Biology Reference
In-Depth Information
This paste can be easily prepared by mixing graphite powder
with epoxy resin in a 1:4 (w/w) ratio. The soft paste is thoroughly
hand mixed to ensure the uniform dispersion of the graphite pow-
der throughout the polymer. The moldable soft paste is put on the
body of the electrodes and cured at 100
◦
Cfor2daystoobtain
therigidgraphite-epoxycomposite(GEC)[25].Amagnetographite-
epoxy composite (m-GEC) electrode is prepared in the same way as
the GEC transducer, but in this case, a small magnet (3 mm i.d.) is
placedinthecenterofthiselectrodeaftertheadditionofathinlayer
of GEC paste in order to avoid the direct contact between the mag-
net and the electrical connector. After filling the electrode body gap
completely with the soft paste, the electrode is tightly packed and
then cured at the same temperature. This magneto electrode can be
easily coupled withmagnetic particles [71, 72].
Biocomposites can also be easily prepared by adding the biore-
ceptor (an enzyme [18] and antibody [23], or an a
nity receptor
suchasProteinA[73]oravidin[74,75]).
Asanexample,inthecaseofavidingraphite-epoxybiocomposite
(Av-GEB), graphite powder and epoxy resin are also hand mixed in
a ratio of 1:4 (w/w). In this case, for every gram of graphite/epoxy
mixture, an additional 20 mg of avidin is added—resulting in a 2%
(w/w) avidin-graphite-epoxy biocomposite. This mixture is thor-
oughly hand mixed to ensure the uniform dispersion of the avidin
and carbon throughout the polymer. The moldable soft paste is put
onthebodyoftheelectrodesandcuredat40
◦
Cfor1weektoobtain
the rigidavidin-graphite-epoxy biocomposite(Av-GEB).
Finally, gold nanocomposites are prepared by hand-mixing the
following ratios of gold-NPs, graphite powder, and epoxy resin:
0.075/0.925/4 (w/w) for nanoAu(7.5%)-GEC. The resulting soft
pasteisplacedinthegapofelectrodeandcuredat80
◦
Cfor1weekto
obtain the rigidgold NPsgraphite-epoxy composite(nanoAu-GEC).
The GEC-based transducers present numerous advantages over
more traditional carbon-based materials: higher sensitivity, robust-
ness,andrigidity.Additionally,thesurfaceofGECcanberegenerated
by a simple polishing procedure.
An ideal material for electrochemical genosensing should allow
an effective immobilization of the probe on its surface, a robust
hybridization of the target with the probe, a negligible non-specific
