Atmospheric Plasma Technology Research Articles

Recovery of Noble metal elements from effluents of the semiconductor industry as nanoparticles, by dielectric barrier discharge (DBD) plasma treatment

The fabrication of semiconductor products for the microelectronic industry requires the deposition of thin noble metal layers (e.g. Au-Sn and Pd) by means of processes involving fluid baths that contain metal ions (e.g. electrowinning and electroless plating). After several cycles, the plating solutions are used up and must be replaced, generating large volumes of discarded solutions containing precious metals. The metals (Au and Pd) are recovered either by electrowinning, a slow batch process, or by the use of toxic molecules (e.g. cyanides). This study demonstrates the possibility of using an atmospheric plasma technology to recover Au and Pd from these solutions, which provides a faster and greener process. Plasma discharges are generated at the surface of the solutions, causing ions to precipitate as nanoparticles. The treatment (few minutes only) allows the recovery of >95% gold, and >60% palladium. The process separates Au (NPs) from Sn ions (remaining in solution), as confirmed by elemental analysis and XPS. Particle size distributions of the nanoparticles recovered through the process suggests that as-synthesized nanoparticles could integrate value-added products (e.g. catalyst industry). Overall, the use of plasma technology could open several possibilities for the recycling of metals contained in solutions discarded from the semiconductor industry.

Effect of Cold Atmospheric Plasma processing on quality and shelf-life of ready-to-eat rocket leafy salad

The effect of Cold Atmospheric Plasma (CAP) on ready-to-eat (RTE), fresh cut, leafy rocket salad (ready-to-eat arugula leaves packed in pouches of 125 g) was investigated, aiming at quality retention and shelf-life extension. CAP was generated via a surface dielectric barrier discharge source and its efficiency on rocket leaves was evaluated at different processing times through microbial, texture, pH value and colour analyses. A reduction of 0.57 to 1.02 log CFU/g was observed for the total microbial load after processing times ranging from 5 to 20 min, respectively. A CAP processing time of 10 min was considered as optimum, for a sufficient reduction of the microbial load while maintaining colour and texture. The shelf-life of the optimum CAP-processed rocket stored at 2-9 °C was estimated through analysis of specific quality parameters. Pseudomonas spp. growth (higher count of approximately 7.0 log CFU/g) was considered to be the dominant deterioration factor. The shelf-life of the CAP-treated leafy rocket salad was estimated as 116, 84 and 55 h compared to 63, 57 and 37 h for the control samples after storage at 2, 5 and 9 °C, respectively. Industrial relevanceSpoilage of fresh-cut vegetables due to microbial growth has a significant economic impact causing food waste by reducing the shelf-life of the products and posing a risk for the public health through possible foodborne illnesses. As a result, there is a real need to seek for alternative methods for preservation of fresh produce. Cold Atmospheric Plasma technology could potentially be applied for microbial load reduction of leafy salads. The proposed protocol along with the device used for Surface Dielectric Barrier Discharge treatment, could be a potential solution for extending the shelf-life of significantly perishable fresh produce.

The Emerging Role of Cold Atmospheric Plasma in Implantology: A Review of the Literature.

In recent years, cold atmospheric plasma (CAP) technologies have received increasing attention in the field of biomedical applications. The aim of this article is to review the currently available literature to provide an overview of the scientific principles of CAP application, its features, functions, and its applications in systemic and oral diseases, with a specific focus on its potential in implantology. In this narrative review, PubMed, Medline, and Scopus databases were searched using key words like “cold atmospheric plasma”, “argon plasma”, “helium plasma”, “air plasma”, “dental implants”, “implantology”, “peri-implantitis”, “decontamination”. In vitro studies demonstrated CAP’s potential to enhance surface colonization and osteoblast activity and to accelerate mineralization, as well as to determine a clean surface with cell growth comparable to the sterile control on both titanium and zirconia surfaces. The effect of CAP on biofilm removal was revealed in comparative studies to the currently available decontamination modalities (laser, air abrasion, and chlorhexidine). The combination of mechanical treatments and CAP resulted in synergistic antimicrobial effects and surface improvement, indicating that it may play a central role in surface “rejuvenation” and offer a novel approach for the treatment of peri-implantitis. It is noteworthy that the CAP conditioning of implant surfaces leads to an improvement in osseointegration in in vivo animal studies. To the best of our knowledge, this is the first review of the literature providing a summary of the current state of the art of this emerging field in implantology and it could represent a point of reference for basic researchers and clinicians interested in approaching and testing new technologies.

