Biomedical Engineering Reference
In-Depth Information
The Chinese government is stepping up inspection measures along its border amid
concerns about a bird flu outbreak in Vietnam. The bird flu has most countries stockpiling
vaccines in preparation for an outbreak. Britain however believes that it is impossible to
determine what and who to vaccinate.
A Russian scientist has alarmingly announced that one billion people stand to die from
the coming global flu pandemic. In the United States alone, as many seven million
Americans may be killed by bird flu. Epidemiologists are racing to create a vaccine to
protect humans from the bird flu as the disease continues to spread through Southeast Asia.
New evidence shows that a deadly bird flu virus that has broken out across Asia may attack
all of the human body, not just the lungs as previously known. Asian nations are stocking
up on Tamiflu and making plans for civil-defense-type measures in the event of an out-
break of bird flu. The World Health Organization officials are concerned that February's
Lunar New Year celebrations across Vietnam might lead to more bird flu outbreaks [24].
Bird flu is on the rise, and studies show that it may be able to be spread among humans.
It is impossible to get the flu vaccine for everyone; however, the United Nations issued a
strong warning recently to the growing number of Asian nations where a killer bird flu
virus has broken out in recent weeks. Dozens of workers in Hong Kong's hospitals and
clinics have come down with SARS or bird flu virus in recent months, but, until now,
employees are yet to be compensated.
Therefore, detection and prevention are important. Biosensors for influenza viruses
should meet or exceed certain requirements so as to make them comparable or even
better than the traditional analytical systems. They must be simple to handle, small,
cheap, and able to provide reliable information in real time. They also need to be sen-
sitive and selective for the analyte of interest, and suitable for in situ monitoring [25].
The exceptional combination of a biological element in straight contact with a physical
transducer makes it possible to fulfill all of these requirements. When designing
biosensors, it is important to understand the multiple factors that influence the per-
formance of the sensing system. It is also important to consider the limitations of the
biosensor, especially when the final goal is for application in real-sample monitoring.
Despite extensive research in biosensors, few biosensors are routinely used in real
applications [26
28].
The major analytical parameters of amperometric immunoenzyme sensors, such as
detection limit, analytical range, and signal to background ratio related with amount of
bound conjugate and conditions of its detection. The results of optimization of graphite
powder immunosorbent amount and composition of substrate solution for PIV detection
are presented in Figure 22.8a,b.
It shows dependence of the amperometric immunosensor responses on concentration of
H
2
O
2
in substrate solution, amount of immunosorbent, and their influence on signal to
background ratio. The best signal to background ratio was obtained with 5 mg of graphite
anti-PIV immunosorbent, and substrate solution contains 0.5 mM H
2
O
2
and 1 mM KI.
Figure 22.9 describes the amperometric sensor response to different concentrations of
PIV in ng/mL. Lower detection limit 0.5 ng/mL with a coefficient of variation (COV) of
0.06. The upper detection limit is as high as 10,000 ng/mL. Once the sample is injected, it
takes four min to reach a steady state, and the total time of the assay from the beginning
to the end is about 22 min. The current is proportional to the concentration with the upper
limit of our device of 15
A.
Figure 22.10 of IAV response illustrates similar results to PIV and describes the amper-
ometric sensor response to different concentrations of IAV in ng/mL (lower detection limit
0.4 ng/mL with a COV of 0.05).
The upper detection limit is high as 300 ng/mL. Once the sample is injected, it takes
four min to reach a steady state (Figure 22.11), and the total time of the assay from the
