Biomedical Engineering Reference
In-Depth Information
the literature for monitoring toxic compounds, including the electrodes and the method
used for signal transduction and quantification of the results. Most of the multiarray
biosensors reported in literature are optical sensors, while relatively few use electrochem-
ical detection. These biosensors have a large number of application including environ-
mental monitoring, homeland security, agriculture, and toxicology.
A typical example of an array-sensor configuration is the electronic nose technology
consisting of an array of chemical sensors coupled with appropriate transducers and pattern-
recognition techniques. This technique is commonly used to detect analytes by mimicking the
human sense of smell. In the context of toxicity monitoring, this technology has been
successfully used for identifying and correctly classifying organophosphate (OP) nerve
agents and bacterial pathogens and will be discussed in detail later on in this chapter. Another
class of multiarray biosensors that has received considerable attention for toxicity monitoring
is the immunosensors, considered as one of the most promising methods for identifying
biological species (13). Although immunological sensors have been the most successful,
sensors based on DNA hybridization reactions have also been employed (14-16). Compared
with other techniques, these sensors have provided enhanced sensitivities toward toxicants
and by adapting the well-known DNA microarrays it may be possible to construct new mul-
tiarray sensors with enhanced performance (17). At present, DNA sensors have been mainly
reported in a single sensor configuration, while many of the multiarray formats are simple
DNA probes. More innovative methods have reported the development of a microarray
containing over 1,000 electrodes per square centimeter using conventional integrated
circuitry in conjunction with sandwich-immunoassay protocols and electrochemical-based
enzyme amplification detection (18).
In the following section, specific examples of multiarray biosensors for monitoring toxic
chemicals and bacterial pathogens, including details regarding their fabrication, detection
limits, and applications, are discussed.
19.3
Multiarray Biosensors for Monitoring Toxic Chemicals
The most studied toxic chemicals are pesticides, polychlorinated biphenyls, phenols, and
heavy metals (2). Recent reports from our group presented the most recent advances and
trends in analytical technologies (3) including biological sensors for environmental moni-
toring and public safety (2,3). In this work, we focused on several examples of multiarray
biosensors designed for multidetection and multianalysis of chemical toxicants.
19.3.1
Electrochemical Multisensor Array
Among sensors with electrochemical detection, the most successful are the enzyme
sensors mainly based on enzyme inhibition. An important line of development is directed
toward disposable biosensors for semiquantitative analysis and direct on field simultane-
ous screening of multiple samples. For this purpose, electrochemical multichannel instru-
mentation is now available while other custom-made portable electrochemical
multisensors are currently being developed in many biosensor laboratories. Most of these
sensors are designed for amperometric or chronoamperometric measurements at constant
applied potential.
Recently, Solna et al. (19) reported an electrochemical array sensor for simultaneous
determination of pesticides (carbaryl, heptenophos, and fenitrothion) and phenols
(
p
-cresol, catechol, and phenol). The array consists of four disposable screen-printed
