Moogega Cooper

Nonthermal Dielectric-Barrier Discharge Plasma-Induced Inactivation Involves Oxidative DNA Damage and Membrane Lipid Peroxidation in Escherichia coli

ABSTRACT Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as α-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria.

Mechanism of Blood Coagulation by Nonthermal Atmospheric Pressure Dielectric Barrier Discharge Plasma

Mechanisms of blood coagulation by direct contact of nonthermal atmospheric pressure dielectric barrier discharge (DBD) plasma are investigated. This paper shows that no significant changes occur in the pH or Ca2+ concentration of blood during discharge treatment. Thermal effects and electric field effects are also shown to be negligible. Investigating the hypothesis that the discharge treatment acts directly on blood protein factors involved in coagulation, we demonstrate aggregation of fibrinogen, an important coagulation factor, with no effect on albumin. We conclude that direct DBD treatment triggers selective natural mechanisms of blood coagulation.

Biological responses of Bacillus stratosphericus to Floating Electrode-Dielectric Barrier Discharge Plasma Treatment

Aims:  Dielectric barrier discharge (DBD) plasma is used for sterilization of contaminated inanimate surfaces but seldomly optimized and depends upon the type of organisms and the plasma treatment duration, (net energy deposited) this efficacy varies. The proposed study was designed to see biological responses of one of the robust organism, Bacillus stratosphericus.

Decontamination of Surfaces From Extremophile Organisms Using Nonthermal Atmospheric-Pressure Plasmas

We showed that nonthermal dielectric barrier discharge (DBD) plasma compromises the integrity of the cell membrane of Deinococcus radiodurans, an extremophile organism. In samples of D. radiodurans, which were dried in a laminar flow hood, we observe that DBD plasma exposure resulted in a six-log reduction in CFU (colony-forming unit) count after 30 min of treatment. When the Deinococcus radiodurans cells were suspended in distilled water and treated, it took only 15 s to achieve a four-log reduction of CFU count.

Applications of Non Thermal Atmospheric Pressure Plasma in Medicine

Non-thermal atmospheric pressure plasma is now being developed for use in various medical applications. Over the past few years a lot of clinical applications of non-thermal plasma have been tested and the results show promising potential for Plasma Medicine. In this paper we present a review of various applications of non-thermal plasma in medicine like non-thermal plasma assisted blood coagulation and skin sterilization, melanoma skin cancer treatment and treatment of cornea lesions.

Uniform and Filamentary Nature of Continuous-Wave and Pulsed Dielectric Barrier Discharge Plasma

Observations of atmospheric pressure DBD plasma were conducted through the transparent electrode in Air, Argon, Helium, Nitrogen and Oxygen gasses at 1 and 3 standard liters per minute (s1pm) flow rates through the discharge gap, utilizing three types of excitation waveforms. Three phenomena were observed: (1) plasma filaments travel with the gas at the same speed as the gas for some but not all gases; (2) propagation of excitation is observed in Nitrogen plasma and the filament motion has no directional preference with gas flow direction; and (3) Oxygen, Nitrogen and Helium plasmas were observed to be rather uniform at least over longer time periods.

Mechanism of Blood Coagulation by Non-Thermal Atmospheric Pressure Dielectric Barrier Discharge

Mechanisms of blood coagulation by direct contact of non-thermal atmospheric pressure dielectric barrier discharge plasma are investigated. This study shows that no significant changes occur in pH or Ca2+ concentration of blood during discharge treatment. Thermal effects and electric field effects are also shown to be negligible. Investigating the hypothesis that the discharge treatment acts directly on blood protein factors involved in coagulation, we demonstrate aggregation of fibrinogen, an important coagulation factor, with no effect on albumin. We conclude that direct dielectric barrier discharge treatment triggers selective natural mechanisms of blood coagulation.

Sterilization of conductive and nonconductive surfaces using atmospheric pressure dbd plasma

NASA spacecrafts are composed of a variety of conductive and non-conductive materials. For this reason, it is important to study sterilization efficacy of DBD plasma on varying substrates which are conductive, non-conductive, in wet conditions, and in dry conditions. In the experimental setup, “wet” bacteria designates that it is suspended in a 10 µl drop of water and when allowed to dry for 30 minutes, it is designated as “dry”. The bacteria chosen for these experiments are Escherichia coli and Deinococcus radiodurans. Initial results demonstrate an 8-log reduction in wet E. coli deposited on stainless steel after 30 seconds of plasma treatment; a 4-log reduction in dry E. coli deposited on a polyethylene substrate after 30 seconds of plasma treatment; and a 4-log reduction of wet D. radiodurans which was deposited on stainless steel after 15 seconds of plasma treatment. The results will allow NASA researchers to better design spacecraft for higher sterilization efficacy.

Effects of substrate conductivity on dielectric barrier discharge sterilization efficacy

Summary form only given. Non-equilibrium atmospheric pressure plasma is an ideal solution for sterilizing spacecraft before flight and upon return to Earth without thermal or chemical degradation to the surface. Spacecrafts are composed of a variety of conductive and non-conductive components. For this reason, it is important to study sterilization efficacy on varying substrates which are conductive, non-conductive, wet, dry, grounded, and un-grounded. The bacteria chosen for these experiments are Escherichia coli, Bacillus subtilis, Bacillus pumulis, and Deinococcus radiodurans. The results will allow NASA researchers to better design spacecraft for higher sterilization efficacy. Further, it will ultimately aide in preventing forward and reverse contamination for NASA space missions.

Phemenological estimation of sterilization kinetics using dielectric barrier discharge

Summary form only given. Atmospheric pressure non-thermal plasma discharge has been observed to have strong antimicrobial properties. In an effort to understand the mechanism of plasma sterilization, a limited and basic kinetic model was made as a first step toward a fully descriptive and detailed model. The goal for this phenomenological estimation was to identify biologically active components of plasma discharge that were influential on the exposure time required for complete sterilization. This estimation is currently capable of predicting the sterilization times of an airborne microorganism sterilization setup and a surface sterilization setup on agar within one order of magnitude. The biologically active components of plasma included in this estimation are ozone, hydroxyl radicals, ultraviolet radiation, nitric oxide, and nitrogen ions. Using empirical data, reaction rate coefficients were developed to describe the rate at which microorganisms will inactivate when in presence of each of these plasma components. Using the reaction rate coefficients and calculated concentrations of each plasma species, the estimation predicts the bacteria population reduction given plasma exposure time and vice versa.