Single molecule measurement of large DNA induced damage of non-thermal plasma-treated water

Water safety regarding residual radicals as a result of water exposure to non-thermal plasma (NTP) is reported using single-molecule measurements. In this study the kinetic of strand breakages of large DNA molecules suspended in water exposed to an argon plasma jet was analyzed¹. The single molecule measurements investigation was also conducted on pure water after post exposure to plasma. Results show that plasma (Argon jet) exposure caused a marked reduction in length of DNA molecules suspended in water. The rate of strand breakages k (compare the average length of DNA) was estimated using a simple mathematical model. The estimated k was less than 1/20 of that of the direct exposure. Data analysis show that k-value decreased by increasing the post-exposure time to plasma. Evidence of fragmentation of DNA molecules lasted at least 1 hour after plasma exposure (the longest post exposure time measured in the experiment). It is not clear from the data if the increase in exposure time causes an increase in the number of radicals or another mechanism is taking place. This direct DNA fragments analysis allows the evaluation of safety of plasma treated water effectively. The method also permits the comparison between the effects of different plasma treatments and doses on the rate of DNA fragmentation. In addition, we have analyzed DNA damage induced by Fenton reaction as a comparison standard (relatively simple reaction rather than the plasma).Analysis shows that at high concentration of hydrogen peroxide induced DNA damage is only slightly. However adding Fe²⁺, the induced DNA damage was increased dramatically (by Fenton reaction).