Magesh Thiyagarajan

In this paper, an atmospheric pressure low-temperature plasma pencil generated in helium and helium/ oxygen gas mixtures was characterized in detail for its discharge characteristics, plasma power, reactive plasma species produced, plasma density, and plasma temperatures using electrical and optical emission spectroscopy (OES) diagnostics, and its efficacy for biomedical application. A visible plasma plume length of approximately 27 mm was generated using a 60-kHz ac HV power supply. The OES results showed the most intensive plasma emission lines of OH transition A ² Σ ⁺ (v = 0, 1)→X ² Π(Δν = 0) at 308 nm and OH transition A ² Σ ⁺ (v = 0, 1)→X ² Π(Δν = 1) at 287 nm, O I transition 3p ⁵ P→3s ⁵ S ⁰ at 777.41 nm, O I transition 3p ³ P→3s ³ S ⁰ at 844.6 nm, and N ₂ (C-B) second positive system with electronic transition C ³ Π _u →B ³ Π _g in the range 300-450 nm. The effects of controlled oxygen content on the plasma pencil and on various helium plasma emissions and electrical properties are studied. A spatial distribution of reactive plasma species produced by the plasma pencil is presented. The electron density of plasma jet was estimated to be in the order of 2.1 × 10 ¹⁴ cm ^-3 using Stark broadening line profile of the hydrogen alpha emission. The temperatures of afterglow plasma pencil were evaluated using OH rotational temperatures, and the results demonstrate temperatures of 316 and 362 K for pure He and He/O ₂ gas mixtures (0.1% O ₂ ), respectively. Preliminary results on inactivation of Streptococcus pneumoniae on a solid surface and in liquid suspension were carried out using the plasma pencil for biomedical applications.

Cold atmospheric plasma (CAP), an ambient temperature ionized gas, is gaining extensive interest as a promising addition to anti‐tumor therapy primarily due to the ability to generate and control delivery of electrons, ions, excited molecules, UV photons, and reactive species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) to a specific site. The heterogeneous composition of CAP offers the opportunity to mediate several signaling pathways that regulate tumor cells. Consequently, the array of CAP generated products has limited the identification of the mechanisms of action on tumor cells. The aim of this work is to assess the cell death response of human myeloid leukemia cells by remote exposure to CAP generated RNS by utilizing a novel resistive barrier discharge system that primarily produces RNS. The effect of variable treatments of CAP generated RNS was tested in THP‐1 cell (human monocytic leukemia cell line), a model for hematological malignancy. The number of viable cells was evaluated with erythrosine‐B staining, while apoptosis and necrosis was assessed by endonuclease cleavage observed by agarose gel electrophoresis and detection of cells with the exclusionary dye propidium iodide and fluorescently labeled annexin‐V by flow cytometry and fluorescent microscopy. Our observations indicate that treatment dosage levels of 45 s of exposure to CAP emitted RNS‐induced apoptotic cell death and for higher dosage conditions of ≥50 s of exposure to CAP induced necrosis. Overall the results suggest that CAP emitted RNS play a significant role in the anti‐tumor potential of CAP. Biotechnol. Bioeng. 2014;111: 565–574.

A portable atmospheric pressure resistive barrier plasma (RBP) device is designed, constructed, and characterized for plasma surface treatment procedures applied in biomedical applications. The design and construction aspects of the RBP plasma device are presented including the electrode configuration, electrical, cooling, and gas flow rates. The RBP device can operate in both dc (battery) as well as in standard 60/50 Hz low frequency ac power input. The RBP device can function effectively in both direct and indirect plasma exposure configurations depending on the type of treatment targets. The portable RBP device is characterized for plasma jet exit velocity, plasma temperatures, and reactive nitrogen species (RNS) using laser shadowgraphy, emission spectroscopy, and gas analyzer diagnostics. We have measured the average velocity of the plasma jet to be 150–200 m/s at 1 cm from the probe end. The gas temperature which is equivalent to the rotational (T_rot) temperatures of the plasma is measured by simulation fitting the experimental emission spectra. A high-temperature ceramic fiber-insulated-wire thermocouple probe is used to measure the temperatures of the downstream jet after 2 cm where the plasma emission drops. Addition of external cooling unit brought the temperatures of reactive species and other gases close to room temperature. The spatial concentrations of the reactive oxygen species from the plasma jet tip are measured at 5 cm distance from the electrode. The nitric oxide level is measured to be in the range of 500–660 ppm and it drops to ∼100 ppm at 60 cm. The ppm values of nitric oxides after the cooling unit are observed to be at the same order of magnitude as the plasma jet. The preliminary results on the effectiveness of the portable RBP device for bacterial inactivation as well as the effects of indirect exposure of the portable RBP device on monocytic leukemia cancer cells (THP-1) are briefly presented.

