Search

In this paper, we report a qualitative model of operation and energy release in pulsed dielectric barrier discharges (DBDs). We demonstrate that pulsed DBDs operate according to the “maximum power principle” and explain the relevant physical processes. Compared to experimental data, the proposed model allows an accurate estimation of the discharge pulse energy as a function of dielectric properties, electrode size, and pulse parameters (shape and voltage amplitude).

Realizing active, light-emitting fibers made of conjugated polymers by the electrospinning method is generally challenging. Electrospinning of plasma-treated conjugated polymer solutions is here developed for the production of light-emitting microfibers and nanofibers. Active fibers from conjugated polymer solutions rapidly processed by a cold atmospheric argon plasma are electrospun in an effective way, and they show a smoother surface and bead-less morphology, as well as preserved optical properties in terms of absorption, emission, and photoluminescence quantum yield. In addition, the polarization of emitted light and more notably photon waveguiding along the length of individual fibers are remarkably enhanced by electrospinning plasma-treated solutions. These properties come from a synergetic combination of favorable intermolecular coupling in the solutions, increased order of macromolecules on the nanoscale, and resulting fiber morphology. Such findings make the coupling of the electrospinning method and cold atmospheric plasma processing on conjugated polymer solutions a highly promising and possibly general route to generate light-emitting and conductive micro- and nanostructures for organic photonics and electronics.

Bioaerosols (aerosolized particles with biological origin) are strongly suspected to play a significant role in the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), especially in closed indoor environments. Thus, control technologies capable of effectively inactivating bioaerosols are urgently needed. In this regard, cold atmospheric pressure plasma (CAP) can represent a suitable option, thanks to its ability to produce reactive species, which can exert antimicrobial action. In this study, results; on the total inactivation of SARS-CoV-2 contained in bioaerosols treated using CAP generated in air are reported, demonstrating the possible use of CAP systems for the control of SARS-CoV-2 diffusion through bioaerosols.

Niemann-Pick type C disease (NPC) is a rare inherited neurodegenerative disorder characterized by an accumulation of intracellular cholesterol within late endosomes and lysosomes due to NPC1 or NPC2 dysfunction. In this work, we tested the hypothesis that retromer impairment may be involved in the pathogenesis of NPC and may contribute to increased amyloidogenic processing of APP and enhanced BACE1-mediated proteolysis observed in NPC disease. Using NPC1-null cells, primary mouse NPC1-deficient neurons and NPC1-deficient mice (BALB/cNctr-Npc1m1N), we show that retromer function is impaired in NPC. This is manifested by altered transport of the retromer core components Vps26, Vps35 and/or retromer receptor sorLA and by retromer accumulation in neuronal processes, such as within axonal swellings. Changes in retromer distribution in NPC1 mouse brains were observed already at the presymptomatic stage (at 4-weeks of age), indicating that the retromer defect occurs early in the course of NPC disease and may contribute to downstream pathological processes. Furthermore, we show that cholesterol depletion in NPC1-null cells and in NPC1 mouse brains reverts retromer dysfunction, suggesting that retromer impairment in NPC is mechanistically dependent on cholesterol accumulation. Thus, we characterized retromer dysfunction in NPC and propose that the rescue of retromer impairment may represent a novel therapeutic approach against NPC.

