Cong-Wei Yao

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.

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.

Investigation on the characteristics of dielectric barrier discharge in methane with parallel-plate and multi needle-plate electrode in low pressure

Summary form only given. Non-equilibrium plasma-assisted combustion has been extensively studied over the last few decades and has shown promising effects on combustion controlling, such as reducing ignition delay time, increasing flame propagation speed, enhancing flame stabilization and so on. In this paper, we investigated on the characteristics of dielectric barrier discharge (DBD) in methane with parallel-plate and multi-needle-to-plate electrodes under low pressure with sinusoidal waveform (20 kHz, 0-30 kV) power supply. A mechelle spectrometer (Mechelle 5000, Andor) is used to capture the plasma spectra. The results show that the discharge produces abundant active components related to combustion, such as CH (λ=392.5, 430.1, 438.7, 440.9nm), and C2 (A=473.6nm) in the excited level. Temperature of the active particles is calculated by LIFBASE software and platinum-rhodium thermocouple. With the increasing of applied voltage, the gas temperature and the number and average energy of the high-energy electrons are increased, leading to more free particles which are in the excited state, and finally the corresponding emission spectrum intensity is enhanced. Under the same gas pressure and electrode gap except for generation by different the electrode structure, the temperature of gas in multi needle-plate electrode is lower than plate-plate electrode. And it is proven that multi needles in a honeycomb structure layout can be made in more stable discharge, which can be used in sub-atmospheric even under atmospheric pressure, and it is better for plasma-assisted combustion application.

Effects of atmospheric pressure plasma jet with floating electrode on murine melanoma and fibroblast cells

Atmospheric pressure cold plasma jets have been recently shown as a highly promising tool in certain cancer therapies. In this paper, an atmospheric pressure plasma jet (APPJ) with a one inner floating and two outer electrode configuration using helium gas for medical applications is developed. Subjected to a range of applied voltages with a frequency of 19.8 kHz at a fixed rate of gas flow (i.e., 3 l/min), electrical and optical characteristics of the APPJ are investigated. Compared with the device only with two outer electrodes, higher discharge current, longer jet, and more active species in the plasma plume at the same applied voltage together with the lower gas breakdown voltage can be achieved through embedding a floating inner electrode. Employing the APPJ with a floating electrode, the effects of identical plasma treatment time durations on murine melanoma cancer and normal fibroblast cells cultured in vitro are evaluated. The results of cell viability, cell apoptosis, and DNA damage detection sho...

Effects of low temperature atmospheric pressure plasma on skin wound healing of mice in vivo

Summary form only given. Low temperature plasma (LTP) has proven to be an effective way in wound healing, skin diseases, sterilization, and so on. This paper presented an atmospheric pressure discharge plasma jet in flowing argon by means of dielectric barrier discharge (DBD). Then, the effects of LTP on skin wound healing of mice in vivo were evaluated. Two wounds of 4 mm in diameter along the both sides of the spine were created on the back of each mouse (n=50). The mice were divided into fine groups equally. Five exposure time intervals of 10s, 20s, 30s, 40s and 50s were set, with the left side wound of each mouse was treated by LTP and the right one was left to heal naturally as a control part. The experiment last for 14 consecutive days, and sizes of the wounds were recorded every day. Finally, the wounds were removed, routinely fixed, paraffin-embedded, sectioned and hematoxylin-eosin stained. Experimental results showed that all wounds healing naturally as the control part were almost completely closed at day 14, and the wounds with 10-40s plasma exposure showed a significant daily improvement and almost complete closure at different days. Whereas, the wounds under 50s plasma exposure were still worse at day 14. Furthermore, it can be seen from images of pathological section, the number of fibroblast and blood capillary increased markedly within 30s exposure time, undergoing the course of reparative phase. However, lots of inflammatory cells infiltrated in the wound tissues with 50s exposure, meaning that the wounds were damaged by LTP. It was concluded that appropriate doses of LTP could inactivate bacteria around wound, activate fibroblast proliferation in wound tissue and eventually promote wound healing. Contrary, over doses of LTP could suppress wound healing through causing cell apoptosis or necrosis. Both positive and negative effects of LTP on mice skin wound healing were related to existence of reactive oxygen and nitrogen species (ROS and RNS) in the plasma jet, which were detected by optical emission spectroscopy.

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.

Atmospheric Pressure Plasma Jet Array With Multivariate Cells

A large-scale atmospheric pressure plasma jet (APPJ) device with variable discharge cells is developed using a special designed electrode configuration, and a maximum of fifteen APPJ cells work simultaneously. The properties of APPJ arrays are investigated from plasma profile and statistical parameters. From one to fifteen cells, the peak value of discharge current rises gradually when increasing cell numbers. The APPJ images and current waveforms present good synchronism and repeatability of discharge, and the effective plasma area up to 20 cm2 is achieved.

Inactivation Effect of Surface Microdischarge Plasma on Bacillus cereus

A kind of nonequilibrium air plasma based on surface microdischarge is developed, behaving as per editing aspect. Please confirm the change. as large homogeneous scalable discharge area. Its inactivation effect on Bacillus cereus is investigated and 5.3-log reduction in cell viability is achieved within 150-s exposure. The pH value, hydroxyl (OH), and nitric oxide (NO) concentration in the extracellular solution after plasma treatments are detected. In addition, a transmission electron microscope is utilized to observe the cell damage from the morphology. Some potential chemical and biomedical processes involved are discussed. It is considered that the oxidation effect of reactive oxygen species plays a crucial role, and the nitration effect as well as the synergistic effect in the acid milieu, jointly contribute to the NAP-induced bactericidal process.

Electrical and spectral characterization of an atmospheric pressure He/CF4 plasma jet

Surface modification of polymeric materials based on non-equilibrium plasma fed with helium (He) and tetrafluoromethane (CF4) has gained much attention. In this paper, an atmospheric pressure plasma jet (APPJ) generated in He/CF4 mixtures is developed, and it is characterized systematically by electrical and optical methods. It is found that the He/CF4 APPJ presents three kinds of discharge modes, i.e., glow discharge, unstable glow discharge, and filamentary discharge under different operation parameters including applied voltage and gas composition. With the increase in applied voltage, the discharge mode transits from glow to filamentary discharge gradually, while the gas composition has significant influences on ignition/extinction voltages and excited species. The discharge modes under different parameters are obtained, and the applied voltage is regarded as the main reason for discharge mode transition. The excited species in the He/CF4 APPJ mainly include the excited helium atoms, the fluorine groups, and the impurities originated from air, whose generation reactions are discussed. The evolution of excited species under different parameters and discharge modes is acquired. The discharge modes and excited species of the He/CF4 APPJ can be well modulated by changing applied voltage and CF4 volume fraction.Surface modification of polymeric materials based on non-equilibrium plasma fed with helium (He) and tetrafluoromethane (CF4) has gained much attention. In this paper, an atmospheric pressure plasma jet (APPJ) generated in He/CF4 mixtures is developed, and it is characterized systematically by electrical and optical methods. It is found that the He/CF4 APPJ presents three kinds of discharge modes, i.e., glow discharge, unstable glow discharge, and filamentary discharge under different operation parameters including applied voltage and gas composition. With the increase in applied voltage, the discharge mode transits from glow to filamentary discharge gradually, while the gas composition has significant influences on ignition/extinction voltages and excited species. The discharge modes under different parameters are obtained, and the applied voltage is regarded as the main reason for discharge mode transition. The excited species in the He/CF4 APPJ mainly include the excited helium atoms, the fluorine grou...