Safety Implications of Plasma-Induced Effects in Living Cells – a Review of in Vitro and in Vivo Findings

Cold atmospheric plasma is a versatile new tool in the biomedical field with applications ranging from disinfection, wound healing and tissue regeneration to blood coagulation, and cancer treatment. Along with improved insights into the underlying physical, chemical and biological principles, plasma medicine has also made important advances in the introduction into the clinic. However, in the absence of a standard plasma ‘dose’ definition, the diversity of the field poses certain difficulties in terms of comparability of plasma devices, treatment parameters and resulting biological effects, particularly with regards to the question of what constitutes a safe plasma application. Data from various in vitro cytotoxic and genotoxic studies along with in vivo findings from animal and human trials are reviewed to provide an overview of the current state of knowledge on the safety of plasma for biological applications. Treatment parameters employed in clinical studies were well-tolerated but intense treatment conditions can also induce tissue damage or genotoxicity. There is a need identified to establish both guidelines and safety limits that ensure an absence of (long-term) side effects and to define treatments as safe for applications, where cell stimulation is desired, e.g. in wound healing, or those aimed at inducing cell death in the treatment of cancer

Developing Sous Vide/Freezing Systems for Ready-Meal omponents

End of project reportSous vide cooking involves sealing raw or par-cooked food in a vacuumised laminated plastic pouch or container, cooking by controlled heating, rapid chilling and then re-heating for consumption. The chilled storage period is up to 21 days at 0 to 3oC. The recommended thermal process for sous vide products is 90oC for 10min or its time-temperature equivalent. Concerns about the safety of sous vide products, mainly due to the potential for temperature abuse in the chill chain, has prevented the widespread use of this technology. The role of the current project, therefore, was to investigate sous vide cooking followed by freezing, as a safe alternative to sous vide/chilling for 10 ready-meal components i.e. carbohydrates (potatoes, pasta, rice), vegetables (carrots, broccoli) and muscle foods (salmon, cod, chicken, beef and lamb).National Development Plan (NDP

Efficacy of Plasma Activated Saline in a Co‑Culture Infection Control Model

Plasma activated liquids have demonstrated antimicrobial effects and receive increasing attention due to the potential to strengthen the armoury of novel approaches against antibiotic resistant bacteria. However, the antibacterial activity and cytotoxic effects of these solutions need to be understood and balanced before exposure to humans. In this study, the antibacterial effects of plasma activated saline (PAS) were tested against Gram negative and positive bacteria, and HaCaT keratinocytes were used for cytotoxicity studies. For the first time, a co-culture model between these bacteria and eukaryotic cells under the influence of PAS has been described. Exposure of saline to plasma resulted in high concentrations of nitrate, hydrogen peroxide and a reduction of pH. PAS caused high antibacterial effects in the co-culture model, accompanied by high cytotoxic effects to the monolayer of mammalian cells. We present evidence and provide a deeper understanding for the hypothesis that upon treatment with PAS, chemical species generated in the liquid mediate high antimicrobial effects in the co-culture setup as well as mitochondrial depolarization and glutathione depletion in HaCaT cells and cell lysis due to acidic pH. In conclusion, PAS retains strong antibacterial effects in a co-culture model, which may have unintended negative biological effects on mammalian cells

Understanding The Differences Between Antimicrobial and Cytotoxic Properties of Plasma Activated Liquids

The aqueous environment plays an important role in the transmission of cold plasma effects to both prokaryotic and eukaryotic cells. The exposure of liquids to cold atmospheric plasma discharges results in the generation of secondary reactive species; specifically, hydrogen peroxide (H2O2) seems to be one of the most important amongst the reactive species contained in plasma activated liquids (PALs) in causing cytotoxicity. Detailed understanding of the effects of PALs on cells is essential to harness this new technology. Liquids acting as models for non-complex solutions were generated using a dielectric barrier discharge atmospheric cold plasma (DBD-ACP) system. The chemical characterization of the PAL included its pH and concentrations of hydrogen peroxide, nitrite, and nitrate. The antimicrobial effects of PALs on Gram-positive and Gram-negative bacteria were examined, and cytotoxicity assays were used to elucidate the cytotoxic properties of PALs. The research outcomes showed acidification of plasma activated nonbuffered solutions and differences in concentrations of hydrogen peroxide, nitrite, and nitrate. PALs with different compositions varied in their antibacterial activity and cytotoxic effects, indicating that different reactive species may be responsible for these inactivation processes. Our results suggest that antimicrobial and cytotoxic effects are distinct from each other, which may offer promising approaches for future targeted applications in medicine

