Nanotechnology for Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 288

copper wire and a permanent magnet. The device had two stages; the first
being sample isolation and concentration using antibodies conjugated to the
MNPs; and the second being detection with fluorescent QDs. The authors
stated that the use of the MNPs facilitated the capture of the antigen in a
confined space thus enhancing the subsequent fluorescence signal. Cd-Te
QDs with different emission wavelengths were conjugated to capture E. coli
and Salmonella typhimurium , respectively. Detection was possible in the range
of from 10 3 to 10 7 cfu mL −1 for a 20 µL sample. The recovery rate of the
concentration stage was not reported.
9.4. NANOTECHNOLOGY IN PATHOGEN DETECTION
Most reviews of nanotechnology for pathogen detection consider
a wide range of applications without a specific focus upon waterborne
pathogens. Biomedical applications seem to have received the most atten-
tion. 1,26 Some 2010 reviews by Hauck, 26 and also by Tallury, 6 are particu-
larly interesting in that they focus on the application of nanotechnology
as a means of improving detection for developing country settings. 6,26
A table adapted from the second review gives an overview of the uses of nano-
technology in the detection of a range of pathogens, many of them waterborne
( Table 9.1 ). Here we review how nanotechnology has been applied to enhance
the detection of waterborne pathogens, or to enable new detection schemes.
9.4.1. Optical detection
Improved optical properties are a well-known feature for a variety of dif-
ferent nanomaterials, in particular gold and silver NPs and QDs. Section
9.4.1 describes the application of these nanomaterials to enhance fluores-
cent detection schemes, including in flow cytometry, the use of AuNPs in
the colorimetric assays enabled by the unique color change properties of
AuNPs, and the use of NPs to enhance Raman detection through surface
enhanced Raman scattering (SERS).
Another strategy employing AuNPs for detection is through fluorescence
quenching. For example, Philipps and colleagues achieved a limit of detec-
tion (LOD) of 10 2 bacteria mL −1 in solution for E. coli using enzyme linked
gold NPs. 27 The cationic gold NPs were functionalized with quaternary
amine groups, and electrostatically bound to the enzyme, β-galactosidase.
Upon binding of the bacteria, the enzyme is released, restoring its activity
and amplifying the signal ( Fig. 9.4 ). The LOD increased to 10 4 bacteria mL −1