Development of a Corona Discharge Plasma Source for Sterilization Procedures at Atmospheric Pressure

Abstract

Sterilization refers to any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses, prions, spore forms, etc.) from a surface, equipment, foods, medications, or biological culture media. In general, surgical instruments and medications that enter an already sterile part of the body (such as the blood, or beneath the skin) must have a high sterility assurance level (SAL). In order to reach this SAL, several sterilization agents have been applied: heat, steam under pressure, radiation, electron beam, and chemical products. However, none of the sterilization methods available has a universal application, and the choice of the ideal technique depends on the physical and chemical properties of the materials that are going to be sterilized. The use of non-thermal plasmas on sterilization has been recognized as a successful technology for it congregates safety, effectiveness and quickness. In this work, we present some results of a plasma source developed at the Plasma Laboratory of the University of Brasilia for sterilization procedures at atmospheric pressure. We used ordinary air and Argon as the precursor gases. Our apparatus consists of two coaxial cylindrical tubes with different radii connected to a high voltage power source. The plasma characterization was made with spectroscopic analysis, Langmuir probes and indirect measurements, such as the discharge current. The validation of the procedure was made with the Bacillus subtilis' and the Bacillus stearothermophilus' spores and vegetative cells. We counted the viable cells after the exposure to the plasma with the pour plate technique. We also used scanning electron microscopy images to investigate the interaction of the plasma with the sterile material packages available at hospitals, in order to evaluate the compatibility of our device with the products used nowadays. Finally, we studied the biocide mechanisms of the plasma and related the inactivation of the microorganisms to their interactions with the ultraviolet radiation emitted by the plasma, with the free radicals in the plasma, and to etching processes.978-1-4244-2636-2/09/$25.00 ©2009 IEEE