Biology Reference
In-Depth Information
comparedinordertopreparessDNAbiosensorsfordetectionofthe
hybridization event [81]. The best results were obtained using PANI
and PEI-modified DNA biosensors. PDAB-modified DNA biosensors
showed some unselective binding. Moreover, PANI allowed finer
control and monitoring of the deposition process. Similarly to Ppy,
PANI can also be doped by anionic dopants, which improve the
conductivity and stability of the resulting polymer. PANI fibers were
used as electrodes to study the influence of electrolyte counterions
and pH on the electrochemical behavior of PANI fibers [82]. The
highest currents were observed in a solution of HCl and HNO
3
,and
the authors concluded that the size of counterions is less important
than the anion charge. Moreover, only fully protonated PANI fibers
showed the same electrochemical properties as the PANI film. DNA
was covalently attached onto PANI nanotubes synthesized on the
graphite electrode [83]. The collective effect of PANI nanotubes as
well as enhanced conductivity led to an extremely high sensitivity
and fast hybridization kinetics. Biotinylated ODN specific to
E.
coli
was immobilized onto an avidin-PANI-modified Pt electrode
[84]. The bioelectrode enabled faster, ultrasensitive, and direct
reagentless detection of
E. coli
. A PANI-PVS film was prepared at
the surface of the ITO electrode by electropolymerization of aniline
in the presence of PVS, LiClO
4
, and DNA [85]. The increase in the
conductivitywiththeincreasedconcentrationofPVSwasattributed
to an acidic microenvironment for PANI formation. The DNA
biosensor was prepared using the copolymer of PANI and chitosan
[86]. The biosensor showed enhanced electron-transfer properties
toward [Fe(CN)
6
]
3
−
/
4
−
, which was attributed to the combination
of the excellent conductivity of PANI and the cationic character of
chitosan.PANInanowiresweresynthesizedelectrochemicallyonthe
surface of GCE [87]. Then phosphate-ended ODNs were covalently
attached onto the amino groups of PANI nanowires. The biosensor
effectively discriminated complementary and noncomplementary
DNA sequences. The positive effect of nanomaterials on the PANI
properties was reported. Due to the synergistic effect of MWCNTs
and PANI, a high amount of the DNA probe was immobilized on the
surfaceoftheelectrode[88].EnhancedstabilityofthePANIfilmwas
observedwhenitwaselectropolymerizedinthepresenceofssDNA-
wrapped single-walled carbon nanotubes (ssDNA-SWCNTs) [89].
