The importance of sample preparation technique is underlined
by an example of a non-culture based techniques for
detecting E. coli O157:H7 in spent leafy green wash water.
Here, filtration was applied to concentrate the target from
50 L of water. The concentrated sample in 400 ml of retentate
was subject to electrochemiluminescence assay using
antibodies labeled with silica encapsulated ruthenium (II) tribipyridal
(Magana, et al., 2013). The combined filtration and
immunoassay could detect low levels of the target
(0.39 log cfu/ml) introduced into the 50 L of sample water.
Although the system does stretch the definition of nanobiosensor
it demonstrates the need for those interested in detecting
foodborne pathogens to consider sample size rather than
drive for miniaturization as in the health care sector