Biology Reference
In-Depth Information
and using hydroquinone as a mediator. If the PCR product—or any
other double-stranded DNA—is directly adsorbed on GEC trans-
ducer,adenaturingalkalineprocedureaftertheDNAdryadsorption
is mandatory to break the hydrogen bonds linking the comple-
mentary DNA strands in order to ensure proper hybridization
[79].
Although a compact thick ssDNA layer can be achieved by
dry adsorption, DNA preserves its unique hybridization properties,
which can be monitored using different strategies, suggesting that
theDNAbasesarenotfullycommittedintheadsorptionmechanism.
DNAbasesaremostlyavailableforhybridization,takingintoaccount
the differences in signal compared with the non-specific adsorption
[79, 80]. This strategy was able to electrochemically detect the PCR
amplicon coming from
Salmonella
spp. in a very simple and cheap
way [79].
Besides this strategy in which the DNA target can be easily
attached and detected by its complementary DNA signaling probe,
a sandwich assay in which the DNA target is in solution can be
easily performed by a double hybridization with a capture and a
signaling probe [25]. This strategy was demonstrated to be use-
ful for the detection of a novel determinant of
β
-lactamase resis-
tance in
S. aureus
using one- and two-step capture format. Accord-
ing to the results, the one-step capture format is more convenient,
as a higher sensitivity was achieved [25]. When compared with
other reported genosensor designs using a similar capture format
[81] and the same labeling system, the genosensor design based on
dry adsorption is simpler and cheaper, showing detection limits of
the same order of magnitude. The procedures based on previous
activation/modification of the surface transducer and subsequent
immobilization,aswellassomeblockingandwashingstepsthatare
tedious, expensive, and time-consuming, were avoided using GEC as
electrochemicalplatform.ThesearetheprincipaladvantagesofGEC
platform with respect to other reported devices [37, 81, 82].
Moreover, by easily controlling the concentration of the DNA
solution being dried on GEC platform, a thick or a thin layer of DNA
can be formed on the GEC surface by dry adsorption [36]. Depend-
ing on the application of the DNA-modified substrate, a thick or thin
DNAlayerwouldbenecessary.Ifastringencycontrolofnon-specific
