Microbiological interactions with cold plasma

Toxicity and virucidal activity of a neon-driven micro plasma jet on eukaryotic cells and a coronavirus

Plasma medicine is a developing field that utilizes the effects of cold physical plasma on biological substrates for therapeutic purposes. Approved plasma technology is frequently used in clinics to treat chronic wounds and skin infections. One mode of action responsible for beneficial effects in patients is the potent antimicrobial activity of cold plasma systems, which is linked to their unique generation of a plethora of reactive oxygen and nitrogen species (ROS). During the SARS-CoV-2 pandemic, it became increasingly clear that societies need novel ways of passive and active protection from viral airway infections. Plasma technology may be suitable for superficial virus inactivation. Employing an optimized neon-driven micro plasma jet, treatment time-dependent ROS production and cytotoxic effects to different degrees were found in four different human cell lines with respect to their metabolic activity and viability. Using the murine hepatitis virus (MHV), a taxonomic relative of human coronaviruses, plasma exposure drastically reduced the number of infected murine fibroblasts by up to 3000-fold. Direct plasma contact (conductive) with the target maximized ROS production, cytotoxicity, and antiviral activity compared to non-conductive treatment with the remote gas phase only. Strikingly, antioxidant pretreatment reduced but not abrogated conductive plasma exposure effects, pointing to potential non-ROS-related mechanisms of antiviral activity. In summary, an optimized micro plasma jet showed antiviral activity and cytotoxicity in human cells, which was in part ROS-dependent. Further studies using more complex tissue models are needed to identify a safe dose-effect window of antiviral activity at modest toxicity.

Inactivation efficacy and mechanisms of atmospheric cold plasma on Alicyclobacillus acidoterrestris: Insight into the influence of growth temperature on survival

The bactericidal effect of dielectric barrier discharge-atmospheric cold plasma (DBD-ACP, 20, and 30 kV) against Alicyclobacillus acidoterrestris on the saline solution and apple juice was investigated. Results show that DBD-ACP is effective for the inactivation of A. acidoterrestris by causing significant changes in cell membrane permeability and bacterial morphology. The effect of culture temperatures on the resistance of A. acidoterrestris to DBD-ACP was also studied. A. acidoterrestris cells grown at 25°C had the lowest resistance but it was gradually increased as the culture temperature was increased (25–45°C) (p < 0.05). Moreover, results from Fourier transform infrared spectroscopy (FT-IR) and Gas Chromatography-Mass Spectrometer (GC-MS) analysis showed that the increase in the culture temperature can gradually cause the decreased level of cyclohexaneundecanoic acid in the cell membrane of A. acidoterrestris (p < 0.05). In contrast, cyclopentaneundecanoic acid, palmitic acid, and stearic acid showed an increasing trend in which the fluidity of the bacterial cell membrane decreased. This study shows a specific correlation between the resistance of A. acidoterrestris and the fatty acid composition of the cell membrane to DBD-ACP.

Control of aflatoxin M1 in skim milk by high voltage atmospheric cold plasma

Cold plasma has potential for the degradation of aflatoxins in corn and hazelnuts; however, this has not been demonstrated for aflatoxin in milk. In this study, the efficacy of high voltage atmospheric cold plasma (HVACP) on the reduction of aflatoxin M1 (AFM1) in skim milk improved with increasing treatment times (1-20 min), using gas containing 65% oxygen (MA65) rather than air, increasing voltage (60-80 kV) and reducing sample volume (30 mL-10 mL). Direct treatment was more effective than indirect treatment. AFM1 in milk was degraded by 65.0 % and 78.9 % by air and MA65 respectively in 20 min with no change in milk colour. The toxicity of AFM1 after treatment was assessed using a brine shrimp model. A five-minute HVACP treatment reduced the toxicity of AFM1 by 83.9 % based on the increase in brine shrimp survival. HVACP is a promising method to reduce AFM1 in milk.