Current and Future Technologies for Microbiological Decontamination of Cereal Grains

Cereal grains are the most important staple foods for mankind worldwide. The constantly increasing annual production and yield is matched by demand for cereals, which is expected to increase drastically along with the global population growth. A critical food safety and quality issue is to minimize the microbiological contamination of grains as it affects cereals both quantitatively and qualitatively. Microorganisms present in cereals can affect the safety, quality, and functional properties of grains. Some molds have the potential to produce harmful mycotoxins and pose a serious health risk for consumers. Therefore, it is essential to reduce cereal grain contamination to the minimum to ensure safety both for human and animal consumption. Current production of cereals relies heavily on pesticides input, however, numerous harmful effects on human health and on the environment highlight the need for more sustainable pest management and agricultural methods. This review evaluates microbiological risks, as well as currently used and potential technologies for microbiological decontamination of cereal grain

Antimicrobial Activity of Plant Essential Oils Using Food Model Media: Efficacy, Synergistic Potential and Interaction with Food Components

The aim of this study was to optimise the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria spp. and spoilage bacteria using food model media based on lettuce, meat and milk. The EOs evaluated were lemon balm, marjoram, oregano and thyme and their minimum inhibitory concentrations (MIC) were determined against Enterobacter spp., Listeria spp., Lactobacillus spp., and Pseudomonas spp. using the agar dilution method and/or the absorbance based microplate assay. MICs were significantly lower in lettuce and beef media than in TSB. Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs. EO combinations were investigated using the checkerboard method and Oregano combined with thyme had additive effects against spoilage organisms. Combining lemon balm with thyme yielded additive activity against Listeria strains. The effect of simple sugars and pH on antimicrobial efficacy of oregano and thyme was assessed in a beef extract and tomato serum model media. EOs retained greater efficacy at pH 5 and 2.32% sugar, but sugar concentrations above 5% did not negatively impact EO efficacy. In addition to proven antimicrobial efficacy, careful selection and investigation of EOs appropriate to the sensory profile of foods and composition of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars

Cold Plasma For Insect Pest Control: Tribolium Castaneum Mortality and Defense Mechanisms in Response to Treatment

The insecticidal properties and mechanisms of high-voltage air-based atmospheric cold plasma using a contained dielectric barrier discharge reactor were investigated against Tribolium castaneum as an important bio-contaminant in stored grains spoilage. The mortality of 95.0%–100% for preadult stages can be achieved within seconds of treatment, but longer plasma exposure (5 min) is required to kill adult insects. Cold plasma treatment reduces both the respiration rate and the weight of insects and affects the levels of oxidative stress markers in adult populations. Sufficient toxicity is achievable through plasma process control in air to address the range of insect lifecycle stages that are disease vectors and pose risks for grain stability in storage. Balancing insecticidal activity with grains\u27 quality retention can provide a route to sustainable integrated pest management

The Anti-Microbial Efficacy of Plant Essential Oil Combinations and Interactions with Food Ingredients

