Biology Reference
In-Depth Information
Figure 3.3.
Different strategies for ssDNA probe immobilization in
genosensing devices based on GEC composites, biocomposites, and
nanocomposites. (A) Dry or wet multisite adsorption on GEC; (B) avidin-
biotin linkage on Av-GEB; (C) (strept)avidin-biotin linkage on magnetic
beads captured on m-GEC; (D) chemisorption on nanoAu-GEC. See also
Color Insert.
to induce changes in DNA molecule) or heated until 100
◦
C. DNA can
adopt a variety of conformations depending on the degree of hydra-
tion. As an example, the most familiar double helix DNA—called
“B-DNA”—can become into the “A-DNA” form if it is strongly dehy-
drated. A structural alteration occurs due to a greater electrostatic
interaction between the phosphate groups, leading to A-DNA. When
the DNA solution is evaporated to dryness, the bases of DNA which
have been dehydrated are exposed, thus the hydrophobic bases are
stronglyadsorbedflatontheelectrodesurfaces.Onceitisadsorbed,
DNA is di
cult to re-hydrate. Hence, DNA is not desorbed, no mat-
ter how long the adsorbed-DNA is soaked in water, characteristic of
irreversible adsorption.
The “irreversible” behavior of the dry adsorbed DNA layer has
beenpreviouslyreportedonglassycarbonelectrodes[77].DNAcan
be tightly and irreversibly immobilized on GEC by both dry and wet
adsorptionproceduresunderstaticconditions[78].Thedualnature
