82 results
Search Results
Now showing 1 - 10 of 82
- ItemDifferent Radial Modification Profiles Observed on APPJ-Treated Polypropylene Surfaces according to the Distance between Plasma Outlet and Target(Basel : MDPI, 2022) do Nascimento, Fellype; Silva Leal, Bruno; Quade, Antje; Kostov, Konstantin GeorgievThe plasma jet transfer technique relies on a conductive wire at floating potential, which, upon entering in contact with a primary discharge, is capable of igniting a small plasma plume at the distal end of a long flexible plastic tube. In this work, two different long tube configurations were employed for the surface modification of polypropylene (PP) samples using argon as the working gas. One of the jet configurations has a thin copper (Cu) wire, which was installed inside the long tube. In the other configuration, the floating electrode is a metallic mesh placed between two plastic tubes in a coaxial arrangement. In the first case, the tip of the Cu wire is in direct contact with the working gas at the plasma outlet, whereas, in the second, the inner plastic tube provides an additional dielectric barrier that prevents the conductor from being in contact with the gas. Water contact angle (WCA) measurements on treated PP samples revealed that different surface modification radial profiles are formed when the distance (d) between the plasma outlet and target is changed. Moreover, it was found that the highest WCA reduction does not always occur at the point where the plasma impinges the surface of the material, especially when the d value is small. Through X-ray photoelectron spectroscopy (XPS) analysis, it was confirmed that the WCA values are directly linked to the oxygen-functional groups formed on the PP surfaces after the plasma treatment. An analysis of the WCA measurements along the surface, as well as their temporal evolution, together with the XPS data, suggest that, when the treatment is performed at small d values, the plasma jet removes some functional groups at the point where the plasma hits the surface, thus leading to peculiar WCA profiles.
- ItemInactivation of airborne bacteria by plasma treatment and ionic wind for indoor air cleaning(Hoboken, NJ : Wiley Interscience, 2020) Prehn, Franziska; Timmermann, Eric; Kettlitz, Manfred; Schaufler, Katharina; Günther, Sebastian; Hahn, VeronikaAirborne 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.
- ItemEffect of Cold Atmospheric Plasma Jet Associated to Polyene Antifungals on Candida albicans Biofilms(Basel : MDPI, 2021) Leite, Lady Daiane Pereira; Oliveira, Maria Alcionéia Carvalho de; Vegian, Mariana Raquel da Cruz; Sampaio, Aline da Graça; Nishime, Thalita Mayumi Castaldelli; Kostov, Konstantin Georgiev; Koga-Ito, Cristiane YumiThe increasing incidence of antifungal resistance represents a great challenge in the medical area and, for this reason, new therapeutic alternatives for the treatment of fungal infections are urgently required. Cold atmospheric plasma (CAP) has been proposed as a promising alternative technique for the treatment of superficial candidiasis, with inhibitory effect both in vitro and in vivo. However, little is known on the association of CAP with conventional antifungals. The aim of this study was to evaluate the effects of the association between CAP and conventional polyene antifungals on Candida albicans biofilms. C. albicans SC 5314 and a clinical isolate were used to grow 24 or 48 h biofilms, under standardized conditions. After that, the biofilms were exposed to nystatin, amphotericin B and CAP, separately or in combination. Different concentrations of the antifungals and sequences of treatment were evaluated to establish the most effective protocol. Biofilms viability after the treatments was compared to negative control. Data were compared by One-way ANOVA and post hoc Tukey (5%). The results demonstrate that 5 min exposure to CAP showed more effective antifungal effect on biofilms when compared to nystatin and amphotericin B. Additionally, it was detected that CAP showed similar (but smaller in magnitude) effects when applied in association with nystatin and amphotericin B at 40 µg/mL and 60 µg/mL. Therefore, it can be concluded that the application of CAP alone was more effective against C. albicans biofilms than in combination with conventional polyene antifungal agents.
