A new configuration of a discharge chamber and power source for the treatment of up to 1 L of liquid is presented. A leakage transformer, energizing two metal electrodes positioned above the liquid, limits the discharge current inductively by utilizing the weak magnetic coupling between the primary and secondary coils. No additional means to avoid arcing (electric short-circuiting), e.g., dielectric barriers or resistors, are needed. By using this technique, exceeding the breakdown voltage leads to the formation of transient spark discharges, producing non-thermal plasma (NTP). These discharges effected significant changes in the properties of the treated liquids (distilled water, physiological saline solution, and tap water). Considerable concentrations of nitrite and nitrate were detected after the plasma treatment. Furthermore, all tested liquids gained strong antibacterial efficacy which was shown by inactivating suspended Escherichia coli and Staphylococcus aureus. Plasma-treated tap water had the strongest effect, which is shown for the first time. Additionally, the pH-value of tap water did not decrease during the plasma treatment, and its conductivity increased less than for the other tested liquids.
The efficient enzyme-catalysed reaction of morpholines as model structures for bioactive compounds with para-dihydroxylated aromatic systems was carried out using the oxidoreductase laccase and atmospheric oxygen to produce eight novel morpholine-substituted aromatics. The laccase of Myceliophthora thermophila was used for cross-linking morpholines containing primary or secondary amino groups with para-dihydroxylated laccase substrates. We demonstrate that not only primary amino groups, but also secondary amino groups, are able to couple with para-dihydroxylated aromatic systems in laccase-catalysed reactions. The resulting model products (yields up to 80%) were isolated, structurally characterized and tested for their antibacterial, antifungal and cytotoxic activities. Four of the eight products showed low to moderate growth inhibition against several Gram-positive and -negative bacterial strains and against the yeasts Candida maltosa and Candida albicans. The antibacterial and antifungal activities were determined by an agar disc diffusion test and a modified method according to the EUCAST discussion document E.Dis 7.1 [Rodríguez-Tudela et al. (2003) Clin. Microbiol. Infect. 9, i-viii] for the evaluation of MIC (minimal inhibitory concentration). Differences in cytotoxicity against the human urinary bladder carcinoma cell line 5637 are discussed.
Laccases are able to mediate both cleavage and synthesis processes. The basis for this dual reaction capability lies in the property of the enzyme laccase to oxidize phenolic, and to some extent non-phenolic substances, to reactive radicals which can undergo on the one hand separations of small substitutents or large molecule parts from the parent compound and on the other hand coupling reactions with other radicals or molecules which are not themselves oxidizable by laccase. The cleavage of the non-phenolic compound 4-morpholinoaniline as well as the deamination of 4-aminophenol and the dechlorination of 4-chlorophenol resulted in the formation of 1,4-hydroquinone which is immediately oxidized by laccase to 1,4-benzoquinone. The formation of the 1,4-hydroquinone/1,4-benzoquinone is the rate limiting step for the synthesis of the heteromolecular dimers and trimers composed of 1,4-benzoquinone and one or two molecules of morpholine. In addition to the synthesis of new compounds from the cleavage products, 4-morpholinoaniline polymerized probably via azo groups and C-N bonds to a homomolecular dimer and trimer. Similarities and differences in cleavage and synthesis reactions catalyzed by the low redox potential laccase of Myceliophthora thermophila (0.46 V) and the high redox potential laccase of Pycnoporus cinnabarinus (0.79 V) were determined. In addition, the dependency of the cleavage and synthesis efficiencies on the (a) structure and redox potential of the laccase, (b) structure and redox potential of the substrate, (c) pH value of the buffer used, (d) incubation temperature, (e) solvent concentration, and (f) laccase activity is discussed in general.
A commercial air-fed and piezoelectric-driven plasma pen (piezobrush®, relyon plasma GmbH, Regensburg, Germany) including three different nozzles was investigated for its suitability as a medical plasma device. In this regard, potential risk factors for human health, which originate from gas temperature, thermal output, patient leakage current, ultraviolet radiation and gas emissions, were assessed according to DIN SPEC 91315:2016–06. As a result, safe treatment distances were determined for each nozzle. The antimicrobial efficacy was investigated subsequently by inhibition zone assays with five different clinical relevant microorganisms. All results were compared to an approved medical plasma source fed with argon (kINPen® MED, neoplas tools GmbH, Greifswald, Germany). It was observed that the antimicrobial efficacy differs not only between the two devices as a result from different feed gases, but also between the nozzles. This could be traced back to a different plasma chemistry, which accompanying Fourier-transform infrared absorption spectroscopy suggests. The measured physical properties of the piezoelectric plasma pen at the determined operating parameters do not show human health risks. Due to its distinct antimicrobial efficacy, the piezoelectric plasma pen shows a high potential for a medical application.