Ready-to-eat vegetables offer great advantages to consumers due to their nutritional value and convenience, although they are an ideal substrate for microbial growth. Rocket (E. sativa) is appreciated by consumers for its pleasant bitter flavor and its high content of vitamins C and K, Calcium, fibers and glucosinolates. The major post-harvest problems of rocket are wilting, senescence and microbial spoilage which limits its shelf-life. Also decontamination from pathogenic microorganisms is a critical aspect for food safety. In the food industry, fresh rocket is usually washed with chlorine sanitizers (e.g. NaOCl, ClO2) to limit degradative processes and the microbial growth. However, this procedure releases on the rocket leaves several by-products including chloramines which are potentially harmful to human health. Plasma Activated Water (PAW), obtained by exposing water to cold plasma discharges, could be an alternative method for the decontamination of fresh rocket. In this contest, the aim of this study was to use PAW for the decontamination of fresh rocket leaves to extend their shelf-life without affecting their quality characteristics. PAW was generated with distilled water exposed to a Microsecond Pulsed Corona device for 4 minutes. Subsequently, rocket leaves were washed with PAW for 2, 5, 10 and 20 min then dried and finally stored at 4°C up to 10 days in PP bags under ordinary atmosphere. The load of spoilage microbiota on rocket salad treated with PAW was compared to those washed with sodium hypochlorite solution (100 ppm). Also, the effects of PAW washing on product quality traits were evaluated by measuring pH, color parameters and the content of some bioactive compounds. Data showed that PAW resulted in an immediate reduction of 1-1.5 log CFU/g for the target microbial groups. Sodium hypochlorite, which is the reference sanitizer, exhibited a similar efficacy to the PAW against mesophilic and psychrotrophic bacteria, while its activity against Enterobacteriaceae was higher than PAW. During storage at 4°C, cell loads of the spoilage microbiota increased suggesting that survivors were able to repair Second International Conference on Advances in Plasma Science and Technology (ICAPST), 2021, Coimbatore, India ISBN 978-93-90853-30-4 | ICAPST’21| 69 damages. However, the same trend was detected also for rocket samples washed with sodium hypochlorite. Moreover, minimal variations in the qualitative parameters were observed. Overall, these results showed that PAW can be a promising innovative post harvest treatment to preserve perishable foods such as ready to eat vegetables. The present work is part of the research activities developed within the project “PLASMAFOOD - Study and optimization of cold atmospheric plasma treatment for food safety and quality improvement” founded by MIUR - Ministero dell’Istruzione dell’Università e della Ricerca – PRIN Progetti di Ricerca di Rilevante Interesse Nazionale, Bando 2017.

Purpose In Endodontics, in order to complete a root canal treatment, the use of guttapercha to completely seal the root apex must be coupled with endodontic cements known as sealers to improve the adhesion with dentine, despite their cytotoxicity and solubility. The present study investigates the effect of enhancement of adhesion between these materials and Cold Atmospheric Plasma (CAP)-treated dentine of the apical region of ex-vivo teeth as a first step towards the reduction on the use of cytotoxic materials and the use of CAP in-vivo at a clinical stage. Methods A dielectric barrier discharge (DBD) helium plasma jet was used to treat for 180 sec the shaped root canal dentin. Pushout tests and confocal microscopy analysis have been performed to evaluate the effect of cold plasma treatment in terms of adhesion performances and interaction between filling materials and dentin respectively. Results The pushout test results highlight how a 180 seconds CAP treatment of dentin promotes an enhancement of bonding strength between filling materials and dentine in all investigated cases. In particular, when the dentine is CAP-treated in the apical region, the adhesion performances of guttapercha achieved a relevant increase (~ +200%), revealing how it was able to “self-bond” with the substrate with results comparable with the conventional procedure but without any sealer application, while the conventional (guttapercha+sealer) apical sealing procedure shows an improvement around +50%. Moreover, confocal images qualitatively confirmed the higher spreading and penetration of both guttapercha and sealer into dentinal tubules. The ergonomics of the prototype has been also improved to comply with the dimensions of devices commonly used in the dental field, with a plasma source diameter of 21.5 mm and with a choice of materials to minimise its weight. Conclusion CAP treatment of dentin increases the adhesion performances and paves the way for a sealer-free and safer procedure for apical restoration.

In this study, two different cold atmospheric‐pressure plasmas are used for the production of plasma‐activated water (PAW). To evaluate the effectiveness of PAW as a possible means to control plant diseases, grapevines in an open field and a greenhouse are treated, evaluating qualitative and quantitative yield parameters, phytoplasma presence, and gene expression. The results show the capability of PAW to enhance plant defense mechanisms and, as demonstrated in the field trials, confirm its ability to improve the health status of the treated plants.

The accidental contamination of food and food packaging surfaces with SARS-CoV-2 is of increasing concern among scientists and consumers, particularly in relation to fresh foods that are consumed without further cooking. The use of chemical sanitizers is often not suitable for these kinds of commodities, therefore, a non-thermal sanitation technology could help to increase safety in relation to the food supply chain. Cold plasma has proven to be a promising strategy for virus inactivation. This research is aimed at evaluating the ability of a cold plasma sanitation system to inactivate SARS-CoV-2 RNA on packaged foods. Two different plastic materials were investigated and subjected to 5- and 10-min exposure to plasma after experimental inoculum of the RNA. In addition to viral degradation, possible changes in the performance of the materials were evaluated. Shelf-life of the foods, after exposure of the packages to plasma, was also investigated. Results showed that 10 min of exposure was sufficient to almost completely eliminate the viral RNA from package surfaces. The treatment did not produce any significant variation in packaging material performance or the shelf-life of the tested packaged products, indicating the potentiality of this treatment for the decontamination of packaged products.