Complex coacervation of zein-chitosan via atmospheric cold plasma treatment: Improvement of encapsulation efficiency and dispersion stability

Zein-polysaccharide complex coacervations were modified using atmospheric cold plasma (ACP) technology in order to decrease zein's hydrophobicity and consequent aggregation. The ACP-induced interaction between zein and chitosan in 70% ethanol-water solution was investigated. To evaluate the application potential of the modified complex in nutrition delivery, the encapsulation efficiency and dispersion stability of resveratrol-loaded nanoparticles were investigated. It was found that the novel zein-chitosan complex coacervation re-assembled in 70% ethanol-water solution after ACP treatment, displaying smaller particle sizes (from 1191 nm to 370 nm) and higher conductivity (from 36.6 ds/cm to 43.1 ds/cm) than non-ACP-treated samples. UV–vis spectrum, IR, AFM and SDS-PAGE analysis demonstrated that the ACP treatment caused conformational changes and unfolding of the zein polypeptide chain, increased hydrogen bonding and electrostatic interactions between zein and chitosan. No effects were observed on the primary structure of zein. The aggregation of complex coacervations was also reduced after treatment. With ACP treatment (40 V), resveratrol-loaded nanoparticles showed higher encapsulation efficiencies (from 51.8% to 82.7%) and better dispersion stability compared to untreated samples. A possible assembly mechanism between zein and chitosan under ACP exposure is proposed. These findings clarify the interaction between protein and polysaccharide under ACP exposure and demonstrate the promise of ACP technology in modifying zein-chitosan complex coacervation as a promising delivery carrier in the functional food field.

Enhancing Activities of Salt-Tolerant Proteases Secreted by Aspergillus oryzae Using Atmospheric and Room-Temperature Plasma Mutagenesis.

Aspergillus oryzae 3.042 was mutagenized using atmospheric and room-temperature plasma (ARTP) technology to enhance its salt-tolerant proteases activity. Compared to the starting strain, mutant H8 subjected to 180 s of ARTP treatment exhibited excellent genetic stability (15 generations), growth rate, and significantly increased activities of neutral proteases, alkaline proteases, and aspartyl aminopeptidase during fermentation. Mutant H8 significantly enhanced the contents of 1-5 kDa peptides, aspartic acid, serine, threonine, and cysteine in soy sauce by 16.61, 7.69, 17.30, 8.61, and 45.00%, respectively, but it had no effects on the contents of the other 14 free amino acids (FAAs) due to its slightly enhanced acidic proteases activity. Analyses of transcriptional expressions of salt-tolerant alkaline protease gene (AP, gi: 217809) and aspartyl aminopeptidase gene (AAP, gi: 6165646) indicated that their expression levels were increased by approximately 30 and 27%, respectively. But no mutation was found in the sequences of AP and AAP expression cassettes, suggesting that the increased activities of proteases in mutant H8 should be partially attributed to the increased expression of proteases. ARTP technology showed great potential in enhancing the activities of salt-tolerant proteases from A. oryzae.

Role of SiC nanoparticles on tribological properties of atmospheric plasma sprayed 5 wt% SiC–Ni60 coatings

In order to comparatively investigate the role of SiC nanoparticles on tribological properties under dry and water-lubricated conditions, Ni60 and 5 wt% SiC–Ni60 coatings were deposited by atmospheric plasma technology. The morphologies and phase composition of coatings were inspected by scanning electron microscopy and X-ray diffraction, respectively. And friction interface of coatings was examined by X-ray photoelectron spectroscopy and high-resolution transmission electron microscope to reveal the wear mechanisms of coatings after friction. Results illustrated that SiC nanoparticles could function as reinforcing phases, inducing friction-reducing and anti-wear. And tribological properties of 5 wt% SiC–Ni60 coating under dry and water-lubricated conditions were superior to those of Ni60 coating. The analysis of worn surface revealed that SiC nanoparticles could fill pits on the surface of coatings. According to FIB-TEM analyses and XPS results, SiC nanoparticles released onto friction interface can undergo hydrolysis reaction under water-lubricated condition, and the film containing SiO2 is formed by the hydrolysis reaction of SiC nanoparticles, which improves good boundary lubrication effect.

