The modified HET-CAM as a model for the assessment of the inflammatory response to tissue tolerable plasma

Plasma medicine is a novel, highly interdisciplinary field of research. Although the knowledge is rare concerning plasma based biomedical mechanisms, correct dosages and treatment times, animal experiments have been carried out. To follow the 3Rs (reduction, refinement, replacement), it is necessary to define methods for the screening of plasma parameters. In order to determine a reliable test and validate the use of tissue tolerable plasma (TTP) for the treatment of chronic wounds, we have selected the modified hen's egg test on the chorioallantoic membrane (mod. HET-CAM) as a model to benchmark the inflammation potential of plasma. Inflammations of different intensities provoked by using an HF-plasma jet corresponded to the time of plasma-tissue interaction. Additionally, the plasma mode and the gas composition were changed to assess their influence on the efficacy of treatment. Pulsed plasma led to the mildest inflammation, while the addition of 0.1% oxygen to the argon carrier gas led to the most distinct reaction. It was found that the influence of the exposure time was greater than that of the mode and the gas composition. All inflammations were alleviated, when hydrocortisone (HC) was added immediately after plasma treatment. The results of the study demonstrate that the modified HET-CAM test is suitable for screening plasma sources and for the determination of the optimum parameters for treatment of chronic wounds. To transfer the chronic wound into an acute healing wound without harmful inflammation, the maximum time for plasma-tissue interaction should not exceed 5s with the tested plasma source. Furthermore, it is possible to induce defined plasma-inflammations on the chorioallantoic membrane and to determine the anti-inflammatory potential of test substances.