The Effect of Low-Temperature Atmospheric Pressure Plasma Jet Parameters on Hydroxyl Radical Production*

The antitumor effects of low temperature plasma jets at atmospheric pressure has been well established. In order to continue the development of plasma applications in the medical field, the effects that plasma parameters have on radical production must be further investigated. We focused on hydroxyl radicals due to their high reactivity and ability to damage DNA. 

We prepared samples of ultra-pure water, coumarin, and phosphate buffer. The samples were irradiated by an atmospheric pressure low-temperature plasma jet at time intervals between 0 s and 90 s. We irradiated samples at voltages of 8 kV, 9 kV, and 10 kV and frequencies of 1 kHz, 2 kHz, 3 kHz, and 4 kHz, with every combination of parameters being tested. The irradiated samples were analyzed with fluorescence spectroscopy and compared to calibration samples to indirectly quantify the amount of 7-hydroxycoumarin produced. Higher levels of 7-hydroxycoumarin correspond to higher levels of hydroxyl radical production. 

Here we will present results showing how the concentration of 7-hydroxycoumarin changes as the plasma voltage and frequency is increased. We will discuss the trends that arise in these results and how the results can be improved.