Biomedical Engineering Reference
In-Depth Information
device able to rapidly provide qualitative information about the presence of a toxin in
multiple samples before more complex tests could be performed would significantly
reduce the cost and time of analysis (3). Such screening methods could be used to provide
a simple “yes or no” answer (4) regarding the toxicity of the sample and complement the
traditional techniques. Owing to their unique characteristics, biosensors are able to
provide rapid qualitative information about the toxicity of an analyte prior to extensive
laboratory analysis (1). However, most biosensors developed to date are designed in a
single sensor format and the analysis is usually restricted to a single component in a
specific sample. In this configuration, samples are analyzed one at a time and, in some
cases, additional polishing, reequilibration, and calibrations are required. Advances have
been reported with the development of disposable single-use sensors that can be easily
mass-produced by photolithography or chemical vacuum deposition (5-7). While most of
these sensors are often used for single analysis, their reproducibility and stability must be
strictly ensured. To increase the sample throughput and respond to current requirements
for multianalysis and multidetection in toxicity monitoring, recently, there has been a
great interest in designing multiarray biosensors.
In this chapter the challenges and opportunities in designing multiarray biosensors for
toxicity monitoring, using example from our laboratory and existing published literature
data, are described. This includes the description of existing fabrication techniques, trans-
duction and amplification of sensor signal, and data quantification. Applications of such
devices for monitoring chemical toxicants and bacterial pathogens are presented with
special emphasis on their use for toxicity screening.
19.2
Multiarray Biosensors: Concept, Design, and Opportunities for Toxicity
Monitoring
Currently, a significant amount of scientific research has been devoted to developing
biosensor systems for monitoring toxic chemicals. Almost all types of biosensors (enzyme-,
DNA-, cell-, and tissue-based sensors with electrochemical, optical, thermal, impedimetric,
or piezoelectric, detection) have been used. It is now generally recognized that such systems
provide unique solutions to many problems encountered with traditional technologies for
toxicity monitoring and screening (e.g., time-consuming, in situ analysis, selectivity and
sensitivity, and price) (1-3). One of the advantages of biosensors is their size and the possi-
bility of assembling several sensors to form arrays, thus increasing the sample throughput,
which is almost impossible using conventional methods.
In a typical arrangement, a biosensor has two main components: a (bio)receptor that
provides specificity and selectivity of the sensor and a physicochemical transductor that is
responsible for conversion and amplification of the biomolecular recognition process into
a quantifiable analytical signal (1-3). In a multiarray sensor, this conventional design is
completely changed. For instance, the system may consist of multiple transductors with
similar or different functions, onto which one or more biological receptors are deposited.
Owing to a large number of variables that have to be considered, fabrication of multiarray
biosensors is clearly more complex and involves additional design and optimization steps
specific to multichannel devices and also depends on the type and number of sensing ele-
ments as well as the final application of the system. This includes: (i) multiarray fabrica-
tion and assembly; (ii) availability of specific instrumentation for signal transduction,
processing, and recording data generated on multiple channels; and (iii) availability of
adequate software for data collection and quantification of the results. Using such devices,
