Nevena Puač

We investigated the influence of humidity on development of helium sinusoidal-driven atmospheric-pressure plasma streamers using Intensified Charge-Coupled Device (ICCD) imaging, mass spectrometry (MS), and laser-induced fluorescence (LIF). A critical humidity threshold of ∼20 ppm was identified, below which streamers become diffuse and unstable. Importantly, the origin of water vapor (adsorbed in the gas line vs bubbler injection) was found to significantly affect streamer morphology. ICCD observations of streamer length correlate with changes in dominant ion species detected by MS, and with spatial OH distributions revealed by LIF. Although OH density was measured only at 250 ppm, the results confirm that humidity is the main source of reactive OH radicals. These findings highlight the crucial role of trace humidity in plasma jet behavior and demonstrate the need for precise humidity control in plasma diagnostics and applications.

We present characterization of atmospheric pressure Ar streamer jet, diagnostics of physico‐chemical properties of Plasma Activated Water (PAW), and modeling of Reactive Oxygen and Nitrogen Species (RONS) deposited in PAW. Additional focus is on the toxicity of the created PAW to model plant Lemna minor . The streamer jet is characterized by analyzing electrical properties, gas‐phase characteristics through plasma emission, and laser‐induced fluorescence of OH(X) radicals. Measured OH densities are in the range of 10 ²⁰ m ⁻³ depending on the mean power deposited to plasma. Gas phase species are linked to measured RONS concentrations, while modeling results confirmed the production mechanisms of H ₂ O ₂ , NO₂⁻ and NO₃⁻ species. Experiments with Lemna minor show both favorable and negative effects of PAW depending on the PAW concentration.

The aim of this study was to explore the effectiveness of cold atmospheric plasma (CAP) treatments for reducing the deoxynivalenol (DON) content in spiked white wheat flour samples containing 750 μg kg⁻¹ DON. The flour samples were treated with plasma generated in air for durations of 30 s, 60 s, 90 s, 120 s, 150 s, and 180 s and at four distances from the cold plasma source: 6 mm, 21 mm, 36 mm, and 51 mm. An artificial neural network (ANN) model with three layers utilizing the Broyden–Fletcher–Goldfarb-Shanno (BFGS) iterative algorithm was developed to predict the reduction in deoxynivalenol (DON) content, moisture content, and temperature in wheat flour samples following cold atmospheric plasma (CAP) treatment. The model accounted for two key variables: the distance from the plasma source and the treatment duration. The ANN model exhibited excellent predictive performance, achieving coefficient of determination (r²) values of 0.999, 0.996, and 0.996 for DON reduction, moisture content, and temperature, respectively, during the training phase. The ANN model successfully identified the experimental optimal CAP conditions (51 mm distance and 150 s treatment), resulting in a 71% reduction in DON content. Multi-objective optimization (MOO) using the ANN further predicted the same level of reduction but at 168 s while maintaining acceptable moisture and temperature levels, representing the model-derived optimal treatment within the investigated design space. The study highlights the potential of ANNs to model complex relationships and optimize CAP treatment for efficient mycotoxin reduction in wheat flour.

Ovaj rad prikazuje eksperimentalnu analizu produkata sagorevanja različitih građevinskih materijala u prisustvu dizel goriva kao akceleratora, primenom masene spektrometrije. Ispitivani su uzorci cigle, laminata, tepisona, tarketa i vinila. Sagorevanje uz dodatak dizel goriva rezultovalo je pojavom karakterističnih masenih obrazaca akceleratora, sa dominantnim signalima u oblastima m/z 43 i 57, kao i u višem masenom opsegu m/z 69–71 i m/z 91, koji se mogu dovesti u vezu sa fragmentacijom alifatskih i aromatskih komponenti dizel goriva. Primenom diferencijalne analize masenih spektara omogućeno je izdvajanje signala koji potiču od produkata sagorevanja u prisustvu akceleratora, uz efikasno uklanjanje uticaja atmosferskih gasova. Posebno je uzeto u obzir da detektovani signali potiču od neutralnih vrsta uzorkovanih iz gasne faze, koje se jonizuju unutar masenog spektrometra. Dobijeni rezultati pokazuju da kombinacija masene spektrometrije i diferencijalne analize predstavlja pouzdan pristup za identifikaciju prisustva dizel goriva u složenim požarnim ostacima.

The scope of the antibacterial effects of plasma-activated water (PAW) is not yet fully comprehended. We investigated the activity of PAW produced by the in-house 3-pin atmospheric pressure plasma jet against carbapenem-resistant Klebsiella pneumoniae and vancomycin-resistant Enterococcus faecalis, with a focus on PAW’s potential to promote susceptibility to conventional antibiotics in these bacteria. Bacterial inactivation was determined by the colony count after 15 and 60 min PAW treatments. Minimum inhibitory concentrations (MICs) measured following repeated exposures to PAW across multiple generations of bacteria enabled the assessment of changes in susceptibility to antibiotics. The PAW’s efficacy was also analyzed through the detection of intracellular reactive oxygen and nitrogen species in treated bacteria. Time-dependent significant inactivation efficiency against K. pneumoniae was observed (log reduction 6.92 ± 0.24 after 60 min exposure), while effects on E. faecalis were limited. PAW demonstrated potential to decrease the MICs of crucial antibiotics. Namely, a 50 to 62.5% decrease in the MICs of colistin against K. pneumoniae and a 25% reduction in the MICs of vancomycin against enterococci were recorded. We found a significant increase in the superoxide anion concentration in K. pneumoniae and E. faecalis cells after PAW treatments. This study indicates that PAW’s inactivating efficacy coupled with the capacity for the potentiation of antibiotic effects is a promising combination against multidrug-resistant bacteria.

