Nanotechnology for Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 302

where the output signal was the quantification of small magnetic field varia-
tions induced by the binding of the MNPs. 89 Maalouf et al. took a different
approach using MNPs for E. coli detection using the MNPs to attract the
pathogens to a gold surface where impedimetric measurements were per-
formed. 60 This yielded detection in the range of 10-10 3 cfu mL −1 .
Superconducting quantum interference devices have also been developed
using MNPs to detect pathogens. The principle behind this mechanism of
detection is the differential oscillations of MNPs in the absence or presence of
the target pathogen during exposure to ac magnetic fields. Free unbound NPs
quickly relax by Brownian motion, whereas those bound to the target undergo
Neel relaxation leading to a gradually dissipating flux. Grossman et al. achieved
an LOD of 10 6 cells in a sample volume of 20 µL for Listeria monocytogenes . A
similar concept was used for the detection of avian flu virus with an LOD of
5 pg mL −1 . The advantage of this approach is that no washing step to remove
unbound MNPs is required. This strategy has been applied to viruses and bac-
teria, though not yet to protozoa or waterborne pathogens in particular.
9.5. SUMMARY
In 2009, writing in the Clinical Microbiology Newsletter, Driskell and
Tripp predicted that nanotechnology for pathogen detection will have a major
impact in healthcare, medicine, food and agriculture, biodefense, and the envi-
ronment. Other authors have added their voice to the view that nanotechnol-
ogy will revolutionize pathogen diagnostics over the course of this century. 14,76
Research into nanotechnology has yielded many developments over the past
decades; searching the literature has revealed many recent articles applying
nanomaterials and nanodevices to the detection of pathogens found in water.
As seen in this chapter, there is a wide variety of different nanomaterials
which can be applied in various ways, i.e. for signal enhancement of most
other types of detection protocol or to create novel methods of detection.
We have reviewed in this chapter the applications of nanomaterials to optical,
electrical, biosensor, and molecular methods of detection, focusing on exam-
ples for waterborne pathogens. While there have been several recent reviews
of the topic, these have mainly focused on medical, bioterrorism or food-
borne pathogens, rather than the particular challenges of detecting pathogens
in water. However, often the pathogens are similar. Our search of the literature
revealed the use of nanotechnology for bacteria detection. In particular, E. coli
has been a popular area of study, whereas there are relatively fewer reports of
nanotechnology applied to viruses and protozoa detection is common.