Cold Atmospheric-pressure Air Plasma Research Articles

Combatting the antigenicity of common ragweed pollen and its primary allergen Amb a 1 with cold atmospheric pressure air plasma

Airborne allergens, especially those originating from various types of pollen, significantly compromise the health and well-being of individuals on a global scale. Here, cold atmospheric pressure plasma (CAP) created in ambient air was used to treat highly allergenic and invasive Ambrosia artemisiifolia pollen. Immunoassays were used to evaluate the impact of CAP on the principal A. artemisiifolia allergen Amb a 1, demonstrating that > 90 % reduction in antigenicity could be achieved. Chemical analyses using Fourier Transform infrared revealed that CAP induced significant alterations to proteins on the surface of pollen grains, resulting in a 43 % increase in the amide I peak area and a 57 % increase in the amide II peak area. These findings were corroborated by Raman and X-ray photoelectron spectroscopy, which indicated that the protein modifications induced by CAP were due to carbonylation and nitration/nitrosylation processes. Beyond protein transformations, CAP also induced notable oxidation and modification of lipid-like compounds, polysaccharides and sporopollenin. Evident transformations at the chemical level translated into morphological changes at the grain surface, manifesting as increased roughness via significant outer-layer etching. These findings underscore the potential of CAP technology as a viable approach for mitigating against the allergenicity of pollen, providing a deeper understanding into the underlying chemical mechanisms.

Cold atmospheric pressure air plasma jet disinfection of table eggs: Inactivation of Salmonella enterica, cuticle integrity and egg quality

Eggshell cuticles are first lines of defense against egg-associated pathogens, such as Salmonella enterica serovar Enteritidis (SE). Infections from eggs contaminated with this strain remain a significant risk. In addition, changes in the cuticle are closely related to changes in egg safety. The emerging non-thermal atmospheric pressure plasma technology enables a high rate of microbial inactivation at near-ambient temperatures, making it ideal for food safety applications. This study examines the effects of a cold atmospheric pressure air plasma jet (CAAP-J) on eggshell cuticle and egg quality whilst inactivating SE. Shell eggs inoculated with SE (7 log10 cfu/egg) were used as the samples to test the decontamination performance of the device. The tests were conducted using an industrial CAAP-J with different power levels (600–800 W), exposure times (60–120 s), at a fixeddistance of 20 mm from the plasma jet and an air flow rate of 3600 L/h. It was found that the best results were obtained after 120 s at maximum plasma power (800 W). Subsequent to the implementation of this plasma procedure, it was determined that no viable cells could be detected. After CAAP-J treatment, the temperature remains below 50.5 °C, thereby minimizing the risk of altering egg quality. All specific measurements (egg white pH, yolk pH, yolk color, HU, and eggshell breaking strength) have shown that CAAP-J treatment has no negative effect on egg quality. No changes in eggshell cuticle quality after CAAP-J treatment was confirmed through scanning electron microscope (SEM).

A Magnetic Field Induced Cold Atmospheric Pressure Air Plasma Jet

Cold atmospheric pressure plasma jets (APPJs) using air as working gas are of particular interest and desirable but with significant challenge. In this article, an air APPJ induced by an external radial magnetic field is reported. The experimental results show that with the external magnet, an air plasma jet can be obtained with a length of 7 mm and a width of 10 mm. While without the external magnet, the plasma only exists in the dielectric tube. The dynamic behavior shows that its propagation velocity is close to the gas flow velocity. The plasma jet appears no difference when it is in contact with a ground conductive object. On the other hand, optical emission spectrum shows that they are dominated by the N2 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{N}_{2}^{+}$ </tex-math></inline-formula> emission. The electrical characteristic shows that the peak of the discharge current and the breakdown voltage increase when the magnet is used. The gas temperature of the plasma jet is about 310 K. Laser-induced fluorescence measurement shows that high concentration of OH radicals appears along the plasma jet. In the sterilization experiment, the application of external magnetic field has increased the sterilization effect by about two times