Effect of atmospheric cold plasma (ACP) on chlorine adapted Salmonella enterica on spring onion

One of the main drawbacks of chlorine disinfectants is the emergence of chlorine adapted (CA) or resistant microbial cells. This research aimed to investigate the effect of chlorine adaptation on resistance of Salmonella enterica upon atmospheric cold plasma (ACP) application at different voltages (6, 8, and 11 kV) and times (5, 10, and 15 min). Due to higher conversion efficiency and reduced dielectric barrier discharge (DBD) power consumption, this method was used for cold plasma generation in this study. A higher lethality effect was observed from a higher voltage and longest times (11 kV-15 min) on CA S. enterica than non-CA (p<0.05). Still, it induced higher percentages of injured cells in CA (58.77%) than non-CA (0.61%) (p<0.05). The highest ACP effect on the inactivation of the indigenous natural flora of onion leaves was observed at the lowest voltage (p<0.05). More than 3 log CFU/g reduction (p<0.05) was observed at 6 kV after 5 and 10 min. ACP reduced CA and non-CA S. enterica cells on onion leaf surface to a lower extent than pure treated cells in broth media. Nevertheless similar to broth media, a high percentage of injury (61.03%) was induced on CA cells at higher voltage (11 kV-10 min) compared to non-CA (2.15%) (p<0.05). Biofilm results revealed ACP application (6 kV-5 min) reduced average ODs in CA and non-CA cells (p<0.05). Chlorine adaptation and ACP treatment influenced the antibiotic resistance pattern according to applied voltage, time, and antibiotic type. The finding showed despite highest lethality of high voltages and long times (11 kV-15 min), given the high percentages of injured cells, lower voltages may offer acceptable inactivation of pathogenic bacteria with lower injury induction. In conclusion, ACP has the potential ability to eliminate CA cells of S. enterica, which is predominant in fresh-cut vegetable outbreaks.

Synergistic Action of Reactive Plasma Particles and UV Radiation to Inactivate Staphylococcus Aureus

The direct application of low-pressure plasma for the decontamination of microorganisms was examined herein. The inactivation efficiency was studied on a Gram-positive bacterium (Staphylococcus aureus) using a plasma process by means of synergistic action of reactive plasma particles and UV radiation. N2 was added to an argon/oxygen plasma mixture in order to improve the effectiveness of S. aureus inactivation. It was found that the decontamination mechanism is based on both the chemical sputtering effect due to the plasma particles and the UV emission originating from the NOγ system from NO radicals in the wavelength range 200–300 nm. The best plasma bactericidal activity was found for an N2 percentage of roughly 10–12%. A count reduction of more than 5 log cycles in a few minutes of S. aureus proves the potentiality of an industrial-grade plasma reactor as a decontamination agent.

The potential of gas plasma technology for targeting breast cancer

Despite therapeutic improvements in recent years, breast cancer remains an often fatal disease. In addition, breast cancer ulceration may occur during late stages, further complicating therapeutic or palliative interventions. In the past decade, a novel technology received significant attention in the medical field: gas plasma. This topical treatment relies on the partial ionization of gases that simultaneously produce a plethora of reactive oxygen and nitrogen species (ROS/RNS). Such local ROS/RNS overload inactivates tumour cells in a non-necrotic manner and was recently identified to induce immunogenic cancer cell death (ICD). ICD promotes dendritic cell maturation and amplifies antitumour immunity capable of targeting breast cancer metastases. Gas plasma technology was also shown to provide additive toxicity in combination with radio and chemotherapy and re-sensitized drug-resistant breast cancer cells. This work outlines the assets of gas plasma technology as a novel tool for targeting breast cancer by summarizing the action of plasma devices, the roles of ROS, signalling pathways, modes of cell death, combination therapies and immunological consequences of gas plasma exposure in breast cancer cells in vitro, in vivo, and in patient-derived microtissues ex vivo.

Disinfection of corona and myriad viruses in water by non-thermal plasma: a review

Nowadays, in parallel to the appearance of the COVID-19 virus, the risk of viruses in water increases leading to the necessity of developing novel disinfection methods. This review focuses on the route of virus contamination in water and introduces non-thermal plasma technology as a promising method for the inactivation of viruses. Effects of essential parameters affecting the non-thermal discharge for viral inactivation have been exposed. The review has also illustrated a critical discussion of this technology with other advanced oxidation processes. Additionally, the inactivation mechanisms have also been detailed based on reactive oxygen and nitrogen species.

A Cold Plasma Technology for Ensuring the Microbiological Safety and Quality of Foods

Changing consumers’ taste for chemical and thermally processed food and preference for perceived healthier minimally processed alternatives is a challenge to food industry. At present, several technologies have found usefulness as choice methods for ensuring that processed food remains unaltered while guaranteeing maximum safety and protection of consumers. However, the effectiveness of most green technology is limited due to the formation of resistant spores by certain foodborne microorganisms and the production of toxins. Cold plasma, a recent technology, has shown commendable superiority at both spore inactivation and enzymes and toxin deactivation. However, the exact mechanism behind the efficiency of cold plasma has remained unclear. In order to further optimize and apply cold plasma treatment in food processing, it is crucial to understand these mechanisms and possible factors that might limit or enhance their effectiveness and outcomes. As a novel non-thermal technology, cold plasma has emerged as a means to ensure the microbiological safety of food. Furthermore, this review presents the different design configurations for cold plasma applications, analysis the mechanisms of microbial spore and biofilm inactivation, and examines the impact of cold plasma on food compositional, organoleptic, and nutritional quality.