The spatial profile of atomic oxygen in a cylindrical afterglow chamber with a height of 41 cm and an inner diameter of 30 cm was measured. The source of oxygen atoms was a remote microwave plasma operating at a discharge power of about 250 W. The gas flowed through a quartz-glass tube with inner and outer diameters of 3.8 and 6.0 mm, respectively. The exhaust of the quartz tube widened to cones of various geometries. The spatial distribution of atomic oxygen was determined for cones with an outer diameter of up to 40 mm. The tube with the widest cone (Tube 3) provided the largest O-atom density of 6 × 10²⁰ m⁻³ in the upper part of the afterglow chamber away from the main gas stream in the pressure range from 50–200 Pa, while the tube (Tube 1) with the narrowest cone enabled an O-atom density of up to 2 × 10²⁰ m⁻³. The differences in measured oxygen density for three tubes at positions ‘up’ and ‘down’ decreased with increasing pressure and were below the detection limit at pressures above 350 Pa. In the case of the ‘middle’ position, Tube 2 with an outer diameter of 19.3 mm exhibited a sharper decrease in oxygen density compared to Tube 1 and Tube 3. The O-atom density in the middle of the afterglow chamber increased with the increase in the percentage of pump valve opening at the lowest probed constant pressure of 40 Pa, but it stayed constant for the opening of the pump valve above 70%. For constant pressures above 100 Pa the O-atom density decreases with the larger pump valve opening. The pressure is kept constant by the corresponding increase in oxygen gas flow while increasing the percentage of the pump valve opening. The spatial profiles are explained by the effects of gas flow and diffusion.

Background/Objectives: Cold atmospheric plasma (CAP) has shown a strong anticancer effect on a variety of tumors, presenting a new approach for the effective treatment of oral squamous cell carcinoma (OSCC), one of the most prevalent malignant neoplasms with a high mortality rate. Here, we aimed to comprehensively investigate the antitumor potential of two approaches of CAP treatment on both two-dimensional and three-dimensional OSCC cell line models, as well as to analyze whether plasma treatment enhances the sensitivity of OSCC to chemotherapy. Methods: An in-house designed plasma needle, with helium as a working gas, was used to treat the SCC-25 cell line directly or indirectly via plasma-treated medium (PTM). The antitumor effect of CAP was assessed by measuring cell viability, apoptosis, adhesion, and migration. In addition, the combined effect of PTM and cisplatin was analyzed in SCC-25 tumor spheroids, as a more complex and reliable in vitro model. Results: Both plasma treatments showed time-dependent antitumor effects affecting their viability, adhesion, and migration. The rate of apoptosis was higher after incubation with PTM and is mediated by the intrinsic pathway. By utilizing the 3D spheroid carcinoma model, we confirmed the antitumor potential of CAP and additionally demonstrated an increased chemosensitivity of PTM-treated carcinoma cells. Conclusions: The results of our study illustrate a promising avenue for the application of CAP as a therapeutic option for OSCC, either as a standalone treatment or in combination with cisplatin.

Diabetic foot ulcers have an enormous impact on patients’ quality of life and represent a major economic burden. The cause is delayed and incomplete wound healing due to hyperglycemia, reduced blood flow, infections, oxidative stress and chronic inflammation. Plasma-activated water (PAW) is emerging as a new therapeutic approach in wound treatment, as it has many of the advantages of cold atmospheric plasma but is easier to apply, thus allowing for widespread use. The aim of this study was to investigate the potential of PAW to improve wound healing in diabetic rats, with a focus on uncovering the underlying mechanisms. Two full-thickness wounds in control and diabetic animals were treated with PAW, and healing was monitored for 15 days at five time points. PAW improved wound healing in diabetic rats and mainly affected the inflammatory phase of wound healing. Application of PAW decreased the number of inflammatory cells, myeloperoxidase (MPO) and N-acetyl-b-D-glycosaminidase (NAG) activity, as well as the mRNA expression of proinflammatory genes in diabetic rats. Ten days after injury, PAW treatment increased collagen deposition in the diabetic animals by almost 10% without affecting collagen mRNA expression, and this is in correlation with a decrease in the Mmp-9/Timp-1 ratio. In conclusion, PAW treatment affects wound healing by reducing the inflammatory response and influencing extracellular matrix turnover, suggesting that it has great potential to accelerate the healing of diabetic wounds.

In this review, we give an overview of the applications of plasma activated water (PAW) and its chemistry in the field of agriculture. This article concentrates on the chemistry of long‐lived reactive species and their roles in plant cell mechanisms. The chemical reactions important for the creation of nitrate, nitrite, and hydrogen peroxide inside water during the production of PAW and their chemical paths inside the plant cells are discussed. We describe the use of different types of discharges for PAW production and present the results of PAW application to seeds and plants. We address the decontamination of agricultural chemicals in water along with the scarcely explored topic of water remediation. The major challenges and future possibilities for PAW in agriculture are also discussed.