Processes occurring in the NaCMC/glauconite suspension under the cold plasma treatment. Influence of plasma on adsorptive and stabilizing properties of the system

The paper presents the studies on the processes at the interface of the colloidal suspensions composed of clay mineral - glauconite (GT) and polysaccharide - sodium carboxymethyl cellulose (NaCMC) with the cold plasma treatment (CPT). The surface composition and chemical binding in NaCMC and GT changes are determined by means of FTIR and XPS (both methods detected the incorporation of oxygen-related functional groups). Moreover, the additional information about both the textural properties and morphological changes on the surfaces before and after CPT are studied using the BET, CHN, SEM HRTEM and STEM-EDS methods. The elemental mapping and scanning electron microscope imaging confirmed the NaCMC adsorption on GT (carbon mapping) and proved the GT surface lost its "house of card structure" after the CPT. As follows the CPT causes the protonation of NaCMC and the polymer cross-linking whereas the GT sample is more oxidized. Moreover, it was found that a significant improvement in the GT/NaCMC system stability and the NaCMC adsorption on the GT surface were a result of the CPT. The obtained data could be used for the colloidal stability of polymer/solid suspensions, thus providing new opportunities for the chemical industry; particularly for preparation of new functionalized materials.

Evaluation of Selected Properties of Dielectric Barrier Discharge Plasma Jet

In the technological processes requiring mild treatment, such as soft materials processing or medical applications, an important role is played by non-equilibrium plasma reactors with dielectric barrier discharge (DBD), that when generated in noble gases allows for the effective treatment of biological material at a low temperature. The aim of this study is to determine the operating parameters of an atmospheric pressure, radio-frequency DBD plasma jet reactor for the precise treatment of biological materials. The tested parameters were the shape of the discharge (its length and volume), current and voltage signals, as well as the power consumed by the reactor for various composition and flow rates of the working gas. To determine the applicability in medicine, the temperature, pH, concentrations of H₂O₂, NO₂^- and NO₃^- and Escherichia coli log reduction in the plasma treated liquids were determined. The obtained results show that for certain operating parameters, a narrow shape of plasma stream can generate significant amounts of H₂O₂, allowing for the mild decontamination of bacteria at a relatively low power of the system, safe for the treatment of biological materials.

The impact of cold plasma on the phenolic composition and biogenic amine content of red wine

The effect of cold plasma (CP) on phenolic compound (PC) and biogenic amine (BA) contents of red wine was investigated for the first time. The influence of CP was compared with the effects of a wine preservation using potassium metabisulfite and a combined method. The PC profile was determined by UPLC-PDA-MS/MS while BAs using DLLME-GC-MS. Chemometric analysis also was used. The content of PCs was 3.1% higher in the sample preserved by CP treatment (5 min, helium/nitrogen) compared to a sample preserved by the addition of potassium metabisulfite (100 mg/L). On a positive note, CP treatment reduced the concentration of BAs in the wine samples. The lowest BA contents were recorded after 10 min of cold plasma (helium/oxygen) treatment with the addition of potassium metabisulfite (1120.85 μg/L). The results may promote interest in CP as a potential alternative method for the preservation of wine and other alcoholic beverages.

The Effect of Liquid Rubber Addition on the Physicochemical Properties, Cytotoxicity, and Ability to Inhibit Biofilm Formation of Dental Composites

The aim of this study was to evaluate the effect of modification with liquid rubber on the adhesion to tooth tissues (enamel, dentin), wettability and ability to inhibit bacterial biofilm formation of resin-based dental composites. Two commercial composites (Flow-Art–flow type with 60% ceramic filler and Boston–packable type with 78% ceramic filler; both from Arkona Laboratorium Farmakologii Stomatologicznej, Nasutów, Poland) were modified by addition of 5% by weight (of resin) of a liquid methacrylate-terminated polybutadiene. Results showed that modification of the flow type composite significantly (p < 0.05) increased the shear bond strength values by 17% for enamel and by 33% for dentine. Addition of liquid rubber significantly (p < 0.05) reduced also hydrophilicity of the dental materials since the water contact angle was increased from 81–83° to 87–89°. Interestingly, modified packable type material showed improved antibiofilm activity against Steptococcus mutans and Streptococcus sanguinis (quantitative assay with crystal violet), but also cytotoxicity against eukaryotic cells since cell viability was reduced to 37% as proven in a direct-contact WST-8 test. Introduction of the same modification to the flow type material significantly improved its antibiofilm properties (biofilm reduction by approximately 6% compared to the unmodified material, p < 0.05) without cytotoxic effects against human fibroblasts (cell viability near 100%). Thus, modified flow type composite may be considered as a candidate to be used as restorative material since it exhibits both nontoxicity and antibiofilm properties.

