a b s t r a c tCold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coli a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (∼ 1.0 W) with different exposure time. Sterilization of E. coli and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy.

This work proposes an experimental configuration for the generation of a cold atmospheric pressure plasma jet at the downstream end of a long flexible plastic tube. The device consists of a cylindrical dielectric chamber where an insulated metal rod that serves as high-voltage electrode is inserted. The chamber is connected to a long (up to 4 m) commercial flexible plastic tube, equipped with a thin floating Cu wire. The wire penetrates a few mm inside the discharge chamber, passes freely (with no special support) along the plastic tube and terminates a few millimeters before the tube end. The system is flushed with Ar and the dielectric barrier discharge (DBD) is ignited inside the dielectric chamber by a low frequency ac power supply. The gas flow is guided by the plastic tube while the metal wire, when in contact with the plasma inside the DBD reactor, acquires plasma potential. There is no discharge inside the plastic tube, however an Ar plasma jet can be extracted from the downstream tube end. The jet obtained by this method is cold enough to be put in direct contact with human skin without an electric shock. Therefore, by using this approach an Ar plasma jet can be generated at the tip of a long plastic tube far from the high-voltage discharge region, which provides the safe operation conditions and device flexibility required for medical treatment.

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This work reports the development of atmospheric pressure plasma reactor with dielectric barrier discharge DBD for material treatment. The DBD discharge has been generated in planar geometry reactor powered by ac voltage provided by conventional high voltage transformer. The dielectric barrier consisted of two glass slabs, which cover both reactor electrodes. The air discharge gap between the dielectric layers was varied from 1.0 to 3.0mm. The power consumption of the DBD reactor was evaluated by the Lissajous figures method. The optimization of reactor geometry for material processing is discussed.

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The goal of this study was to analyze the effects of cold atmospheric pressure plasma jet operated with Helium (He-CAPPJ) on C. albicans virulence traits and biofilms. The study also aimed to evaluate the cytotoxicity of He-CAPPJ to fibroblasts. Methods: The effective operational parameters of He-CAPPJ against C. albicans SC 5314 were determined. Subinhibitory times of exposure were used to evaluate the effect of He-CAPPJ on morphogenesis (yeast-hyphae transition), adherence to epithelial cells, and exoenzymes production. Cytotoxicity to Vero cells was also assessed by MTT assay. Results: A promising effect of He-CAPPJ on morphogenesis was observed, with an almost 40 times reduction of the filamentation rate comparing to the non-exposed group. He-CAPPJ was able to reduce C. albicans adherence and to decrease fungal biofilm viability. No effect on exoenzymes production was observed. Conclusion: He-CAPPJ was able to attenuate fungal adherence and morphogenesis with low cytotoxicity to fibroblasts. Therefore, He-CAPPJ has potential to be applied as an adjuvant in the treatment of C. albicans superficial infections. Additionally, the ability of C. albicans to develop resistance against antifungals is remarkable [1,2]. Although azoles and polyenes are drugs of choice for the treatment of these infections, they are not always effective [7,8]. Besides, other adverse effects may occur, such as toxicity and interactions with other drugs [9], limiting the number of therapeutic alternatives. For this reason, the search for new antifungal therapies is of utmost importance. Cold atmospheric pressure plasma (CAPP) has emerged as a promising technology in recent years. Due to their low operational cost, absence of residual and toxic emissions and operation at room temperature, cold plasmas have drawn much attention for biomedical applications [10-12]. Among different atmospheric plasma sources, special interest has been driven to cold atmospheric pressure plasma jets (CAPPJs), since plasma plumes can be obtained in open space instead of confined volumes [13]. The plasma plume propagates into the surrounding environment and interacts with air molecules creating

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