Biomedical Engineering Reference
In-Depth Information
process - denaturation, annealing, and extension that is repeated in several cycles.
At each stage of the process, the number of copies is doubled - from two, to four,
to eight, and so on. The reactions are controlled by changing the temperature using
a special heat-stable Taq polymerase. After 20 cycles, roughly 1 million copies
exist, or enough material to detect the desired DNA by conventional means such as
color reaction.
RNA can also be studied by making a DNA copy of the RNA using the enzyme
reverse transcriptase. Such an approach enables the study of mRNA in cells that use
the molecule to synthesize specific proteins or the detection of the genome of RNA
viruses. PCR has been fully automated via use of thermal cycling. It is a fast, sensi-
tive, and specific test with applications in diagnosis of various diseases.
Development of microarray/technology has further advanced the applications of
molecular diagnostics (Jain
2011b
). It will facilitate the point-of-care (POC) diag-
nosis of genetic cardiovascular disorders and enable the development of personal-
ized cardiology.
Biosensors used in molecular diagnostics are based on antibodies, enzymes, ion
channels, or nucleic acids. Biosensors incorporate a biological sensing element that
converts a biological event into an electrical signal that can be processed. Almost
all analytical systems combine sensing (i.e., detection) and transducing compo-
nents; the distinct feature of biosensors is that the two functions are coupled in a
single physical entity. A biosensor's input is a specific biological event (e.g., bind-
ing of an antigen to an antibody). Its output is a measurable signal that corresponds
to the input. A biosensor's biological component provides specificity, the ability to
selectively recognize one type event. Its transducer confers sensitivity, the ability
to transform the very low energy of the biological event into a measurable signal.
Molecular Imaging of Cardiovascular Disorders
Technologies encompassed within molecular imaging include optical, magnetic
resonance imaging (MRI), and nuclear medicine techniques, which are refinements
of conventional imaging techniques such as positron emission tomography (PET).
Molecular single photon emission CT (SPECT) and PET imaging strategies can be
used for the evaluation of cardiovascular disease, including investigation of myo-
cardial metabolism and neurohumoral activity of the heart as well as for evaluation
of processes such as atherosclerosis, ventricular remodeling after myocardial
infarction, and ischemia-associated angiogenesis at molecular level (Dobrucki and
Sinusas
2010
).
Molecular imaging provides in vivo information in contrast to the in vitro
diagnostics. Cardiovascular magnetic resonance (CMR) molecular imaging can
identify and map the expression of important biomarkers on a cellular scale using
contrast agents that are specifically targeted to the biochemical signatures of dis-
ease and are capable of generating sufficient image contrast. Contrast agents may
help to integrate diagnosis with therapy as they can be designed to be sensitive to
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