In this study, the effect of a Polylactic acid (PLA) antimicrobial biodegradable packaging activated with lysozyme by cold plasma on a pear juice and rice milk-based smoothie was investigated. The antimicrobial effect of the active innovative packaging was evaluated In-vitro and on the smoothie inoculated with Listeria monocytogenens and Lactobacillus plantarum. After a preliminary evaluation of the lysozyme release kinetics in different conditions, its influence on some smoothie quality parameters (water activity, pH, colour and microbial growth) was evaluated. In-vitro trials showed an antimicrobial activity of the activated film against different microorganisms. Inoculated smoothies packed in activated and not materials were stored at 10 and 4 °C and analysed overtime. Results showed the capability of the activated package to inhibit Listeria monocytogenes and to maintain a better and a more stable colour compared to control ones. Activated pouches showed the best antimicrobial effect on samples stored at 10 °C compared to 4 °C, difference due to the faster lysozyme release kinetic from the packaging material at the highest storage temperature. Obtained results highlight the potentiality of the biodegradable packaging activated with lysozyme to be applied successfully in food industry, to improve safety and extend shelf-life of juice-based product.

The present work aims to investigate the interaction between a plasma jet and targets with different physical properties. Electrical, morphological and fluid-dynamic characterizations were performed on a plasma jet impinging on metal, dielectric and liquid substrates by means of Intensified Charge-Coupled Device (ICCD) and high-speed Schlieren imaging techniques. The results highlight how the light emission of the discharge, its time behavior and morphology, and the plasma-induced turbulence in the flow are affected by the nature of the target. Surprisingly, the liquid target induces the formation of turbulent fronts in the gas flow similar to the metal target, although the dissipated power in the former case is lower than in the latter. On the other hand, the propagation velocity of the turbulent front is independent of the target nature and it is affected only by the working gas flow rate.

The COVID-19 crisis profoundly disguised the vulnerability of human societies and healthcare systems in the situation of a pandemic. In many instances, it became evident that the quick and safe reduction of viral load and spread is the foremost principle in the successful management of such a pandemic. However, it became also clear that many of the established routines in healthcare are not always sufficient to cope with the increased demand for decontamination procedures of items, healthcare products, and even infected tissues. For the last 25 years, the use of gas plasma technology has sparked a tremendous amount of literature on its decontaminating properties, especially for heat-labile targets, such as polymers and tissues, where chemical decontamination often is not appropriate. However, while the majority of earlier work focused on bacteria, only relatively few reports are available on the inactivation of viruses. We here aim to provide a perspective for the general audience of the chances and opportunities of gas plasma technology for supporting healthcare during viral pandemics such as the COVID-19 crisis. This includes possible real-world plasma applications, appropriate laboratory viral test systems, and critical points on the technical and safety requirements of gas plasmas for virus inactivation.

Cold atmospheric plasma (CAP) has received attention as a potential anticancer strategy. In this study, culture medium was exposed to a microsecond-pulsed dielectric barrier discharge jet to produce plasma-activated medium (PAM). On the T-lymphoblastic cell line, PAMinduced apoptosis through the activation of the intrinsic pathway and inhibited the cell-cycle progression. The use of the scavengers N-acetylcysteine or O-phenantroline significantly decreased the PAM proapoptotic activity. The genetic impact of PAM on TK6 cells was assessed, resulting in an increased micronuclei frequency. PAM exhibited cytotoxic effects even on leukemia cells cultivated in hypoxia, which plays a critical role in promoting chemoresistance. PAM was also tested on normal lymphocytes, showing its partial selectivity. Taken together, these results contribute to understand the pharmacotoxicological profile of CAP.

The synthesis of nanoparticles by reaction of liquid aerosol droplets containing precursors in a flow-through, atmospheric-pressure, non-thermal plasma offers a continuous, scalable, substrate- and stabilizer-free approach for direct deposition into liquids or onto soft substrates. However, the combination of multiphase and non-equilibrium chemistry makes the process complicated and poorly understood. Here, we present ion mobility spectrometry measurements of liquid water droplets containing silver nitrate passing through an atmospheric-pressure dielectric barrier discharge reactor that allows us to monitor silver nanoparticle formation online for the first time. Mobility diameter distributions were obtained with the plasma on and off, and exhibited a shift, which was related to the degree of conversion of silver nitrate. The silver nanoparticles were also collected and characterized by UV–visible absorbance spectroscopy and transmission electron microscopy to support the online measurements. Importantly, negligible conversion was found when the water was removed by a diffusion dryer, suggesting that the key reducing species are in the liquid phase, such as solvated electrons. Overall, the study demonstrates how ion mobility spectrometry measurements can be applied to provide insight into this approach to nanoparticle synthesis.

