his paper presents the results of an experimental investigation of voltammetric and impedimetric DNA-based
biosensors for monitoring biological and chemical redox cycling reactions involving free radical intermediates.
The concept is based on associating the amounts of radicals generated with the electrochemical signals produced,
using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). For this purpose,
a pencil graphite electrode (PGE) modified with multiwall carbon nanotubes and poly-diallydimethlammonium
chloride decorated with double stranded fish sperm DNA was prepared to detect DNA damage induced by the
radicals generated from a redox cycling quinone (i.e., menadione (MD; 2-methyl-1,4-naphthoquinone)). Mena-
dione was employed as a model compound to study the redox cycling of quinones. A direct relationship was
found between free radical production and DNA damage. The relationship between MD-induced DNA damage
and free radical generation was investigated in an attempt to identify the possible mechanism(s) involved in
the action of MD. Results showed that DPV and EIS were appropriate, simple and inexpensive techniques for
the quantitative and qualitative comparisons of different reducing reagents. These techniques may be recom-
mended for monitoring DNA damages and investigating the mechanisms involved in the production of redox cy-
cling compounds.