Effect of low-pressure cold plasma processing on decontamination and quality attributes of Saffron (Crocus sativus L.)

This study investigated the microbial decontamination of saffron using the low-pressure cold plasma (LPCP) technology. Therefore, other quality characteristics of saffron that create the color, taste, and aroma have also been studied. The highest microbial log reduction was observed at 110 W for 30 min. Total viable count (TVC), coliforms, molds, and yeasts log reduction were equal to 3.52, 4.62, 2.38, and 4.12 log CFU (colony-forming units)/g, respectively. The lowest decimal reduction times (D-values) were observed at 110 W, which were 9.01, 3.29, 4.17, and 8.93 min for TVC, coliforms, molds, and yeasts. LPCP treatment caused a significant increase in the product's color parameters (L*, a*, b*, ΔE, chroma, and hue angle). The results indicated that the LPCP darkened the treated stigma's color. Also, it reduced picrocrocin, safranal, and crocin in treated samples compared to the untreated control sample (p < .05). However, after examining these metabolites and comparing them with saffron-related ISO standards, all treated and control samples were good.

Disinfection of an ambulance using a compact atmospheric plasma device

AIMS

The worldwide spread of the coronavirus SARS-CoV-2 has highlighted the need for fast and simple disinfection processes, amongst others for ambulance cars on site. To overcome current drawbacks regarding room disinfection, the use of cold atmospheric plasma in remote operation represents a promising alternative for the disinfection of larger volumes. In this study, a compact plasma system was evaluated regarding its disinfection efficiency inside an ambulance car.

METHODS AND RESULTS

The developed plasma device is based on a dielectric barrier discharge (DBD) and operates with ambient air as process gas. The humidified afterglow from the plasma nozzle was introduced into an ambulance car with a volume of approximately 10 m³ while B. atrophaeus endospores, S. aureus or Phi 6 bacteriophages dried on different surfaces (PET-films, glass slides or aluminum foil) were exposed to the reactive gas inside the ambulance vehicle at eight different positions. Reductions of spores by more than 4 orders of magnitude were found on all surfaces and positions within 2 hours. Due to their higher susceptibility, Phi 6 bacteriophages and S. aureus counts were reduced by at least 4 orders of magnitude within 30 min on all surfaces.

CONCLUSION

The results show that different microorganisms dried on variable surfaces can be inactivated by several orders of magnitude inside an ambulance by plasma gas from of a compact DBD plasma nozzle.

SIGNIFICANCE AND IMPACT OF STUDY

Plasma gas generated on site by a DBD plasma nozzle proved to be highly efficient for the disinfection of the interior of an ambulance car. Compact plasma systems could be a viable alternative for the disinfection of vehicles or rooms.

Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine

The use of thermal and non-thermal atmospheric pressure plasma to solve problems related to agriculture and biomedicine is the focus of this paper. Plasma in thermal equilibrium is used where heat is required. In agriculture, it is used to treat soil and land contaminated by the products of biomass, plastics, post-hospital and pharmaceutical waste combustion, and also by ecological phenomena that have recently been observed, such as droughts, floods and storms, leading to environmental pollution. In biomedical applications, thermal plasma is used in so-called indirect living tissue treatment. The sources of thermal plasma are arcs, plasma torches and microwave plasma reactors. In turn, atmospheric pressure cold (non-thermal) plasma is applied in agriculture and biomedicine where heat adversely affects technological processes. The thermodynamic imbalance of cold plasma makes it suitable for organic syntheses due its low power requirements and the possibility of conducting chemical reactions in gas at relatively low and close to ambient temperatures. It is also suitable in the treatment of living tissues and sterilisation of medical instruments made of materials that are non-resistant to high temperatures. Non-thermal and non-equilibrium discharges at atmospheric pressure that include dielectric barrier discharges (DBDs) and atmospheric pressure plasma jets (APPJs), as well as gliding arc (GAD), can be the source of cold plasma. This paper presents an overview of agriculture and soil protection problems and biomedical and health protection problems that can be solved with the aid of plasma produced with electrical discharges. In particular, agricultural processes related to water, sewage purification with ozone and with advanced oxidation processes, as well as those related to contaminated soil treatment and pest control, are presented. Among the biomedical applications of cold plasma, its antibacterial activity, wound healing, cancer treatment and dental problems are briefly discussed.

