Biology Reference
In-Depth Information
enteritidis
,
Streptococcus sobrinus
and hepatitis B virus [14, 15,
19, 27]. However, most of these electrochemical genosensors have
the drawback that they require an extra hybridization step with a
probe before the PCR amplicon signal is detected The rapid method
for detection of DNA on screen-printed carbon chips described in
this chapter eliminates this hybridization step by labeling the PCR
ampliconwithbothbiotinandfluoresceinviamodifiedprimers.The
PCR amplicon is directly applied to the modified SPC and the HRP
enzymaticreaction is read within15 s [8].
Thus, in this assay, rapid method has eliminated the two steps
that are normally included in the conventional electrochemical
genosensor assay: the denaturation of the PCR amplicon and
its hybridization. Here, we merely immobilized the biotin- and
fluorescein-labeled PCR amplicon on a streptavidin-modified SPC,
followed by incubation with HRP-conjugated anti-fluorescein anti-
body, and the direct detection of the amperometric signal [8].
However, there is a need to incorporate PCR and electrochemical
analysis into a single device for this method to be fully usable for
field applications [13].
15.4 Discussions
Electrochemical enzyme-based biosensor techniques can be used
for DNA and immunoassays (antigen-antibody) based on amper-
ometry [16, 18, 26, 28]. Although the SPC was designed for
DNA detection, it can also be used for the detection of bacterial
cells using antigen-antibody interactions. Rao
et al.
[2] reported
an antibody-based
V. cholerae
electrochemical biosensor assay
using alkaline phosphatase (AP) and the Autolab PGSTAT 12
potentiostat/galvanostat equipment However, the lowest detection
limit was around 10
5
CFU/mL, compared to 10 CFU/mL with a
genosensor, hence it is less sensitive than a genosensor. Moreover,
theassayusedanAPenzymaticsystemfordetectionwhichrequires
more time (10 min) to read the oxidation signals[8].
Conventional DNA microarrays are based on sequence-specific
DNA detection, but their application in diagnostic tests for field
settings is limited by the large biological samples required and