Possibility to extend the shelf life of NFC tomato juice using cold atmospheric pressure plasma

Cold Atmospheric pressure Plasma (CAP) is a non-thermal method used in food processing. CAP generated with the use of nitrogen in a Glide-arc device for 300 to 600 s exhibited high potential for microbial decontamination and did not induce substantial changes in the physicochemical properties of NFC tomato juice. Samples exposed to cold atmospheric plasma had mostly an intact structure, as revealed by digital microscopy. The investigations indicate that CAP can be applied for biological and chemical waste-free decontamination of food and extension of its shelf life.

Morphological and physiological changes in Lentilactobacillus hilgardii cells after cold plasma treatment

Atmospheric cold plasma (ACP) inactivation of Lentilactobacillus hilgardii was investigated. Bacteria were exposed to ACP dielectric barrier discharge with helium and oxygen as working gases for 5, 10, and 15 min. The innovative approach in our work for evaluation of bacterial survival was the use in addition to the classical plate culture method also flow cytometry which allowed the cells to be sorted and revealed different physiological states after the plasma treatment. Results showed total inhibition of bacterial growth after 10-min of ACP exposure. However, the analysis of flow cytometry demonstrated the presence of 14.4% of active cells 77.5% of cells in the mid-active state and 8.1% of dead cells after 10 min. In addition, some of the cells in the mid-active state showed the ability to grow again on culture medium, thus confirming the hypothesis of induction of VBNC state in L .hilgardii cells by cold plasma. In turn, atomic force microscopy (AFM) which was used to study morphological changes in L. hilgardii after plasma treatment at particular physiological states (active, mid-active, dead), showed that the surface roughness of the mid-active cell (2.70 ± 0.75 nm) was similar to that of the control sample (2.04 ± 0.55 nm). The lack of considerable changes on the cell surface additionally explains the effective cell resuscitation. To the best of our knowledge, AFM was used for the first time in this work to analyze cells which have been sorted into subpopulations after cold plasma treatment and this is the first work indicating the induction of VBNC state in L. hilgardii cells after exposure to cold plasma.

The State of Research on Antimicrobial Activity of Cold Plasma

Microbiological contamination is a big challenge to the food industry, medicine, agriculture, and environmental protection. For this reason, scientists are constantly looking for alternative methods of decontamination, which ensure the effective elimination of unwanted biological agents. Cold plasma is a new technology, which due to its unique physical and chemical properties becomes a point of interest to a growing group of researchers. The previously conducted experiments confirm its effective action, e.g. in the disinfection of skin wounds, air, and sewage treatment, as well as in food preservation and decontamination. The reactive compounds present in the plasma: high-energy electrons, ionized atoms and molecules, and UV photons are the key factors that cause an effective reduction in the number of microorganisms. The mechanism and effectiveness of the cold plasma are complex and depend on the process parameters, environmental factors and the type and properties of the microorganisms that are to be killed. This review describes the current state of knowledge regarding the effectiveness of the cold plasma and characterizes its interaction with various groups of microorganisms based on the available literature data.

Evaluation of selected microbial and physicochemical parameters of fresh tomato juice after cold atmospheric pressure plasma treatment during refrigerated storage

The Cold Atmospheric pressure Plasma (CAP) technology is an emerging technology used for conditioning and microbiological decontamination of biomaterials including food. A novel tool for inactivation of juice background spoilage microorganisms, as well as high count of inoculated yeast while maintaining physicochemical properties in tomato juice - CAP technology was utilized in this study. Dry matter content and pH were not significantly influenced by CAP generated in GlidArc reactor. Small increase of lycopene, and slight loss of vitamin C content were observed.