Yongdong Liang

A study of oxidative stress induced by non-thermal plasma-activated water for bacterial damage

Ar/O2 (2%) cold plasma microjet was used to create plasma-activated water (PAW). The disinfection efficacy of PAW against Staphylococcus aureus showed that PAW can effectively disinfect bacteria. Optical emission spectra and oxidation reduction potential results demonstrated the inactivation is attributed to oxidative stress induced by reactive oxygen species in PAW. Moreover, the results of X-ray photoelectron spectroscopy, atomic absorption spectrometry, and transmission electron microscopy suggested that the chemical state of cell surface, the integrity of cell membrane, as well as the cell internal components and structure were damaged by the oxidative stress.

Rapid inactivation of biological species in the air using atmospheric pressure nonthermal plasma.

Here, nonthermal plasma generated by a dielectric barrier discharge (DBD) system was applied to inactivating aerosolized Bacillus subtilis cells and Pseudomonas fluorescens as well as indoor and outdoor bioaerosols. The culturability, viability, and diversity losses of the microorganisms in air samples treated by the plasma for 0.06-0.12 s were studied using culturing, DNA stain as well as polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods. In addition, the viable fraction of bacterial aerosols with and without the plasma treatment was also quantified using qPCR coupled with ethidium monoazide (EMA). It was shown that less than 2% of B. subtilis aerosols survived the plasma treatment of 0.12 s, while none of the P. fluorescens aerosols survived. Viability tests, EMA-qPCR results, and Scanning Electron Microscopy (SEM) images demonstrated that both bacterial species suffered significant viability loss, membrane, and DNA damages. Exposure of environmental bacterial and fungal aerosols to the plasma for 0.06 s also resulted in their significant inactivations, more than 95% for bacteria and 85-98% for fungal species. PCR-DGGE analysis showed that plasma exposure of 0.06 s resulted in culturable bacterial aerosol diversity loss for both environments, especially pronounced for indoor environment. The results here demonstrate that nonthermal plasma exposure could offer a highly efficient air decontamination technology.

Assessment of the roles of various inactivation agents in an argon-based direct current atmospheric pressure cold plasma jet

Three types of gases, pure argon (99.999%), argon with 2% oxygen, and argon with 2% oxygen and 10% nitrogen were used as operating gases of a direct current atmospheric pressure cold plasma jet to inactivate Staphylococcus aureus (S. aureus) suspended in a liquid. The inactivation efficacies for the plasma jets operating in the three gases decrease from Ar/O2(2%) to Ar/O2(2%)/N2(10%) to pure Ar. Optical emission spectroscopy, electron spin resonance spectroscopy, high performance liquid chromatography, and atomic absorption spectrophotometry were employed to identify and monitor the reactive species in the plasma-liquid system for the three operating gases and revealed the presence of O, 1O2, OH, NO, H2O2, O3, and NO3−/NO2− as well as Cu+/Cu2+. The S. aureus inactivation results indicate that atomic oxygen (O) is the key inactivation agent, while other species play a lesser role in the inactivation progress studied here.

MS2 Virus Inactivation by Atmospheric-Pressure Cold Plasma Using Different Gas Carriers and Power Levels

ABSTRACT In this study, airborne MS2 bacteriophages were exposed for subsecond time intervals to atmospheric-pressure cold plasma (APCP) produced using different power levels (20, 24, and 28 W) and gas carriers (ambient air, Ar-O2 [2%, vol/vol], and He-O2 [2%, vol/vol]). In addition, waterborne MS2 viruses were directly subjected to the APCP treatment for up to 3 min. MS2 viruses with and without the APCP exposure were examined by scanning electron microscopy (SEM), reverse transcription-PCR (RT-PCR), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Viral inactivation was shown to exhibit linear relationships with the APCP generation power and exposure time (R 2 > 0.95 for all energy levels tested) up to 95% inactivation (1.3-log reduction) after a subsecond airborne exposure at 28 W; about the same inactivation level was achieved for waterborne viruses with an exposure time of less than 1 min. A larger amount of reactive oxygen species (ROS), such as atomic oxygen, in APCP was detected for a higher generation power with Ar-O2 and He-O2 gas carriers. SEM images, SDS-PAGE, and agarose gel analysis of exposed waterborne viruses showed various levels of damage to both surface proteins and their related RNA genes after the APCP exposure, thus leading to the loss of their viability and infectivity.