Combination of ARTP mutagenesis and color-mediated high-throughput screening to enhance 1-naphthol yield from microbial oxidation of naphthalene in aqueous system

Strain QCG of the aerobic bacteria Bacillus cereus is capable of producing 1-naphthol from naphthalene, this strain was first isolated and characterized in this study. Strain QCG was mutagenized to enhance 1-naphthol production, using atmospheric and room temperature plasma (ARTP) technology. Then, a microbial clone screening system was used to accelerate the operation. Meanwhile, a novel color-mediated high-throughput screening using 4-aminoantipyrine was performed to screen mutants. The optimal mutant strain QCG4 produced 19.58±0.34 mg∙L−1 1-naphthol from naphthalene that was 47.32% higher than that of the original strain (13.29±0.28 mg∙L−1). In addition, the optimal conditions for 1-naphthol production via whole-cell catalysis of strain QCG4 were determined to be an OD600 of 40,150 mg∙L−1 naphthalene, and 7.5% dimethyl formamide as a co-solvent at pH 7.5 and 26°C for 3 h, resulting in 41.18±0.12 mg-L−1 1-naphthol, i.e., the mutant strain produces a 2.1-fold higher yield compared to the original strain.

Efficient extraction of chitin from shrimp waste by mutagenized strain fermentation using atmospheric and room-temperature plasma

Chitin extraction from shrimp waste by protease-producing microorganisms was a positive and simple method. To improve the protease activity of microorganism used for the extraction of chitin, atmospheric and room temperature plasma technology was adopted to induce mutations in Exiguobacterium profundum, a protease-producing bacterium, which was isolated from traditional fermented shrimp paste. After several rounds of screening, the mutant numbered 10017 was screened. The hereditary properties of the mutant were found to be stable after a series of passages. This strain was subsequently used in the deproteinization process, which could remove 91.48% ± 2.60% protein, and the chitin recovery was 70.18 ± 2.68%. Fourier transform infrared spectrometry, X-ray diffraction, and scanning electron microscopy was adopted to compare the characteristics of the chitin extracted from mutagenized and wild-type strain fermentation. The crystallinity indices were 80.72% and 82.46%, and the degrees of deacetylation were 15.78% and 27.84%. These results indicated that the deproteinization by mutagenized strain fermentation might be applied to the production of chitin. Thus, the present study provides an appropriate strategy to develop an efficient method to improve protease activity in microbial fermentation.

EXTH-10. THE ACTIVATION AND SENSITIZATION OF GLIOBLASTOMA CELLS VIA COLD ATMOSPHERIC PLASMA TREATMENT

Abstract BACKGROUND Treatment of glioblastoma multiforme (GBM) continues to remain a challenge using conventional treatment. Through an in vitro study we assessed the efficacy of our novel cold atmospheric plasma technology (CAP) to sensitize GBM cells to temozolomide (TMZ). METHODS The CAP jet is formed through the discharge (Pk-Pk: 5.8 kV) between a ring grounded cathode and a central anode and with He flow through a glass tube. The discharge process is driven by an AC high voltage (3.16 kV) with a frequency of 12.5 kHz. Human glioblastoma (U87MG) cells were cultured in DMEM supplemented by 1% (v/v) penicillin and streptomycin solution and 10% (v/v) FBS. CAP was delivered to U87 cells in a 96-well plate for 1 min in combination with 10 and 15 μM H2O2. The cell viability was measured by using the MTT assay. We then tested TMZ concentrations of 10 and 50 uM. Cell viability was monitored with the Cell Titer Glo 2.0. luminescent assay. All experiments were performed in triplicate and were independently repeated at least 3 times. RESULTS We identified an activation state of U87MG cells after the plasma treatment. This activation state resulted in GBM cells sensitized to reactive species identified by decreased cell viability after treatment with H2O2 as compared to the H2O2 treatment alone (p< 0.005). In addition, the plasma-activated cells were sensitized to TMZ. Cells treated with CAP in combination with TMZ displayed decreased cell viability at TMZ concentrations of (10 uM) (p< 0.05) and (50 uM) (p< 0.005) as compared to TMZ alone. CONCLUSIONS This study demonstrates the activation phenomenon on GBM cells via direct CAP treatment. Due to this activation, the GBM cells were sensitized to both H2O2 and TMZ identified via decreased cell viability. Future work looks to assess this effect of cell activation/sensitization with chemotherapy plus radiation treatment.