Diagnostics of Air Purification Plasma Device by Spatially Resolved Emission Spectroscopy

A non-thermal plasma, air purification device (PlasmaShield®, MD250, Keswick, SA, Australia), was investigated using spatially resolved optical emission spectroscopy. The emission spectra were measured with two spatial dimensions to analyze and identify the transition lines of excited NO–γ (A2Σ–X2Π), N2 (C3Π–B3Π), and N2+ (B2Σ–X2Σ) systems. The N2 emission band at 337 and 316 nm were used to determine the spatially resolved vibrational temperature of N2 molecules, TvibN2. It was found that the average N2 vibrational temperatures in the x and y directions are almost the same. Two key operating parameters, supplied power and air flow, influence the N2 vibrational temperature. The results demonstrate that applying higher supplied power increases the vibrational temperature, while changes in air flow velocity do not affect the vibrational temperature values. The phenomenological plasma temperature (PPT) was also estimated from the N2 vibrational temperature. It was observed that PlasmaShield® generates excited N2 and NO only within a narrow region around the discharge electrode tip (with peak intensity below 100 µm from the tip). The study also shows no presence of excited OH*, O*, and other radicals.

Cold plasma technology: An insight on its disinfection efficiency of various food systems

Cold plasma technology is considered as one of the novel potential non-thermal techniques for food disinfection. The acceptability of any food product depends upon its physicochemical properties and shelf life. Recent studies have confirmed that plasma can effectively reduce the pathogenic microbes in various food systems. Further, there are reports that cold plasma showed minimal or no effect on the physicochemical and sensory properties of the foods owing to its low-temperature operation. The present review explores the recent reports on cold plasma technology emphasizing its disinfection efficacy on different food categories. Various researchers have demonstrated that plasma successfully reduced the microorganisms on cereals, milk, meat, fish and spices. Therefore, based on the current research, it can be suggested that cold plasma is an effective disinfectant technology for the inactivation of pathogenic microorganisms, and its non-thermal and environmentally friendly nature is an added advantage over traditional processing technologies.

Biochemical and Physiological Plant Processes Affected by Seed Treatment with Non-Thermal Plasma

Among the innovative technologies being elaborated for sustainable agriculture, one of the most rapidly developing fields relies on the positive effects of non-thermal plasma (NTP) treatment on the agronomic performance of plants. A large number of recent publications have indicated that NTP effects are far more persistent and complex than it was supposed before. Knowledge of the molecular basis and the resulting outcomes of seed treatment with NTP is rapidly accumulating and requires to be analyzed and presented in a systematic way. This review focuses on the biochemical and physiological processes in seeds and plants affected by seed treatment with NTP and the resulting impact on plant metabolism, growth, adaptability and productivity. Wide-scale changes evolving at the epigenomic, transcriptomic, proteomic and metabolic levels are triggered by seed irradiation with NTP and contribute to changes in germination, early seedling growth, phytohormone amounts, metabolic and defense enzyme activity, secondary metabolism, photosynthesis, adaptability to biotic and abiotic stress, microbiome composition, and increased plant fitness, productivity and growth on a longer time scale. This review highlights the importance of these novel findings, as well as unresolved issues that remain to be investigated.

Chronic wounds treated with cold atmospheric plasmajet versus best practice wound dressings: a multicenter, randomized, non-inferiority trial

The use of phase-adapted wound dressings represents best practice (BP) in chronic wound treatment. However, efficacy is often limited and associated care requirements are high. Cold atmospheric plasmajet (CAP-jet) is a promising new therapeutic tool for these wounds. In the present multicenter, randomized, open-label, prospective, clinical trial, non-inferiority of the CAP-jet versus BP was assessed in 78 patients with infected or non-infected chronic wounds of different etiology. Primary outcome measure was the sum of granulation tissue, furthermore wound area reduction, healing rate, time to complete healing, changes in wound pH value, infection score, exudate level and local tolerability were assessed. In CAP-jet treated wounds compared to control, the sum of granulation tissue was significantly higher (p < 0.0001) and wound area reduced significantly faster (p < 0.001). Furthermore, wound pH value decreased significantly faster (p = 0.0123) and local infection was overcome more rapidly by CAP-jet therapy. In 58.97% CAP-jet- vs. 5.13% BP-treated patients, complete healing of chronic ulcers was documented after 6 weeks. Treatment with CAP-jet appeared not only non-inferior, but even superior to BP in all wound entities analyzed with a favorable tolerability profile. Thus, treatment with the CAP-jet provides beneficial effects in chronic wound treatment regarding promotion of the wound healing process.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

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.

