Combination of pulsed electric fields and non-thermal plasma jet for more effective bacterial decontamination

Exposures to pulsed electric fields and non-thermal plasmas have both been investigated as methods for the inactivation of microorganisms. In our studies we have combined treatments with an argon-operated, rf-driven plasma jet (kINPen 09) with the application of pulsed electric fields of microsecond duration. Inactivation efficacy against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aerugionsa was determined by viability counts. Treatments of 3 minutes with plasma alone or treatments with consecutive pulsed electric fields of 100-μs duration and 15-kV/cm amplitude alone were found to result in some but not complete inactivation. Conversely, a combination of treatments exhibits significant synergies versus individual treatments, resulting in a complete inactivation when bacteria suspensions are first treated with the plasma¹. Membrane integrity, membrane potential and intracellular ROS were studied by flow cytometry. Leakage of intracellular compounds, such as DNA and protein, was measured spectrophotometrically at 260 nm and 280 nm. The properties of the cell suspension, such as pH-value, conductivity, and RNS&ROS, were also investigated. Studies of the underlying mechanisms suggest that in the plasma activated liquid environment, cells become more vulnerable to electroporation.