Epithelial Ovarian Cancer (EOC) is one of the leading causes of cancer-related deaths among women and is characterized by the diffusion of nodules or plaques from the ovary to the peritoneal surfaces. Conventional therapeutic options cannot eradicate the disease and show low efficacy against resistant tumor subclones. The treatment of liquids via cold atmospheric pressure plasma enables the production of plasma-activated liquids (PALs) containing reactive oxygen and nitrogen species (RONS) with selective anticancer activity. Thus, the delivery of RONS to cancer tissues by intraperitoneal washing with PALs might be an innovative strategy for the treatment of EOC. In this work, plasma-activated Ringer&rsquo, s Lactate solution (PA-RL) was produced by exposing a liquid substrate to a multiwire plasma source. Subsequently, PA-RL dilutions are used for the treatment of EOC, non-cancer and fibroblast cell lines, revealing a selectivity of PA-RL, which induces a significantly higher cytotoxic effect in EOC with respect to non-cancer cells.

Nowadays, one of the main challenges is moving towards an eco-sustainable agriculture, able to preserve the food production through a reduced use of pesticides. Current global food sustenance by intensive agriculture is mainly based on economic crop monocultures and drastically reduces the biodiversity, increasing the yield losses due to the presence of biotic and abiotic stresses. A technology based on plasma activated water (PAW), characterized by the presence in liquid of reactive oxygen and nitrogen species, was tested to try to ensure yield stability also enhancing the plant resistance responses and to promote an eco-sustainable management of plant diseases. In PAW-treated micropropagated periwinkle shoots, periwinkle and grapevine plants, qRT-PCR and small RNAs high-throughput sequencing were used to analyse the differential expression of genes involved in the major plant defence pathways. The results indicate that PAW treatment enhances the plant defence responses and provide an encouraging framework for future applications in plant disease management programs.

Monocytes are involved in innate immune surveillance, establishment and resolution on inflammation, and can polarize versus M1 (pro-inflammatory) or M2 (anti-inflammatory) macrophages. The possibility to control and drive immune cells activity through plasma stimulation is therefore attractive. We focused on the effects induced by cold-atmospheric plasma on human primary monocytes and monocyte-derived macrophages. Monocytes resulted more susceptible than monocyte-derived macrophages to the plasma treatment as demonstrated by the increase in reactive oxygen (ROS) production and reduction of viability. Macrophages instead were not induced to produce ROS and presented a stable viability. Analysis of macrophage markers demonstrated a time-dependent decrease of the M1 population and a correspondent increase of M2 monocyte-derived macrophages (MDM). These findings suggest that plasma treatment may drive macrophage polarization towards an anti-inflammatory phenotype.

Schlieren imaging has been widely used in science and technology to investigate phenomena occurring in transparent media. In particular, it has proven to be a powerful tool in fundamental studies and process optimization for atmospheric pressure plasma diagnostics, providing qualitative and (in some cases) also quantitative information on the fluid-dynamic characteristics of plasmas generated by many different types of sources. However, obtaining significant and reliable results by schlieren imaging can be challenging, especially when considering the variety of geometries and applications of atmospheric pressure plasma sources. Therefore, it is necessary to adopt solutions that can address the specific issues of different plasma-assisted processes. In this paper, an overview on the use of the schlieren imaging technique for atmospheric pressure plasma characterization is presented. In the first part, the physical principles behind this technique and the different setups that can be adopted to perform it are presented. In the second part, examples of schlieren imaging applied to different kinds of atmospheric pressure plasmas (non-equilibrium plasma jets, plasma actuators for flow control and thermal plasma sources) are presented, showing how it was used to characterize the fluid-dynamic behavior of plasma-assisted processes and reporting best practices in performing this diagnostic technique.

