Characterization of Portable Resistive Barrier Plasma Jet and Its Direct and Indirect Treatment for Antibiotic Resistant Bacteria and THP-1 Leukemia Cancer Cells

An atmospheric pressure nonthermal resistive barrier plasma (RBP) jet was designed, constructed, and characterized for plasma surface treatment procedures applied in biomedical applications. The RBP source can operate in both dc (battery) and standard 60/50-Hz low-frequency ac excitation and can function effectively in both direct and indirect plasma exposure configurations, depending on the type of treatment targets and applications. The design and construction aspects of the RBP source are presented, including the electrode configuration, electrical, cooling, and gas flow aspects. The RBP jet is tested, and its characteristics such as the propagation velocity of the plasma jet, electrical properties, plasma gas temperature, and nitric oxide concentration are characterized using optical laser plasma shadowgraphy, voltage–current characterization, optical emission spectroscopy (OES), and gas analyzer diagnostic measurements, respectively. Using a laser shadowgraphy diagnostic, we have measured the average propagation velocity of the plasma jet to be 150–200 m/s at 1 cm from the probe end. The discharge power is calculated from voltage–current characterization, and the plasma power is 26.33 W. An OES was applied, and the gas temperature which is equivalent to the nitrogen rotational
$(T_{rot})$
temperatures was measured. After approximately 2 cm from the tip, along the axis, the plasma emission drops, and the high-temperature ceramic fiber-insulated-wire thermocouple probe was used to measure the temperatures of the gas flows along the downstream jet. The addition of a small portable external cooling unit has brought the temperatures of reactive oxygen species (ROS) and other gases close to room temperature at the tip of the handheld plasma source unit. The concentrations of the ROS at different spatial distances from the tip of the plasma jet were measured; at a 5-cm distance from the electrode, the nitric oxide level was measured to be in the range of 500–660 ppm, and it drops to
$\sim$
100 ppm at 60 cm. The parts-per-million values of nitric oxides after the cooling unit are observed to be of the same order of magnitude as compared to that of the plasma jet. The portable RBP source was tested to be very effective for the decontamination and disinfection of a wide range of food-borne and opportunistic nosocomial pathogens such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus, and the preliminary results are presented. The effects of the indirect exposure of the portable RBP source on monocytic leukemia cancer cells (THP-1) were also tested, and the results demonstrate a preference for apoptosis in plasma-treated THP-1 cells under particular plasma parameters and dosage levels.