Biology Reference
In-Depth Information
hybridization occurred with target sequence. Biotinylated signal-
ing probe was added onto PCR target and accumulation with
streptavidine-alkaline phosphatese conjugate was monitored by
impedance spectrometry. Based on this method, we used alpha
napthol as indicator [74]. Capture probe was modified onto
graphitesurfaceandhybridizationoccurredwithbiotinylatedtarget
sequence. Avidine-alkalinephosphatase complex was coupled with
hybrid and napthyl phosphate was added onto the surface. The
DPV reduction signal of napthol was used as an indicator. For
detection of different bacterial food contaminations [75], Legionella
pneumophila with hairpin DNA probe [76] was performed by using
this system.
13.3.2
Label-Free Electrochemical Genosensing
The main disadvantage of electrochemical nucleic acid biosensors
discussed above is requirement for an indicator to transduce
hybridization.Manyscientistshavefocusedondevelopinglabel-free
methods for directly monitoring the hybridization event. Wang and
coworkers[77]studiedtheoxidationsignalofguaninebaseatabout
1.00 V. Wang and coworkers [78] have determined that guanine is
the most electroactive base when compared with cytosine, timine,
and adenine. In this study, Wang used a pencil-based renewable
electrodeforsensorsurface.Formersolutionbasedelectrochemical
reports have shown that the electron transfer from the uncatalyzed
guanine bases was slow at most electrode surfaces, however,
guanine oxidation could well be observed by using voltammetric
techniqueswhen theguaninewas adsorbed onto the CPE [79].
Tomschik
et al.
[80] observed the oxidation signals of guanine
and adenine at low concentrations of DNA and PNA by applying
chronopotentiometry and voltammetry with a suitable baseline
correction system at pyrolytic graphite electrode (PGE). By using
carbon nanotubes, Wang enhanced the surface area for label-free
detection of hybridization [81]. Prado
et al.
[82] used boron-doped
diamond electrodes for sensing surface. They monitored guanine
oxidation in ssDNA and dsDNA by cyclic voltammetry.
Label-free genosensing techniques have a great importance for
sequence specific detections in pharmaceutical and environmental