Amine/amide-rich coatings possessing good biocompatibility are of high interest in the medical field. A new type of coatings with high content of NH groups has been prepared in a single step plasma process. Deposition is performed by atmospheric pressure plasma which is coupled to aerosol injection of liquid precursor. The method is applied for the polymerization of N,N'-methylenebisacrylamide precursor. The surface analyses, including X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR), show polymerization of the precursor with formation of amide-rich coatings with up to 8 at.% of N-containing groups. The coatings are stable in phosphate buffer saline (PBS) solution and characterized by improved biocompatibility to STEM cells.

The aim of this work was to evaluate cold atmospheric plasma bactericide activity towards biofilm formation on soft reline oral palatal obturators. Plasma was generated using two dielectric barrier discharge and tested against the oral biofilm formers Streptococcus mutans and Aggregatibacter actinomycetemcomitans. Relines were either plasma treated before being infected with 24 h biofilm, or infected with 90 min (early) or 24 h (mature) biofilm prior to be plasma treated for 30, 60, or 120 s. Bacteria numbers and viability were evaluated by Colonies Forming Units counts (CFU) and quantitative colorimetric metabolic 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenyl amino) carbonyl]-2H-tetrazolium hydroxide assay (XTT). cytocompatibility was assayed towards human primary fibroblasts and keratinocytes cultivated on plasma-treated specimens by colorimetric metabolic 3-(4,5-Dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay and light microscopy. Results demonstrated that both plasma sources were effective. Plasma treatment of sterile reline affected bacterial adhesion, reducing CFU number and viability by 2 logs and by 50%, in comparison with untreated controls (p < 0.05). Plasma efficacy was marked against early biofilm: after 120 s, CFUs were reduced by 3 logs, and viability decreased by about 60% (p < 0.05). Significant results were also observed for mature biofilm: CFUs and viability were reduced by approximately 2 logs and 40% (p < 0.05), after 120 s exposure. Lastly, MTT did not show any toxic effect on human cells. Thus, plasma could represent a very promising skill for soft reline shutters decontamination.

Plasma Activated Water (PAW) obtained by exposing water to cold atmospheric pressure plasma, has recently emerged as a promising alternative for food decontamination, compared to the use of traditional chemical sanitizers. The aim of the study was to evaluate the efficacy of PAW treatments for rocket salad decontamination. Washing with PAW for 2, 5, 10 and 20 min was assessed against different endogenous spoilage microorganisms and compared to untreated water and hypochlorite solution. The chemical composition of PAW as a function of treatment and delay time was characterized and the effect on product quality and nutritional parameters was evaluated. Results showed that PAW allowed an average reduction of 1.7–3 Log CFU/g for total mesophilic and psychrotrophic bacteria and Enterobacteriaceae following 2–5 min washing with minimal variation of qualitative and nutritional parameters. Overall, experimental results highlighted the potentiality of PAW treatments as a promising alternative to chlorine having the advantage of a minor adverse impact on environment and consumers' health. Industrial relevance To meet consumers demand, the minimally processed fruit and vegetable industry needs to find sustainable solutions as alternative to the use of traditional chemical sanitizers that allow to increase product shelf-life and preserve safety, qualitative and nutritional characteristics. Plasma activated water represents a promising strategy for food decontamination, but its effects on foods have been only limitedly investigated. The present research is the first study on the use of plasma activated water on fresh rocket leaves, providing new and important information on microbial inactivation and quality of the fresh cut product.

Sterilization of equipment and tissues is a common clinical practice: there are different chemical, mechanical, and electromagnetic aseptic techniques for inactivating microorganisms. In particular, skin tissue banks are investigating new methods to efficiently decolonize skin tissues, while preserving their structural features. In recent years, cold atmospheric plasma (CAP) has demonstrated bactericidal, virucidal, and fungicidal properties, due to the generation of reactive species and charged particles. For this reason, the aim of this paper is to demonstrate that the implementation of a dielectric barrier discharge (DBD) treatment in air can effectively decontaminate skin tissue from Staphylococcus aureus , retaining cell viability and skin integrity. Fresh skin samples, taken from multitissue donors, were contaminated with Staphylococcus aureus and treated with a DBD source, to verify the level of bacterial decontamination induced by plasma. Cell viability and structural properties of skin tissue were investigated using MTT assay and hematoxylin-eosin staining, respectively. Our results show that CAP can sterilize skin tissue with a bacterial load up to 103 CFU/cm2; moreover, it does not affect cell viability, and no loss of skin structural properties was observed. Thus, CAP treatment could be considered an innovative method for decolonization of human skin, without inducing any microscopic tissue damage, while keeping good cell viability.