Recent developments in cold plasma-based enzyme activity (browning, cell wall degradation, and antioxidant) in fruits and vegetables

According to the Food and Agriculture Organization of United Nations reports, approximately half of the total harvested fruits and vegetables vanish before they reach the end consumer due to their perishable nature. Enzymatic browning is one of the most common problems faced by fruit and vegetable processing. The perishability of fruits and vegetables is contributed by the various browning enzymes (polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase) and ripening or cell wall degrading enzyme (pectin methyl-esterase). In contrast, antioxidant enzymes (superoxide dismutase and catalase) assist in reversing the damage caused by reactive oxygen species or free radicals. The cold plasma technique has emerged as a novel, economic, and environmentally friendly approach that reduces the expression of ripening and browning enzymes while increasing the activity of antioxidant enzymes; microorganisms are significantly inhibited, therefore improving the shelf life of fruits and vegetables. This review narrates the mechanism and principle involved in the use of cold plasma technique as a nonthermal agent and its application in impeding the activity of browning and ripening enzymes and increasing the expression of antioxidant enzymes for improving the shelf life and quality of fresh fruits and vegetables and preventing spoilage and pathogenic germs from growing. An overview of hurdles and sustainability advantages of cold plasma technology is presented.

Corona Discharge Power of Plasma Treatment Influence on the Physicochemical and Microbial Quality of Enoki Mushroom (Flammulina velutipes)

Plasma treatment was widely known as an effective technology applied for contact-surface decontamination. Enoki (Flammulina velutipes) was an edible-medicinal mushroom with different phytochemicals and bioactive components beneficial for human health. Enoki mushroom had high respiration rate therefore it was highly perishable after harvesting. Moreover, it was greatly susceptible to microbial contamination but it was not feasible to be decontaminated by normal water washing. It’s urgent to extend shelf-life and control microbial criteria on this mushroom in dry manner without aqueous treatment. Corona discharge plasma was among 4 kinds of diverse cold atmospheric pressure plasma sources widely applied in food industry. This study demonstrated the influence of corona discharge plasma power values (control, 120, 150, 180, 210 W) on the physicochemical and microbial characteristics of Enoki mushroom during 10 days of storage at ambient temperature. Results showed that Enoki mushroom should be treated at 150 W of corona discharge plasma power to retain weight loss, total soluble solid, vitamin C in acceptable values while reducing total Aerobic count, Coliform, Enterobacteriaceae as much as possible. At the 10th day of storage, the weight loss, total soluble solid, vitamin C, total Aerobic count, Coliform, Enterobacteriaceae were recorded at 3.35±0.07%, 6.98±0.03 oBrix, 14.81±0.04 mg/100 g, 4.71±0.05 log CFU/g, 3.17±0.02 log CFU/g, 2.13±0.01 CFU/g, respectively. Findings of this research proved that corona discharge plasma pretreatment would be appropriate to maintain physicochemical properties and retard microbial loads on Enoki mushroom during preservation.

The Antimicrobial Efficacy Of Plasma Activated Water Against Listeria and E. coli Is Modulated By Reactor Design And Water Composition

AIMS

This study aimed to compare the efficacy of plasma activated water (PAW) generated by two novel plasma reactors against pathogenic foodborne illness organisms.

METHODS AND RESULTS

The antimicrobial efficacy of PAW produced by a bubble spark discharge (BSD) reactor and a dielectric barrier discharge-diffuser (DBDD) reactor operating at atmospheric conditions with air, multiple discharge frequencies and Milli-Q and tap water, was investigated with model organisms Listeria innocua and Escherichia coli in situ. Optimal conditions were subsequently employed for pathogenic bacteria Listeria monocytogenes, E. coli and Salmonella enterica. DBDD-PAW reduced more than 6-log of bacteria within 1 minute. The BSD-PAW, while attaining high log reduction, was less effective. Analysis of physicochemical properties revealed that BSD-PAW had a greater variety of reactive species than DBDD-PAW. Scavenger assays designed to specifically sequester reactive species demonstrated a critical role of superoxide, particularly in DBDD-PAW.

CONCLUSIONS

DBDD-PAW demonstrated rapid antimicrobial activity against pathogenic bacteria, with superoxide the critical reactive species.

SIGNIFICANCE AND IMPACT OF STUDY

This study demonstrates the potential of DBDD-PAW produced using tap water and air as a feasible and cost-effective option for antimicrobial applications, including food safety.