Effects of cold atmospheric plasma on mackerel lipid and protein oxidation during storage

The present study investigated the effects of cold atmospheric plasma on the shelf-life stability of lipids and proteins of commercially packaged mackerel fillets. The results showed no significant effects on lipid oxidation between the control samples and those treated at 80 kV for extended treatment times of 5 min using an in-package plasma system. In addition, no significant changes (p > 0.05) were found in the fatty acid composition or nutritional quality indices after treatment. Finally, the formation of carbonyls was accelerated by plasma treatment at the end of the storage period for 4 °C and 8 °C. These results suggest that cold atmospheric plasma technologies are potentially suitable as processing technologies for the fish industry.

Degradation of antibiotic resistance contaminants in wastewater by atmospheric cold plasma: kinetics and mechanisms

ABSTRACT This work employed the atmospheric cold plasma technology to efficiently control the antibiotic resistance contaminants in the wastewater effluent. We found that the plasma inactivated the antibiotic-resistant Escherichia coli through multiple damages on the cell membranes and intracellular components (enzymes and DNA). Plasma treatment at an influence of 0.71 kJ/cm2 resulted in a more than 3 log10 CFU/ml reduction (>99.999%) of E. coli in an actual wastewater system. We further estimated the effect of plasma on the ampicillin (blaTEM ) and tetracycline (tet) resistance genes. The results demonstrated that an applied plasma dose of 1.06 kJ/cm2 could significantly (P < .05) eliminate the extracellular (e-) blaTEM and tet genes by 3.26 and 3.14 log10 copies/ml, respectively. Higher plasma intensity was required for the efficient reduction of intracellular (i-)antibiotic resistance genes (ARGs) than extracellular (e-)ARGs due to the shielding effect of the outer envelopes or intracellular components. The inactivation of E. coli and the degradation of e- and i-ARGs can be well described by the Weibull models. The results here provide the evidence for the potential of the plasma technology as a water/wastewater treatment technology.

Aspergillus decontamination in hazelnuts: Evaluation of atmospheric and low-pressure plasma technology

Abstract The decontamination effects of non-thermal atmospheric-pressure (AP) and low-pressure (LP) plasma systems were investigated on hazelnuts artificially contaminated with Aspergillus parasiticus and Aspergillus flavus spores. Furthermore, AP-plasma treatment conditions were also optimized. Spore reductions of 5.6 and 4.7 log cfu/g in Aspergillus parasiticus and Aspergillus flavus, respectively, were achieved after 100 W-30 min of LP-air-plasma treatment. Similarly, 5.5 and 5.4 log cfu/g of reductions in Aspergillus parasiticus and Aspergillus flavus, respectively, were achieved after AP-air-plasma treatment at 3000 L/h of gas flow rate, frequency of 25 kHz and reference voltage of 100% (655 W) for 5-cycles (1.7 min). Deformation of spores and loss of spore integrity after plasma treatments were demonstrated with scanning electron microscope (SEM). This study showed that LP and AP plasma treatments might be an alternative method for inactivation of aflatoxin- producing fungi. Industrial relevance Non-thermal (cold) plasma is a promising technology for decontamination of foods due to its safety, ease of use and low temperature processing capability. The results of this study showed that plasma system can be incorporated into a food processing chain, and when initial Aspergillus spp. spores were 7.8–7.9 cfu/g in hazelnut, plasma treatment with reductions of up to 5.6 log cfu/g can compete with other decontamination methods.

