Cold atmospheric pressure plasma has been shown to be effective in the treatment of cancer, and in recent years there has been an increasing amount of research for plasma generating devices, the most widely used of which are the pin–ring and double-ring structures. We have combined these two conventional discharge structures and compared their discharge and anticancer effects with use of a single structure. We added a needle-ring as the first preionization layer on top of the conventional two-ring structure, and compared the discharge characteristics and anticancer effects of the double-electrode and the quadruple-electrode structures under three working gases, namely, He, He + 0. 5%N2 and He + 0. 5%O2. The discharge images, photoemission spectra, and H2O2 and NO₂^ - concentration analyses showed that the plasma jet intensity was higher for the quadruple-electrode structure. This is attributed to the fact that the increased pre-ionization layer promotes the full ionization of the gas from top to bottom, which increases the density of charged particles in the subsequent double-loop jet, and thus enhances the strength of the discharge—the upper pin-loop discharge effectively strengthens the lower double-loop discharge. We detreated A549 cancer cells with activated water prepared by the plasma device and examined cell survival, and the results showed that cells treated with He + 0. 5%N2 quadruple-electrode had a lower survival rate. In addition, apoptosis increased significantly with the duration of plasma treatment. The study suggests that a quadruple-electrode plasma jet using He + 0. 5%N2 may be a novel approach for cancer treatment.
Ni et al. (Wed,) studied this question.