Biomedical Engineering Reference
In-Depth Information
cholesterol biosensor (
Shin and Liu, 2007
), (c) a doubly amplified electrochemical assay for
carcinoembryonic antigen (CEA) (
Gao et al., 2009
), (d) a cholesterol biosensor based on
poly-(3-hexylthiophene) self-assembled monolayer using surface plasmon resonance technique
(
Arya et al., 2007
), (e) protein kinase assay using peptide-conjugated gold nanoparticles (
Kim
et al., 2008a,b
), (f) aptamer evolution for assay-based diagnostics for thrombin in solution (
Platt
et al., 2009a,b
), (g) detection of thrombin by an electrochemical aptamer-based assay coupled to
magnetic beads (
Centi et al., 2008
), (h) gold nanoparticles for quantification of prostate specific
antigen (PSA) protein biomarker (
Cao et al., 2009
), (i) label-free analysis of transcription
factors using microcantilever arrays (
Huber et al., 2006
), (j) carp vitellogenin (a potent fish
biomarker for estrogenic activity;
Kim et al., 2008a,b
), and (k) point-of-care (POC) biosensor
systems for cancer diagnostics/prognostics (
Soper et al., 2006
).
Commercial reports on biomarkers (available at a price; generally expensive, though) have also
recently appeared. These include, “In-vitro diagnostics: market analysis 2009-2024” (email from
ewa-malkowska@vg-sales.com
,
Malkowska, 2009
), and “Cancer biomarkers: adoption is driving
growth” (email from
jimp@healthtech.com
,
Jimp, 2009
). The first report highlights the detection
of biomarkers, and points out that this constitutes a major advance and an expanding market
opportunity. The second report reviews emerging cancer biomarker types. It presents business
models behind cancer biomarker products and a SWOT profile analysis associated with specific
strategies. Projection for growth areas within the cancer biomarker products are also given.
15.2 Theory
Havlin (1989)
has reviewed and analyzed the diffusion of reactants towards fractal surfaces.
The details of the theory and the equations involved for the binding and the dissociation phases
for analyte-receptor binding are available (
Sadana, 2001
). The details are not repeated here;
only the equations are given to permit an easier understanding. These equations have been
applied to other biosensor systems (
Sadana, 2001, 2005; Ramakrishnan and Sadana, 2001
).
For most applications, a single- or a dual-fractal analysis is often adequate to describe the bind-
ing and the dissociation kinetics. Peculiarities in the values of the binding and the dissociation
rate coefficients in the systems being analyzed will be carefully noted, if applicable.
15.2.1 Single-Fractal Analysis
Binding Rate Coefficient
Havlin (1989)
reports that the diffusion of a particle (analyte [Ag]) from a homogeneous
solution to a solid surface (e.g., receptor [Ab]-coated surface) on which it reacts to form a
product (analyte-receptor complex; (Ab
Ag)) is given by:
t
ð
3
D
f
,
bind
Þ=
2
,
t
<
t
c
ð
Ab
Ag
Þ
ð
15
:
1
Þ
t
1
=
2
,
t
>
t
c
