Biomedical Engineering Reference
In-Depth Information
Surface imprinting techniques on polymer-coated quartz-crystal microbalances (QCM)
have been used to detect tobacco mosaic virus (TMV) in aqueous media. Molecularly
imprinted polymers (MIP), tailor-made by self-organization of monomers around a tem-
plate (TMV), were generated directly on the gold electrodes. Imprinted trenches on the
polymer surface mimicking the shape and surface functionality of the virus serve as recog-
nition sites for readsorption after washing out of the template [89].
Nucleic acid sequence-based amplification with electrochemiluminescent detection
(NASBA/ECL) is an isothermal technique allowing rapid amplification and detection of
specific regions of nucleic acid from a diverse range of sources. It is especially suitable for
amplifying RNA. A NASBA/ECL technique has been developed allowing the detection of
RNA from avian Influenza virus subtype H7 [90].
21.2.8
Capillary Electrophoresis (CE)
A review is presented on the CE analysis of colloidal or nano particles. Topics discussed
include the CE separation of polymeric, inorganic, microbial (i.e., virus, bacteria, fungi,
and whole cells), and subcellular particles (i.e., mitochondria and nuclei). Several of the
encountered difficulties in analysis as well as the methods employed to overcome them
are presented in the article by Rodriguez and Armstrong [91].
21.2.9
Biosensors for Environmental Applications
Biosensors can be excellent analytical tools for monitoring programs that implement
legislation. In this chapter, biosensors for environmental analysis and monitoring are
extensively reviewed. Examples of biosensors for the most important families of environ-
mental pollutants, including some commercial devices, are presented in this chapter.
Finally, future trends in biosensor development are discussed. In this context, bioelectronics,
nanotechnology, miniaturization, and especially biotechnology seem to be the growing
areas that will have a marked influence on the development of new biosensing strategies
in the near future [92].
21.2.10
Electrochemical Biosensors
Potentiometric biosensors are usually based on ion-selective electrodes. These devices
measure the change in ion concentration during a reaction. Generally, a simple sensor con-
sists of an immobilized enzyme membrane surrounding the probe of a pH meter where
the catalyzed reaction generates or absorbs hydrogen ions [93-95]. This leads to a change
in pH that can be easily read. Three main types of ion-selective electrodes are often used
in biosensors: normal-glass pH electrodes, glass-pH electrodes coated with a selective
gas-permeable membrane, and solid-state electrodes consisting of a thin membrane of a
specific ion conductor [96]. It is also possible to use metal-oxide semiconductors (MOS),
which can measure charge on a surface that causes a current flow proportional to
the charge. MOS devices are small and so they have fast response time due to reduced
diffusion. However, the sensitivity of these can be affected by the ionic strength and con-
centrations of the solutions being analyzed. Potentiometric biosensors have been widely
used for bacterial analyses. Examples include the detection of bacterial contamination in
milk using an L-lactate biosensor, bacterial growth, and sequence-specific biosensing of
DNA. Electrochemical detection of DNA hybridization involves the monitoring of a
current under controlled potential conditions [97]. The hybridization is detected via
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