- ItemBiological Risk Assessment of Three Dental Composite Materials following Gas Plasma Exposure(Basel : MDPI, 2022) Bekeschus, Sander; Miebach, Lea; Pommerening, Jonas; Clemen, Ramona; Witzke, KatharinaGas plasma is an approved technology that generates a plethora of reactive oxygen species, which are actively applied for chronic wound healing. Its particular antimicrobial action has spurred interest in other medical fields, such as periodontitis in dentistry. Recent work has indicated the possibility of performing gas plasma-mediated biofilm removal on teeth. Teeth frequently contain restoration materials for filling cavities, e.g., resin-based composites. However, it is unknown if such materials are altered upon gas plasma exposure. To this end, we generated a new in-house workflow for three commonly used resin-based composites following gas plasma treatment and incubated the material with human HaCaT keratinocytes in vitro. Cytotoxicity was investigated by metabolic activity analysis, flow cytometry, and quantitative high-content fluorescence imaging. The inflammatory consequences were assessed using quantitative analysis of 13 different chemokines and cytokines in the culture supernatants. Hydrogen peroxide served as the control condition. A modest but significant cytotoxic effect was observed in the metabolic activity and viability after plasma treatment for all three composites. This was only partially treatment time-dependent and the composites alone affected the cells to some extent, as evident by differential secretion profiles of VEGF, for example. Gas plasma composite modification markedly elevated the secretion of IL6, IL8, IL18, and CCL2, with the latter showing the highest correlation with treatment time (Pearson’s r > 0.95). Cell culture media incubated with gas plasma-treated composite chips and added to cells thereafter could not replicate the effects, pointing to the potential that surface modifications elicited the findings. In conclusion, our data suggest that gas plasma treatment modifies composite material surfaces to a certain extent, leading to measurable but overall modest biological effects.
- ItemCombining Biocompatible and Biodegradable Scaffolds and Cold Atmospheric Plasma for Chronic Wound Regeneration(Basel : Molecular Diversity Preservation International (MDPI), 2021) Emmert, Steffen; Pantermehl, Sven; Foth, Aenne; Waletzko-Hellwig, Janine; Hellwig, Georg; Bader, Rainer; Illner, Sabine; Grabow, Niels; Bekeschus, Sander; Weltmann, Klaus-Dieter; Jung, Ole; Boeckmann, LarsSkin regeneration is a quite complex process. Epidermal differentiation alone takes about 30 days and is highly regulated. Wounds, especially chronic wounds, affect 2% to 3% of the elderly population and comprise a heterogeneous group of diseases. The prevailing reasons to develop skin wounds include venous and/or arterial circulatory disorders, diabetes, or constant pressure to the skin (decubitus). The hallmarks of modern wound treatment include debridement of dead tissue, disinfection, wound dressings that keep the wound moist but still allow air exchange, and compression bandages. Despite all these efforts there is still a huge treatment resistance and wounds will not heal. This calls for new and more efficient treatment options in combination with novel biocompatible skin scaffolds. Cold atmospheric pressure plasma (CAP) is such an innovative addition to the treatment armamentarium. In one CAP application, antimicrobial effects, wound acidification, enhanced microcirculations and cell stimulation can be achieved. It is evident that CAP treatment, in combination with novel bioengineered, biocompatible and biodegradable electrospun scaffolds, has the potential of fostering wound healing by promoting remodeling and epithelialization along such temporarily applied skin replacement scaffolds.
- ItemEndothelial Differentiation of CCM1 Knockout iPSCs Triggers the Establishment of a Specific Gene Expression Signature(Basel : Molecular Diversity Preservation International, 2023) Pilz, Robin A.; Skowronek, Dariush; Mellinger, Lara; Bekeschus, Sander; Felbor, Ute; Rath, MatthiasCerebral cavernous malformation (CCM) is a neurovascular disease that can lead to seizures and stroke-like symptoms. The familial form is caused by a heterozygous germline mutation in either the CCM1, CCM2, or CCM3 gene. While the importance of a second-hit mechanism in CCM development is well established, it is still unclear whether it immediately triggers CCM development or whether additional external factors are required. We here used RNA sequencing to study differential gene expression in CCM1 knockout induced pluripotent stem cells (CCM1−/− iPSCs), early mesoderm progenitor cells (eMPCs), and endothelial-like cells (ECs). Notably, CRISPR/Cas9-mediated inactivation of CCM1 led to hardly any gene expression differences in iPSCs and eMPCs. However, after differentiation into ECs, we found the significant deregulation of signaling pathways well known to be involved in CCM pathogenesis. These data suggest that a microenvironment of proangiogenic cytokines and growth factors can trigger the establishment of a characteristic gene expression signature upon CCM1 inactivation. Consequently, CCM1−/− precursor cells may exist that remain silent until entering the endothelial lineage. Collectively, not only downstream consequences of CCM1 ablation but also supporting factors must be addressed in CCM therapy development.
