Biomedical Engineering Reference
In-Depth Information
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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 .
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