Continuous in-line decontamination of food-processing surfaces using cold atmospheric pressure air plasma

This study assessed a continuous in-line decontamination system for food contact surfaces and processing equipment that utilized cold atmospheric pressure plasma (CAP) generated from ambient air. The plasma system was evaluated against two common foodborne pathogens (Salmonella Typhimurium, Listeria monocytogenes) on stainless steel surfaces and against S Typhimurium on commercial poly[ether]-thermoplastic poly[urethane] (PE-TPU) conveyor belts, under simulated conditions of a food-processing facility. A significant level of microbial inactivation was achieved, up to 3.03 ± 0.18 and 2.77 ± 0.71 logCFU/mL reductions of L. monocytogenes and S. Typhimurium respectively within 10 s total treatment on stainless steel surfaces, and a 2.56 ± 0.37 logCFU/mL reduction of S. Typhimurium within 4 s total treatment on the PE-TPU material, according to a procedure based on the well-established EN 13697:2015 industrial protocol. CAP exposure was shown to have a minor impact on the morphology and composition of the treated surfaces. The results indicated that CAP can be applied for effective and continuous disinfection against common foodborne pathogens in food-processing facilities. Industrial relevanceLow temperature plasmas have shown great promise for microbial decontamination, yet industrial uptake of the technology has been limited due to scaling limitations. In this study, a prototype conveyor-based CAP decontamination system was developed and tested under realistic conditions expected within a food-processing facility. The results showed a high level of antimicrobial action against two common foodborne pathogens within a few seconds of CAP exposure, a timescale in line with industrial line processing speeds. Our findings demonstrated that CAP shows great promise for the continuous in-situ decontamination of food contact surfaces, with the potential to mitigate against the costly downtimes incurred in current production line practices implementing chemical disinfectants.

Treatment modalities for peri-implantitis: A review of literature

Introduction: Implant Dentistry was created to show reliable treatment approaches for restoring the oral cavity’s esthetic and function. However, while dental implants have a high long-term success rate, dental implants are exposed to mechanical or biological complications. Objective: The therapeutic approaches will be addressed in this review, which is the main objective of this study. Materials and Methods: Data sources: The PubMed/MEDLINE, SCOPUS, and Web of Science databases were used to conduct the literature search from June to September 2021. Study selection: Non-surgical and surgical peri-implantitis treatment modalities are the main themes of this study. Result: Implant dentistry was created to show reliable treatment approaches for restoring the oral cavity’s esthetic and function. However, while dental implants have a high long-term success rate, dental implants are exposed to mechanical or biological complications. Conclusion: Peri-implantitis appears to be a multifactorial disease including the patient’s host/microbe response, implant characteristics, soft tissue and the hard conditions surrounding the implant, and the dentist’s surgical and prosthetic part experience. Different treatment modalities are present today, all are used to treat peri-implantitis, such as surgery, laser therapy, and innovative treatments such as cold atmospheric pressure air plasma jet (CAPAJ), enamel matrix derivative, and PRF gel.

Cold atmospheric-pressure air plasma jet: Physics and opportunities

Cold atmospheric-pressure plasma jet generates rich reactive species including reactive oxygen species and reactive nitrogen species with gas temperature close to or at room temperature, which is very attractive for applications such as plasma medicine. However, under one atmospheric pressure, due to the high electron–neutral particles collision frequency (1011–12/s), it is difficult to generate atmospheric pressure plasma while keeping the gas temperature close to or at room temperature. Furthermore, when air rather than noble gases is used as working gas, due to the low energy levels of rotational and vibrational states of nitrogen and oxygen, it becomes extremely challenging to generate cold atmospheric pressure air plasma jet (CAAP-J) with gas temperature close to or at room temperature. Fortunately, after decades of research, several CAAP-Js have been reported. In this review, the state-of-the-art of the development of CAAP-Js is presented. The CAAP-Js are grouped into six categories based on their electrode configuration. A brief discussion on each group of the CAAP-Js is presented. Moreover, the physics of CAAP-Js is discussed, including the dynamics, the striation phenomenon, the temporal behavior of plasma parameters, and the nonequilibrium characteristic of CAAP-Js. Furthermore, the measurements of the reactive species generated by CAAP-Js are briefly reviewed. Finally, discussions and perspective of future research on CAAP-Js are presented.

