Spatial-temporal distributions of ROS in model tissues treated by a He+O₂ plasma jet

The transportation of reactive oxygen species (ROS) to lesion site through human tissue is crucial for plasma medicine. For this reason, the spatial-temporal distributions of ROS in model tissues irradiated by a He + O₂ plasma jet were investigated in this paper. It was found that the ROS formed a ring-shaped surface pattern on the model tissue, of which the diameter increased with the gas flow rate but remained unchanged with the plasma treatment time. The surface pattern changed significantly with the inclination angle of plasma irradiation, suggesting that the ROS dosage is difficult to precisely control for clinical applications. Moreover, the penetration depth of O₃ increased linearly with the plasma treatment time or the water content of the model tissue.