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the electrochemical activity of quinone in the polymer for the
detection of the hybridization event [34, 102]. By the electropoly-
merizationofpoly(JUG-co-JUGA)ontoanMWNT-modifiedelectrode
in nonaqueous media, an interpenetrated conductive network
electroactiveinbothaqueousandnonaqueousmediawasproduced
[103]. An electropolymerized polyquinone film was derivatized
with glutathione [104]. Glutathione was used as a precursor
for subsequent biomolecule linkage via carboxylic groups. Free
carboxylic groups were first transformed into ester groups using
EDC, and then amino-terminated DNA was immobilized. Because
the polymeric film is a cation exchanger, the negatively charged
DNA cannot be nonspecifically adsorbed at the surface. A solution
of poly(1,4-benzoquinone) prepared by enzymatic synthesis was
cast at the surface of carbon fiber electrodes, and then DNA was
immobilized [105]. The polymer film allowed the hybridization
detection by scanning electrochemical microscopy in the positive-
feedback mode.
10.4.2.2 Redox-active polymers containing organometalic
redox center
Redox-active polymers containing ferrocene as redox center were
employed in DNA biosensors. Poly(vinylferrocene) is a soluble
polymer which can be easily deposited at the surface of Pt [106,
107] or graphite working electrode [108] by its electrooxidation
resulting in a less soluble polymer, poly(vinylferrocenium). Such an
electrodecanthenbeadvantageouslyusedfortheimmobilizationof
negatively charged DNA. Low nonspecific immobilization of DNA on
thispolymerwasreported[108].Theelectrochemicalsignalofsuch
polymer can be used for the detection of the hybridization event
[107]. Another approach was used by Cui
et al.
[109]. First GCE was
modified with DNA. After drying, the layer of poly(ferrocenylsilane)
was cast at DNA/GCE. It was shown that the DNA at the surface of
GCEenhancedtheadsorptionofthepolymeraswellastheelectron-
transferproperties.Therefore,thepreparedbiosensorshowedgood
electrocatalytic activity toward oxidation ofascorbic acid.
Osmium bipyridyl complexes are known to catalyze the elec-
trooxidation of the guanine base in DNA and also enhance the
