Biology Reference
In-Depth Information
dentonboththeDNAadsorptionconditionsaswellasthesubstrate
on which DNA is being adsorbed, thus requiring a meticulous con-
trol of the DNA adsorbed layer. Although it is very simple, this strat-
egy requires multisite attachment—such as adsorption—as immo-
bilization technique. Among the different kinds of electrochemical
transducers, it is expected that composites will have the greatest
impactofnanotechnologyforimprovedelectrochemicalbiosensors.
Next section is focused on the main features of composites as elec-
trochemical transducers.
3.2 Composites Materials: Main Features and
Classification
Whendifferentmaterialsarecombined,thepropertiesoftheresult-
ing composite material depend on the properties of the constituent
materials, the length scale, as well as chemical and morphological
details of the dispersion. Each individual component maintains its
originalcharacteristicswhilegivingthecompositedistinctivechem-
ical, mechanical, physical, or biological qualities [45]. These global
features are different and synergist from those shown by the indi-
vidual elements ofthe composite [18, 46].
The first classification of composite can be made in terms of the
nature, in
biological
and
engineering composites
. Two simple, bio-
logical polymer-based examples of composites are wood, made up
of fibrous chains of cellulose in a matrix of lignin and bone, com-
posed of hard inorganic crystals (hydroxyapatite) embedded in a
tough organic matrix (collagen). Composite materials that consist
ofamatrix(metal,polymer,ceramic)withembeddedreinforcement
(filament, whiskers, particles) comprise of many high performance
engineering materials.
A
nanostructured composite
or
nanocomposite
results when the
characteristic length scales of at least one of the components is in
the nanometer range. Nanometer-sized filler materials, with their
inherently large surface-area-volume ratios, are particularly inter-
esting as they facilitate increasing e
ciency of a given property.
Moreover,duetothesmallsizeofthefiller,certainpropertiesmaybe
modified while not affecting others [47]. Being in the nanotechnol-
