Sterilization of Living Human and Animal Tissue by Non-Thermal Atmospheric Pressure Dielectric Barrier Discharge Plasma

Summary form only given. Sterilization prior to a medical procedure (pre-operative), during, or following such a procedure has always been an issue at a hospital. Sterilization by liquid chemistry (alcohol, or Betadinetrade) has been available for a long time; however, such a procedure becomes difficult if not impossible when attempting to sterilize an open wound, a diabetic sore, or a burn site. Thus, controllable and targeted sterilization of living tissue without contact with or damage to this tissue is needed. Non-thermal atmospheric pressure plasmas have long been used in sterilization of various surfaces without damage to such surfaces and offer a good solution for skin sterilization as well. Presented is a method of sterilization of living tissue using a floating electrode dielectric barrier discharge (FF-DBD), based on a conventional DBD. Here plasma is bounded by quartz dielectric on one side and tissue of a living animal or human on the other side. Complete sterilization (> 7-log reduction in viable colony forming units) is shown from common bacteria abundant on human skin (Streptococcus staphylococcus, and yeast), and from model bacteria such as Escherichia coli, Bacillus subtilis spores, etc. Sterilization is normally achieved, depending on initial microorganism concentration, in 2 to 6 seconds of treatment (up to 15 seconds in some special cases), while no damage is observed during such treatment either visually or microscopically. Microscopic tissue damage assessment is carried out via tissue collection, sectioning, Haematoxylin and Eosin stain (H&E), and microscopic analysis. Mechanisms of this interaction and plasma selectivity to killing bacteria without damaging skin will be discussed. Data from a differential skin toxicity trial on SKIII hairless mice will be presented. During this trial, plasma doses are escalated until damage to animal skin is observed. Plasma-chemical effects are separated from thermal damage by use of FE-DBD plasma in non-thermal (microfilament temperature ~300 K +/-30 K) or thermal (~500-700 K) regimes. Non-thermal plasma regimes are shown to be less damaging while achieving nearly the same sterilization efficiency.