An evaluation of anti-oxidative protection for cells against atmospheric pressure cold plasma treatment

With the development of plasma medicine, safety issues are emerging as a serious concern. In this study, both intracellular (genetic engineering) and extracellular (scavengers) measures were tested in an effort to determine the best protection for cells against plasma-induced oxidative stress. All results of immediate reactive species detection, short term survival and long term proliferation, suggest that intracellular pathways are superior in reducing oxidative stress and cell death. This work provides a potential mechanism to enhance safety and identifies precautionary measures that should be taken in future clinical applications of plasmas.

Evaluation of Cold Plasma Treatment and Safety in Disinfecting 3-week Root Canal Enterococcus faecalis Biofilm In Vitro

Many studies have demonstrated that Enterococcus faecalis (E. faecalis) is the most important species responsible for persistent endodontic infection. E. faecalis biofilm often exhibits increased resistance to antimicrobial agents compared with planktonic bacteria. The aim of this study is to evaluate the effectiveness and safety of cold plasma therapy in disinfecting 21-day E. faecalis biofilms. Teeth with 21-day E. faecalis biofilm were treated with an argon/oxygen cold plasma for various treatment times and compared to those treated with Ca(OH)2, 2% CHX gel and Ca(OH)2/CHX gel for 7 days (positive controls). Negative control groups included normal saline treatment and Ar/O2 gas treatment. Antimicrobial efficacy was determined by colony forming unit (CFU) method. Scanning Electron Microscopy (SEM) was employed to assess the morphological changes of E. faecalis biofilm by plasma. Confocal Laser Scanning Microscopy (CLSM) was used to confirm the viability of the biofilm after the plasma treatment. Microhardness and microroughness changes caused by plasma were tested with Vickers Hardness Tester and 3D Laser Scanning Microscope respectively. Energy Dispersive X-ray Spectroscopy (EDS) was used for elemental analysis of root canal dentin. The results indicated that a 12 min cold plasma treatment could inactivate E. faecalis 21-day biofilm completely. Atmospheric pressure cold plasma is an effective tool in endodontics for its strong biofilm sterilization effect and has an accepted safety for its low temperature without significantly affecting the microhardness and microroughness of tooth enamel if placed at proper working distance.

Rapid allergen inactivation using atmospheric pressure cold plasma.

Summary form only given. Exposure to environmental allergens from various sources can cause a wide range of adverse health effects, including asthma, eczema, allergic rhinitis, inflammable and toxic reactions. Among them, asthma is one of the most common and major human diseases that are attributable to allergen exposure. And such a problem continues to rise e.g., the asthma prevalence among children in the United States alone was indicated to have nearly doubled over the last two decades. Allergy has become a global problem, and effective control is greatly needed. Here, the inactivation effects of the atmospheric pressure cold plasma (APCP) on aerosolized allergens including dog allergen Can f 1, house dust mite allergens (Der p 1 and Der f 1), fungal allergens (Asp f 1 and Alt a 1) as well as those from indoor and outdoor environments were investigated. The effectiveness of the APCP treatment was further studied using blood sera from the allergen sensitized humans. In addition, the allergen samples were also analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Results revealed that the APCP was highly effective in reducing the allergenicity of both lab-prepared and environmental allergen aerosols. The airborne reductions were shown to range from 30% for Der p 1 to 80% for Can f 1 allergen for 0.12 s exposure. Allergnicity tests showed that the APCP treated Asp f 1 allergens caused 50% less binding with IgEs in the blood sera compared to the control. The observed allergenicity loss was due to hydroxyl radicals produced by the plasma device. The results from SDS-PAGE showed that the plasma treatment resulted in decreased size of the Asp f 1 allergen. The developed technology holds great promise in combating the allergic diseases.

Decontamination of salmonella on sliced fruits and vegetables surfaces using a direct-current, atmospheric-pressure cold plasma

Foodborne illnesses are on the rise in recent decades. Salmonella is a common microbiological agent that is considered to be responsible for a large number of cases of foodborne illnesses. They can be found in fresh, peeled, ready-to-eat fruit and vegetables, such as salads. The approaches to clean the surface of fruits and vegetables include thermal processing and chemical decontamination, which can result in some undesirable sensory, nutrition, and taste changes.

Vehicle Exhaust Gas Clearance by Low Temperature Plasma-Driven Nano-Titanium Dioxide Film Prepared by Radiofrequency Magnetron Sputtering

A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO2) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O3 destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas.

Rapid allergen inactivation using atmospheric pressure cold plasma

Exposure to environmental allergens from various sources can cause a wide range of adverse health effects, including asthma, eczema, allergic rhinitis, inflammable and toxic reactions. Among them, asthma is one of the most common and major human diseases that are attributable to allergen exposure. And such a problem continues to rise e.g., the asthma prevalence among children in the United States alone was indicated to have nearly doubled over the last two decades. Allergy has become a global problem, and effective control is greatly needed.