Oscillation modes of dc microdischarges with parallel-plate geometry

Two different oscillation modes in microdischarge with parallel-plate geometry has been observed: relaxation oscillations with frequency range between 1.23 and 2.1 kHz and free-running oscillations with 7 kHz frequency. The oscillation modes are induced by increasing power supply voltage or discharge current. For a given power supply voltage, there is a spontaneous transition from one to other oscillation mode and vice versa. Before the transition from relaxation to free-running oscillations, the spontaneous increase of oscillation frequency of relaxation oscillations form 1.3 kHz to 2.1 kHz is measured. Fourier Transform Spectra of relaxation oscillations reveal chaotic behaviour of microdischarge. Volt-Ampere characteristics associated with relaxation oscillations describes periodical transition between low current, diffuse discharge and normal glow. However, free-running oscillations appear in subnormal glow only.Comment: Submitted to: New Journal of Physic

Plasma-Activated Medium Potentiates the Immunogenicity of Tumor Cell Lysates for Dendritic Cell-Based Cancer Vaccines

Autologous dendritic cells (DCs)-based vaccines are considered quite promising for cancer immunotherapy due to their exquisite potential to induce tumor antigen-specific cytotoxic T cells. However, a lack of efficient protocols for inducing immunogenic tumor antigens limits the efficacy of DC-based cancer vaccines. Here, we found that a plasma-activated medium (PAM) induces immunogenic cell death (ICD) in tumor cells but not in an immortalized L929 cell line or human peripheral blood mononuclear cells. PAM induced an accumulation of reactive oxygen species (ROS), autophagy, apoptosis, and necrosis in a concentration-dependent manner. The tumor lysates prepared after PAM treatment displayed increased immunogenicity in a model of human monocyte-derived DCs, compared to the lysates prepared by a standard freezing/thawing method. Mature DCs loaded with PAM lysates showed an increased maturation potential, as estimated by their increased expression of CD83, CD86, CD40, IL-12/IL-10 production, and attenuated PDL1 and ILT-4 expression, compared to the DCs treated with control tumor lysates. Moreover, in co-culture with allogeneic T cells, DCs loaded with PAM-lysates increased the proportion of cytotoxic IFN-γ+ granzyme A+ CD8+ T cells and IL-17A-producing T cells and preserved the Th1 response. In contrast, control tumor lysates-treated DCs increased the frequency of Th2 (CD4+IL-4+), CD4, and CD8 regulatory T cell subtypes, none of which was observed with DCs loaded with PAM-lysates. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients

Modulating chemosensitivity of oral carcinoma to Cisplatin by combination with plasma activated medium on 3D cell models

Oral squamous cell carcinoma (OSCC) is one of the most malignant neoplasms of the oral cavity, with a high mortality rate. Since the long-term survival rate of patients diagnosed with OSCC has remained unchanged over the past several decades, it is of utmost importance to discover new treatment modalities or enhance existing ones [1]. Since we previously demonstrated the antitumor efficacy of cold atmospheric pressure plasma (CAP) on OSCC cell lines in a two-dimensional (2D) monolayer cell model, we moved further and tried to explain the mechanism of these cytotoxic events as well as analyze the effect of plasma-activated medium (PAM) in combination with chemotherapy as a gold standard in carcinoma treatment. The modified plasma needle operating at 13.56MHz with He as working gas was used for PAM generation with the distance of 3 mm between liquid surface and the tube and applying different exposure intervals [2]. OSCC cell line (SCC25) was cultivated in 2D or 3D culture systems when regular culture medium was changed for PAM for 24 h before performing assays. PAM treatment showed cytotoxic effects on 2D-cultured OSCC by inducing apoptotic cell death through the activation of the intrinsic caspase pathway. To analyze the combined effect of cisplatin and PAM we used a 3D cell culture approach with OSCC spheroids, as this method reflects more closely the in vivo cellular response to chemotherapeutics [3]. When PAM was combined with the increasing concentrations of cisplatin, the results showed an almost linear dose dependent decrease in OSCC spheroid viability. These arepromising and encouraging results for a potential application of CAP in the treatment of oral carcinoma. By combining the effects of chemotherapeutics with PAM, we developed a new prospect for a possible cancer treatment in which the same or even better antitumor effects could be achieved with lower doses of cytotoxic drugs. Consequently, it means that with lower doses of chemotherapeutics, we could minimize potential side effects associated with the high-dose usage of cytostatics and improve the quality of life for patients with these malignancies

