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The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
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4. Nitric Oxide as a Part of the Immune
System...................................................... 241
5. Electrochemical Measurements of Nitric
Oxide..................................................... 241
6. Dimensions of Porphyrinic Sensors for Nitric
Oxide............................................... 243
D. Preparation and Measurement of Nitric Oxide with Amperometric
Sensors............................... 245
1. Single-Cell
Sensors..................................................................
............ 245
2. Catheter-Protected
Sensors..................................................................
..... 245
3. Cell Culture
Sensors..................................................................
........... 246
4.
Calibration..............................................................
........................ 246
5. Single-Cell Measurements of Nitric
Oxide......................................................... 246
6. In Vitro Measurements of Nitric Oxide in
Tissue.................................................. 248
7. In Vivo Measurements of Nitric Oxide in the
Lung................................................. 248
8. In Vivo Measurements of Nitric Oxide in the
Heart................................................ 249
9. Measurements of Nitric Oxide in Human
Beings..................................................... 250
III. Potentiometric Porphyrinic Sensors for Detection of
Ions............................................. 251
A. Preparation of Porphyrin-Based Potentiometric Sensors for
Anions.................................... 252
1. Salicylate-Selective
Sensors..................................................................
... 253
2. Nitrite-Selective
Sensors..................................................................
...... 253
3. 2-Hydroxybenzyhydroxamate
Sensors................................................................
253
B. Potentiometric Sensor for
Nickel...................................................................
. 254

References...............................................................
.............................. 255
The Porphyrin Handbook
K.M. Kadish, K.M. Smith, R. Guilard, Eds.
Volume 6/Applications: Past, Present and Future
Copyright (c) 2000 by Academic Press 231 All rights of
reproduction in any form reserved.
ISBN 0-12-393200-9/$30.00
232
Malinski
I. Introduction
Porphyrin-based electrochemical sensors possess a unique set of
characteristics that may make them of fundamental importance in solving
some of the problems in pure and applied biology and medicine.1 Sensor
properties that are particularly advantageous are small size and fast
response time, as well as the ability to provide both qualitative and
quantitative information about an electroactive analyte. The main
challenge in the development of a successful electrochemical sensor is
the improvement of its selectivity.
Most amperometric and voltammetric methods are based on a signal
generated by heterogeneous electron exchange between a dissolved
electroactive analyte and a conductor of the first kind (metal or
carbon). These conductors show such poor selectivity that they cannot be
used for direct measurement of any electroactive analyte in a complex
biological matrix. Discrimination between the many electroactive species
in biological environments has been addressed through chemical
modification of the electrode surface.2 The use of chemically modified
electrodes, especially carbon-fiber electrodes, has allowed the
development of amperometric and voltammetric microsensors with a diameter
smaller than a micrometer and a detection limit approaching 10 9M.3 The
small size of these microsensors is crucial especially for the
measurement of short-lived secretory products of biochemical reactions.4
The sensors can be placed in close proximity to where the short-lived
molecules are generated. In addition to this obvious advantage, the small
size of the microsensor reduces the double-layer capacitance (background
dif-fusional transport signal), which improves the faradaic to
nonfaradaic ratio and the detection limit of the microsensor in
comparison to similarly modified larger sensors.
Porphyrins and metalloporphyrins possess several important structural
features that make them desirable thin-film coatings for transforming
nonselective bare-electrode surfaces into selective amperometric and
voltammetric sensors. These features include the possibility of
modification of the porphyrin ring by attaching different substituents,
and the possibility of coordinating different central metals to the
porphyrin ring.5'10 Depending on these modifications, the redox
properties of the porphyrin as well as the axial ligation to the central
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