Enhancement Propagation of Protocorms in Orchid (Cymbidium tracyanum L. Castle) by Cold Atmospheric Pressure Air Plasma Jet

Propagation of orchid (Cymbidium tracyanum L. Castle) treated by using an air cold atmospheric pressure plasma jet at room temperature was investigated. The peak-to-peak voltage discharge and flow rate of the air atmospheric pressure plasma jet were set at 10.5 kV and 10 L/min, respectively. The constituent particles of the air cold atmospheric pressure plasma jet were revealed by optical emission spectroscopy. At the end of the jet nozzle, the constituent particles were observed, such as hydroxyl radical ˙OH, N2 first negative system (N2 1 −), N2s positive system (N2 2 +), and atomic oxygen. The average size, average number of buds, fresh and dry weights simultaneously increased by cold air plasma treatment compared with the control ones. The highest positive effects of treated protocorms on average size, average number of buds, fresh and dry weight were significantly improved by 238.2, 475.9, 85.6, and 152.5%, respectively. The transmission electron microscope showed the cytoplasmic cell wall in orchid protocorm disturbed by air cold plasma. Thus, the effects of constituent particles of air plasma might attack in the cell wall of protocorm leading to cell loosening, which improved elongation and released bud dormancy. These results indicated that the propagation of orchid protocorms depended on the effects of air cold plasma treatment with different plasma time durations.

Hemostasis Efficacy and Mechanism of Cold Atmospheric Air Plasma

The capacity of a cold atmospheric-pressure air plasma (CAAP) device for advanced first aid is presented. Using swine as an animal model, two trials: 1) a large, curved cut in hindquarters area and 2) amputation of a front leg, were performed. Cold atmospheric-pressure air plasma effluent, which carries reactive oxygen species (ROS) atomic oxygen (OI), is applied for wound treatments. Swift hemostasis of the wounds by the CAAP treatment was demonstrated. The pressure applied by a finger on the cut arteries in trial 1 and the tourniquet applied in trial 2 could be removed immediately after the treatment and there was no re-bleed in both cases. CAAP hemostasis mechanism was explored via in-vitro tests. The tests on sodium citrate mixed blood-droplet samples show that 1) the heat delivered by the CAAP has no impact on the observed clot formation, 2) plasma effluent activates platelets to promote coagulation state and cascade, and 3) the degree of clotting increases with the total amount of applied OI by means of the CAAP effluent. It took only 16 s of the CAAP treatment to reach full clotting, which was considerably shortened from the natural clotting time of about 25 minutes. The tests on smeared blood samples show that the reduction of the platelet count and the increase of RBC count are proportional to the amount of applied OI. A plausible CAAP hemostasis mechanism is concluded from the in vitro test results and the animal model trials.

Cold Atmospheric Pressure Plasma Can Induce Adaptive Response in Pea Seeds

This study investigated the effect of cold atmospheric pressure air plasma pre-treatment on pea (Pisum sativum L.) seeds. The aim of our study was to verify the plasma impact on DNA damage and the induction of positive adaptive response in pea seedlings. The pea seeds were treated by plasma at the exposure times ranging from 60 to 300 s. Plasma was generated using the coplanar type of dielectric surface barrier discharge. The main plasma properties were estimated by electrical and by optical emission spectroscopy measurements. The DNA damage was evaluated by the alkaline comet assay. The adaptive response on seedlings was tested using the toxic concentration of zeocin. The positive effect of plasma pre-treatment and the reduction of DNA damage of pea seedlings in comparison to control samples without plasma was observed at all exposure times used. The strongest repairing effect was observed at the plasma treatment time in the range from 120 to 240 s. These results verify the safety of plasma application in agriculture at germination and growth enhancement and the existence of a plasma induced adaptive response.

