Electrochemical Detection - Waterborne Pathogens: Detection Methods and Applications - page 137

CHAPTER SIX
Electrochemical Detection
Timothée Houssin, Vincent Senez
University Lille Nord de France, Villeneuve d'Ascq, France Institute of Electronics,
Microelectronics and Nanotechnology (IEMN), UMR CNRS 8520, Villeneuve d'Ascq, France
6.1. INTRODUCTION
The focus of this chapter is on analytical methods that use a measure-
ment of electrical potential, charge, or current that can find applications in
the detection of a pathogen and in the analysis of its potential effect on a
living organism.
The contact between an electrical conductor and an ionic conductor
induces several electrochemical phenomena occurring in series and/or in
parallel. They involve mass transport and (electro)-chemical reactions. Phe-
nomenological models 1,2 and microscopic theories 3 predict relatively well
the observations in a large spectrum of experimental conditions. However,
there is no general theory of charge transfer in these electrical-ionic sys-
tems. 4 Over the last century, various techniques have been developed to
identify these various phenomena and when possible to develop practi-
cal applications. Recently, interest in electrochemistry has been renewed,
driven by new nanotechnology applications in energy conversion, water
treatment, materials processing, and biotechnology.
The measurement of the electrical impedance changes of a biological
tissue contaminated by pathogens ( Fig. 6.1(a) ) 5 and the measurement of the
oxidation-reduction potential changes of a functionalized carbon nanotube
(CNT) by a captured pathogen ( Fig. 6.1(b) ) 6 are good examples to illustrate
the challenges facing the development of electrochemical biosensors. In the
first case, we want to detect the variation in charge transport far from the
electrode due to the interaction between the pathogen and the cell tissue;
while in the second case, we want to detect the variation in the concentra-
tion of the redox species at the interface between the ionic and electronic
conductors due to the presence of the pathogen. These systems are particu-
larly complex, and they involve various electrochemical phenomena that
are characterized by different time constants.