T. H. Chung

Reactive oxygen species-related plasma effects on the apoptosis of human bladder cancer cells in atmospheric pressure pulsed plasma jets

Helium/oxygen atmospheric pressure plasma jets driven by pulsed dc voltage with repetition rate of several tens of kilohertz are utilized for plasma-cell interactions. The effect of operating parameters on the apoptosis of cultured human bladder (EJ) cancer cells is investigated. The parameters such as applied voltage, pulse repetition frequency, and duty ratio determine the plasma dose. The apoptotic changes in cells with plasma treatment are detected by staining assay and flow cytometry. Apoptosis rates are observed to correlate well with both the plasma dose and the levels of intracellular and extracellular reactive oxygen species.

Optical and electrical characterization of an atmospheric pressure microplasma jet with a capillary electrode

A microplasma jet with a capillary electrode working at atmospheric pressure is developed to create nonthermal plasma. This jet can be operated at an excitation frequency either in several tens of kilohertz ac range (or pulsed voltage with a repetition rate of kilohertz range) or in radio-frequency range. The working gas, helium or argon, and the additive gas, oxygen, are fed into the plasma jet. The discharge has been characterized by optical emission spectroscopy. The electrical property of the discharge has been studied by means of voltage and current probes. The dynamic nature of the plume is investigated by using intensified charged coupled device camera. The electron temperature is estimated from the modified Boltzmann plot method utilizing the Ar 4p→4s transitions. The plume temperature is determined by using the fitting the fine structure of the emission bands of OH molecules and by utilizing the line shape of the transition. They are compared with the results obtained by optical fiber thermometer...

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

Characterization of an inductively coupled nitrogen-argon plasma by Langmuir probe combined with optical emission spectroscopy

The properties of low-pressure inductively coupled nitrogen-argon plasmas were investigated by using a Langmuir probe combined with optical emission spectroscopy (OES) under the conditions of pressures in the range of 1–30 mTorr and applied rf powers of 200–600 W. In the experiments, the argon was introduced as an actinometer and as an adding gas. The effect of the argon content in the gas mixture was examined in the range of 5%–80%. The electron energy probability function (EEPF), the electron density, and the electron temperature were obtained by using an rf-compensated Langmuir probe. The dissociation fractions were obtained from the OES actinometry. The electron temperature was also obtained by OES corona model and compared with that measured by the probe. The second positive and first negative systems of spectral bands from nitrogen molecules were analyzed to estimate the vibrational and rotational temperatures. The effects of the control parameters on the plasma parameters and dissociation fraction ...

Comparison of the characteristics of atmospheric pressure plasma jets using different working gases and applications to plasma-cancer cell interactions

Atmospheric pressure plasma jets employing nitrogen, helium, or argon gases driven by low-frequency (several tens of kilohertz) ac voltage and pulsed dc voltage were fabricated and characterized. The changes in discharge current, optical emission intensities from reactive radicals, gas temperature, and plume length of plasma jets with the control parameters were measured and compared. The control parameters include applied voltage, working gas, and gas flow rate. As an application to plasma-cancer cell interactions, the effects of atmospheric pressure plasma jet on the morphology and intracellular reactive oxygen species (ROS) level of human lung adenocarcinoma cell (A549) and human bladder cancer cell (EJ) were explored. The experimental results show that the plasma can effectively control the intracellular concentrations of ROS. Although there exist slight differences in the production of ROS, helium, argon, or nitrogen plasma jets are found to be useful in enhancing the intracellular ROS concentrations in cancer cells.

Pressure dependence of dissociation fraction and optical emission characteristics in low-pressure inductively coupled N2-Ar plasmas

A diagnostics study of low-pressure inductively coupled N2-Ar plasmas was performed by using optical emission spectroscopy (OES) and an rf-compensated Langmuir probe under the conditions of pressures of 1 - 30 mTorr and powers of 300 - 600 W. In the OES experiments, the argon was used as an actinometer and as an adding gas. The effect of the argon content in the gas mixture was examined in the range of 5 - 30%. The investigation of the effects of pressure on the dissociation fraction of nitrogen molecules and on the optical emission characteristics were carried out. The correction factors for estimating the dissociation fraction by OES actinometry accounting for argon effect were formulated and calculated. It was found that the dissociation fraction increased with increasing power and Ar content, while it decreased with increasing pressure. In addition, the electron energy probability function (EEPF), the electron density, and the electron temperature were obtained by using a Langmuir probe to investigate...