Bone Regeneration Potential of Periodontal Ligament Stem Cells in Combination with Cold Atmospheric Plasma-Pretreated Beta-Tricalcium Phosphate: An In Vivo Assessment

In regenerative bone tissue medicine, combining artificial bone substitutes with progenitor cells is a prospective approach. Surface modification via cold atmospheric plasma (CAP) enhances biomaterial–cell interactions, which are crucial for successful bone regeneration. Using a rabbit calvarial critical-size defect model, we assessed the use of CAP-pretreated beta-tricalcium phosphate (β-TCP), alone or with periodontal ligament stem cells (PDLSCs), for bone regeneration. Histological and histomorphometric analyses at two and four weeks revealed significantly improved bone regeneration and reduced inflammation in the CAP-treated β-TCP with PDLSCs compared to β-TCP alone. Immunohistochemical analysis also showed an increase in the bone healing markers, including bone morphogenic proteins 2 and 4, runt-related transcription factor 2, collagen-1, and osteonectin, after two and four weeks in the CAP-treated β-TCP implants with PDLSC. This in vivo study demonstrates for the first time the superior bone regenerative capacity of CAP-pretreated β-TCP seeded with PDLSCs, highlighting the therapeutic potential of this combined approach in osteoregeneration

Destruction of chemical warfare surrogates using a portable atmospheric pressure plasma jet

Today’s reality is connected with mitigation of threats from the new chemical and biological warfare agents. A novel investigation of cold plasmas in contact with liquids presented in this paper demonstrated that the chemically reactive environment produced by atmospheric pressure plasma jet (APPJ) is potentially capable of rapid destruction of chemical warfare agents in a broad spectrum. The decontamination of three different chemical warfare agent surrogates dissolved in liquid is investigated by using an easily transportable APPJ. The jet is powered by a kHz signal source connected to a low-voltage DC source and with He as working gas. The detailed investigation of electrical properties is performed for various plasmas at different distances from the sample. The measurements of plasma properties in situ are supported by the optical spectrometry measurements, whereas the high performance liquid chromatography measurements before and after the treatment of aqueous solutions of Malathion, Fenitrothion and Dimethyl Methylphosphonate. These solutions are used to evaluate destruction and its efficiency for specific neural agent simulants. The particular removal rates are found to be from 56% up to 96% during 10 min treatment. The data obtained provide basis to evaluate APPJ’s efficiency at different operating conditions. The presented results are promising and could be improved with different operating conditions and optimization of the decontamination process

ON THE ADSORPTION OF CIPROFLOXACIN BY CLINOPTILOLITE AND USE OF NON THERMAL ATMOSPHERIC PRESSURE PLASMA FOR REGENERATION OF THE SPENT ZEOLITE

The use of antibiotics constantly increases which has a notable negative impact on water bodies. Ciprofloxacin (CIP) is widely applied antibiotic in both human and veterinary medicine, as well as in a livestock breeding. Due to its extensive use, CIP has been found in wastewater effluents in a wide concentration range from ng to mg dm^(–3). An extremely high concentration of up to 50 mg dm^(–3) has been found near drug manufacturing plants [1]. Since CIP, as well as many other pharmaceuticals, cannot be efficiently removed from wastewater streams by conventional wastewater treatments, it is of a great importance to find an acceptable method for their removal. This study reports the use of natural calcium-rich clinoptilolite (CLI) for the adsorption of CIP and regeneration of the spent adsorbent (CLI-CIP) by non-thermal atmospheric pressure plasma (NTP). The results show that the CLI possesses a high adsorption efficiency in removal of CIP at 283, 288 and 293 K in a slightly acidic medium (pH= 5) for the initial concentrations from 15 to 75 mg dm^(–3). The CIP adsorption by CLI follows the Lagergren’s pseudo-second-order kinetics and it can be described well by the Langmuir isotherm model. For all studied temperatures and initial concentrations more than 85% of the CIP is removed within the first 10 minutes. The results also indicate that the CIP adsorption mechanism includes two phenomena: 1) electrostatic interactions between negatively charged aluminosilicate lattice and cationic form of CIP species and 2) ion-exchange reaction. The use of NTP for the regeneration of CLI-CIP was based on the assumption that NTP generates highly reactive species which can induce a cleavage of the bonds formed between active sites on the CLI surface and CIP, and also induce the CIP decomposition. The NTP treatment was performed for a short time, with a low energy consumption, and without using the additional chemicals. All these make the procedure acceptable not only from economical point of view but also regarding environmental issues [2]. A surface dielectric barrier discharge plasma source was used for the treatment of CLI-CIP. The regeneration study was consisted of five successive adsorption/NTP cycles. Powder X-ray diffraction and Brunauer–Emmett–Teller surface area analyses confirmed that the plasma treatment did not influence the CLI lattice nor its textural properties. Moreover, X-ray photoelectron spectroscopy confirmed that the NTP reduces carbon content in the regenerated CLI for more than 90% and that the plasma reactive species are involved in the CLI regeneration process. The obtained results strongly support the applicability of the NTP treatment in regeneration of zeolite-based adsorbents used in pharmaceutical removal from wastewater

