Molecular Methods for the Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 243

differentiate between polystyrene beads and bacteria using the appropriate
operating frequency; however, the ability to differentiate between two types
of bacteria was still ambiguous. More information about the dielectropho-
retic behavior of bacterial cells under different environmental conditions
is necessary before this method can be applied to the rapid detection and
separation of bacteria from water resources.
Chapter 10 provides a comprehensive overview of the field of microflu-
idics as well as a review of how the technology has been applied to various
different detection methods for waterborne pathogens.
8.2.3.10. Biosensors
Biosensors are described and reviewed in Chapter 7. That chapter mainly
focuses upon detection of whole organisms, while molecular methods
are discussed in this chapter. However, many of the biosensor techniques
explained in Chapter 7 are applicable to the detection of small molecules.
Indeed, the detection of small molecules is often easier and more sensitive
than whole-cell detection. Chapter 7 also provides an overview of the types
of molecule adopted for surface recognition of the target. Antibodies are
widely used for whole cells, but many emerging recognition elements have
great promise for highly selective molecular detection on a biosensor.
A biosensor is an analytical device for the detection of an analyte once
bound to a biological component (probe molecule) such as an antibody,
enzyme, protein, peptide, nucleic acid, etc. For medical applications, analytes
can be whole cells, viral capsids, small proteins, nucleic acid, etc. The main
advantages of biosensing devices are their specificity, sensitively, simplicity,
and short detection times. 104
The detector ( Fig. 8.13 ) transforms the signal resulting from the
interaction of the analyte with the probe molecule into another signal
(i.e. transducers) that can be more easily measured and quantified. Detec-
tion methods include thermal, optical, electrochemical, and mass-based.
The whole reaction takes place usually on a sensing surface that is able to
detect signals even at low concentrations or frequencies of the analyte-
probe interaction. Bioreceptors are immobilized onto solid phase trans-
ducers to form sensing platforms. The immobilization of the bioreceptor
is fundamental for the functionality and integrity of the sensor. 105 Detec-
tion of the binding of the analyte to the bioreceptor can be measured
many ways, including electrochemically, optically, and piezoelectrically.
The advent of nanomaterials with advanced chemical and optical proper-
ties should increase the ability to detect analyte-bioreceptor interactions.