Assay and analysis for anti- and pro-oxidative effects of ascorbic acid on DNA with the bulk acoustic wave impedance technique.

A bulk acoustic wave (BAW) impedance sensor has been applied for in situ monitoring of the whole process of DNA oxidative damage induced by the vitamin C (Vc)-Fe (III) system, based on its real-time responses to the density-viscosity change of the tested solution due to the damages occurring on the DNA molecules. The results showed that Vc exhibited two conflicting effects, i.e., pro-oxidation and anti-oxidation on the DNA at different Vc concentrations in the damage system, and the "threshold" concentration of Vc for these two effects was estimated to be about 100 micromol/L. The end-point frequency change of the sensor (Deltaf(m)) was found to be linearly related to the initial concentration of the soybean DNA (C(DNA)) in the range of 40-1000 microg/mL, and the exponential relationship between the frequency change (Deltaf(0)) vs damaging time suggested that the Fe (III)-mediated DNA damage by Vc could be described as a first-order kinetics reaction. The effects of variations in concentrations of Vc and Fe3+ on the DNA oxidative damage were discussed, and based on investigations for the enhancing influence of H2O2 and inhibiting influence of HO* scavengers on the DNA damage, the nature and physiological toxicity of the damage in biological system were also examined. In addition, UV-vis spectra and electrophoresis analysis were also used, and the experimental observations were in good agreement with the above results. Copyright 2002 Elsevier Science (USA).