Nanotechnology for Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 296

that detected multiple foodborne pathogens. 58 In this latter work, silica
coated magnetic immunoprobes were utilized for initial pathogen capture.
When using nanoparticles, one further challenge is the batch-to-batch vari-
ability of nanoparticle size, which is crucial to achieve a reproducible and
quantitative assay. 14
9.4.2. Electrical
One example of the use of electrical methods in the detection of patho-
gens with nanotechnology is the method developed by Dobozi-King et al.
which exploits the changes in electrical conductivity of the sample solution
upon bacteriophage lysis of bacteria. 59 Another is the work by Maalouf and
co-workers using MNPs to capture and transport bacterial pathogens to a
gold surface at which impedimetric measurements were undertaken. 60 Oth-
erwise, the area of electrical methods combined with nanotechnology has not
attracted much attention, particularly for waterborne pathogen, while the use
of electrochemical biosensors is a popular topic (covered in Section 9.4.3 ). 61
9.4.3. Biosensors
There are three main ways of performing biosensors signal transduction,
optical, electrical and mass-sensitive approaches are described in Chapter 7.
The magnetic approaches described in Section 9.4.5 represent an alterna-
tive transduction approach, with the examples described there enabled by
nanomaterials. Nanotechnology can act to improve the performance in dif-
ferent ways, which is illustrated for AuNPs in Fig. 9.6 .
Optical detection methods, including some approaches described by the
authors as biosensors, were covered in detail in Section 9.4.1 . Photonic
crystals are nanoarrays of dielectric scatters, and were covered in Chapter 7.
In their recent review, Shinde et al. claim that nanotechnology offers
a solution to the classical problems of electrochemical biosensors, e.g. the
limitations of poor sensitivity and false negative results. 61 There are certainly
a large number of electrochemical studies reported, indicating the popular-
ity of this approach. Sensitivity can be improved by the deposition of metal
nanoparticles thus increasing the surface area, and enhancing the interac-
tion of the recognition element ( Fig. 9.7 ). CNTs have also been utilized in
electrochemical detection protocols.
Early studies of amperometric nanobiosensors for E. coli were reported by
Hasebe et al. 62 and Brewster and Mazenko. 63 The former achieved an LOD
of 10 3 -10 4 cells mL −1 when coupled with a 3 h pre-enrichment period. The
latter authors improved on this by combining the electrochemical detection