Biomedical Engineering Reference
In-Depth Information
kinetics was quantitatively evaluated based on a time-course anal-
ysis of the fluorescence intensity.
Compared with radioisotope assays or fluorometry, electro-
chemical methods certainly include rapid detection, a sensitive
transducer, minimal power consumption and even low production
costs. By offering those advantages, electrochemical DNA biosen-
sors, which have been used in a range of unique research activities,
should have the potential to overcome the limits of the current
DNA array platforms. Microelectronics arrays are composed of
patterned, typically platinum ultramicroelectrodes, fabricated on
thermally oxidized silicon substrates by using a standard photoli-
thography process. Initially, they were intended to electrostatically
allow traffic of any charged species to and from electronic test
sites by a superimposed potential from an outer power source.
15
An
agarose permeation layer containing streptavidin coats the chips, to
prevent denaturation of the biological materials by the harsh elec-
trochemical environment near the electrode, and allows the bind-
ing of biotinylated DNA samples. Each electrode may be individu-
ally polarized positively or negatively to concentrate or exclude
the test species arbitrarily. This type of
active
hybridization is up to
1000 times faster than a traditional, passive mode.
Collaboration with the lab-on-a-chip technology
16
has recently
redefined the position of the microelectronics arrays as versatile
automated gene analysis devices. Liu et al. reported an electronics
array with 12,000 features, which can handle automate fluidic
handling steps required to carry out a gene expression study by
Aside from DNA arrays, DNA biosensors that rely on electro-
chemical principles have continued to earn cross-disciplinary in-
novations. For example, they now include conjugation with a wide
variety of enzyme labels
19
and artificial nanoarchitectures involv-
ing gold nanoparticles
20
and carbon nanotubes.
21
Useful interfacial
parameters have been actively prompted for measurements; they
cover intrinsic charge,
22
space charge,
23-25
impedance
26
and capac-
itance.
27
These achievements can definitely boost research on elec-
tronics arrays, which are currently in the early phase of develop-
ment.
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