The analysis of the gas phase chemistry of a cold atmospheric plasma is a fundamental step for a more thorough understanding of the effects it can induce on target substrates. This work aims at investigating, by means of optical spectroscopic techniques, the kinetics of O3, NO2 and NO3 produced by a Surface Dielectric Barrier Discharge. The phenomenon of discharge poisoning (or ozone quenching) in static ambient air was investigated varying the electrical power density applied to the plasma source. Kinetics of the reactive oxygen and nitrogen species production were obtained by means of time resolved UV/VIS optical absorption spectroscopy and highlighted how the discharge poisoning takes place once the applied power density ovecomes a critical value of 0.11 W cm−2. An ozone-enriched atmosphere (with a maximum O3 density around 3000–4000 ppm) is thus obtained when the source is operated below the critical power density, while a NO x -enriched atmosphere (highest concentrations of NO2 around 1250 ppm and NO3 around 35 ppm) is obtained at higher applied power densities. Moreover, since the production of NO, one of the most important quenchers of O3, is directly related to the vibrational energy of nitrogen molecules, the vibrational population of N2, determined by processing emission spectra of N2(B → C) band, was studied. Finally, considerations regarding both the energy cost of production of a reactive oxygen species and reactive nitrogen species atmosphere and the possibility of on-line monitoring its chemical composition, were presented in order to emphasize the potential of optical absorption spectroscopy techniques for the on-line control of plasma assisted industrial processes.

Plant bacterial diseases are routinely managed with scheduled treatments based on heavy metal compounds or on antibiotics; to reduce the negative environmental impact due to the use of such chemical compounds, as pollution or selection of antibiotic resistant pathogens, the integrated control management is required. In the frame of a sustainable agriculture the use of bacterial antagonists, biological agents, plant defence response elicitors or resistant host plant genotypes are the most effective approaches. In this work, cold atmospheric pressure plasma (CAP) was applied to sterile distilled water, inducing the production of a hydrogen peroxide, nitrite and nitrate, and a pH reduction. In particular, an atmospheric pressure dielectric barrier discharge (DBD) has been used to produce plasma activated water (PAW), that was firstly assayed in in vitro experiments and then in planta through application at the root apparatus of tomato plants, against Xanthomonas vesicatoria (Xv), the etiological agent of bacterial leaf spot. Moreover, the transcription abundance of five genes related to the plant defense was investigated in response to PAW treatment. PAW did not show direct antimicrobial activity against Xv in in vitro experiments, but it enhanced the tomato plants defenses. It was effective in reducing the disease severity by giving relative protections of ca. 61, 51 and 38% when applied 1 h, 24 h and 6 days before the experimental inoculation, respectively. In addition, the experiments highlighted the pal gene involvement in response to the PAW treatments and against the pathogen; its transcription levels resulted significantly high from 1 to 48 h until their decrease 192 h after PAW application.

An atmospheric pressure DC transferred arc twin torch thermal plasma system has been characterized by 3D simulation in order to assess its potential for the synthesis of Cu nanoparticles from solid precursors. The numerical model also takes into account the non-negligible effect on process temperature of radiative losses, transport and thermodynamic properties of Cu vapour. In the frame of design-oriented simulation and optimization of the synthesis process, mean diameter and yield of the synthetized nanoparticles have been investigated for different current levels, gas flow rates, precursor feed rates and nanoparticles model. Results show that evaporation efficiency is considerably high even at precursor feed rates up to 25 kg d-1, while the presence of vortices inside the chambers causes a significative loss of nanoparticles to the reactor walls, with a detrimental effect to the yield.

Plasma activated water (PAW) possesses significant antimicrobial properties due to the synergistic effect of reactive oxygen and nitrogen species (RONS) produced by the plasma treatment. To test its efficacy as plant resistance inducer, trials were carried out in five Glera and one Chardonnay vineyards in grapevine plants preliminary tested for the presence and identity of phytoplasmas. The PAW treatments were performed for two years injecting into the plant vascular tissues 10-20 ml of PAW or sterile distilled water (SDW) as control in a total of 130 plants (105 treated with PAW and 25 with SDW). A relevant number of PAW treated symptomatic plants showed a reduction of the symptoms, an higher number of the bunches and a higher berry weight per plant, compared to the SDW treated. Moreover the molecular analyses after the two year-treatment show a decrease of phytoplasma infected plant number treated with PAW (35.5%) compared with the SDW treated ones (12,5 %).

