Biology Reference
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depending on the kind of transducer and biosensor application,
and detailed experimental conditions have to be optimized for each
special application. The role of transducers (working electrodes)
is fulfilled by bulk electrodes - typically mercury-based (mercury
film,mercuryamalgam),carbon-based(glassycarbon,carbonpaste,
graphite, graphite-epoxy composite), and some other (gold, indium
tin-oxide) electrodes, or by various thin- and thick-film electrodes
(e.g.,screen-printedcarbonandgoldelectrodes).DNAarraysensors
utilizetransducersrealizedwithinterdigitatedelectrode[12].There
are also a variety of techniques used for DNA immobilization [13-
15]. Surface and also “bulk” phase of the electrodes have been
modified by DNA [16]. Measurements with electrochemical DNA
biosensors are mostly performed in voltammetric and chronopo-
tentiometric detection modes [17]. With general improvement in
impedimetric biosensors, electrochemical impedance spectroscopy
(EIS) has become popular as the measurement technique for DNA-
based biosensors[18, 19].
Electrochemical DNA-based biosensors and electrochemical
sensing (assay) without use of the true biosensor are sometimes
confused in the literature [8]. While in the electrochemical DNA
biosensor the DNA layer has to be in an intimate contact with the
electrode prior to and during the NA interaction with an analyte,
in electrochemical sensing the DNA itself or product of any DNA
interaction, which was performed in solution or even at another
solid surface (magnetic beads, etc.), is detected electrochemically,
usually after preconcentration by an accumulation on the electrode
surface.
1.2 Detection Features of DNA-Based Biosensors
DNA-based biosensors possess specificity of response, which is
typical for biosensors taking advantage of the bioa nity properties
of DNA. Compared with enzyme sensors and immunosensors,
DNA biosensors are mostly used for the investigation of DNA
interactions rather than for conventional determination of the
concentration of an analyte. They exhibit typical biosensor selec-
tivity/specificity to the analyte (e.g., nucleotide bases sequence,
 
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