Application of cold atmospheric-pressure plasma (CAP) for wound treatment and decontamination of food or water often includes the presence of proteins. These proteins contain amino acids with functional groups, such as thiol (SH) groups. Plasma-mediated effects in biological systems involve reactive oxygen and nitrogen species. In this regard, redox signaling is often mediated via thiol groups. The aim of this study was to investigate the influence of a protein and an SH group containing amino acids on the antimicrobial properties of plasmatreated saline solution (0.85% NaCl, w/v) and on the direct CAP efficacy on solid wet agar plates. Plasma treatment of saline solution was realized using an ACdriven pin-to-liquid discharge. After plasma treatment for 10 minutes, the amino acids L-cysteine (contains SH group) or L-alanine (no SH group) or bovine serum albumin (BSA; with approximately 6% cysteine content) were added together with the test microorganism Escherichia coli K-12 (DSM 11250/ NCTC 10538) for an exposure time of up to 60 min. The total viable cell count was determined at appropriate time intervals. A concentration-dependent repeal of the antimicrobial efficacy was determined. Therefore, 0.0025% of BSA did not have any influence, whereas 0.25% of BSA w/v, as well as the tested amino acids, did not result in the inactivation of E. coli. The difference between L-alanine and L-cysteine was negligible, suggesting only a minor effect of the presence of SH groups. Dimerization of L-cysteine was shown by LC/MS analyses, whereas no derivatization of L-alanine was detected. To test the influence of proteins in direct plasma treatment on wet surfaces, E. coli was plated together with BSA on soybean-casein digest agar surface. Another setup was based on agar plates, which contained different concentrations of peptone (a mixture of peptides and amino acids). The agar plates were regularly treated by the argon-driven CAP jet kINPen Med (neoplas tools GmbH, Greifswald, Germany). After overnight incubation, inhibition zones were analyzed. The bacterial growth was independent of protein or peptone content for this direct plasma treatment. Summarizing all, the antibacterial effect of the Plasma Process Polym. 2019;16:e1800164 www.plasma-polymers.com
The green and environmentally friendly synthesis of highly valuable organic substances is one possibility for the utilization of laccases (EC 1.10.3.2). As reactants for the herein described syntheses, different o-substituted arylamines or arylthiols and 2,5-dihydroxybenzoic acid and its derivatives were used. In this way, the formation of phenothiazines, phenoxazines, and phenazines was achieved in aqueous solution mediated by the laccase of Pycnoporus cinnabarinus in the presence of oxygen. Two types of phenothiazines (3-hydroxy- and 3-oxo-phenothiazines) formed in one reaction assay were described for the first time. The cyclization reactions yielded C–N, C–S, or C–O bonds. The syntheses were investigated with regard to the substitution pattern of the reaction partners. Differences in C–S and C–N bond formations without cyclization are discussed.
Airborne bacteria are a general problem in medical or health care facilities with a high risk for nosocomial infections. Rooms with a continuous airflow, such as operation theaters, are of particular importance due to a possible dissemination and circulation of pathogens including multidrug‐resistant microorganisms. In this regard, a cold atmospheric‐pressure plasma (CAP) may be a possibility to support usual disinfection procedures due to its decontaminating properties. The aim of this study was to determine the antimicrobial efficacy of a plasma decontamination module that included a dielectric barrier discharge for plasma generation. Experimental parameters such as an airflow velocity of 4.5 m/s and microbial contaminations of approximately 6,000 colony‐forming units (cfu)/m3 were used to simulate practical conditions of a ventilation system in an operating theater. The apathogenic microorganism Escherichia coli K12 DSM 11250/NCTC 10538 and the multidrug‐resistant strains E. coli 21181 and 21182 (isolated from patients) were tested to determine the antimicrobial efficacy. In summary, the number of cfu was reduced by 31–89% for the tested E. coli strains, whereby E. coli K12 was the most susceptible strain toward inactivation by the designed plasma module. A possible correlation between the number or kind of resistances and susceptibility against plasma was discussed. The inactivation of microorganisms was affected by plasma intensity and size of the plasma treatment area. In addition, the differences of the antimicrobial efficacies caused through the nebulization of microorganisms in front (upstream) or behind (downstream) the plasma source were compared. The presence of ionic wind had no influence on the reduction of the number of cfu for E. coli K12, as the airflow velocity was too high for a successful precipitation, which would be a prerequisite for an increased antimicrobial efficacy. The inactivation of the tested microorganisms confirms the potential of CAP for the improvement of air quality. The scale‐up of this model system may provide a novel tool for an effective air cleaning process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.