Biology Reference
In-Depth Information
combination of the unique properties of conducting polymers and
those of nanomaterials exhibits a synergic effect, which positively
affects the stability, electron transfer, and performance of the
final biosensors. The Ppy film possessed the uniform surface
for the immobilization of Au-Pt hybrid nanoparticles [74]. Ppy
was also prepared by electropolymerization in the presence of
multiwalled carbon nanotubes (MWCNTs) ended with carboxylic
groups [75]. MWCNTs served as the nano-sized backbone for Ppy
polymerization, which allowed the formation of porous Ppy film
covered around the MWCNTs in a cylindrical structure and offered
stable surface for DNA immobilization. The activity of MWCNT
surface can lower the nucleation energy required for the beginning
of electropolymerization of the Ppy/DNA film [41]. Therefore, the
growthofthepolymerfilmoccurredatpotential
+
0.4Vvs.Ag/AgCl
in contrast to
+
0.6 V observed at bare GCE. The high surface area
of MWCNTs also allowed the deposition of greater volume of the
polymer withoutincreasing the thicknessof the film.
10.4.1.2 Polyaniline
Polyanilineiswidelyusedforthepreparationoftheelectrochemical
enzyme biosensors and immunosensors [76]. However, several
applications in DNA biosensors can also be found. PANI can be pre-
pared by electropolymerization using the galvanostatic method or
the potentiostatic method, leading to a polymer adhered weakly at
the electrode surface or potential cycling, which produces polymer
welladheredattheelectrodesurface[77].Theelectropolymerizaton
of PANI is usually provided from acidic media [78]. The properties
of the PANI synthesized from different acids were investigated
[79]. The authors showed that polymer synthesized with perchloric
acid had the highest conductivity in neutral solutions (pH of 6.6),
which is environmentally convenient for biomolecules. Abdullin
et al.
[80] studied the redox properties of the DNA-polyaniline film
over a wide range of pH. Authors found that the well-reproducible
and reversible voltammetric signals of the DNA-PANI film were
observed at physiological pH values. Screen-printed carbon elec-
trodes modified with electropolymerized PANI, electropolymerized
polydiaminobenzene (PDAB), and polyethyleneimine (PEI) were
