Plasma medicine: The advent of the plasma kill - plasma heal paradigm

Low temperature plasmas in air or air-containing mixtures produce reactive oxygen species (ROS) such as O, O₂^-, and OH and reactive nitrogen species (RNS) such as NO and NO₂ which exhibit strong oxidative properties and/or trigger signaling pathways in biological cells. In such chemically reactive environment bacterial cells were found to die in minutes or even seconds. However, controlled low doses of low temperature plasma appear to cause little damage to living animal and plant tissues. For example, skin fibroblast cells are found to remain viable under plasma conditions that can be lethal to bacterial cells. The proliferation of fibroblasts is an important step in the wound healing process. Therefore, the ability of plasma to kill bacteria and to accelerate the proliferation of specific healthy tissue cells opened up the possibility to use plasma for the healing of wounds including chronic wounds such as diabetic ulcers. Under some conditions, low temperature plasmas can induce apoptosis (or programmed cell death). The induction of apoptosis opened the possibility to use plasma to kill aberrant cancerous cells. Promising results have so far been achieved in vitro which show that plasma can effectively kill prostate cancer cells, leukemia cells, squamous cells carcinoma, and others. In this presentation, the various research efforts that have been conducted at our laboratory will be reviewed with emphasis on sterilization/ decontamination and the killing of cancer cells by the plasma pencil. As will be evident throughout the presentation, biologists and biochemists still have large roles to play in order to elucidate the various pathways of interaction between biological cells and plasmas on the subcellular and molecular levels.