Zheng-Shi Chang

Dual effects of atmospheric pressure plasma jet on skin wound healing of mice.

Cold plasma has become an attractive tool for promoting wound healing and treating skin diseases. This article presents an atmospheric pressure plasma jet (APPJ) generated in argon gas through dielectric barrier discharge, which was applied to superficial skin wounds in BALB/c mice. The mice (n = 50) were assigned randomly into five groups (named A, B, C, D, E) with 10 animals in each group. Natural wound healing was compared with stimulated wound healing treated daily with APPJ for different time spans (10, 20, 30, 40, and 50 seconds) on 14 consecutive days. APPJ emission spectra, morphological changes in animal wounds, and tissue histological parameters were analyzed. Statistical results revealed that wound size changed over the duration of the experimental period and there was a significant interaction between experimental day and group. Differences between group C and other groups at day 7 were statistically significant (p < 0.05). All groups had nearly achieved closure of the untreated control wounds at day 14. The wounds treated with APPJ for 10, 20, 30, and 40 seconds showed significantly enhanced daily improvement compared with the control and almost complete closure at day 12, 10, 7, and 13, respectively. The optimal results of epidermal cell regeneration, granulation tissue hyperplasia, and collagen deposition in histological aspect were observed at day 7. However, the wounds treated for 50 seconds were less well healed at day 14 than those of the control. It was concluded that appropriate doses of cold plasma could inactivate bacteria around the wound, activate fibroblast proliferation in wound tissue, and eventually promote wound healing. Whereas, over doses of plasma suppressed wound healing due to causing cell death by apoptosis or necrosis. Both positive and negative effects may be related to the existence of reactive oxygen and nitrogen species (ROS and RNS) in APPJ.

Influence of Penning effect on the plasma features in a non-equilibrium atmospheric pressure plasma jet

Non-equilibrium atmospheric pressure plasma jet (APPJ) is a cold plasma source that promises various innovative applications. The influence of Penning effect on the formation, propagation, and other physical properties of the plasma bullets in APPJ remains a debatable topic. By using a 10cm wide active electrode and a frequency of applied voltage down to 0.5Hz, the Penning effect caused by preceding discharges can be excluded. It was found that the Penning effect originating in a preceding discharge helps build a conductive channel in the gas flow and provide seed electrons, thus the discharge can be maintained at a low voltage which in turn leads to a smaller propagation speed for the plasma bullet. Photographs from an intensified charge coupled device reveal that the annular structure of the plasma plume for He is irrelevant to the Penning ionization process arising from preceding discharges. By adding NH3 into Ar to introduce Penning effect, the originally filamentous discharge of Ar can display a rather extensive plasma plume in ambient as He. These results are helpful for the understanding of the behaviors of non-equilibrium APPJs generated under distinct conditions and for the design of plasma jet features, especially the spatial distribution and propagation speed, which are essential for application. V C 2014 AIP Publishing LLC.

Experimental and Numerical Investigation on the Interaction Between Ar Flow Channel and Ar Plasma Jet at Atmospheric Pressure

In this paper, the interaction between Ar flow channel and atmospheric pressure plasma jet (APPJ) is investigated quantitatively by combining 3-D species transport simulation and optical schlieren observation together. The turbulence model, gravity force, and electrostatic force model are included into the Ar flow channel simulation. It is found that, with the increment of the Ar flow rate, the plasma plume reaches the maximum length at 3.5 L/min and then decreases sharply, which is corresponding to the Ar flow status. The simulations of the Ar flow channel show good agreement with the captured schlieren images. At small flow rates, the Ar flow channel bends downward due to the gravity. Under laminar flow, the high Ar mole fraction region near the axis of the Ar flow channel increases with the flow rate. However, the Ar flow presents as twist and radial diffusion, and the Ar mole fraction decreases rapidly when the Ar flow transits into turbulence, which leads the length of the Ar plasma plume to decrease sharply correspondingly. The plasma plume bestows the Ar flow channel a forward momentum, which decreases the curvature of bending downward and reinforces the twist and instability of the Ar flow channel under turbulence flow. By coupling the optical emission spectra and flow channel investigation together, it is revealed that Ar APPJ propagates along the core of the conelike flow channel. The Ar mole fractions at the head of the plasma plume are about 0.985 and 0.45 under laminar and turbulence flow, respectively.

Effect of Low-Temperature Plasma on Deactivation of Hepatitis B Virus

In recent years, low-temperature plasma (LTP) has been widely applied in biological and medical fields. This paper is aimed to investigate the deactivation effect of LTP on hepatitis B virus (HBV). Dielectric barrier discharge (DBD) is employed to generate the atmospheric-pressure LTP for treatment of HBV. HBV serum collected from hepatitis B patients with HBsAg, HBeAg, and anti-HBc positive is used as the treatment model. LTP treatment time intervals are set as 10, 20, 30, and 40 s, respectively. Concentrations of HBsAg and S/N value for each different treatment are calculated. The liver function and HBV deoxyribonucleic acid (DNA) copy number are also detected. It is found that, compared with the control group, the concentrations of HBsAg and HBV DNA copy number of different treatment groups have statistically significant differences. With time going of LTP treatment, both the concentration of HBsAg and the copy number of HBV DNA gradually decrease, and all the S/N values are less than 2.1, indicating that HBsAg becomes negative after LTP treatment. Comparing the liver functions (i.e., enzymatic, proteinic, and bilirubin indicators) before and after LTP treatment, all the data are in the range of normal reference values. It is concluded that LTP induced by DBD is effective for HBV deactivation, and the liver function is kept normal during the process of plasma killing HBV.

