Victor N. Vasilets

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.

Nanosecond-Pulsed Uniform Dielectric-Barrier Discharge

The authors report a new nanosecond-pulsed dielectric-barrier discharge (DBD) for sterilization and other medical applications. In the literature, several discharges have been reported, with pulse durations on the order of hundreds of nanoseconds. In this paper, a novel pulsed DBD has been developed, with only few tens of nanosecond pulsewidths working uniformly over large range of electrode gap distance in air under atmospheric pressure.

Rapid Inactivation of Airborne Bacteria Using Atmospheric Pressure Dielectric Barrier Grating Discharge

Dielectric barrier discharge plasma has been known to inactivate many different microorganisms on surfaces when treatment times are on the order of seconds or minutes in duration. In this paper, a unique plasma air cleaning facility was created which combines a dielectric barrier grating discharge (DBGD) with a filterless laboratory-scale ventilation system and is used to treat concentrated bacterial bioaerosol in a moving air stream at air flow rates of 25 L/s. Results indicate that plasma treatment times on the order of milliseconds corresponding to one pass through the DBGD device can achieve 1.5-log reduction in culturable E. coli immediately after contact with plasma and 5-log reduction totally following in the minutes after the plasma treatment. A numerical characterization study was performed to help predict and understand the mechanism of bacteria inactivation in the DBD plasma from a variety of plasma factors.

Microwave CO2 plasma-initiated vapour phase graft polymerization of acrylic acid onto polytetrafluoroethylene for immobilization of human thrombomodulin.

The functionalization of polytetrafluoroethylene (PTFE) for human thrombomodulin (hTM) binding has been achieved by CO2 plasma activation and subsequent vapour phase graft polymerization of acrylic acid (AA). The PTFE surfaces after CO2 plasma treatment, AA grafting and hTM immobilization were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy, as well as by zeta potential and wetting measurements to quantitatively control each step of modification. The activity of immobilized hTM was estimated by the protein C activation test.

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.

Photolysis of a fluorinated polymer film by vacuum ultraviolet radiation

We studied the photolysis of a fluoroethylene–fluoropropylene copolymer (FEP) film by vacuum ultraviolet (VUV) radiation from a resonance Xe lamp at a wavelength of 147 nm and air pressures of 0.05 and 2.5 Torr. The chemical changes in the FEP surface layer were investigated by Fourier-transform infrared spectroscopy with attenuated total reflection attachment and X-ray photoelectron spectroscopy. Double bonds were found to be the main product in the case of VUV treatment at 0.05 Torr, while photo-oxidation of FEP occurred predominantly by VUV treatment at 2.5 Torr under formation of the —CF2C(O)F group. This oxygen-containing group was more effectively formed in the FEP surface layer by VUV photo-oxidation than by conventional surface oxidation techniques such as treatments by plasma and corona discharge and ozone. Storage of the VUV-treated polymers in air at 50% relative humidity resulted in hydrolysis of —CF2C(O)F to the —CF2COOH group. Substantial improvement of the film wettability was noticed after VUV photo-oxidation. These findings suggest that VUV irradiation provides a high potential for surface modification of fluorinated polymers which are known to be particularly resistant against functionalization by conventional surface modification techniques such as plasma treatment.

Bio-Medical Applications of Non-Thermal Atmospheric Pressure Plasma

Non-Thermal Floating Electrode Dielectric Barrier Discharge (FE-DBD) Plasma in Direct Contact with Living Tissue The focus of this work is direct application of non-thermal atmospheric pressure plasma to human tissue, where this tissue serves as a second active electrode. Such use has significant advantages over the existing technologies. Ultra Violet (UV) radiation, especially high energy Vacuum UV (VUV), does not have good penetration depth in air and VUV exists only in the discharge area. Short-lived active species and radicals (like OH, NO, O2( + Δ g 1 ) and other electronically excited species, atomic Oxygen, etc.) do not,

Improvement of the micro-wear resistance of silicone by vacuum ultraviolet irradiation

Abstract The change in micro-wear of polymers, especially a silicone rubber after vacuum ultraviolet(VUV) irradiation at the wavelength of 147 nm, was studied by means of AFM in scratching mode. It was found that the effect of VUV irradiation on polymer surface micro-wear was related to the extent of crosslinking, strongly depending on the chemical structure of polymers and irradiation conditions. The VUV treatment both in the presence of air and in vacuum resulted in a significant decrease in the micro-wear of silicone. In addition, VUV irradiation made the siloxane smoother, characterized by about a three-fold decrease in the average roughness. ESCA spectra revealed that the improvement in the micro-wear of silicone by VUV irradiation in vacuum (0.05 torr) and VUV photooxidation in air (2.5 torr) was associated with the formation of two different types of crosslinks via CH 2 groups and O atoms, respectively.

Heating Effect of Dielectric Barrier Discharges for Direct Medical Treatment

Several variations of dielectric barrier discharge (DBD) have been developed for nondamaging living-tissue sterilization and blood coagulation. This so-called floating electrode DBD (FE-DBD) has been shown by histology to not damage the treated tissue. Nevertheless, preliminary experiments show that a person who touches the FE-DBD can feel the discharge action. Some of these unpleasant sensations are related to the thermal effects of the plasma. These thermal effects and other important parameters of the discharge are strongly dependent on the electrical properties of the discharge, i.e., driving voltage and waveform shape. In this paper, we first employed sinusoidal driving waveform for medical applications. After that, in order to increase the uniformity and decrease the temperature, we employed a microsecond-pulsed waveform system with a few microsecond pulse durations. Both plasma systems have been analyzed and compared for thermal effects and temperature of the discharge in order to determine the possibilities to control the heating effect with driving waveform.

Inactivation of Bacteria in Flight by Direct Exposure to Nonthermal Plasma

Plasma treatment is a promising technology for fast and effective sterilization of surfaces, waterflow, and airflow. The treatment of airflow is an important area of healthcare and biodefense that has recently gained the interest of many scientists. In this paper, we describe a dielectric barrier grating discharge (DBGD) which is used to study the inactivation of airborne Escherichia coli inside a closed air circulation system. Earlier published results indicate approximately 5-log reduction (99.999%) in the concentration of the airborne bacteria after single DBGD exposure of 10-s duration. This paper investigates plasma species influencing the inactivation. The two major factors that are studied are the effect of charged and short-lived species (direct exposure to plasma) and the effect of ozone. It is shown that for a 25% reduction in direct exposure, the inactivation falls from 97% to 29% in a single pass through the grating. The influence of ozone was studied by producing ozone remotely with an ozone generator and injecting the same concentration into the system, as that produced by the DBGD plasma. The results show a 10% reduction in the bacterial load after 10-s exposure to ozone; thus, ozone alone may not be one of the major inactivating factors in the plasma.