Biology Reference
In-Depth Information
known base sequences related to genetic diseases or microorgan-
ismssuch as viruses, bacteria, etc.
Typical DNA probes take 15 to 25 base pair long that are able to
detecttheirtargetsequences.Besidesprobe,calfthymusdouble(ds)
or single-stranded DNA (ssDNA) molecules also immobilized onto
the recognition element of abiosensor.
If we look from the viewpoint of compound-DNA interactions,
dsDNA has been used in numerous sensor applications [14] for the
detectionofDNAdamagebasedonelectrochemicalsignalofnucleic
acids especially guaninebase.
DNA immobilization step plays the most important role in
determining the performance of an electrochemical genosensor
(DNA-based biosensor) [15]. Control of the DNA binding surface
in terms of surface orientation and coverage is essential for the
sensitive monitoring of DNA-DNA and compound-DNA interactions
by electrochemistry.
12.4.1
Adsorption (Wet Adsorption/Electrostatic
Accumulation)
The adsorption method at controlled potential or without potential
application called “wet adsorption” [16, 17] is the easiest way to
immobilize DNA (or probes) onto carbon transducers [2, 18, 19].
Thereisnoneedofspecialreagents,expensivelabelednucleicacids,
or long experimental steps in adsorption-based immobilization
technique. Hovewer, random immobilization of DNA were obtained
withthistechniqueandnucleicacidsboundweaklytothesurfaceas
parallellayers.Additionally,itispossibletoaglomerateDNAontothe
surface and when the electrode is rinsed stringently, noncovalently
boundDNA can be removed from the transducer surface.
12.4.2
Covalent Binding to Activated/Nonactivated
Surfaces
DNA was first bound to a pretreated electrode via covalent
attachment using carbodiimide molecules by Millan
et al.
[20] in
1992. After the carbodiimide reaction, DNA was bound to the
surface from its guanine bases. This method was later improved
