Molecular Methods for the Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 244

Figure 8.13 The main types of bioreceptors and transducers that have been used to
produce biosensors. (For color version of this figure, the reader is referred to the online
version of this topic.)
The use of biosensors for the detection of viruses is relatively new
and has been applied mostly to viruses from clinical specimens, not to
the detection of viruses from environmental or water samples. The limi-
tation of using biosensors for the detection of viruses from water samples
is that many current viral biosensors rely on the culturing of the virus
to detect antibody reactions in the host cells. Water samples would also
need to be concentrated to overcome low concentrations of pathogen
in samples.
The microcystin toxin, produced by species of cyanobacteria such as
Microcystis , Oscillatoria , Anabaena , and Nostoc , has been found in freshwater
bodies worldwide and has been the target of biosensors for cyanobacteria
detection. Microcystins are monocyclic heptapeptides with many varia-
tions in structures. The microcystin version containing leucine and argi-
nine (MR-LR) is the most widely associated with toxicity due to water
consumption. 106 The target of the microcystin toxin is serine/threonine
protein phosphatases type 1 (PP1A) and type 2A (PP2A). This charac-
teristic has been exploited for the development of the biosensors. PP1A
bound to optic fibers has been used to determine the amount of MC-LR
in a sample by measuring the amount that binds to the PP1A when in
direct competition with labeled MC-Cys-FITC (fluorescein isocyanate
label). The resultant signals are inversely related to the concentration of the
MC-LR in the samples. 107 Electrochemical biosensors, which are more
cost-effective, have also been used to detect MCs in water samples. 108
Their sensitively is limited, however, by the type of electrode used.