This research investigated the modulation of cell death through exposure of non-thermal resistive barrier based indirect air plasma on monocytic leukemia cancer cells (THP-1). Specifically, we explored cell death through apoptosis and necrosis, since generally apoptotic cell death has a limited inflammatory response as compared to necrosis. We have demonstrated a preference for apoptosis in plasma treated THP-1 cells, under specific plasma characteristics and dosage levels, using fluorescent dyes conjugated with annexin V followed by identification of the cells through fluorescent microscopy and flowcytometry diagnostics. At much higher plasma dosages, the necrotic morphologies in the THP-1 cells were observed. The presented outcomes in the death morphologies of plasma treated THP-1 cells signify the need for further investigation on the cellular mechanisms induced by the indirect plasma exposure. The results obtained from this research indicate the significant potential for the use of our portable non-thermal resistive barrier based indirect plasma treatment method as an inexpensive and less invasive method for treating leukemia and other cancerous lesions.

In this work an atmospheric pressure non-thermal resistive barrier (RB) plasma jet was constructed, characterized and was applied for biomedical applications. The RB plasma source can operate in both DC (battery) as well as in standard 60/50 Hz low frequency AC excitation, and it functions effectively in both direct and indirect plasma exposure configurations. The characteristics of the RB plasma jet such as electrical properties, plasma gas temperature and nitric oxides concentration were determined using voltage-current characterization, optical emission spectroscopy and gas analyzer diagnostic techniques. Plasma discharge power of 26.33 W was calculated from voltage-current characterization. An optical emission spectroscopy was applied and the gas temperature which is equivalent to the nitrogen rotational (Trot) temperatures was measured. The concentrations of the reactive oxygen species at different spatial distances from the tip of the plasma jet were measured and the ppm concentration of NO is at the preferred level for a wide range of standard biomedical treatment applications. The ppm values of nitric oxides after the cooling unit are observed to be of the same order of magnitude as compared to plasma jet. The portable RB plasma source was tested to be very effective for decontamination and disinfection of a wide range of foodborne and opportunistic nosocomial pathogens such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus cereus and the preliminary results are presented. The effects of indirect exposure of the portable RBP source on monocytic leukemia cancer cells (THP-1) were also tested and the results demonstrate that a preference for apoptosis in plasma treated THP-1 cells under particular plasma parameters and dosage levels.

This research study examined the effect of non-thermal portable atmospheric air plasma system on leukemia cancer cells. Acute monocytic leukemia cells (THP-1) were exposed to atmospheric pressure non-thermal plasma. To assess death caused by plasma exposure, cells were subjected to trypan blue exclusion assays and a kill-curve and assessment of death overtime were compiled using data from the assays. In addition to this, DNA was harvested from treated and untreated samples to determine if apoptotic ladders were present. Results have indicated that non-thermal plasma can cause cell death in THP-1 cells overtime, and the death that occurs corresponds directly to the amount of time that the cells were exposed to ionized plasma. Preliminary fluorescent imaging of the treated cells revealed that higher treatment doses are not only more likely to induce cellular death but are likely to induce necrotic death, while lower treatment doses that are capable of inducing death may induce apoptotic or programmed cellular death. Ideally the results obtained from these experiments will allow for further investigation of the effects of ionized non-thermal plasma on melanoma cell lines and will lead to an inexpensive method for treating early stage skin cancer and cancerous lesions.

The purpose of this study was to determine the effects of plasma treatment on bacteria in liquid phases. We predict that the plasma gas can penetrate the liquid culture media and plasma treatment will efficiently kill the bacteria at unique time and distance parameters. It is also hypothesized that less stringent plasma treatment will negatively affect the growth rate of some species of bacteria and possibly their pathogenicity. The bacteria were exposed to hot and cold plasma at various time lengths and distance parameters. Our results indicated that 2 minutes of hot plasma treatment with the plasma torch 5 cm away from the liquid culture is effective in killing/sterilizing cultures of S. aureus, S. pyogenes, Salmonella spp, N. meningitidis, and E. coli. Five minutes of cold plasma with the probe immersed 1-2 cm inside the liquid culture were needed to kill the bacteria. The portable nonthermal plasma system can be used for infection treatment and wound healing applications affected by the microbes studied in this research.