The investigation of the efficiency of a handheld Plasma Gun (PG) in the decontamination of tooth root canals is here reported. The antibacterial efficacy of the PG was first assessed on Enterococcus faecalis contaminated agar plates to determine optimal operating conditions that were then quantitatively evaluated treating contaminated liquid suspensions. Moreover, two different procedures for the inactivation of bacteria in realistic tooth models, resembling procedures conventionally adopted in endodontic practice, were investigated: (A) irrigation of contaminated tooth models with plasma activated water (indirect treatment) produced using the PG and (B) direct exposure of the contaminated tooth models to the plasma plume produced by the PG (direct treatment). The experiments were performed with the root canal model both in wet (root canal filled with bacteria suspension) and in dry (root canal contaminated and dried) conditions. From the obtained results, the direct treatment under dry conditions turned out to be the most effective, leading to a bacterial load mean reduction of 4.1.

One of the major concerns in the COVID-19 pandemic is related to the possible transmission in poorly ventilated spaces of SARS-CoV-2 through aerosol microdroplets, which can remain in the air for long periods of time and be transmitted to others over distances '1 m. Cold atmospheric pressure plasmas can represent a promising solution, thanks to their ability in producing a blend of many reactive species, which can inactivate the airborne aerosolized microorganisms. In this study, a dielectric barrier discharge plasma source is used to directly inactivate suitably produced bioaerosols containing Staphylococcus epidermidis or purified SARS-CoV-2 RNA flowing through it. Results show that for low residence times ('0.2 s) in the plasma region a 3.7 log R on bacterial bioaerosol and degradation of viral RNA can be achieved.

Figure S1. Elevated transcript levels of cathepsins in aged Grn−/− mice. Figure S2. PGRN loss results in accumulation of LAMP1 and saposin D in MEF. Figure S3. Altered maturation of CatD and activity of cathepsins can be rescued by stable PGRN expression. Figure S4. PGRN, elastase digested PGRN and granulin E do not affect in vitro activity of cathepsins. Figure S5. Selectively enhanced CatD in vitro activity in non-microglial brain cells of aged Grn−/− mice. (PPTX 1753 kb)

Atmospheric pressure plasma jets (APPJs) have been one of the most studied nonthermal discharges in the past decade. Recently, the use of multiple jets in order to cover larger areas has become desirable. However, the interaction between neighboring jets is a common phenomenon that can greatly modify plasma characteristics up to the point of merging several jets into a single one. The present study focus on bringing new insight on this phenomenon, named jet-to-jet coupling, investigating the discharge modes (coupled and uncoupled) of a plasma source composed of an array of seven plasma jets arranged adjacent to one another and driven by a sinusoidal excitation. The experimental results achieved by means of mass spectrometry, show a considerable increase in ion concentrations in the plasma, up to some orders of magnitude in the case of negative ions, as an effect of jet-to-jet coupling. Temporally resolved imaging of the discharge also shows how the evolution and intensity of the discharge are greatly affected by jet-to-jet interaction. Air/helium mole fraction and negative ions concentration are regarded as the main possible parameters affecting the coupling phenomenon. Moreover, experimental results suggest that the presence of remnant conductive channels behind the ionization fronts governs the propagation of the next ionization fronts, independently from the direction of propagation (from the source toward the target or vice versa). Furthermore, a parametrical investigation of the coupled mode discharge showed the presence of a critical value of the imposed voltage for which a drastic change in the electrical characteristics of the discharge is observed.

In this work, an atmospheric pressure dielectric barrier discharge was used to produce plasma activated water (PAW). In order to evaluate its effectiveness as an alternative method to control plant diseases, three different pathosystems (i.e. plants infected by phytopathogens) were treated. The results on reduction of disease severity and gene transcription suggest that PAW acts as a plant resistance inducer.

