Biomedical Engineering Reference
In-Depth Information
that chitosan not only acts as an immobilizer for the enzyme but also provides the active sites
for the nanoparticles to grow.
Sheng et al. (2008)
point out that biocatalysis has provided an avenue for the synthesis and
enlargement of nanoparticles. This biocatalytic concept has been used for the design of sim-
ple and sensitive electrochemical and optical biosensors (
Katz et al., 2004
;
Medintz et al.,
2005; Moller et al., 2005
). These biocatalytically induced particle growth processes have
been shown to be used for enzyme assays (
Xiao et al., 2004; Baron et al., 2005a,b;
Shlyahovsky et al., 2005
;
Xiao et al., 2005a,b; Zayata et al., 2005
).
Sheng et al. (2008)
point
out that
Hwang et al. (2005)
initially reported the metal deposition by the enzymatically
produced reducing agent. They did this for the electrochemical detection of DNA. A self-
assembled monolayer modified electrode with a biologically catalytic reaction for the
biosensing of cholesterol has been reported (
Zhou et al., 2006a,b
).
Sheng et al. (2008)
report
that this reduction and deposition of metal onto the nanoparticles by an enzymatically gener-
ated reducing agent has been used for the monitoring of quite a few enzymatic reactions.
Sheng et al. (2008)
report that the biocatalyzed synthesis of metallic nanoparticles and the
biocatalyzed synthesis of semiconductor or magnetic nanoparticles is an attractive area of
research (
Willner et al., 2006
).
Sheng et al. (2008)
have developed a novel method to help improve biosensor detection by
using metal hexacyanoferrate nanoparticles from the biocatalyzed synthesis of real earth
hexacyanoferrate (neodymium hexacyanide). They have used this as a model example to
show the application of their protocol.
Figure 6.7
shows the binding of glucose in solution to a neodymium hexacyanoferate nano-
particle on the glucose oxidase/chitosan-modified GCE (
Sheng et al., 2008
). A dual-fractal
analysis is required to adequately describe the binding kinetics. The values of (a) the binding
rate coefficient,
k
, and the fractal the fractal dimension,
D
f
, for a single-fractal analysis,
and (b) the binding rate coefficients,
k
1
and
k
2
, and the fractal dimensions,
D
f1
and
D
f2
, for
a dual-fractal analysis are given in Table 6.5. As expected, and as noted throughout the dif-
ferent chapters for different analyte-receptor systems binding (and dissociation) on biosensor
surfaces, an increase in the degree of heterogeneity or the fractal dimension on the biosensor
surface leads to an increase in the binding rate coefficient.
Lee et al. (2008)
have recently developed a disposable glucose biosensor. These authors used
an electroless-plated Au/Ni/copper low electrical resistance electrode. They point out that
glucose control is required not only for quality control in the food industry, but in particular
for managing diabetes (
American Diabetic Association, 1994, 1999
). Also, the monitoring of
blood glucose level is essential in the case of diabetic patients (
Owen, 1985
;
Nakamura and
Karube, 2003; Neumann and Turner, 2005
). Standard conditions for monitoring of glucose