- ItemHmox1 Upregulation Is a Mutual Marker in Human Tumor Cells Exposed to Physical Plasma-Derived Oxidants(Basel : MDPI, 2018-10-27) Bekeschus, Sander; Freund, Eric; Wende, Kristian; Gandhirajan, Rajesh; Schmidt, AnkeIncreasing numbers of cancer deaths worldwide demand for new treatment avenues. Cold physical plasma is a partially ionized gas expelling a variety of reactive oxygen and nitrogen species, which can be harnesses therapeutically. Plasmas and plasma-treated liquids have antitumor properties in vitro and in vivo. Yet, global response signatures to plasma treatment have not yet been identified. To this end, we screened eight human cancer cell lines to investigate effects of low-dose, tumor-static plasma-treated medium (PTM) on cellular activity, immune-modulatory properties, and transcriptional levels of 22 redox-related genes. With PTM, a moderate reduction of metabolic activity and modest modulation of chemokine/cytokine pattern and markers of immunogenic cell death was observed. Strikingly, the Nuclear factor (erythroid-derived 2)-like 2 (nrf2) target heme oxygenase 1 (hmox1) was upregulated in all cell lines 4 h post PTM-treatment. nrf2 was not changed, but its baseline expression inversely and significantly correlated with hmox1 expression after exposure to PTM. Besides awarding hmox1 a central role with plasma-derived oxidants, we present a transcriptional redox map of 22 targets and chemokine/cytokine secretion map of 13 targets across eight different human tumor cell lines of four tumor entities at baseline activity that are useful for future studies in this field.
- ItemSelf-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity(Weinheim : Wiley-VCH, 2023) Mohamed, Mana Abdirahman; Arnold, Stefanie; Janka, Oliver; Quade, Antje; Presser, Volker; Kickelbick, GuidoInorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C6H10N2]2[Mo8O26] ⋅ 6 H2O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C6H9N2]4[NH4]2[Mo7O24] ⋅ 3 H2O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g−1 at 100 mA g−1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2MoO4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.
- ItemEffect of cold atmospheric pressure plasma treatment of eggshells on the total bacterial count inoculated Salmonella Enteritidis and selected quality parameters(Hoboken, NJ : Wiley Interscience, 2021) Moritz, Maike; Wiacek, Claudia; Weihe, Thomas; Ehlbeck, Jörg; Weltmann, Klaus‐Dieter; Braun, Peggy G.In the European Union, foodborne outbreaks caused by Salmonella Enteritidis, related to eggs and egg products, have even been reported in 2018. Atmospheric pressure plasma is becoming increasingly important as a decontamination method. A semidirect cold atmospheric pressure plasma, the flexible electrode plasma source, was developed for treating whole hen's eggs. An average reduction of 1.16 and 0.95 log colony-forming units (CFU)/egg was achieved for the total bacterial count of clean and dirty eggs, respectively. An inactivation of 4.1 log CFU/egg Salmonella Enteritidis was achieved with artificially inoculated eggshells. Selected quality parameters and sensory properties were analysed. Overall, the present study yielded promising results for a realistic implementation of an industrial prototype plasma source.
- ItemThermal analysis of aliphatic polyester blends with natural antioxidants(Basel : MDPI, 2020) Olejnik, Olga; Masek, Anna; Kiersnowski, AdamThe aim of this research was to enhance thermal stability of aliphatic polyester blends via incorporation of selected natural antioxidants of plant origin. Thermal methods of analysis, including differential scanning calorimetry (DSC) and thermogravimetry (TGA), are significant tools for estimating the stabilization effect of polyphenols in a polymer matrix. Thermal stability was determined by analyzing thermogravimetric curves. Polymers with selected antioxidants degraded more slowly with rising temperature in comparison to reference samples without additives. This property was also confirmed by results obtained from differential scanning calorimetry (DSC), where the difference between the oxidation temperatures of pure material and polymer with natural stabilizers was observed. According to the results, the materials with selected antioxidants, including trans-chalcone, flavone and lignin have higher oxidation temperature than the pure ones, which confirms that chosen phytochemicals protect polymers from oxidation. Moreover, based on the colour change results or FT-IR spectra analysis, some of the selected antioxidants, including lignin and trans-chalcone, can be utilized as colorants or aging indicators. Taking into account the data obtained, naturally occurring antioxidants, including polyphenols, can be applied as versatile pro-ecological additives for biodegradable and bio-based aliphatic polyesters to obtain fully environmentally friendly materials dedicated for packaging industry.