Investigation of double stranded DNA damage induced by quercetin–copper(II) using piezoelectric quartz crystal impedance technique and potentiometric stripping analysis

DNA damage by quercetin–Cu 2+ was monitored in real time by piezoelectric quartz crystal impedance (PQCI) technique. In the PQCI analysis, the frequency change was caused mainly by the changes in density–viscosity of DNA solution in the damage course. The influences of DNA, Cu 2+, and quercetin concentrations on the motional resistance change (Δ R m) were investigated in detail. The results showed that quercetin exhibited pro-oxidative damage at lower concentrations while anti-oxidative protection at higher concentrations, and Δ R m exhibited a linear relationship in the DNA concentration range from 200 to 1600 μg/ml. Potentiometric stripping analysis (PSA) was also used to observe the electrochemical behavior of damaged DNA. From PSA, a new peak at 0.84 V and a higher peak at 1.06 V were discovered, which suggested that more purines were exposed to the electrode surface during the damage course. In agarose-gel electrophoresis, catalase and biquinoline were found to effectively inhibit DNA damage, therefore, a possible damage mechanism was proposed.