Biomedical Engineering Reference
In-Depth Information
0.3
0.25
0.2
0.15
0.1
0.05
0
0
0.5
1
1.5
2
2.5
3
Fractal dimension,
D
f
or
D
f1
Figure 15.5
Increase in the binding rate coefficient, k or k
1
with an increase in the fractal dimension, D
f
or D
f1
.
binding rate coefficients are plotted together on the same graph. For the data presented in
Figure 15.5
, the binding rate coefficients
k
or
k
1
are given by:
2
:
7
k
or
k
1
¼ð
0
:
0069
þ
0
:
0181
ÞðD
f
or
D
f1
Þ
ð
15
:
4
Þ
The fit is not good, and this is not unexpected as two different binding rate coefficients are
plotted together due to the lack of data points for each of them. The binding rate coefficients
exhibit an order of dependence between 2.5 and 3.0 (equal to 2.7) on the fractal dimension or
the degree of heterogeneity that exists on the biosensor surface.
Cao et al. (2009)
have recently developed an alternative sensitive platform for the detection
of protein biomarkers, PSA, and PSA-ACT complex. These authors indicate that their biosensor
translates the immunosensing event to a gold nanoparticle growth signal. This signal, the
authors claim, can either be recognized by the unaided eye or by an UV-vis spectrophotometer.
Cao et al. (2009)
report that the use of protein biomarkers for disease detection is still a
major driving force for biosensor research.
Ambrosi et al. (2007)
had indicated that gold
nanoparticles (NPs) coupled with antigens or antibodies were used as optical labels.
Das
et al. (2006) and Zhou et al. (2006)
have used these AuNPs as electrochemical markers.
Cao et al. (2009)
have recently used a homogeneous detection assay that incorporates Au
nanocrystalline growth with the use of MMPs (magnetic microbeads). They used a sandwich
type assay to detect protein biomarkers, and used prostate specific antigen (PSA-ACT) as a
model reaction. This, the authors report, is a valuable signature in the diagnosis of prostate
cancer (
Linstedt et al., 1990
;
Curry et al., 1996
).
Cao et al. (2009)
affirm that their highly
sensitive detection technique is much better for PSA as far as detection limits are concerned,
when compared with presently available commercial detection techniques.
