Biology Reference
In-Depth Information
observed in the case of CHIT. However, DNA and CHIT can form
stable complexes of specific sizes, influenced by the molecular
weight and pH of CHIT [121]. An assembled film composed of DNA
and CHIT was prepared using the layer-by-layer technique at the
surface of the pyrolytic graphite electrode [122]. CHIT enabled the
effective intercalation of 9,10-anthraquinone-2,6-disulfonate into
the double helix of DNA. A biosensor was successfully applied for
the detection of DNA damage caused by the Fenton reagent. Cu(II)
ions were successfully immobilized in the DNA/CHIT layer due to
the formation of Cu(II)-DNA complexes [123]. This amperometric
biosensor showed excellent electroactivity toward hydrogen per-
oxide with the detection limit of 3
μ
mol/l. CHIT was also used
to disperse MWCNTs [124-126]. CHIT as GCE modifier partially
blockedtheelectrochemicalresponseofelectroactivespecies[124].
Introduction of MWCNTs enhanced the electron-transfer properties
of the electrode surface, although values obtained at the bare GCE
were still better. It was shown that CHIT strongly enhanced the
homogeneity of MWCNT deposition onto the electrode surface in
comparison to dispersion indimethylformamideandMWCNT-CHIT
formed a suitable interface for the immobilization of the DNA
layer in order to study the DNA damage [125]. Electrochemical
properties of screen-printed electrodes modified with composites
of SWCNT-CHIT, MWCNT-CHIT, and (SWCNT-COOH)-CHIT were
studied[127].ItwasshownthatCHITalonewasabletodecreasethe
charge-transfer resistance (
R
CT
) of the electrode surface. However,
the decrease in
R
CT
was much more significant when the carbon
nanotube-CHIT composite was used as an electrode modifier. The
best results were obtained in the case of (SWCNT-COOH)-CHIT
because of electrostatic interaction of the negative charge of the
carboxylic group of SWCNTs and the positive charge of CHIT.
Moreover, the (SWCNT-COOH)-CHIT composite was shown as the
bestenvironmentforDNAimmobilizationandwassuccessfullyused
for the study ofDNA damage caused by lipid peroxidation products.
Overoxidized Ppy(Ppyox) is another example of nonconducting
polymers. It is known that Ppy irreversibly loses electroactivity at
potentials more positive than
+
1.0 V vs. Ag/AgCl yielding into the
formation of an insulating layer with the porous structure [128]
andthenanoporousdiffusionactivity[28],bothconvenientforDNA
