Chapter 18
Affinity Electrochemical Biosensors for
Pollution Control
M.Mascini
18.1
Introduction
DNA electrochemical biosensors, realized by immobilizing an oligonucleotide sequence of the calf thymus DNA on a suitable electrode surface, are simple to assemble
and can provide reliable results; such DNA biosensors hold enormous potential for
environmental monitoring (Wang et al. 1997a,b).
A major application of a DNA biosensor will be the testing of water, food, soil, and
plant samples for the presence of analytes (carcinogens, drugs, mutagenic pollutants,
etc.) with binding affinities for the structure of DNA. Binding of small molecules to
DNA and general DNA damage by ionizing radiation, dimethyl sulphate etc. has been
described through the variation of the electrochemical signal of guanine (Mecklenburg
et al.1997; Wang et al. 1996a,b,c; Jelen et al.1997a,b).
The objective of our work was to develop a disposable electrochemical DNA sensor to evaluate the presence of small DNA binding compounds by measuring changes
of the electrochemical signal of guanine in calf thymus DNA extract. Single-use sensors have several advantages, such as avoidance of contamination among samples,
constant sensitivity and reproducibility, and ease of use (Del Carlo et al. 1997).
This biosensor was realized by immobilizing calf thymus DNA onto the electrode
surface (Wang et al.1997b; Marrazza et al.1999a,b). The DNA biosensor was then immersed in the sample solution containing the analyte. After two minutes of interaction, the DNA sensor was washed, immersed in a suitable clean buffer and a chronopotentiometric analysis (PSA) was carried out to evaluate the oxidation of guanine
residues on the electrode surface. We report some preliminary experiments showing
clear electrochemical effects due to the presence of genotoxic compounds. We can
extrapolate and evaluate such electrochemical signals as resulting from potentially
genotoxic compounds present in real water samples.
18.2
Procedures
18.2.1
Electrochemical Measurements
All electrochemical measurements were carried out at room temperature in 2 ml Teflon
beakers. Potentiometric stripping analysis at a constant current (PSA) was performed
with the following parameters; the potentials were sampled at a frequency of 33 kHz,
and the derivative signal (dt/dE) was recorded vs. the potential.
Affinity Electrochemical Biosensors for
Pollution Control
M.Mascini
18.1
Introduction
DNA electrochemical biosensors, realized by immobilizing an oligonucleotide sequence of the calf thymus DNA on a suitable electrode surface, are simple to assemble
and can provide reliable results; such DNA biosensors hold enormous potential for
environmental monitoring (Wang et al. 1997a,b).
A major application of a DNA biosensor will be the testing of water, food, soil, and
plant samples for the presence of analytes (carcinogens, drugs, mutagenic pollutants,
etc.) with binding affinities for the structure of DNA. Binding of small molecules to
DNA and general DNA damage by ionizing radiation, dimethyl sulphate etc. has been
described through the variation of the electrochemical signal of guanine (Mecklenburg
et al.1997; Wang et al. 1996a,b,c; Jelen et al.1997a,b).
The objective of our work was to develop a disposable electrochemical DNA sensor to evaluate the presence of small DNA binding compounds by measuring changes
of the electrochemical signal of guanine in calf thymus DNA extract. Single-use sensors have several advantages, such as avoidance of contamination among samples,
constant sensitivity and reproducibility, and ease of use (Del Carlo et al. 1997).
This biosensor was realized by immobilizing calf thymus DNA onto the electrode
surface (Wang et al.1997b; Marrazza et al.1999a,b). The DNA biosensor was then immersed in the sample solution containing the analyte. After two minutes of interaction, the DNA sensor was washed, immersed in a suitable clean buffer and a chronopotentiometric analysis (PSA) was carried out to evaluate the oxidation of guanine
residues on the electrode surface. We report some preliminary experiments showing
clear electrochemical effects due to the presence of genotoxic compounds. We can
extrapolate and evaluate such electrochemical signals as resulting from potentially
genotoxic compounds present in real water samples.
18.2
Procedures
18.2.1
Electrochemical Measurements
All electrochemical measurements were carried out at room temperature in 2 ml Teflon
beakers. Potentiometric stripping analysis at a constant current (PSA) was performed
with the following parameters; the potentials were sampled at a frequency of 33 kHz,
and the derivative signal (dt/dE) was recorded vs. the potential.