Electrical and optical properties of Ar/NH3 atmospheric pressure plasma jet

Inspired by the Penning effect, we obtain a glow-like plasma jet by mixing ammonia (NH3) into argon (Ar) gas under atmospheric pressure. The basic electrical and optical properties of an atmospheric pressure plasma jet (APPJ) are investigated. It can be seen that the discharge mode transforms from filamentary to glow-like when a little ammonia is added into the pure argon. The electrical and optical analyses contribute to the explanation of this phenomenon. The discharge mode, power, and current density are analyzed to understand the electrical behavior of the APPJ. Meanwhile, the discharge images, APPJs length, and the components of plasma are also obtained to express its optical characteristics. Finally, we diagnose several parameters, such as gas temperature, electron temperature, and density, as well as the density number of metastable argon atoms of Ar/NH3 APPJ to help judge the usability in its applications.

Experimental Research on Mode Transitions of Atmospheric Pressure Helium Dielectric Barrier Discharge

The discharge mode transitions and the characteristics of atmospheric pressure dielectric barrier discharge in pure helium (He-DBD) are studied. Different discharge modes of He-DBD are clarified, including filament-diffuse mixed mode, filamentary mode, diffuse mode, and multichannels coupled mode. The transitions of different modes are explored by changing the gap width and applied voltage. According to the luminous structure of discharge [short exposure (100~300 ns) image], it is found that there should be only Townsend-like and glow-like discharges that appear in the above modes. In Townsend-like discharge, the secondary electron emission coefficient (SEEC) of dielectric is estimated. Based on which, a fluid model coupled with an external circuit is built to explain the He-DBD mode transitions mechanism and the applied voltage drops influence on He-DBD. Through the temporal evolution of a luminous structure, a discharge filament is believed to be a contractive state of discharge channel, which should be an unstable glow-like discharge. The radius of discharge channel, changing with gap width and applied voltage, is measured. The discharge contraction is attributed to the nonlinear relationship between Townsend ionization coefficient and electric field. The enhancing interaction between different discharge channels inhibits the appearing of diffuse discharge around discharge filament, leading to the transition from mixed mode to filamentary mode. In the end, the multichannels coupled mode is proven to be glow-like discharge, and its formation mechanism is explained by the overlap of discharge channels.

Viability Reduction of Melanoma Cells by Plasma Jet via Inducing G1/S and G2/M Cell Cycle Arrest and Cell Apoptosis

This paper is aimed to investigate the inhibition effect and mechanism of low-temperature plasma (LTP) on melanoma cells. An argon atmospheric pressure plasma jet is used to generate LTP for the treatment of B16 murine melanoma cells cultured in vitro. LTP treatment time intervals are set as 5, 10, 15, and 20 s, respectively. After being treated with LTP, cell viability, cell apoptosis, cell cycle distribution, and cycle-related proteins expression of melanoma cells are, respectively, measured. It is found that, compared with the control cells, treatment of melanoma cells with 10, 15, and 20 s of plasma, result in a significant reduction in cell viability. Furthermore, investigation demonstrates that LTP may reduce cell viability of melanoma cells via inducing G1/S and G2/M cell cycle arrest and cell apoptosis, and alteration of cell cycle is due to down-modulation of the expression of CyclinB1 and CyclinD1 protein induced by LTP.

Effects of Atmospheric DBCD Plasma on Three Kinds of Typical Microorganisms

Dielectric barrier corona discharge (DBCD) is a robust plasma reactor with high efficiency and large scalable area. Nonthermal plasma is generated by DBCD in open condition under atmospheric pressure. Products of plasma are analyzed by using spectroscopy technology. The DBCD plasma is used to treat three kinds of typical microorganisms such as Escherichia coli, Staphylococcus aureus, and Candida albicans. Then, the inactivation effects of the plasma are discussed and compared with our formerly published results of parallel-plate dielectric barrier discharge (DBD) plasma. The results show that the DBCD plasma damages microbe cells by reactive species (RS) and lower pH values, while the parallel-plate DBD plasma works mainly through microdischarge channel and RS. In addition, different cell wall configurations result in different treatment effects.

Dynamic Evolution of Helium Atmospheric Pressure Plasma Jet with ITO-PET Electrodes

A helium atmospheric pressure plasma jet configured with transparent double ring electrodes is driven by an ac high voltage power, and its dynamic evolution in a whole cycle is carefully investigated with ns scale intensified-charge coupled device images. During the positive current pulse, a plasma bullet appears at downstream of active electrode and donut shape plasma presents inside ground electrode, respectively, and wavepacket-like behavior emerges in Dielectric Barrier Discharge (DBD) zone. However, for negative current pulse, the phenomena with double plasma bullets occur beneath active electrode, and plasma inside ground electrode is formed via overflow of diffuse plasma in DBD zone.

Inactivation Effect of Low-Temperature Plasma on Pseudomonas aeruginosa for Nosocomial Anti-Infection

Disinfection and sterilization in hospitals and other public places have always been the focus of attention. In our studies, dielectric barrier corona discharge (DBCD) was used to generate low-temperature plasma (LTP) to treat Pseudomonas aeruginosa (P. aeruginosa, one kind of bacteria responsible for nosocomial infections). The survival colonies of P. aeruginosa were counted with the standard plate-counting method after 30-, 60-, 90-, and 120-s exposures to DBCD. We discovered that LTP could lead to more than 5-log reduction of P. aeruginosa after 120-s treatment. Further experiments indicated that OH and excited N2 in LTP and lower pH value in bacterial suspension might synergistically inactivate P. aeruginosa by destroying its outer structure.