Quantitation of Reactive Oxygen Species Generated by Cold Atmospheric Pressure Plasma Discharge

Cold Atmospheric Pressure Plasma (CAPP) devices have many promising uses, ranging from killing bacteria in industrial and medical settings to etching materials in the fabrication of computer parts. While CAPP jets have been commonly studied, the first novel CAPP device which we developed generates a linear discharge of plasma, allowing for broad, sweeping treatments. The other novel CAPP device we developed generates multiple linear discharges grouped together such that they completely cover about 5 cm² of area, which allows for more consistent exposures over large surfaces. One important aspect of the effectiveness of the CAPP device is its production of reactive oxygen species (ROS), such as ozone, hydroxyl radicals, and hydrogen peroxide. Here we demonstrate that, through the use of fluorescence assays and molecular probes, including Amplex Red (for peroxide), Terephthalic acid (TPA, for hydroxyl radicals), and an ozone probe (Forensics Detectors, FD-90A-O3), the rate of ROS generation from the CAPP device can be quantitated. We also demonstrate that different gas mixtures produce ROS at different rates, and prove that simple compressed air can also produce significant and useful amounts of ROS when used with the CAPP device. Our findings provide insight into some chemical mechanisms through which CAPP devices kill bacteria.