Biology Reference
In-Depth Information
Figure 9.8.
Steps of the sandwich-type assay: (1) The redox polymer
and the oligonucleotide probe are electrodeposited on the screen-printed
electrode(SPE);(2)thecaptureprobeandthetargetarehybridized;(3)the
electrode-boundtargetandtheHRP-labeledoligonucleotidearehybridized,
the HRP labels are in electrical contact with the redox polymer; and (4) the
electrocatalytic reduction current of H
2
O
2
to water is measured. Reprinted
with permission from ACS [38].
chosen monomer, the electropolymerization of a monomer, and the
further covalent bond of the probe strand or the copolymerization
of the monomer in presence of the DNA probe Fig. 9.8 [38,
57, 62].
There is also the possibility of forming self-assembled mono-
layers (SAMs) of oligos functionalizing these with hydrophobic
groups.
9.3.2.2 Immobilization of ssDNA over gold electrodes
Generally, the DNA immobilization onto screen-printed gold elec-
trodes (SPGEs) is carried out by means of SAMs formation of
oligo modified with thiol groups [4-48]. Covered surface and
spacing of oligos can be controlled through the addition of a
short-chain alcanothiol that acts as a solvent [63], blocks the
unspecific adsorptions, and at the same time orientates the
probe strands improving considerably the hybridization reaction
e
ciency.
SAMs formation provides a high stability to the genosensor
Fig. 9.9: it is possible to avoid the oxidation and break of
the sulphur-gold link storing genosensors in a dark and dry
place, remaining unaltered for up to 2 months [64]. In addition,
thiolated oligonucleotides SAMs present a great thermal stability,
not being affected by gradients of temperature of up to 70
◦
C
[65].