Although the majority of atmospheric pressure plasma jet (APPJ) applications involve the interaction between the plasma and a surface, up to now the number of published papers focusing on this subject is limited, even though the nature of the target may strongly influence the plasma characteristics, the discharge structure, the generated reactive species, and consequently, the overall process. Under this framework, we investigated an APPJ impinging on a liquid surface and the effects of changing the stand-off distance, the applied peak voltage, and the pulse repetition frequency, looking at them as variable parameters often used to optimize plasma surface processes. Intensified charge-coupled device (iCCD) and Schlieren acquisitions suggest a key effect of gap width and peak voltage on the discharge morphology, velocity of the ionization front, and effluent fluid-dynamic behavior. The presence of a grounded liquid substrate enhances the electric field downstream of the source outlet: the smaller the gap the faster the ionization wave and the shorter the time for it to reach the surface. Consequently, a small gap favors the charging of the surface capacitance and the formation of surface ionization waves over the liquid target. Schlieren acquisitions highlight the formation of a transient turbulent structure propagating downstream of the gas flow, starting hundreds of microseconds after the initiation of the plasma discharge. The achieved results support the hypothesis that the formation of the turbulence is caused by a heating effect of the high-voltage electrode on the He gas flow. Another observed effect is the variation of the dimple caused by the He flow on the liquid surface as a consequence of the turbulence generated by the plasma discharge. The results presented here confirm how the gas dynamics and the discharge behavior are strongly affected by the presence of the liquid substrate and by its position with respect to the APPJ.

In this paper we developed an innovative, effective and rapid one-step approach to crosslink mucoadhesive gelatin films for buccal drug delivery. The method, which involves the application of non-equilibrium pressure plasma for 3 or 5 minutes/side, was compared with a classical approach based on the use of a chemical crosslinking agent, namely genipin. Econazole nitrate (ECN), an imidazole antifungal agent used for the treatment of skin infections and mucosal candidiasis, was selected as model drug. X-Ray Diffraction characterization performed on the drug-containing gelatin films revealed that ECN undergoes to a topotactic transformation into Econazole (EC) immediately after mixing with gelatin suggesting the occurrence of an acid-base reaction between drug and gelatin during film processing. Plasma treatment, as well as genipin crosslinking, did not provoke any further variation of EC structure. However, plasma exposure significantly improved films adhesiveness and allowed to reach mucoadhesive strength values more than double with respect to those obtained with genipin, ascribable to the presence of polar and hydrophilic groups on the plasma treated film’s surface. A residence time of at least 48 h was obtained by properly selecting the plasma exposure times. These results, together with the in-vitro data showing retention of antifungal efficacy against a strain of Candida albicans, demonstrated that plasma treatment was a valid and rapid alternative, easy to scale-up, to chemical crosslinking methods for the production of highly mucoadhesive gelatin-based films.

Background Heterozygous loss-of-function mutations in the progranulin gene (GRN) lead to frontotemporal lobar degeneration (FTLD) while the complete loss of progranulin (PGRN) function results in neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Thus the growth factor-like protein PGRN may play an important role in lysosomal degradation. In line with a potential lysosomal function, PGRN is partially localized and processed in lysosomes. In the central nervous system (CNS), PGRN is like other lysosomal proteins highly expressed in microglia, further supporting an important role in protein degradation. We have previously reported that cathepsin (Cat) D is elevated in GRN-associated FTLD patients and Grn knockout mice. However, the primary mechanism that causes impaired protein degradation and elevated CatD levels upon PGRN deficiency in NCL and FTLD remains unclear. Methods mRNA expression analysis of selected lysosomal hydrolases, lysosomal membrane proteins and autophagy-related genes was performed by NanoString nCounter panel. Protein expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts (MEF) and brains of Grn knockout mice were investigated. To selectively characterize microglial and non-microglial brain cells, an acutely isolated microglia fraction using MACS microbeads (Miltenyi Biotec) conjugated with CD11b antibody and a microglia-depleted fraction were analyzed for protein expression and maturation of selected cathepsins. Results We demonstrate that loss of PGRN results in enhanced expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts and brain extracts of aged Grn knockout mice. Consistent with an overall enhanced expression and activity of lysosomal proteases in brain of Grn knockout mice, we observed an age-dependent transcriptional upregulation of certain lysosomal proteases. Thus, lysosomal dysfunction is not reflected by transcriptional downregulation of lysosomal proteases but rather by the upregulation of certain lysosomal proteases in an age-dependent manner. Surprisingly, cell specific analyses identified early lysosomal deficits in microglia before enhanced cathepsin levels could be detected in other brain cells, suggesting different functional consequences on lysosomal homeostasis in microglia and other brain cells upon lack of PGRN. Conclusions The present study uncovers early and selective lysosomal dysfunctions in Grn knockout microglia/macrophages. Dysregulated lysosomal homeostasis in microglia might trigger compensatory lysosomal changes in other brain cells. Electronic supplementary material The online version of this article (10.1186/s13024-018-0281-5) contains supplementary material, which is available to authorized users.