On the penetration depth of reactive oxygen and nitrogen species generated by a plasma jet through real biological tissue

In this work, an actual biological tissue is used to investigate how thick the reactive oxygen and nitrogen species (RONS) produced by a plasma jet can penetrate through the tissue. This is one of the most critical questions in plasma medicine. The concentration of RONS (O3, H2O2, OH, NO2 −, NO2 − + NO3 −) produced by the plasma jet penetrating through different thickness of the tissue is measured. It is found that the reactive oxygen species (ROS) produced by the plasma are significantly consumed by the tissue. For the tissue thickness of 500 μm, there is only about five percent or even less of the ROS (O3, H2O2, and OH) penetrating through the tissue. On the other hand, more than 80% of the reactive nitrogen species (NO2 − + NO3 −) are able to penetrate through the 500 μm biological tissue. Furthermore, under certain experimental conditions, some of the RONS can penetrate through 1.25 mm of the biological tissue. Finally, besides H2O2, NO2 −, and NO3 −, there is some other unknown RONS that penetrate through the biological tissue.