(Invited) Plasma Biofilm Decontamination: What Happens to the Underlying Surface?

In natural and manmade environments, bacterial biofilms are ubiquitous, yet the significance of biofilm contamination in a clinical setting is often underestimated [1]. Such contamination presents a particularly virulent form of infection that is shielded from systemic antibiotics, providing ideal conditions for the emergence of multidrug-resistant colonies [2]. There is an unprecedented need to establish new strategies to manage the colonization of clinical surfaces with these complex bacterial communities. This contribution explores the use of cold atmospheric pressure air plasma for the inactivation of clinically relevant biofilms grown on medical grade titanium. Furthermore, the impact of the plasma treatment on the properties of the host surface is investigated. Using a 1D air plasma model [3], supported by experimental measurements, the chemistry of a Surface Barrier Discharge (SBD) suitable for biofilm inactivation was shown to contain a wealth of long-lived species such as O3, NO2 and N2O. Under the influence of a convective flow, the presence of species that are traditionally considered to be too short-lived to reach a downstream sample are predicted, e.g. OH. [4] The SBD system, shown in Figure 1, was found to be highly effective for the decontamination of single and mixed species biofilms, achieving a multiple log reduction within 60 seconds of exposure. Given that the surface composition and morphology are key factors influencing biofilm formation, the impact of the plasma decontamination process on the surface characteristics was assessed and shown to induce considerable changes. The impact of these changes on the ability of bacteria to adhere to plasma treated titanium surfaces was examined. It was shown that biofilm formation on surfaces subjected to the plasma treatment was found to be accelerated in comparison to untreated surfaces. This study demonstrates that cold air plasma is an effective tool for biofilm elimination on clinically relevant surfaces, yet the choice of plasma system must be carefully considered as such treatments can significantly alter the ability of bacteria to attach to the surface. [1] D. Lindsay, A. von Holy, Journal of Hospital Infection. 64, (2006), 313-25. [2] J. Davies, D. Davies, Microbiol Mol Biol Rev. 74, (2010) 417. [3] M. Hasan, J. L. Walsh, J. Appl. Phys. 119, (2016), 203302. [4] M. Hasan, J. L. Walsh, Appl. Phys. Lett. 110, (2017), 134102. [5] Y. Ni, Y., M.J. Lynch, M. Modic, R.D. Whalley, J.L. Walsh. Journal of Physics D: Applied Physics, 49 (35), 355203 (2016). Figure 1

On Hemostasis of Cold Atmospheric Air Plasma

The efficacy and mechanism of a cold atmospheric-pressure air plasma (CAAP), which carries abundant atomic oxygen (OI), on blood coagulation are studied. The tests on sodium citrate mixed blood-droplet samples show that 1) The heat delivered by the CAAP has no impact on the observed clot formation, 2) Plasma effluent activates platelets to promote coagulation state and cascade, and 3) The degree of clotting increases with the OI flux delivered by the CAAP. The full clotting time is shortened from about 25 minutes of the natural clotting time to about 16 s of the CAAP treatment time. The tests on smeared blood samples show that the reduction of the platelet count and the increase of RBC count are proportional to the applied OI flux. In vivo tests, using swine as nimal model, swift hemostasis of large and deep cut wounds on the back by the CAAP treatment was demonstrated. A cut artery was sealed completely with 25 s treatment. The pressure applied by a finger on the cut artery could be removed immediately after the treatment and there was no re-bleed. Based on the in vitro test results and the animal model trials, CAAP coagulation mechanism is presented.

A novel cold atmospheric pressure air plasma jet for peri-implantitis treatment: An in vitro study.

