Biology Reference
In-Depth Information
HAuCl
4
DNA probe
nanoPAN
- 0.2 V, 500 s
25 °C, 2h
Dispersed with
DMF and chitosan
Figure 4.5.
Schematic diagram of the immobilization of DNA on a Au-
NPs/nanoPANI/GCE [21](adapted with permission of Elsevier).
biosensors. Furthermore, PANI hybrid materials constituted of the
polymer and metal nanoparticles have been reported to play an
important role for the design of novel e
cient electrochemical
biosensors. As an example, Fig. 4.5 displays the formation of gold
nanoparticle/polyaniline nanotube membranes on a glassy carbon
electrode for the electrochemical sensing of the immobilization and
hybridization of DNA [21]. The synergistic effect of the two kinds of
nanoparticles, nanogold and nanoPANI, enhanced dramatically the
sensitivity for the DNA hybridization recognition in this particular
case, a DNA sequence-specific phosphinothricin acetyltransferase
gene (PAT)existingin sometransgenic crops.
PNA is a structural DNA analogue containing a neutral N-
(2-aminoethyl)-glycine pseudopeptide backbone to which the
nucleobases are linked. The lack of negative charges on these
molecules allows strong base-pairing interactions with ssDNA.
PNA shows very high specificity in DNA recognition. Nanogold-
modified electrodes can largely increase the ssPNA capture probe
immobilized amount leading to an increase of the electrical signal.
As an example, single-stranded PNA probes were immobilized on
a nanogold-modified electrode for the label-free detection of DNA-
PNA hybridization using a water-soluble ferrocene-functionalized
polythiophene transducer [22]. The ferrocene-containing cationic
polythiophene do not interact electrostatically with the PNA probes
due to the absence of the anionic phosphate groups. However, after
DNA-PNA hybridization, the cationic polythiophene is adsorbed on
