The exposure of aqueous solutions to atmospheric plasmas results in the generation of relatively long-lived secondary products such as hydrogen peroxide which are biologically active and have demonstrated anti-microbial and cytotoxic activity. The use of plasma-activated solutions in applications such as microbial decontamination or anti-cancer treatments requires not only adequate performance on target cells but also a safe operating window regarding the impact on surrounding tissues. Furthermore the generation of plasma-activated fluids needs to be considered as a by-stander effect of subjecting tissue to plasma discharges. Cytotoxicity and mutagenicity assays using mammalian cell lines were used to elucidate the effects of solutions treated with di-electric barrier discharge atmospheric cold plasma. Plasma-treated PBS inhibited cell growth in a treatment time-dependent manner showing a linear correlation to the solutions' peroxide concentration which remained stable over several weeks. Plasma-treated foetal bovine serum (FBS) acting as a model for complex bio-fluids showed not only cytotoxic effects but also exhibited increased mutagenic potential as determined using the mammalian HPRT assay. Further studies are warranted to determine the nature, causes and effects of the cyto-and genotoxic potential of solutions exposed to plasma discharges to ensure long-term safety of novel plasma applications in medicine and healthcare.Non-thermal plasma, generated by the ionisation of gases, consists of free electrons, radicals, positive and negative charged particles has shown strong effects on living cells. Plasma can cause both cell death and stimulate cell proliferation and has found applications in microbial decontamination, wound healing and cancer treatment 1-4 . The inactivation of bacteria and fungi by cold plasma, and similar cytotoxic effects on eukaryotic cells have been suggested to result predominantly from oxidative damage to the cells' membrane and intra-cellular components including DNA through the action of reactive oxygen species (ROS) 5,6 . A number of recent publications have reported on the biological activity of plasma treated solutions such as plasma-activated water (PAW), plasma-activated PBS (PAPBS) or plasma-activated medium (PAM) which were found to possess anti-microbial and/or cytotoxic activity [7][8][9] . These solutions are of interest as novel anti-microbial agents for decontamination of surfaces, wounds and food products 7,8,10 and may offer similar antimicrobial effects as observed with direct exposure to the plasma discharge. The retention of efficacy in solution would provide the advantages of off-site production, storability and ease of application over direct treatment. Plasma-activated medium has furthermore shown selective cytotoxicity in several cancerous cell lines, including chemotherapy resistant types, making it a novel candidate treatment for anti-cancer therapies 9,11,12 . Atmospheric cold plasmas which may be generated by a range of different plasma devices such as plasma...

Atmospheric cold plasma (ACP) is a non-thermal technology, effective against a wide range of pathogenic microorganisms. Inactivation efficacy results from plasma generated reactive species. These may interact with any organic components in a test matrix including the target microorganism, thus food components may exert a protective effect against the antimicrobial mode of action. The effect of an in-package high voltage ACP process applied in conjunction with common meat processing MAP gas compositions as well as bacteria type and meat model media composition have been investigated to determine the applicability of this technology for decontamination of safety challenges associated with meat products. E. coli, L. monocytogenes, and S. aureus in PBS were undetectable after 60 s of treatment at 80 kVRMS in air, while ACP treatment of the contaminated meat model required post-treatment refrigeration to retain antimicrobial effect. The nutritive components in the meat model exerted a protective effect during treatment, where 300 s ACP exposure yielded a maximum reduction of 1.5 log using a high oxygen atmosphere, whilst using air and high nitrogen atmospheres yielded lower antimicrobial efficacy. Furthermore, an ROS assay was performed to understand the protective effects observed using the meat model. This revealed that nutritive components inhibited penetration of ROS into bacterial cells. This knowledge can assist the optimization of meat decontamination using ACP technology where interactions with all components of the food matrix require evaluation.

Cold atmospheric plasma (CAP) is produced by ionizing a chosen gas, thereby creating charged and reactive species. The reactive species generated are capable of inducing a range of biomedically relevant interactions including blood coagulation. However, the underlying biochemical processes of plasma-assisted blood coagulation are largely unknown, and data quantifying blood clot formation or the impact of system parameters on the intensity of the blood clot are scarce. In this study, blood coagulation was quantified by measuring hemoglobin absorbance. System parameters of the kINPen plasma jet were investigated and compared, including treatment time, distance from the plasma source and gas flow rate. These investigations were combined with optical emission spectroscopy to associate the species generated in the plasma effluent with the effect on coagulation efficiency. In this study, we have proposed a method to quantitatively assess plasma-induced blood coagulation to directly compare the clotting capabilities of other plasma systems and to explicate the mechanism of plasma-assisted blood coagulation.

Cold atmospheric plasma is a promising new non-thermal technology for improving microbiological safety and shelf-life of food products, particularly fresh produce and minimally processed fruit and vegetables. Limited research has been conducted on the safety of plasmatreated foods for human or animal consumption. This study focusses on basic safety studies by investigating lettuce broth treated with a di-electric barrier discharge plasma device as a fresh produce model in terms of in vitro cytotoxic and mutagenic effects on mammalian cells and its in vivo toxicity on Galleria mellonella larvae. Low cytotoxic effects were detected in vitro and mutagenic events were likely to be spontaneous mutations. However, a strong response of Galleria larvae to injection with plasma-treated lettuce broth was observed for 5-min treated broth, with less than 10% larvae survival. No significant effects on quality attributes such as colour were detected and only low concentrations of peroxide were generated in the broth. This study highlights the need for more detailed investigations on the impact of plasma treatment on food components and the subsequent in vitro and in vivo effects to ensure a safe implementation of plasma technology for processing of food products.

The potential applications for cold plasma in medicine are extensive, from microbial inactivation and induction of apoptosis in cancer cells to stimulating wound healing and enhancing the blood coagulation cascade. The safe bio-medical application of cold plasma and subsequent effect on complex biological pathways requires precision and a distinct understanding of how physiological redox chemistry is manipulated. Chemical modification of biomolecules such as carbohydrates, proteins, and lipids treated with cold plasma have been characterized, however, the context of how alterations of these molecules affect cell behavior or in vivo functionality has not been determined. Thus, this study examines the cytotoxic and mutagenic effects of plasma-treated molecules in vitro using CHO-K1 cells and in vivo in Galleria mellonella larvae. Specifically, albumin, glucose, cholesterol, and arachidonic acid were chosen as representative biomolecules, with established involvement in diverse bioprocesses including; cellular respiration, intracellular transport, cell signaling or membrane structure. Long- and short-term effects depended strongly on the molecule type and the treatment milieu indicating the impact of chemical and physical modifications on downstream biological pathways. Importantly, absence of short-term toxicity did not always correlate with absence of longer-term effects, indicating the need to comprehensively assess ongoing effects for diverse biological applications.