Physical and chemical mechanisms of direct and controllable plasma interaction with living objects

The number of potential applications of non-equilibrium atmospheric pressure discharges in biology and medicine has grown significantly in recent years; in fact, the activity in this direction lead to the formation of a new field in plasma chemistry titled `Plasma Medicine'. It is now clear that these plasmas can have not only physical (e.g. tissue cutting and cauterization), but medically relevant therapeutic effects — plasmas can trigger a complex sequence of biological responses in tissues and cells. To move ahead in further development of actual commercial tools that will enter the hospital, and in finding novel and perhaps even unexpected uses of these plasmas an understanding of mechanisms of interaction of non-equilibrium gas discharges with living organisms, tissues, and cells becomes essential.This thesis is focused on understanding of the mechanisms of plasma interaction with living objects using a threefold approach: physical, chemical, and biological. First, a physical characterization of a novel microsecond spark discharge ignited in a pin-to-hole electrode configuration is performed. This provides ground for deeper understanding of the physical mechanisms of plasma effects of biological objects, and further adjustment of the discharge for specific applications. A series of in vitro and in vivo experiments on inactivation of bacteria and spores using various types of plasma discharges adds understanding of physicochemical plasma biodecontamination mechanisms. Based on the results of this study, an initial model of such mechanisms is proposed. Results of in vitro and ex vivo experiments show that plasmas are able to produce a number of various reactive species in gas phase, as well as deliver these species into liquid phase and into tissues. Depth of plasma effect penetration is shown to be on the order of several millimeters. Based on these results, an in vitro physicochemical model of tissue is proposed. Biological safety of plasma treatment is revealed through a series of differential skin toxicity trials on live mouse and rat skin tissue, live pig skin tissue, and in an open wound model on pigs. Plasma ability to coagulate blood, decontaminate and accelerate wound healing is shown in a series of in vivo experiments using live rat animal models. The first invasive plasma application for treatment of gastroenterological diseases is presented.Ph.D., Electrical Engineering -- Drexel University, 201