Plasma interactions with living cells

Summary form only given. In pursuit of minimum-invasive surgery one has to develop techniques, that allow specific cell removal or rearrangement without influencing the whole tissue. In conventional or laser surgery individual cells undergo accidental cell death (necrosis), which is followed by inflammation and may lead to permanent tissue damage. In contrast, cold plasma techniques allow cell removal without necrosis. At the Eindhoven University a suitable small-size plasma source has been developed (plasma needle) and several potentially beneficial plasma-cell interactions have been identified. These reactions include: cell detachment without affecting cell viability, induction of apoptosis (programmed cell death), and altering cell proliferation rate. So far the tests have been performed on cells in culture (mouse fibroblasts or human epithelial cells of lung carcinoma), but recently we have introduced a new model: tissue engineered skin. The effect of plasma-induced cell detachment has been already identified in this model. At present we check for early markers of tissue damage and differentiation of keratinocytes after plasma treatment. In parallel, we continue the study on mouse fibroblasts. MTT assay for long-term viability has been performed. Cell proliferation rate has been monitored using the BrdU assay (a marker for newly formed DNA). A strong link between the plasma properties and triggered cell reactions is expected. Moderate cell damage, which leads to (reversible) detachment or apoptosis, may result from interactions with plasma-produced radicals. The ROS (reactive oxygen species) are known to play an important role in these processes. We have shown that plasma radicals can exist in the liquid phase (cell culture medium). Micro-molar concentrations of ROS from the plasma have been detected using a fluorescent probe in combination with (confocal) LIF, and correlated with gas-phase plasma properties. We conclude that ROS concentrations are within the safe range: the radicals can trigger specific cell reactions, but are unable to kill the cells.