Biology Reference
In-Depth Information
not found studies regarding the electrochemical detection of waterborne
viruses and protozoa.
Chapter 7 reported very few biosensors for virus detection, with optical
methods dominating. One of those, developed by Jung et al. employed AuNPs
in a fluorescence-quenching set up for rotavirus.
28
For protozoa, mass-sensitive
approaches were found to be the most common type of biosensor in Chap-
ter 7. While nanotechnology can enhance the performance of mass-sensitive
biosensors as described above, this has not yet been applied to the detection
of waterborne protozoa. Chapter 7 described many bacterial biosensors, par-
ticularly for
E. coli
. Nanoparticles have been utilized to enhance the detection
of bacteria using SPR, quartz crystal microbalance (QCM) and cantilevers.
The sensitivity of SPR is sometimes limited by the inability to measure
small changes in refractive index, and NPs offer a solution to this prob-
lem. Noble metal NPs on the surface of an SPR sensor leads to a local
SPR, which exhibits intense absorption and scattering peaks. This signal
amplification enhances the sensitivity of SPR and has been applied to
detect pathogen RNA and toxins.
76
The former used AuNPs, whereas the
latter employed hybrid Au-AgNPs. Dendrimers and liposomes (chemical
structures on the nanoscale, not described in
Section 9.2
) have also been
employed to improve the detection of
E. coli
and RNA sequences from
E .
coli
and
Cryptosporidium
.
76
Simultaneous detection of bacterial pathogens
with an LOD of less than 10
2
cfu mL
−1
in less than 30min was reported
by Marinakos and colleagues.
77
Using the two-photon Rayleigh scattering
properties of gold nanorods Wang and Irudayaraj achieved a similar level of
detection, reporting 50 cfu mL
−1
detection of
E. coli
O157:H7.
78
Cantilevers can be considered a form of nanotechnology, and were
included in the 2010 review by Kaittanis.
1
Using silicon nitride cantile-
vers, Weeks et al. reported in 2003 the detection of as few as 25
Salmonella
enterica
bacteria by monitoring the cantilever's surface bending, which was
directly associated to the amount of bacteria associating on the cantilever.
79
Miniaturization of cantilevers to nanodimensions has claimed to result in
ultrasensitivity, faster detection, and better mass resolution.
14
MNPs have been used to amplify the signal from microcantilevers from
the sensitive detection of proteins,
80
although not yet for waterborne patho-
gens. Other NPs have also been shown to offer a means of signal amplification
for mass-sensitive biosensors. Wang and colleagues reported an AuNP ampli-
fied QCM DNA sensor for
E. coli
O157:H7 detection, with two amplification
steps.
81
The first step involved the improved surface area offered by the AuNPs,
resulting in a higher binding of the target. The second step employed more
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