Comparison of direct and indirect effects of non-thermal atmospheric-pressure plasma on bacteria

Direct and indirect influence on microorganisms of non-thermal atmospheric-pressure DBD in air is compared in terms of bacterial inactivation rates. It is demonstrated that direct influence of the plasma, where charged particles contact bacteria directly, produces inactivation much faster than the indirect treatment, where plasma afterglow is delivered to the bacteria with a gas flow through the plasma region. This leads to an important conclusion that the effect of charged particles on plasma plays the essential role in interaction with living organisms, although synergy with longer living active molecules and atoms as well as UV radiation generated in plasma and at the surface of tissues may also play a role in inactivation.