Biomedical Engineering Reference
In-Depth Information
200,000
250,000
200,000
150,000
150,000
100,000
100,000
50,000
50,000
0
0
0
0
500
1000 1500 2000 2500 3000 3500
Time (s)
500
1000 1500 2000 2500 3000 3500
Time (s)
A
B
Figure 6.5
-fetoprotein in solution with 4-(4
0
-iodophenylphenol (IPP) to an ultrasensitive
enhanced chemiluminescence enzyme immunoassay biosensor amplified by double-codified gold
nanoparticles. (b) Binding of
(a) Binding of
a
-fetoprotein in solution with PIP to an ultrasensitive immunoassay
biosensor amplified with double-codified gold nanoparticles (
Yang et al., 2008
).
a
Chang et al. (2009)
have recently developed a LSPCF fiber-optic biosensor to detect AFP in
human serum. These authors report that evanescent wave-excited fluorescence (EWF) has
been widely used in immunoassays. These types of optical biosensors are disposable, inex-
pensive, and have a simple geometry (
Wolfbeis, 2006
). A distinct disadvantage of these types
of biosensors when compared to ELISA (enzyme-linked immunosorbent assay) and RIA
(radioimmunoassay) is the lower detection sensitivity (
Ao et al., 2006
). However,
Chang
et al. (2009
) point out that gold nanoparticles (AuNPs) have been used in biosensors that effec-
tively enhance the sensitivity detection limits (
Matsui et al., 2005; Chau et al., 2006; Mao et al.,
2006; Hsieh et al., 2007
). For example,
Martina et al. (2007)
have been able to detect less than
1 picomole of DNA by using AuNPs in biosensors, and
Georganopoulos et al. (2005)
were able
to detect
in vitro
amyloid-
b
-derived diffusive ligands in cerebrospinal fluid at concentrations
lower than 1 picomole exhibited during the early stages of Alzheimer disease.
Chang et al. (2005) have developed a LSPCF fiber-optic biosensor for the clinical diagnosis
of AFP in human serum. These authors report that AFP is a 70 kDa oncofetal glycoprotein
which is a tumor marker for hepatocellular carcinoma and germ cell tumor (
Tsai and Lin,
2005
;
Fu et al., 2006; Xu et al., 2006
).
Figure 6.6a
shows the binding and dissociation of 0.1 mg/ml AFP in solution to anti-AFP
immobilized on a surface plasmon resonance (SPR) biosensor surface (Chang et al., 2005).
A dual-fractal analysis is required to adequately describe the dissociation kinetics. The values
of (a) the binding rate coefficient,
k
, and the fractal dimension,
D
f
, for a single-fractal analy-
sis, (b) the binding rate coefficients,
k
1
and
k
2
, and the fractal dimensions,
D
f1
and
D
f2
, for a
dual-fractal analysis, and (c) the dissociation rate coefficient,
k
d
, and the fractal dimension,
D
fd
, for a single-fractal analysis are given in
Tables 6.3
and
6.4
.