Cold Physical Plasma in Cancer Therapy: Mechanisms, Signaling, and Immunity

Despite recent advances in therapy, cancer still is a devastating and life-threatening disease, motivating novel research lines in oncology. Cold physical plasma, a partially ionized gas, is a new modality in cancer research. Physical plasma produces various physicochemical factors, primarily reactive oxygen and nitrogen species (ROS/RNS), causing cancer cell death when supplied at supraphysiological concentrations. This review outlines the biomedical consequences of plasma treatment in experimental cancer therapy, including cell death modalities. It also summarizes current knowledge on intracellular signaling pathways triggered by plasma treatment to induce cancer cell death. Besides the inactivation of tumor cells, an equally important aspect is the inflammatory context in which cell death occurs to suppress or promote the responses of immune cells. This is mainly governed by the release of damage-associated molecular patterns (DAMPs) to provoke immunogenic cancer cell death (ICD) that, in turn, activates cells of the innate immune system to promote adaptive antitumor immunity. The pivotal role of the immune system in cancer treatment, in general, is highlighted by many clinical trials and success stories on using checkpoint immunotherapy. Hence, the potential of plasma treatment to induce ICD in tumor cells to promote immunity targeting cancer lesions systemically is also discussed.

Do we need cold plasma treated fruit and vegetable juices? A case study of positive and negative changes occurred in these daily beverages

Cold atmospheric pressure plasma (CAPP) is a prospective technology for various branches of industry. As such, much attention has been recently paid towards the use of CAPPs for treating fruit and vegetable beverages as they do not need any more to be thermally pasteurized or sanitized. However, this application of CAPPs is not only limited to the improvement of their shelf-life. It could also contribute to the enhancement of their nutritional properties and anticancer activity. This could be achieved due to the presence of numerous reactive oxygen and nitrogen species (RONS), produced at the plasma-liquid interface, that might contribute to the increase of the content of nutritional and bioactive compounds, simply upgrading the juices. In this context, the present review focuses on the recent advances in the CAPP-based technology towards the processing of fruit and vegetable juices. As such, a series of different CAPP-based reaction-discharge systems and their configurations are reviewed and set together with the physicochemical, nutritional, and antimicrobial characteristics of the CAPP-treated juices, providing an useful insight into the perspective development of emerging CAPP technology.

Inactivation of Enveloped Bovine Viral Diarrhea Virus and Non-Enveloped Porcine Parvovirus Using Low-Pressure Non-Thermal Plasma

As the worldwide population has been experiencing since 2020, viruses represent a serious threat to global well-being. To avoid viral transmission through surgery or medical examination, sterilization of medical material is needed. From emerging sterilization processes, the use of non-thermal plasma (NTP) arises as a promising technique to efficiently reduce microbial burden on medical devices, including new complex polymers as thermosensitive ones. Thus, we evaluated the antiviral efficacy of a low-pressure NTP process taking place in a sealed bag. For this purpose, two different plasmas, O₂ 100% plasma and Ar 80%-O₂ 20% plasma, were tested against two viruses: the bovine viral diarrhea virus and the porcine parvovirus, surrogates of human hepatitis C virus and human parvovirus B19, respectively. The efficacy of both NTP treatments on viral load can be detected after only five minutes. Moreover, the longer the NTP treatments last, the more the load decreases. The most effective load reduction was obtained with a 120-min O₂ plasma treatment inducing a minimum of four-log viral load reduction. So, this process demonstrated strong virucidal capacity inside a sealed bag and represents a very interesting opportunity in the field of fragile medical devices sterilization or disinfection.

Phytochemical Fortification in Fruit and Vegetable Beverages with Green Technologies

BACKGROUND

Phytochemical, bioactive and nutraceutical compounds are terms usually found in the scientific literature related to natural compounds found in plants linked to health-promoting properties. Fruit and vegetable beverages (mainly juice and smoothies) are a convenient strategy to enhance the consumption of horticultural commodities, with the possibility of being fortified with plant byproducts to enhance the content of bioactive compounds.

OBJECTIVE

This review aims to analyse the different green technologies applied in beverage processing with a fortification effect on their health promoting compounds.

RESULTS

Fortification can be performed by several strategies, including physical elicitors (e.g., processing technologies), plant/algae extract supplementation, and fermentation with probiotics, among others. Thermal processing technologies are conventionally used to ensure the preservation of food safety with a long shelf life, but this frequently reduces nutritional and sensory quality. However, green non-thermal technologies (e.g., UV, high-pressure processing, pulsed electric fields, ultrasounds, cold plasma, etc.) are being widely investigated in order to reduce costs and make possible more sustainable production processes without affecting the nutritional and sensory quality of beverages.

