Bioelectronic interfaces based on direct electron transfer to proteins and enzymes immobilised at functional electrode surfaces are currently under development and the potential of two such systems for application to clinical measurement will be outlined. The first is the detection of free radical production via direct electrochemistry of cytochrome c immobilised covalently at modified gold electrodes. The redox protein cytochrome c has been immobilised covalently to gold electrodes surface-modified with N-acetyl cysteine via carbodiimide condensation. The electrodes thus produced were used to measure directly the enzymatic and cellular production of the superoxide anion radical (O2(-). The superoxide radical reduced the immobilised cytochrome c which was immediately re-oxidised by the surface-modified gold electrode poised at a potential of +25 mV (vs Ag/AgCl). The electron transfer rate constant (ket) of this process was 3.4 +/- 1.2 s(-1). The rate of current generation was directly proportional to the rate of O2(-) production. The essentially reagentless system produced was designed to be applied ultimately to continuous monitoring of free radical activity in vivo since there is evidence that oxygen-derived free radical species act as mediators which cause and perpetuate inflammation in disease states, including rheumatoid arthritis and neurodegenerative disorders. The second systems are pseudo-homogeneous immunoassays based on direct electron transfer to horseradish peroxidase. Horseradish peroxidase enzyme electrodes based on activated carbon (HRP-ACE) have been constructed by simple passive adsorption.(ABSTRACT TRUNCATED AT 250 WORDS)
[1]
Lo Gorton,et al.
An electrochemical sensor for hydrogen peroxide based on peroxidase adsorbed on a spectrographic graphite electrode
,
1989
.
[2]
Jonathan M. Cooper,et al.
Direct electron transfer reactions between immobilized cytochrome c and modified gold electrodes
,
1993
.
[3]
C. McNeil,et al.
Mediatorless horseradish peroxidase enzyme electrodes based on activated carbon: potential application to specific binding assay
,
1993
.
[4]
Frieder W. Scheller,et al.
Enzyme Electrodes Using Bioelectrocatalytic Reduction of Hydrogen Peroxide
,
1990
.
[5]
A. L. Crumbliss,et al.
Direct electron transfer at horseradish peroxidase—colloidal gold modified electrodes
,
1992
.
[6]
E. F. Ullman,et al.
Enzyme channeling immunoassay: a new homogeneous enzyme immunoassay technique.
,
1980,
Analytical biochemistry.
[7]
S. J. Holt,et al.
IV. Kinetics of aerial oxidation of indoxyl and some of its halogen derivatives
,
1958,
Proceedings of the Royal Society of London. Series B - Biological Sciences.
[8]
J. Cooper,et al.
Electrochemical sensors for direct reagentless measurement of superoxide production by human neutrophils.
,
1992,
Free radical research communications.
[9]
Nicholas J. Walton,et al.
Surface modifiers for the promotion of direct electrochemistry of cytochrome c
,
1984
.