Biomedical Engineering Reference
In-Depth Information
any independent proof or physical evidence of fractals in the examples presented. It is a con-
venient means (since it provides a lumped parameter) to make the degree of heterogeneity that
exists on the surface more quantitative. Thus, there is some arbitrariness in the fractal model to
be presented. One might justifiably argue that appropriate modeling may be achieved by using
a Langmuirian or other approach. The Langmuirian approach has a major drawback because it
does not allow for or accommodate the heterogeneity that exists on the surface.
E. coli
has recently been detected by different biosensor configurations. Some of the more
recent ones that have appeared in the literature include:
(a) Single-cell level detection of
E. coli
in microfluidic device (Han et al., 2008)
(b) Gold screen-printed based impedimetric immunosensors for direct and sensitive
E. coli
quantization (Escamilla-Gomez et al., 2008)
(c) Cy5-labeled antimicrobial peptides
for enhanced detection of
E. coli
0157:H7
(Arcidiacono et al., 2008)
(d) Magnetoresistive immunosensor for the detection of
E. coli
0157:H7 including a micro-
fluidic network (
Mujika et al., 2009
)
(e) Nano-silver-modified PQC/DNA biosensor for detecting
E.
coli
in environmental water
(
Sun et al., 2009
)
(f) Disposable amperometric immunosensing strips fabricated by Au nanoparticles-modified
screen-printed carbon electrodes for the detection of food borne pathogen
E. coli
0157:H7
(
Lin et al., 2008a,b,c
)
Abu-Rabesh et al. (2009)
have recently developed a highly sensitive disposable amperomet-
ric immunosensor for the detection of
E. coli
. The authors used a double layered configura-
tion at the transducer surface that included a polypyrole NH
2
-anti
E. coli
antibody (PAE)
inner layer and an alginate-polypyrole (Alg-Ppy) outer layer. The authors indicate that in
the presence of the substrate PAPG (
p
-aminophenyl
b
-
D
-galactopyranoside), the bacterial
enzyme,
b
-
D
-
galactosidase produces the PAP (
p
-aminophenol) product. The amperometric
signal is generated due to the electrooxidation of the PAP product.
Abu-Rabesh et al. (2009)
emphasize the need to detect microorganisms for food and water
safety. The presence of
E. coli
may be used as a potential indicator of pathogen presence that
originates from humans and animals (
Tryland and Fiksdal, 1998
). The estimation of
coliforms in water samples is essential for the prevention of enteric disease (
Buchanan,
1997; Tokarsky and Marshall, 2008
) from polluted water supplies that cause public health
concerns (
Tokarsky and Marshall, 2008
).
Abu-Rabesh et al. (2009)
indicate that the conventional method to detect
E. coli
based on cell
cultures grown in differential agar media followed by counting of the target organism takes
1-3 days (
George et al., 2000; Lin et al., 2008a,b,c
). This length of time taken to detect the
pathogens motivates one to develop a rapid and accurate method for their detection.