Peri-implantitis is difficult to treat in clinical settings; this is not only because it is a site-specific infectious disease but also because it impedes osseointegration. In this study, a novel cold atmospheric pressure air plasma jet (CAPAJ) was applied to study the treatment of peri-implantitis in vitro. CAPAJ treated the samples for 2, 4 and 6 min, respectively. To evaluate the titanium surface characteristics, the surface elemental composition (X-ray photoelectron spectroscopy [XPS]), roughness and hydrophilicity were evaluated in each group. Concurrently, the sterilization and osseointegration effect of CAPAJ were also examined. Results revealed that after CAPAJ modification, roughness and hydrophilicity of titanium surfaces were significantly increased. Moreover, XPS results demonstrated that the C1s peak was reduced and N1s and O1s peaks were obviously improved. More importantly, CAPAJ showed favorable sterilization and bone formation effects. CAPAJ seemed a simpler and more efficient strategy for the peri-implantitis treatment.

Cold atmospheric-pressure air plasma treatment of C6 glioma cells: effects of reactive oxygen species in the medium produced by the plasma on cell death

An atmospheric-pressure air plasma is employed to treat C6 glioma cells in vitro. To elucidate on the mechanism causing cell death and role of reactive species (RS) in the medium produced by the plasma, the concentration of the long-lived RS such as hydrogen peroxide, nitrate, and ozone in the plasma-treated liquid (phosphate-buffered saline solution) is measured. When vitamin C is added to the medium as a ROS quencher, the viability of C6 glioma cells after the plasma treatment is different from that without vitamin C. The results demonstrate that reactive oxygen species (ROS) such as H2O2, and O3 constitute the main factors for inactivation of C6 glioma cells and the reactive nitrogen species (RNS) may only play an auxiliary role in cell death.

The Efficacy, Safety, Stability, and Mechanism of Tooth Whitening by a Cold Atmospheric Pressure Air Plasma Microjet Assisted With or Without Hydrogen Peroxide

The aim of this paper was to assess the effectiveness, safety, stability, and mechanism of tooth whitening using a direct current cold atmospheric pressure air plasma microjet (PMJ) with the assistance of whitening gels (blank or containing 3% H2O2). The results were compared with those obtained from teeth treated with blank gel only and with gel containing 35% H2O2 in a cold light bleaching system. Tooth whitening effectiveness right after various treatments as well as 18 months after treatment was evaluated via CIELAB colorimetry. Type K thermocouple, scanning electron microscope and energy dispersive spectroscopy were employed to study the temperature of pulp chamber, tooth surface morphology, and elemental composition of enamel surface, respectively. Teeth in the plasma groups were effectively whitened in 5 min, though no significant difference was observed between the two plasma groups. Pulp chamber temperature was shown to remain below 35 °C. Morphological and surface elemental analysis showed similar changes to tooth enamel in the plasma groups and in the cold light group. These observations suggested that PMJ with blank gel was more effective for tooth whitening with acceptable safety and good stability. Optical emission spectroscopy results revealed that reactive oxygen species, such as O, •OH, and NO, in plasma may play a dominant role in the process of plasma tooth whitening.

Study on DC-Driven Air Cold Plasma Brushes Generated Without Airflow Supplement

In this paper, 30-mm-wide cold atmospheric-pressure air plasma brushes are reported. The brushes driven by a direct current power supply are capable of generating air plasma glows with no noble gas addition and no airflow supplement. There is no risk of glow-to-arc transitions, and the plasma glow appears uniform no matter what kinds of material are being processed. The air plasma glow can be scaled up by using the plasma brush arrays. About 30mm × 30mm × 5mm (W, H, and L) homogeneous air plasma glow is generated by merging seven-brush arrays. Current measurements show that the single-brush discharge appears periodically pulsed, while the brush array discharge actually presents either pulsed with about array-number-times frequency of the single one. A further analysis indicates that the charge particles trapped along the dielectric surface may be responsible for the discharges.

