Biology Reference
In-Depth Information
3.5 Final Remarks
GEC-based platforms are useful and versatile transducer materials
for electrochemical DNA genosensing.
DNA can be attached directly onto a GEC surface by simple
adsorption (the simplest immobilization method and the easiest to
automate),avoidingtheuseofproceduresbasedonpreviousactiva-
tion/modification of the surface transducer and subsequent immo-
bilization, which are tedious, expensive, and time-consuming. This
procedure implies multisite attachment. Although DNA has been
widelyattachedontocarbonaceousmaterials,theunderlyingmech-
anism of adsorption has not been fully clarified. Adsorption is a
complex interplay between the chemical properties, structure, and
porosity of the substrate surface with the molecule being adsorbed.
DNAisastructurallypolymorphicmacromoleculewhich,depending
on nucleotide sequence and environmental conditions, can adopt a
variety of conformations. As a highly negatively charged molecule,
dsDNA isconsidered a hydrophilic molecule.
While dsDNA only partially shows its hydrophobic domain
through its major and minor grooves or through those sites where
dsDNAisopenandexposingDNAbases,ssDNAhasthehydrophobic
bases freely available for their interactions with hydrophobic sur-
faces.
These structural and chemical differences between ssDNA and
dsDNA are reflected in different adsorption patterns for both the
molecules.
ThegreatersizeandthemorerigidshapeofdsDNAwithrespect
to ssDNA are other parameters affecting their adsorption. Besides
the DNA molecule and the solid support, the solvent (normally
water), in particular the ionic strength, pH, and the nature of the
solutes, plays an important role in the adsorption process, mainly
in the stabilizationof the adsorbed molecule on the substrate.
The hybridization event can be detected both with label-free or
enzymaticlabeling procedures.
The single-point attachment of DNA can be achieved by the
immobilizationofbiotinylatedDNAonAv-GEBplatform.Inthiscase,
aone-stepimmobilization/hybridizationprocedureisachieved.The
capability of surface regeneration of the biocomposite electrodes
