Electric field measurements during plasma jet operation on/in biological samples and tissues

International audience; Many recent experiments or treatments related to biological applications of cold plasmas have been recently performed using plasma jets. It concerns either applications in vitro or in vivo. The observed effect are most of the time attributed to the very rich chemistry generated by the interaction of the rare gas plasma plume with the surrounding environment constituted either from the ambient air or this last one in complex interaction with liquids at the interface with the target (nutritious medium for in vitro experiments, organ liquids for in vivo applications). Recent experiments performed on tissue oxygenation1 or breast cancer treatments on immunocompetent mice2 lead to the conclusion that probably the involved chemistry couldn’t, alone, completely allow to describe the observed phenomena. This, especially under very soft treatment conditions, was suggesting possible triggering of some immune system chain processes, but also possible modifications in the microenvironment of tissue and tumors. In this context, there is still an unknown role of the electric field associated with the ionization front or generated in the environment of the plasma plume tip.In this work, we measured the electric field in real conditions of Plasma Gun (GREMI plasma jet) applications on various biological samples and targets (tissues and liquids), also in free jet conditions, using a new device (bi-component EOP Kapteos probe) that allows time (ns) and space (1 mm3) resolved measurements in a two radial and longitudinal directions.We will present data obtained along the discharge capillary together with measurements along and in the plasma plume and at different level in biological samples. Both in the capillary and the plume, high longitudinal induced electric fields have been measured just ahead of the apparition of a strong radial electric field in good agreement with Kushner model results. More interesting, is the measurement of a significant electric field presence rather deep in tissue of euthanatized animals (down to two millimeters) at levels that may affect cell permeability or behavior. 1. G. Collet, E. Robert, A. Lenoir, M. Vandamme, T. Darny, S. Dozias, C. Kieda, , J.M. Pouvesle, “Plasma jet-induced tissue oxygenation: potentialities for new therapeutic strategies” Plasma Sources Sci. Technol. 23 (2014) 0120052. G. Collet, L. Ridou, E. Robert, M. Vandamme, T. Darny, S. Dozias, C. Kieda, , J.M. Pouvesle “NTP antitumor soft treatment: evidence of a triggering effect? ”, ICPM5, May 18-23, 2014, Nara (Japan)______________________* Work supported by Région Centre through APR PLASMEDNORM and MENRES through ANR PAMPA