Biology Reference
In-Depth Information
(b)
(c)
(a)
Figure 10.1.
The mostly used conducting polymers: polypyrrole (a),
polyaniline (b),and polythiophene(c).
simultaneously trapping the biomolecules [41]. It is also possible
to control the polymeric film thickness, the spatial distribution of
the immobilized biomolecule, and modulation of its activity [45].
They are mostly organic conjugated polymers with a conjugated
π
-electron system. In general, conducting polymers are considered
those with the conductivity higher than 10
3
Scm
−
1
, materials with
conductivity in the range from 10
3
to 10
−
8
Scm
−
1
are semiconduc-
tors, and materials with conductivity lower than 10
−
8
Scm
−
1
are
consideredasinsulators[46].Theconductingpolymersmostlyused
inDNAbiosensorsarepolypyrroles,polyanilines,andpolytiophenes
(Fig. 10.1).
10.4.1.1 Polypyrroles
Polypyrroles and their derivatives are one of the most extensively
used polymers for the preparation of biosensors. This group of
polymers has excellent properties which can be advantageously
used in enzyme (transducing the analytical signal generated by
redoxenzymereactions)aswellasa
nitybiosensors(DNAbiosen-
sors, immunosensors) [47]. Polypyrrole (Ppy) can be prepared by
chemical or electrochemical polymerization. For the preparation of
DNA biosensors, usually method of electropolymerization is used.
Cyclic voltammetry or deposition at constant potential is often
used for these purposes. Ramanavicius
et al.
[48] reported the
potential pulse technique as the most suitable method for the
preparation of nanostructured Ppy with entrapped biomolecules.
Ppy films prepared by cyclic voltammetry and normal pulse
