Development of a handheld atmospheric pressure plasma jet (APPJ) for biomedical applications

Atmospheric Pressure Plasma Jets (APPJs) are an example of non-equilibrium plasma at atmospheric pressures and relatively low temperatures (preferably, room temperature) that have a large range of practical biological applications. In particular APPJs find use in biomedical applications because their low temperature causes minimal harm to surrounding tissues, but the reactive oxygen and nitrogen species (RONS) generated in the low temperature plasma (LTP) can effectively kill pathogens. Our goal this summer was to build a handheld APPJ for research purposes. We modified an over-the-counter high output voltage (~ 10 kV), high frequency (~ 25 kHz) AC Neon Sign Transformer (NST) for our plasma source. This was attached to a pin electrode based APPJ design to produce helium plasma at atmospheric pressure. The ideal flow rate for the helium was found to be around 2-3 LPM. We then treated E. Coli and S. Aureus bacteria for 1, 2, and 5 minutes. This was compared to the antibiotic gentamicin which we used as the standard. For the E. Coli, we observed a zone of inhibition of about 7 mm, 18 mm, and 35 mm with 1, 2, and 5 min LTP treatment times respectively compared to 32 mm for the antibiotic. For the S. Aureus, we observed zones of inhibition of 6 mm, 16 mm and 29 mm for treatment times of 1, 2, and 5 minutes respectively compared to 21 mm for the antibiotic. Our conclusion is that APPJs are a promising new technology for various biomedical applications including bacterial sterilization and inhibition.