Biomedical Engineering Reference
In-Depth Information
The earliest DNA arrays were developed as filter arrays that
are capable of the Southern blot technique and the many deriva-
tives thereof. Subsequent improvements in laboratories led to the
creation of high-density macroarrays, in which two different mi-
croarray-based technologies arose; one was the DNA microarrays
from the Stanford University group of Davis and Brown,
3
and the
other was the GeneChip
®
from Affymetrix (Santa Clara, CA,
USA).
4
Currently, a wide selection of DNA microarrays offers
researchers a high throughput method for simultaneously evaluat-
ing large numbers of genes. Some of these arrays have been accu-
mulating real results in gene expression analysis, and these are
useful for disease diagnosis, drug discovery studies and toxicolog-
ical research. Additionally, with a DNA array, it is possible to dis-
cover any single nucleotide polymorphisms (SNPs); the in-
ter-individual differences in the genome. Moreover, a DNA array
has been employed to determine the expression level of RNA and
the abundance of genes that cause this expression of RNA. On one
single DNA array, scientist can simultaneously perform tens of
thousands of bioaffinity reactions, including hybridizations.
To an electrochemist, the microelectronic array, the most re-
cent entry in this class of device, has been an appealing feature for
the last decade. The widget was originally developed to place bi-
omolecules arbitrarily at the test sites through the application of an
electric field.
5
The electronic biochip is typically composed of
arrayed pairs of working electrodes and counter electrodes. Thus,
with any electronically addressable electrode design, electrochem-
ical detection also becomes feasible. In particular, the intimate
combination of this tool with the electrochemical DNA biosensor
has led to a dramatic increase in research using this technology;
the electrochemical detection-based DNA arrays are anticipated to
provide many advantages over radioisotope- or fluorophore-based
detection systems.
Various kinds of scanning probe microscopy (SPM) ap-
proaches have served as engines for a variety of nanotechnology
achievements. The scanning electrochemical microscope (SECM)
that falls under this category has also produced successful results
in a wide range of electrochemical studies, from the fundamental
analysis of the electrode reaction to electrochemical fabrication of
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