Biology Reference
In-Depth Information
undecanol). The usage of the different carbon linkers (C3 or C6)
and blocking agents (MCE MCH or MCU) are based on the different
biosensorrequirements [12].
A few examples of pathogen detection using enzyme-based
electrochemical genosensors have been developed [8, 13-19]. In
addition, Farabullini et al. (2007) and Liao et al. (2006) published
their microfabrication of simultaneous detection of different food
pathogenic bacteria ( Salmonella species, Lysteria monocytogenes ,
Staphylococcus aureus and Escherichia coli ) and uropathogens
( Escherichia coli , Proteus mirabilis, Pseudomonas aeruginosa,
Enterococcus species, Klebsiella species, Enterobacter species and
the Enterobacteriaceae group) in clinical urine specimens by means
of a disposableelectrochemical gold genosensorarray.
These analytical methods relied on the immobilization of
specific-thiolated probes with the optimized concentration on the
screen-printed arrays of gold electrodes. The unlabeled or unmodi-
fied PCR amplicons from the bacteria genomic DNA were captured
onto the capture probes on the transducer surface via sandwich
hybridization (indirect method). The biotinylated hybrids were
bound to a streptavidin-alkaline phosphatase (AP) or horseradish
peroxidase (HRP) conjugate and then exposed to their subtrates,
α -naphthyl phosphate or 3,3'5,5'-tetramethylbenzidine (TMB)-
hydrogen peroxide (H 2 O 2 ). Finally, differential pulse voltammetry
measurement was used to detect the signal [20]. Electrochemical
detection can be achieved by monitoring the oxidation or reduction
signal of a substrate after its hybridization with an enzyme-tagged
probe [24]. The analytical signals were observed only at the specific
positions with the corresponding capture probe. The non-specific
signal observed at other position of the array was comparably
negligible.
15.2.3.2 Screen-printed carbon-chip genosensors
In our recent articles, we described the detection of a food-borne
pathogen, Vibrio cholerae , which causes cholera disease. The assay
relied on detection of Vibrio cholerae -specific PCR amplicons using
an electrochemical genosensor on screen-printed carbon chips. The
signalwasmeasuredbyintermittentpulseamperometry(IPA)using
a portable handheld reader AndCare (Alderon, Durham, NC).
 
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