Electrochemical Sensors in Bioanalysis

313 Pages·2001·42.483 MB·\313

by  Raluca-Ioana Stefan (Author)

Electrochemical Sensors
in Bioanalysis

Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
Electrochemical Sensors
in Bioanalysis
Raluca-loana Stefan
and Jacobus Frederick van Staden
University of Pretoria
Pretoria, South Africa
Hassan Y. Aboul-Enein
King Faisal Specialist Hospital and Research Centre
Riyadh, Saudi Arabia
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
First published 2001 by Marcel Dekker, Inc.
Published 2018 by CRC Press
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© 2001 by Taylor & Francis Group, LLC
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ISBN-13: 978-0-8247-0662-3 (hbk)
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Dedication
To my parents Valeria and Ion Stefan for their continuous encouragement,
support, inspiration and understanding.
Raluca-loana Stefan
To the memory of my parents Anna and Paul for their love, inspiration and
continuous support through the years.
Jacobus Frederick van Staden
To Nagla for her enlightment, understanding and support.
Hassan Y. Aboul-Enein

Introduction
The criteria for validation of electrochemical sensors include not only high
accuracy and precision, but also rapidity and low cost. In addition to all these
qualities, simplicity in operation, simplicity of instrumentation, portability (e.g.,
utilization of glucose monitors by diabetics is based on glucose sensors), and the
possibility of miniaturization are also criteria for validation. For bioanalysis, elec­
trochemical sensors have maximum reliability and can be successfully employed
[1,2].
In the last ten years, electrochemical sensors have had a fast evolution in
terms of electroactive materials [3,4], matrix materials [5], and size [6]. The intro­
duction of biomolecules in the design of the membranes favored the development
of new classes of electrochemical sensors (namely biosensors, immunosensors,
microbial biosensors, etc.). These sensors reach a higher selectivity due to the high
selectivity of the biochemical reaction involved. If the biomolecules are immobi­
lized on highly sensitive electrochemical transducers (e.g., amperometric trans­
ducer) their performances are comparable with those of one of the most sensitive
optical sensors—chemiluminescence based (bio)sensors [7-10].
The physiological measurements became a very dynamic area for measure­
ments in single cells, both in vivo and in vitro. To be able to utilize the electro­
chemical sensors for in vivo measurements, they must be biocompatible, solid,
inert, and nontoxic [11,12]. They can be reliably used for fast diagnosis in emer­
gency situations, as well as the continuous monitoring of some substances respon­
sible for illness, directly in the body [13].
The validation criteria for electrochemical sensors play the main role in their
standardization and employment in bioanalysis. Because the reliability of the con­
struction for electrochemical sensors influences the reliability of their perform­
ance, the validation criteria must take into account both construction and perform­
ance of the sensors [14].
v
vi Introduction
CHALLENGES AND PROMISES OF ION-SELECTIVE, MEMBRANE
ELECTRODES FOR BIOANALYSIS
Since the 1960s when the ion-selective, membrane electrodes were intro­
duced by Pungor, they have had a continuous evolution [15-32]. They are used for
the analysis of both types of ions—inorganic and organic—but the most successful
field of application is organic analysis with emphasis in pharmaceutical analysis.
The sensitivity and selectivity of ion-selective, membrane electrodes made their
utilization for the dissolution tests of drug tablets possible [33].
Several designs are proposed for the membrane of ion-selective electrodes,
from homogeneous-crystalline membrane (e.g., fluoride-selective membrane elec­
trode based on LaF3) to heterogeneous membranes: plastic membranes (e.g., PVC
based matrix), modified carbon paste membranes, sol-gel based membranes, im­
printed polymers based membranes, and liquid membranes (e.g., based on a graph­
ite rod as support). The most reliable heterogeneous membranes proved to be the
liquid membranes and the modified carbon paste membranes.
One of the main conditions of evolution of electrochemical sensors is the
knowledge concerning their theory. Different theories for potential development
were proposed [34-39]. Pungor assumed that the potential development at the
membrane-solution interface is the result of the free energy developed in the reac­
tion between the analyte and the selector, both interacting not in the membrane but
at the membrane-solution interface [38,39]. Stefan and Aboul-Enein proved this
statement for ion-pair complexes based on ion-selective, membrane electrodes and
introduced a relation between the response of the electrode and the stability of the
ion-pair complex formed at membrane-solution interface [34,35].
CHALLENGES AND PROMISES OF BIOSENSORS AND
IMMUNOSENSORS FOR BIOANALYSIS
The development of biosensors started almost 40 years ago with the glucose
oxidase immobilized platinum electrode for glucose assay in blood samples. Im­
provements were recorded in the quality of the matrix of the membrane of this
sensor as well as on the type of immobilization of the enzyme or antibody, respec­
tively [40-46]. So-called new generations of biosensors are continuously being
developed (e.g., the amperometric biosensor based on the direct enzymatic regen­
eration at the electrode surface [2]).
The utilization of biosensors for DNA assay made possible the diagnosis of
some illnesses like HIV and Hepatitis B, which need very fast and efficient treat­
ment and control. The DNA-based biosensors can also be used in environmental
analysis [47], although their selectivity over compounds from the same group is
not as good.
Data processing plays a very important role in the reliability of the analytical
process. To improve the reliability of data processing, Kurganov et al. proposed
Introduction vii
the criterion for the validity of the Hill equation for the description of biosensor
calibration curves [48].
The tendency in immunosensor technology is to design the membrane by
immobilizating only the antibody and not the labeled antibody in the membrane.
The limitation of this design is the electroactivity of the complex formed between
antigen and antibody at the membrane-solution interface [10].
Microbial sensors became a well-defined class of sensors utilized mostly in
diagnosis. The microbial sensors based on amperometric transducers reach very
good selectivities and sensitivities.
CHALLENGES AND PROMISES OF SENSOR ARRAYS FOR
BIOANALYSIS
The introduction of sensor arrays made possible the competition between
electrochemical sensors and chromatographic techniques in terms of the number
of analytes that can be simultaneously determined [49]. The electrochemical sen­
sor arrays are more reliable and faster than the chromatographic techniques, and
they do not require special sampling.
The elimination of interferences can be accomplished by adopting the best
chemometrics in the data processing step. The best results for data processing of
such sensors were achieved by utilization of the multivariate regression method
[2,49,50].
ENANTIOSELECTIVE SENSORS IN BIOANALYSIS
Recently, there has been an emphasis on chiral analysis, especially in phar­
maceutical analysis. The utilization of enantioselective sensors in chiral discrimi­
nation of enantiomers is a very accurate alternative for chiral chromatography.
Potentiometric, enantioselective membrane electrodes, amperometric bio­
sensors, and amperometric immunosensors are utilized successfully in the assay of
enantiomers [51-56]. The selection of one of these enantioselective sensors for
chiral analysis must take into account the structure of the compound that is ana­
lyzed as well as the sensitivity necessary for chiral analysis.
CHALLENGES AND PROMISES OF ELECTROCHEMICAL SENSORS
FOR IN VIVO ANALYSIS
The challenges of electrochemical sensors for in vivo analysis are connected
with the development of biocompatible materials as well as of micromaterials
technologies. The utilization of sensor arrays makes possible a simultaneous in
vivo analysis of substances or ions which control different types of illnesses.