PPPS-2013: Abstract submission plasma sterilization studies using a dielectric barrier discharge in air at atmospheric pressure

Despite the variety of technologies available to health services for the processing of health care products, the characteristics of each instrument are decisive in the choice of the most appropriate method. Currently, the technological challenge is to develop efficient methods to disinfect and sterilize heat-sensitive materials, which cannot be subjected to great physical stress. The plasma sterilization is a technology that draws a lot of attention for it congregates quickness, safety and effectiveness. Although called plasma sterilization systems, the equipment available today have as primary sterilization agents the Hydrogen Peroxide and Peracetic Acid, and the plasma phase is responsible mainly for the removal of toxic residuals from the surface of the sterilized material. One research line of the Plasma Laboratory at the University of Brasilia is the development of plasma sources for pollutant control. The present work is based on the assembly and adjustment of one of these sources for sterilization studies at atmospheric pressure. A single dielectric barrier discharge was produced using ordinary air as the precursor gas and AC voltages of 16.3 kV and 60 Hz. In microbiological validation, we used Geobacillus stearothermophilus´ spores, considered the most resistant to the plasma sterilization process. The validation protocol included the exposure of biological samples with at least 10⁵ viable spores to the plasma for 2, 5, 10, 15, 20 and 40 minutes. Because of the low electrical currents obtained in the discharge, the average power of the system was 14.6 W. The decimal reduction time of viable spores, or D-value obtained was 8.40 minutes, a time slightly higher than the ones reported by authors who work with similar sources. We associated this result to the positioning of the biological samples in our device and the low power of our system. There were variations of 30% in the counting of viable cells for each exposure time to the plasma. We associa- ed the kinetics of the microbial death, and therefore the biocidal capability of the plasma, to the variations on the relative humidity of the air. These variations lead to changes in the concentration of reactive species produced from dissociation of the water molecule in plasma such as the hydroxyl and some oxides. Nevertheless, we observed the elimination of all viable spores after 40 minutes exposure to plasma.