The objective of this study was to evaluate the efficacy of plant essential oils (EOs) in combination and to investigate the effect of food ingredients on their efficacy. The EOs assessed in combination included basil, lemon balm, marjoram, oregano, rosemary, sage and thyme. Combinations of EOs were initially screened against Bacillus cereus, Escherichia coli, Listeria monocytogenes and Pseudomonas aeruginosa using the spot-on-agar test. The influence of varying concentrations of EO combinations on efficacy was also monitored using E. coli. These preliminary studies showed promising results for oregano in combination with basil, thyme or marjoram. The checkerboard method was then used to quantify the efficacy of oregano, marjoram or thyme in combination with the remainder of selected EOs. Fractional inhibitory concentrations (FIC) were calculated and interpreted as synergy, addition, indifference or antagonism. All the oregano combinations showed additive efficacy against B. cereus, and oregano combined with marjoram, thyme or basil also had an additive effect against E. coli and P. aeruginosa. The mixtures of marjoram or thyme also displayed additive effects in combination with basil, rosemary or sage against L. monocytogenes. The effect of food ingredients and pH on the antimicrobial efficacy of oregano and thyme was assessed by monitoring the lag phase and the maximum specific growth rate of L. monocytogenes grown in model media. The model media included potato starch (0, 1, 5 or 10%), beef extract (1.5, 3, 6 or 12%), sunflower oil (0, 1, 5 or 10%) and TSB at pH levels of 4, 5, 6 or 7. The antimicrobial efficacy of EOs was found to be a function of ingredient manipulation. Starch and oils concentrations of 5% and 10% had a negative impact on the EO efficacy. On the contrary, the EOs were more effective at high concentrations of protein, and at pH 5, by comparison with pH 6 or 7. This study suggests that combinations of EOs could minimize application concentrations and consequently reduce any adverse sensory impact in food. However, their application for microbial control might be affected by food composition, therefore, careful selection of EOs appropriate to the sensory and compositional status of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to ready to use foods containing a high protein level at acidic pH, as well as lower levels of fats or carbohydrates

In Vitro Antimicrobial Activity and Mechanism of Action of Novel Carbohydrate Fatty Acid Derivatives Against Staphylococcus Aureus and MRSA

Aims: This study investigates the antimicrobial activity and mode of action of novel carbohydrate fatty acid (CFA) derivatives against Staphylococcus aureus and methicillin-resistant Staph. aureus (MRSA). Methods and Results: Minimum inhibitory concentrations (MIC) and the effect of CFA derivatives on lag phase were determined using a broth microdilution method. Lauric acid carbohydrate esters and corresponding ether analogs showed the greatest antimicrobial activity with MIC values between 0.04 to 0.16mmol l-1. Leakage studies at 260nm following exposure to CFA derivatives at 4X MIC showed a significant increase in membrane permeability for all compounds, after ca. 15 minutes exposure except for the lauric beta ether CFA derivative. Further assessment using both BacLight and luminescence ATP assays, confirmed that an increase in membrane permeability and reduced metabolic activity was associated with CFA treatment. Conclusions: All strains were significantly inhibited by the novel compounds studied and efficacy was related to specific structural features. Cell-membrane permeabilization was associated with CFA treatment and may account for at least a component of the mode of action of these compounds. Significance and Impact of Study: This study reports the antimicrobial action of CFA compounds against a range of Staph. aureus and MRSA strains, and provides insights into their mode of action

Controlled Cytotoxicity of Plasma Treated Water Formulated By Open-air Hybrid Mode Discharge

Plasma‐activated liquids (PAL) attract increasing interest with demonstrated biological effects. Plasma exposure in air produces stable aqueous reactive species which can serve as chemical diagnostics of PAL systems. Here, we tailor aqueous reactive species inside plasma‐activated water (PAW) through treating water with AC air spark and glow discharges in contact with water. Chemical probing demonstrated species specificity between two types of PAW. Spark discharge PAW contains urn:x-wiley:14381656:media:ppap201600207:ppap201600207-math-0006 and urn:x-wiley:14381656:media:ppap201600207:ppap201600207-math-0007, while urn:x-wiley:14381656:media:ppap201600207:ppap201600207-math-0008and urn:x-wiley:14381656:media:ppap201600207:ppap201600207-math-0009 are generated in glow discharge PAW. Species formation in different PAWs have been discussed in terms of discharge mechanisms and liquid phase chemistry process. Species specificity can provide richer parametric spaces for producing PALs with controlled impact and dosage achievable by combining discharge modes or mixing different PALs