Strategy to achieve a 5-log Salmonella inactivation in tender coconut water using high voltage atmospheric cold plasma (HVACP)

This study examined high voltage atmospheric cold plasma (HVACP) technology as a non-thermal intervention for inactivating Salmonella enterica serovar Typhimurium LT2 (ST2) in tender coconut water (TCW). Treatment with HVACP in air at 90 kV for 120 s inactivated 1.30 log10 of ST2. Development of a TCW stimulant suggested an interfering role of magnesium and phosphate salts with HVACP inactivation. Generation of reactive gas species, viz. ozone and hydrogen peroxides were found to be responsible for microbial inactivation. The addition of 400 ppm citric acid to the TCW effectively reduced ST2 by 5 log10 during HVACP treatment. Under these conditions, higher cellular leakage and morphological damage were observed in ST2. Minimal physico-chemical changes in TCW were observed with HVACP treatment, except for an 84.35% ascorbic acid loss (added externally). These results demonstrate a potential pathway for developing highly effective cold plasma treatments to preserve fruit and vegetable juices.

Kinetics of inactivation of peroxidase and polyphenol oxidase in tender coconut water by dielectric barrier discharge plasma

The spoilage enzymes in tender coconut water were inactivated by atmospheric cold plasma technology. The kinetics of peroxidase (POD) and polyphenol oxidase (PPO) inactivation was studied at voltage levels varying between 18 and 28 kV dielectric barrier discharge plasma treatments (DBD) at atmospheric air. The time of treatment and applied voltage were significant factors for inactivation of the enzymes. POD was more resistant than PPO. The experimentally observed data were fitted to establish different kinetics models and model parameters were evaluated. The sigmoidal logistic was the best fitting model to explain the kinetics of browning enzymes inactivation based on high RMSE values. The time required for half maximal activity values for POD was 0.84, 1.67 and 2.53 min at 18 kV, 23 kV and 28 kV, respectively which was higher than PPO with half maximal activity values of 0.67, 1.18 and 1.35 min, respectively. This indicates that POD is more resistant to cold plasma than PPO and its inactivation in tender coconut water by cold plasma can be considered as a crucial quality parameter. DBD generated cold plasma can therefore be used to process fruits and vegetables juices wherein enzymes activity is one of the quality deterioration parameters.

Atmospheric pressure dielectric barrier discharge synthesis of morphology-controllable TiO2 films with enhanced photocatalytic activity

Atmospheric plasma technology is a promising next-generation alternative for replacing thermal chemical vapor deposition or wet chemical processes for the deposition of functional coatings. In this work, TiO2 films with various morphologies and thicknesses are synthesized in a controllable way by atmospheric Dielectric Barrier Discharges (DBD) under argon/oxygen ambient conditions. This method allows varying the density of the deposited coatings, from low density powders to dense compact anatase layers simple tuning of the parameters. The surface morphology and cross section of the as-synthesized films are observed by scanning electron microscopy (SEM). It is demonstrated that the total flow rate together with the absorbed power have a significant effect on the morphology of the film, which changes from granular to compact film by increasing the total flow rate or decreasing the power. In other words, changing the energy density (Ed) in the plasma allows to control the morphology of the TiO2 films. A deposition mechanism is proposed to explain the effect of the synthesis parameters on the formed films. The chemical and phase composition of these films before and after annealing for 2 h in air at 673 K are comparatively studied. The photocatalytic activities and the reusability of the TiO2 films is investigated by degrading a methylene blue (MB) solution under Ultra-Violet (UV) light. It is compared to the activity of a P25 film, deposited by drop-casting. The photocatalytic rate of the annealed TiO2 film synthesized at a total flow rate of 2.5 slm turns out to be about 2 and 15 times higher than the one of P25 and as-synthesized TiO2 films, respectively. The annealed TiO2 film were shown to be reusable for at least three cycles, without significant loss of photocatalytic activity.

USE OF ATMOSPHERIC PLASMA IN GERMINATION OF Hybanthus calceolaria (L.) Schulze-Menz SEEDS

ABSTRACT Plasma technology is a fast, cost-effective, and pollution-free method that can be used in place of conventional methods to overcome seed dormancy. The goal of the present study was to determine the effect of different application times of atmospheric plasma on soaking and germination of Hybanthus calceolaria seeds in order to accelerate these processes. Helium plasma jet produced by dielectric barrier discharge was used to treat H. calceolaria seeds with applications of 1, 5, and 10 minutes. The treated seeds were characterized considering their weight variation during soaking, changes in electrical conductivity, and pH. It was found that germination depended on the plasma application time. The treatment of H. calceolaria seeds with atmospheric plasma for 1 minute provided 3.5 times greater germination in comparison to untreated seeds. Atmospheric plasma technology obtained by dielectric barrier discharge had potential of being used as a germination accelerant in H. calceolaria seeds. The treatment of H. calceolaria seeds using atmospheric plasma for 1 minute favored germination.