CONCLUSIONS

Such green processing technologies may enhance the content of phytochemical compounds through improvement of their extraction/bioaccessibility and/or different biosynthetic reactions that occurred during processing.

Effect of Cold Atmospheric Plasma Jet Associated to Polyene Antifungals on Candida albicans Biofilms

The 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.

Strategies to increase the shelf life of meat and meat products with phenolic compounds

Oxidative reactions and microbial growth are the main processes involved in the loss of quality in meat products. Although the use of additives to improve the shelf life is a common practice in the meat industry, the current trends among consumers are pushing the researchers and professionals of the meat industry to reformulate meat products. Polyphenols are compounds with antioxidant and antimicrobial activity naturally found in several plants, fruits, and vegetables that can be used in the production of extracts and components in active packaging to improve the shelf life of meat products. This chapter aims to discuss the advances in terms of (1) encapsulation techniques to protect phenolic compounds; (2) production of active and edible packages rich on phenolic compounds; (3) use of phenolic-rich additives (free or encapsulated form) with non-thermal technologies to improve the shelf life of meat products; and (4) use of active packaging rich on phenolic compounds on meat products. Innovative strategies to encapsulated polyphenols and produce films are mainly centered in the use of innovative and emerging technologies (such as ultrasound and supercritical fluids). Moreover, the combined use of polyphenols and non-thermal technologies is a relevant approach to improve the shelf life of meat products, especially using high pressure processing. In terms of application of innovative films, nanomaterials have been largely explored and indicated as relevant strategy to preserve meat and meat products.

Inactivation of Acanthamoeba Cysts in Suspension and on Contaminated Contact Lenses Using Non-Thermal Plasma

Water suspensions of cysts of a pathogenic clinical isolate of Acanthamoeba sp. were prepared, and the cysts were inactivated either in suspension or placed on the surface of contact lenses by the non-thermal plasma produced by the DC corona transient spark discharge. The efficacy of this treatment was determined by cultivation and the presence of vegetative trophozoites indicating non-inactivated cysts. The negative discharge appeared to be more effective than the positive one. The complete inactivation occurred in water suspension after 40 min and on contaminated lenses after 50 min of plasma exposure. The properties of lenses seem to not be affected by plasma exposure; that is, their optical power, diameter, curvature, water content and infrared and Raman spectra remain unchanged.

Salmonella inactivation and rapid cooling of fresh cut apples by plasma integrated low-pressure cooling

Fresh food products, including fruits, vegetables, raw meat, and poultry, have been associated with safety concerns and quality issues, owing to their susceptibility to rapid deterioration and microbial contamination. This research aimed to develop an integrated process to simultaneously cool and decontaminate high moisture food products. Cold plasma (CP), a novel decontamination technology, was integrated with vacuum cooling to develop a plasma integrated low-pressure cooling (PiLPC) process. To evaluate the rapid cooling and microbial inactivation efficacies of the PiLPC process, fresh cut Granny Smith apples andSalmonella entericaserovarTyphimurium ATCC 13311 were used as the model food and microorganism, respectively. The influence of process parameters including treatment time, pressure, and post-treatment storage, on the inactivation ofSalmonellaon fresh-cut apples was investigated.Inactivation ofSalmonellaincreased with treatment time, with a maximum reduction of 3.21 log CFU/g after 5 min of CP treatment at atmospheric pressure. Inactivationof Salmonellaafter CP treatment at 200 mbar was not significantly different from that at atmospheric pressure for the same treatment time. CP treatment of 3 min at 200 mbar followed by a post-treatment storage of 3 days at 4 °C reduced the totalSalmonellapopulation on cut apple slices by > 6 log CFU/g. The temperature of the cut apples was reduced from room temperature to 2 °Cin 3 to 9 min depending on the sample surface area to volume ratio, when the pressure was reducedto 7 mbar. However, this PiLPC process resulted in moisture loss in cut apples. The results of this study indicate the potential of the PiLPC process for rapid cooling and microbial inactivation of fresh food products in a single process.

