Biology Reference
In-Depth Information
Figure9.3.
Particle-basedprotocolsforelectrochemicaldetectionofDNA.
Reprinted with permission from Elsevier [33]. See also Color Insert.
the disappearance of the electroactivity of the probe, and the
appearance of anew signalcharacteristic ofthe resulting duplex.
The most used non-electroactive labels have been the enzymes
owed fundamentally to their capacity of amplification of the ana-
lytical signal, providing a great sensitivity. Generally, the analytical
signal is based on a redox process of some enzymatic reaction
product. Enzymes can be joined directly to the DNA strand [38-43],
ortowardtheinteraction(strept)avidin-biotin[44-50]Figs.9.4and
9.5,digoxigenin-antidigoxigeninantibody[51-53],orFITC-antiFITC
antibody [54-56] among others.
The wide use of enzymes as labels in a
nity assays is due to
their aptitude to turn the hybridization reaction into a wide range
of detectable molecules. The most usual enzymes are phosphatase
alkaline (AP), horseradish peroxidase (HRP), or glucose oxidase
(GOD). All of them are relatively stable, cheap, and generally have
high conversionspeed.
9.3.2
Strategies for Immobilization of ssDNA over SPEs
The skill of immobilizing the probe onto the transducer in a
predictable way while keeping its inherent target a
nity intact is
crucial for the development of the genosensor. In addition, if probe
strands are tidy and orientated, it can determine the sensibility
and reproducibility of the genosensor. Thus, independently of every
particular probe, some general aspects must be considered. The
immobilization of the probe must preserve the ability of target
recognition.