Cold atmospheric plasma treatment inhibits growth in colorectal cancer cells.

Plasma oncology is a relatively new field of research. Recent developments have indicated that cold atmospheric plasma (CAP) technology is an interesting new therapeutic approach to cancer treatment. In this study, p53 wildtype (LoVo) and human p53 mutated (HT29 and SW480) colorectal cancer cells were treated with the miniFlatPlaSter - a device particularly developed for the treatment of tumor cells - that uses the Surface Micro Discharge (SMD) technology for plasma production in air. The present study analyzed the effects of plasma on colorectal cancer cells in vitro and on normal colon tissue ex vivo. Plasma treatment had strong effects on colon cancer cells, such as inhibition of cell proliferation, induction of cell death and modulation of p21 expression. In contrast, CAP treatment of murine colon tissue ex vivo for up to 2 min did not show any toxic effect on normal colon cells compared to H2O2 positive control. In summary, these results suggest that the miniFlatPlaSter plasma device is able to kill colorectal cancer cells independent of their p53 mutation status. Thus, this device presents a promising new approach in colon cancer therapy.

Atmospheric plasma coatings for membrane distillation

Membrane distillation is an emerging membrane technology, commonly used for desalination. The development of high performing and cheap membranes is one of the concerns for increasing the industrial applicability of the technology. In this paper, an economically interesting alternative has been found through the deposition of an atmospheric plasma coating on an inexpensive commercial hydrophilic membrane with a microporous structure. This coating enables obtaining the required hydrophobicity in order to retain the feed solution and preventing wetting of the membrane. The effect of the plasma discharge time on the membrane properties and membrane distillation performance was investigated. It was found that by using atmospheric plasma technology, very thin hydrophobic layers of a few μm can be obtained on top of a hydrophilic membrane structure. The thin hydrophobic layer obtained using this technology reduces the mass transport resistance, which results in very high fluxes at seawater salinity. This flux is equal to the flux of more expensive and supported thin PTFE membranes.

Mutation breeding of high 9α-hydroxy-androst-4-ene-3,17- dione transforming strains from phytosterols and their conversion process optimization

In order to improve transformation efficiency of phytosterols into 9α-hydroxylation of 4-androstene-3,17-dione (9α-OH-AD) by Mycobacterium sp. LY-1, we studied the strains breeding using atmospheric and room temperature plasma (ARTP) technology and optimized their conversion process. A high production strain named C33 with a good genetic stability was selected and the product molar yield reached to 15.5%, 34.8% higher than that of original strain with 15 g/L phytosterols. Furthermore, the fermentation medium was optimized through the design of orthogonal experiment. Besides, oil-water bidirectional transformation system was set up to improve the 9α-OH-AD molar yield of mutant strain C33. With adding 12 mL soybean oil to each 1 g phytosterols, the molar yield of 9α-OH-AD reached 47.0%, which increased twice than that of control (15.5%).

High voltage atmospheric cold plasma treatment of refrigerated chicken eggs for control of Salmonella Enteritidis contamination on egg shell

Salmonella Enteritidis (SE) contamination is a major risk for U.S. consumers from chicken eggs. This study is primarily focused on evaluation of a novel High Voltage Atmospheric Cold Plasma (HVACP) technology for inactivation of Salmonella and its effect on the egg quality. Spot inoculated chicken eggs were treated with high voltage cold plasma (85 kV) under direct and indirect mode of exposure in dry air and modified atmospheric gas environment. A reduction of 5.53 log cfu/egg was observed for egg surfaces directly treated under modified atmospheric gas for 15 min. SE reductions was found dependent on treatment times, gas type, and mode of exposure of eggs to the plasma. No significant difference (p > 0.05) in direct and indirect mode of exposure was observed on the egg quality after plasma treatment. These results demonstrate the potential of HVACP to be used as a suitable non-thermal treatment for reducing Salmonella from packaged chicken eggs.