An innovative strategy to rapidly inactivate 8.2-log Enterococcus faecalis in fresh pineapple juice using cold atmospheric plasma

Enterococcus faecalis is a life-threatening bacterium that resists high levels of antibiotics or chemical preservatives. In this study, we aimed to investigate the inactivation of E. faecalis in fresh pineapple juice (FPJ) with two different cold atmospheric plasmas (CAP) reinforced by H₂O₂/H₂O cold vapor: a plasma jet and a surface dielectric barrier discharge (SDBD). CAP treatments for 300 s with plasma jet and 420 s with SDBD caused an 8.2 log reduction of E. faecalis. The concentration of reactive oxygen and nitrogen species induced in FPJ by plasmas was also evaluated. In terms of quality attributes of FPJ, no noticeable color changes (ΔE) were observed. Furthermore, a trifle of loss of organic content such as sugars and organic acids was observed after treatments. These results suggest that our rapid CAP strategy effectively inactivated E. faecalis in FPJ with no change of color and negligible effects on other physicochemical properties.

Moving toward a Handheld "Plasma" Spectrometer for Elemental Analysis, Putting the Power of the Atom (Ion) in the Palm of Your Hand

Many of the current innovations in instrument design have been focused on making them smaller, more rugged, and eventually field transportable. The ultimate application is obvious, carrying the instrument to the field for real time sample analysis without the need for a support laboratory. Real time data are priceless when screening either biological or environmental samples, as mitigation strategies can be initiated immediately upon the discovery that contaminant metals are present in a location they were not intended to be. Additionally, smaller "handheld" instruments generally require less sample for analysis, possibly increasing sensitivity, another advantage to instrument miniaturization. While many other instruments can be made smaller just by using available micro-technologies (e.g., eNose), shrinking an ICP-MS or AES to something someone might carry in a backpack or pocket is now closer to reality than in the past, and can be traced to its origins based on a component-by-component evaluation. While the optical and mass spectrometers continue to shrink in size, the ion/excitation source remains a challenge as a tradeoff exists between excitation capabilities and the power requirements for the plasma's generation. Other supporting elements have only recently become small enough for transport. A systematic review of both where the plasma spectrometer started and the evolution of technologies currently available may provide the roadmap necessary to miniaturize the spectrometer. We identify criteria on a component-by-component basis that need to be addressed in designing a miniaturized device and recognize components (e.g., source) that probably require further optimization. For example, the excitation/ionization source must be energetic enough to take a metal from a solid state to its ionic state. Previously, a plasma required a radio frequency generator or high-power DC source, but excitation can now be accomplished with non-thermal (cold) plasma sources. Sample introduction, for solids, liquids, and gasses, presents challenges for all sources in a field instrument. Next, the interface between source and a mass detector usually requires pressure reduction techniques to get an ion from plasma to the spectrometer. Currently, plasma mass spectrometers are field ready but not necessarily handheld. Optical emission spectrometers are already capable of getting photons to the detector but could eventually be connected to your phone. Inert plasma gas generation is close to field ready if nitrogen generators can be miniaturized. Many of these components are already commercially available or at least have been reported in the literature. Comparisons to other "handheld" elemental analysis devices that employ XRF, LIBS, and electrochemical methods (and their limitations) demonstrate that a "cold" plasma-based spectrometer can be more than competitive. Migrating the cold plasma from an emission only source to a mass spectrometer source, would allow both analyte identification and potentially source apportionment through isotopic fingerprinting, and may be the last major hurdle to overcome. Finally, we offer a possible design to aid in making the cold plasma source more applicable to a field deployment.

Inactivation of Staphylococcus aureus and Escherichia coli Biofilms by Air-Based Atmospheric-Pressure DBD Plasma

Air-based atmospheric-pressure plasma is an effective non-thermal method in deactivating various kinds of microbial biofilms with several advantages, including high bactericidal efficiency and low treatment costs. Bacterial biofilm formation is a major determinant in establishment of bacterial infection and also resistance to antibacterial chemotherapy. This study aims to assess the anti-biofilm potential of air-based atmospheric-pressure DBD plasma against Staphylococcus aureus and Escherichia coli biofilms. The biofilms of Staphylococcus aureus and Escherichia coli were exposed to air-based atmospheric-pressure DBD plasma for up to 4 min (control, 30 s, 90 s, 3 min, and 4 min) and their biofilm formation level, viability, and membrane integrity were determined. Based on the results, plasma exposure caused disruption up to 70% and 85% for S. aureus and E. coli biofilms, respectively. The biofilm disruption potential of air-based atmospheric-pressure DBD plasma was confirmed using the scanning electron microscopy (SEM). Besides, based on confocal laser scanning microscopy (CLSM), plasma exposure caused a significant bacterial inactivation and E. coli was found as more susceptible strain than S. aureus. In conclusion, atmospheric-pressure DBD plasma could be considered an efficient non-thermal approach against bacterial pathogenicity by biofilm disruption and thus prevention of infection establishment.