Regeneration of the ciprofloxacin-loaded clinoptilolite by non-thermal atmospheric plasma

Natural clinoptilolite (CLI) exhibited a high efficacy in ciprofloxacin (CIP) removal from aqueous solution by adsorption. However, the regeneration of the spent adsorbent was a challenge since the adsorption occurred via electrostatic interactions and ion-exchange reaction. Herein, the feasibility of non-thermal plasma (NTP) was studied for the regeneration of ciprofloxacin-containing clinoptilolite (CIP-CLI) in five successive adsorption/NTP regeneration cycles. The NTP treatments were performed using a surface dielectric barrier discharge (SDBD) operating at atmospheric pressure in air. Plasma discharge gap, sample mass, and electrode surfaces were varied to find optimal regeneration parameters. For the plasma source with an electrode surface of 37.2 cm2, the 2 mm electrode gap and 20 min of plasma treatment were found as optimal parameters (sample mass of 0.2 g). The plasma treatment did not affect clinoptilolite features which were concluded from a study of textural properties and powder X-ray diffraction (PXRD) analysis. X-ray photoelectron spectroscopy (XPS) showed a decrease of total carbon content with around 10% of carbon residual left on the surface. The CLI adsorption capacity can be regenerated to at least 90% of its initial capacity during the five successive cycles, showing the involvement of plasma reactive species in decomposition of adsorbed CIP

Treatment of Chrysanthemum Synthetic Seeds by Air SDBD Plasma

Herein, we present the effect of surface dielectric barrier discharge (SDBD) air cold plasma on regrowth of chrysanthemum synthetic seeds (synseeds) and subsequent plantlet development. The plasma system used in this study operates in air at the frequency of 50 Hz. The detailed electrical characterization of SDBD was shown, as well as air plasma emission spectra obtained by optical emission spectroscopy. The chrysanthemum synseeds (encapsulated shoot tips) were treated in air plasma for different treatment times (0, 5 or 10 min). Plasma treatment significantly improved the regrowth and whole plantlet development of chrysanthemum synseeds under aseptic (in vitro) and non-aseptic (ex vitro) conditions. We evaluated the effect of SDBD plasma on synseed germination of four chrysanthemum cultivars after direct sowing in soil. Germination of synseeds directly sowed in soil was cultivar-dependent and 1.6−3.7 fold higher after plasma treatment in comparison with untreated synseeds. The study showed a highly effective novel strategy for direct conversion of simple monolayer alginate chrysanthemum synseeds into entire plantlets by plasma pre-conversion treatment. This treatment reduced contamination and displayed a considerable ex vitro ability to convert clonally identical chrysanthemum plants

Cold atmospheric plasma technology for removal of organic micropollutants from wastewater—a review

Water bodies are being contaminated daily due to industrial, agricultural and domestic effluents. In the last decades, harmful organic micropollutants (OMPs) have been detected in surface and groundwater at low concentrations due to the discharge of untreated effluent in natural water bodies. As a consequence, aquatic life and public health are endangered. Unfortunately, traditional water treatment methods are ineffective in the degradation of most OMPs. In recent years, advanced oxidation processes (AOPs) techniques have received extensive attention for the mineralization of OMPs in water in order to avoid serious environmental problems. Cold atmospheric plasma discharge-based AOPs have been proven a promising technology for the degradation of non-biodegradable organic substances like OMPs. This paper reviews a wide range of cold atmospheric plasma sources with their reactor configurations used for the degradation of OMPs (such as organic dyes, pharmaceuticals, and pesticides) in wastewater. The role of plasma and treatment parameters (e.g. input power, voltage, working gas, treatment time, OMPs concentrations, etc.) on the oxidation of various OMPs are discussed. Furthermore, the degradation kinetics, intermediates compounds formed by plasma, and the synergetic effect of plasma in combination with a catalyst are also reported in this review