Biosensors for the Detection of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 185

Although mAb production is quicker, the costs are considerably higher.
Since mAbs are raised against a single epitope, they tend to be homogeneous
reagents with better-defined specificities and are less likely to undergo non-
specific binding (i.e. binding of the antibody to nonantigenic materials 1 ) .
In contrast, pAbs are nonhomogeneous, which can result in increased lev-
els of nonspecific binding. pAbs recognize different epitopes on the same
pathogen; some of these antigens may be present in other closely related
but nonpathogenic organisms, which may lead to false positive results.
mAbs offer enhanced specificity and can, for example, differentiate Bacillus
anthracis spores from vegetative cells or from spores of other Bacillus spp. 10
However, compared to mAbs, pAbs possess greater potential for antibody
attachment to the antigenic surface and, importantly for waterborne patho-
gen detection, have higher resistance to pH and salt concentration changes.
Additionally, mAbs can be too specific, in which case they may not detect
species variants that lack a particular epitope. The higher production costs
and susceptibility to unfavorable environmental conditions limit the broad
use of monoclonal antibodies in field-ready sensors. 11
The biggest advantage of antibody-based probes is the specificity and
affinity of these polypeptides to target analytes. Antibodies form tight
noncovalent bonds with specific target molecules with apparent K d values
of 10 −7 to 10 −11 M. 12 Thus, antibodies can interact strongly with the target
analyte even in a complex mixture, resulting in a biosensor that is highly
specific. There are, however, several disadvantages with the use of antibod-
ies on biosensors that limit their use in the field, including the potential
for nonspecific binding, the need for physiological pH and temperature
monitoring during immunoassay procedures, varied antibody performance
from batch to batch, their sensitivity to chemicals in drinking water, their
inability to distinguish viable from nonviable organisms, and the high cost
of mAb production. 1 One of the major disadvantages of antibodies is their
relative instability to environmental fluctuations, especially high tempera-
ture, compared to other peptide-based probes. This limitation may require
antibody-based biosensors to be stored in refrigerated containers and can
reduce long-term storage and field applicability. Additionally, antibodies
are only available for organisms that elicit an antigenic response. Some
pathogenic organisms are nonimmunogenic but produce toxic metabolites
in vivo that produce an immune response. Nonetheless, despite the long
list of drawbacks associated with the use of antibodies, they continue to
be the best available option for the selective detection of a broad range of
microorganisms.