsbetweendsDNAandssDNA.
These intercalator molecules have higher binding a
nity to dsDNA
than ssDNA. Mikkelsen and coworkers investigated this approach
by using Co(phen) as a hybridization indicator. The intercalator
molecule was accumulated at ss and dsDNA at covalently attached