A Novel Method of Tooth Whitening Using Cold Plasma Microjet Driven by Direct Current in Atmospheric-Pressure Air

We reported in this paper the tooth-whitening effect by a direct-current cold atmospheric-pressure air plasma microjet (PMJ) and saline solution (0.9%). All teeth were randomly divided into three groups, treated for 20 min with an air blow and saline solution, a PMJ and saline solution, and 35% hydrogen peroxide gel, respectively. Compared with the other groups, the teeth treated with the PMJ and saline solution showed the best tooth-whitening effect. The microhardness of the tooth enamel measurement showed no apparent differences among the three groups. A minor enamel surface morphological change was observed via SEM but was considered acceptable. Singlet oxygen ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and hydroxyl (*OH) radicals were detected by electron spin resonance spectroscopy. Atomic oxygen (O) was observed in the optical emission spectra of the PMJ. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , *OH, and O were considered to be the key agents during the tooth-whitening process. This novel method of tooth whitening has the potential to revolutionize the clinical tooth-whitening procedure.

Tooth Whitening With Hydrogen Peroxide Assisted by a Direct-Current Cold Atmospheric-Pressure Air Plasma Microjet

A tooth-whitening process using hydrogen peroxide (H2O2) enhanced by a direct-current cold atmospheric-pressure plasma microjet (PMJ) is presented. Compared with the conventional clinical method of using H2O2 alone, a significant improvement of the tooth-whitening process was observed when the PMJ was used in the process. The tooth-surface temperature was monitored for safety considerations and did not exceed 37°C at a distance of 1 cm between the exit nozzle of the plasma source and the tooth for a treatment time of 20 min. No apparent differences in the tooth-surface morphology and microhardness were observed between teeth treated with and without the PMJ. The use of the PMJ with H2O2 resulted in an enhanced production of reactive hydroxyl (OH) radicals. This plasma-enhanced tooth-whitening method may be a promising new method for clinical applications.

Inactivation of Staphylococcus aureus and Enterococcus faecalis by a direct-current, cold atmospheric-pressure air plasma microjet

Objective A direct-current, cold atmospheric-pressure air plasma microjet (PMJ) was performed to inactivate Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis) in air. The process of sterilization and morphology of bacteria was observed. We wish to know the possible inactivation mechanisms of PMJ and explore a potential application in dental and other temperature sensitive treatment. Methods In this study, we employed a direct current, atmospheric pressure, cold air PMJ to inactivate bacterias. Scanning electron microscopy was employed to evaluate the morphology of S. aureus and showed rupture of cell walls after the plasma treatment and Optical emission spectrum (OES) were used to understand the possible inactivation mechanisms of PMJ. Results The inactivation rates could reach 100% in 5 min. When the distance between the exit nozzle of the PMJ device and Petri dish was extended from 1 cm to 3 cm, effective inactivation was also observed with a similar inactivation curve. Conclusion The inactivation of bacteria is attributed to the abundant reactive oxygen and nitrogen species, as well as ultroviolet radiation in the plasma. Different life spans and defensibilities of these killing agents may hold the key to understanding the different inactivation curves at different treatment distances.

The Interaction of a Direct-Current Cold Atmospheric-Pressure Air Plasma With Bacteria

A direct-current cold atmospheric-pressure air plasma microjet (PMJ) based on the microhollow cathode discharge design is used to inactivate six types of bacteria within a small well-defined area on a large Petri dish. We show that the PMJ is very effective in inactivating bacteria in their vegetative state as well as in the spore state within the area of plasma exposure. We also observed that bacteria in their vegetative state were inactivated efficiently outside the area of direct plasma exposure. Different bacteria responded differently to an increase in the plasma exposure (dose). Lastly, we observed two types of colony forming unit (CFU) distributions after plasma treatment; one distribution is diffusionlike with a gradual increase of the surviving CFU as one moves radially away from the area of direct plasma exposure, and the other distribution shows an essentially uniform reduction in surviving CFU across the entire Petri dish.

Cold atmospheric pressure air plasma jet for medical applications

By flowing atmospheric pressure air through a direct current powered microhollow cathode discharge, we were able to generate a 2cm long plasma jet. With increasing flow rate, the flow becomes turbulent and temperatures of the jet are reduced to values close to room temperature. Utilizing the jet, yeast grown on agar can be eradicated with a treatment of only a few seconds. Conversely, animal studies show no skin damage even with exposures ten times longer than needed for pathogen extermination. This cold plasma jet provides an effective mode of treatment for yeast infections of the skin.