Biomedical Engineering Reference
In-Depth Information
against electrode fouling caused by the adsorption of macromolecules on the surface,
which results in a gradual loss of response with time.
Optimization of the analysis required large dilution of serum to avoid electrode fouling
and minimize the effect due to the presence of electro-active species at the working poten-
tial capable of producing faradaic interferences as well as macromolecules, like proteins or
lipids, with an electrode fouling effect that may influence biosensor response. Also, it can
be seen from the plot in Figure 22.6 that the amperometric signal for the negative samples
remained almost constant at various dilutions, demonstrating the absence of the effect of
hemolysis and nonspecific signals at higher dilutions of the analyte solution. Any attempts
to increase the concentration of the analyte solution resulted in increasing response for the
negative signal, thereby minimizing the difference between negative and positive analyte
solutions. As the device is sensitive enough to work under such high dilutions, the oper-
ating dilution is chosen to be 1:1000. Optimization of the amount of recombinant SNV pro-
tein envelope used for one-sensing element was also examined. The performance of the
device at two different concentrations of the conjugate solution and three different con-
centrations of the viral envelope immobilized on the highly dispersed carbon particles was
described and is shown in Figure 22.7. The optimum results were obtained at a conjugate
concentration of 0.5
g/mL and a protein concentration of 1.0
g/sensing element.
Increased concentration of conjugate (1.0
g/mL) had a more significant effect on the
response of the negative sample than on the positive one. This is due to the increased non-
specific binding of the conjugate on the active electrode surface. Choosing the lower con-
jugate concentration for the working conditions minimizes this effect. Trial for use of
higher concentrations of protein per sensing element is limited by the cost of the SNV pro-
tein envelope. The statistical performance of the device has been compared with the stan-
dard methods and described in detail [13].
22.4.5
Result and Discussion of Influenza Samples
The bird flu seems to be spreading, increasing the risk of a worldwide pandemic. With the
bird flu taking the lives of nine Vietnamese since December 30, it looks like strain H5N1 is
preparing to spread. Public officials say the disease has hit 18 Vietnamese provinces and
cities in a rampage that has led to many deaths. The bird flu is spreading through Vietnam
at a startling rate; with 232 communes in 23 cities reporting cases of influenza strain H5N1.
Vietnam killed 450 ducks in Ho Chi Minh City in January as part of that nation's fight to
stop the spread of the bird flu virus. Since the end of 2003, 26 Vietnamese people are on
record as having died of influenza strain H5N1, more commonly known as the bird flu.
Influenza strain H5N1, more commonly known as the bird flu, has been diagnosed in
seven Vietnamese people since the start of the year [24].
It has been reported that five people died from Asian bird flu in the last 3 weeks; a
Vietnam woman becomes the latest victim. A 3-week-old bird flu outbreak that has affected
several Asian countries has claimed its fifth human victim. Thailand claims “80 percent
ready” to handle major bird flu outbreak. There are three provinces in Thailand that are
currently considered as bird flu stricken, with another 19 provinces on the danger list.
When news that a dangerous bird flu virus had started to spread among humans reached
top levels of Thailand's government, officials took it as immediate emergency [24].
It is now estimated that as many as 2000 people contracted bird flu during the 2000
epidemic in the Netherlands, which is far higher than the 69 cases. A Dutch investigation
reveals that the 2003 Netherlands outbreak of bird flu was enormously more widespread
than previously estimated. Japanese poultry farmers continue to suffer from the financial
fallout created by last year's bird flu outbreak. Egg prices are 50% higher than before.
