Continuous-wave plasma-generated electric field in 3D collagen gel during cold atmospheric plasma treatment

Cold atmospheric plasma (CAP) devices based on a plasma jet with helium flow are actively used nowadays in the studies of cancer treatment. In addition to well-known factors produced by CAP devices (reactive chemical species, UV radiation, heat) that can reduce the viability of cancer cells, the effect of alternating continuous-wave nonthermal electromagnetic fields generated by a plasma source inside the tissue remains unclear. In this article, we measured the values and frequency composition of the continuous-wave electric field induced inside the model of a living tissue-a three-dimensional artificial tissue composed of bovine type I collagen gel-during its irradiation with a helium plasma jet using the set of probes immersed into the gel. It was found that the electric field in artificial tissue has strong direct current (DC) with the main discharge frequency components, and at least up to four harmonics of the discharge frequency. The e-field absolute values in artificial tissue during plasma treatment were within 300-30,000 V/m, which is significantly lower than the estimated cell membrane field of about similar to 10(7) V/m. The absolute value of the e-field DC component nonmonotonically depends on discharge frequency with the optimal frequency range of 14-16 kHz dependent on the thickness of the artificial tissue.