Biomedical Engineering Reference
In-Depth Information
in the form of band broadening is a concern for electro-osmotic flow. Another ad-
vantage to electro-osmotic flow is the ease of coupling other electronic applications
on-chip. However, the electro-osmotic flow often requires very high voltages, mak-
ing it a difficult technology to miniaturize without off-chip power supplies. An-
other significant disadvantage of the electro-osmotic flow is sensitivity to both so-
lution chemistry and the chemistry of the channel surface. For example, the protein
adsorbtion to the walls substantially changes the surface charge characteristics and
changes the fluid velocity. This often leads to undesired changes in the flow during
an analysis, which compromise reproducibility and quantitation. When transport-
ing fluids using electro-osmotic flow, the large surface area to volume ratio allows
macromolecules to quickly diffuse and adsorb to channel surfaces, reducing the
efficiency of pumping. It is important to develop a fundamental understanding of
the interplay of surface chemistry, solution chemistry, and fluid mechanics in mi-
crofluidic devices in order to realize the full potential of these systems.
9.5.4 MicroarrayTechnology
The development of arrays of surface-immobilized molecules for use as sensors
is helpful in increasing the capacity of testing. Molecular selectivity is achieved
through a binding reaction with a sensor element often comprising a biological
macromolecule (e.g., nucleic acid and protein). In conventional biosensors, sets of
related elements (typically DNA fragments, peptides, or drugs) are tested in batch.
The microarrays use a precise, spatially ordered arrangement of elements that al-
low them to be examined side by side. Microarrays offer many advantages over
the conventional biosensing tools: the ability to simultaneously analyze a variety
of analytes in the same sample, the required sample quantities with a minimal,
low consumption of scarce reagents, and a high sample throughput. Microarray
technology is utilized to assess the large size of genetic information (genomics) or
proteins.
9.5.4.1 Genomics
Genomics is the systematic study of the genetic information of an organism or a
cell. Applications of genomics include the identification of complex genetic dis-
eases, drug discovery and toxicology studies, new diagnostic methods of mutations
and polymorphisms, the analysis of pathogens, the specific genotype-targeted drugs
for food processing, and agriculture product development. The major tools and
methods related to genomics are genetic analysis, measurement of gene expression,
and determination of gene function. One can analyze differing expression of genes
over time, between tissues in healthy and disease states. However, the DNA micro-
array technology based on the parallel processing is used to monitor the large-scale
gene expressions simultaneously. When combined with the metabolic activity, one
can understand the changes in varying conditions.
The Human Genome Project predicted 100,000 to 150,000 genes. The actual
number of genes was nearly 30,000 to 400,000. Having information on all the
genes is useful, but the interaction between the genes should also be understood.
Microarray technology allows the analysis of many genes at once and allows the