Effects of the electrical parameters and gas flow rate on the generation of reactive species in liquids exposed to atmospheric pressure plasma jets

In this work, an atmospheric pressure plasma jet was fabricated and studied for plasma–liquid interactions. The plasma jet consists of a quartz-covered pin electrode and outer quartz tube with a tapered nozzle. Using the current–voltage (I-V) and optical emission characteristics of the plasma jet, the plasma density and the speed of the plume were investigated. The optical emission spectra clearly indicated the excited NO, O, OH, N2, and N2+ in the plasma plumes. Then the plasma jets were applied to the deionized water. We investigated the effects of the operating parameters such as applied voltage, pulse frequency, and gas flow rate on the generation of reactive species in the gas and liquid phases. The densities of reactive species including OH radicals were obtained at the plasma–liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. The nitrite concentration was detected by Griess assay. The data are very suggestive that there is a str...

Effects of the pulse width on the reactive species production and DNA damage in cancer cells exposed to atmospheric pressure microsecond-pulsed helium plasma jets

Plasma-liquid and plasma-cell interactions were investigated using an atmospheric pressure dc microsecond-pulsed helium plasma jet. We investigated the effects of the electrical parameters such as applied voltage and pulse width (determined by the pulse frequency and duty ratio) on the production of reactive species in the gas/liquid phases and on the DNA damage responses in the cancer cells. The densities of reactive species including OH radicals were estimated inside the plasma-treated liquids using a chemical probe method, and the nitrite concentration was detected by Griess assay. Importantly, the more concentration of OH resulted in the more DNA base oxidation and breaks in human lung cancer A549 cells. The data are very suggestive that there is strong correlation between the production of OH in the plasmas/liquids and the DNA damage.

Characterization of a microwave-excited atmospheric-pressure argon plasma jet using two-parallel-wires transmission line resonator

This paper presents a method to produce a microwave-excited atmospheric-pressure plasma jet (ME-APPJ) with argon. The plasma was generated by a microwave-driven micro-plasma source that uses a two-parallel-wire transmission line resonator (TPWR) operating at around 900u2009MHz. The TPWR has a simple structure and is easier to fabricate than coaxial transmission line resonator (CTLR) devices. In particular, the TPWR can sustain more stable ME-APPJ than the CTLR can because the gap between the electrodes is narrower than that in the CTLR. In experiments performed with an Ar flow rate from 0.5 to 8.0u2009L·min−1 and an input power from 1 to 6u2009W, the rotational temperature was determined by comparing the measured and simulated spectra of rotational lines of the OH band and the electron excitation temperature determined by the Boltzmann plot method. The rotational temperature obtained from OH(A-X) spectra was 700u2009K to 800u2009K, whereas the apparent gas temperature of the plasma jet remains lower than ∼325u2009K, which is compatible with biomedical applications. The electron number density was determined using the method based on the Stark broadening of the hydrogen Hβ line, and the measured electron density ranged from 6.5u2009×u20091014 to 7.6u2009×u20091014u2009cm−3. TPWR ME-APPJ can be operated at low flows of the working gas and at low power and is very stable and effective for interactions of the plasma with cells.

Characterization of an atmospheric pressure plasma jet array and its application to cancer cell treatment using plasma activated medium

An atmospheric pressure plasma jet array source driven by a pulsed bipolar voltage of several tens of kilohertz was characterized and utilized for cancer cell treatment. Electrical and optical emission characteristics of plasma jet array were obtained as functions of the applied voltage, gas flow rate, and pulse frequency, and the optimal operating parameters were obtained. The emission intensities from reactive oxygen and nitrogen species (RONS) in a gas phase, such as OH, NO, H, and O, were measured by optical emission spectroscopy. In the plasma-liquid interaction experiment, the OH concentration was measured using the TA solution. The nitrite concentration in the plasma treated media (DW, HBSS, and DMEM) was measured using Griess reaction assay. Human skin cancer cells injected with plasma treated liquid were observed for changes in cell viability using the MTS assay. The results demonstrate that the plasma jet array source can be a good candidate for delivering RONS to liquid for plasma activated medium (PAM).