Selecting the most effective and biologically safe operation regimes of a cold atmospheric plasma jet (CAPJ) is a defining factor in developing the cancer treatments based on the CAPJ. Experimentally and numerically, by changing the pulse duration of the positive pulsed voltage, we determined the optimum CAPJ regimes with regular propagation of streamers and a maximum discharge current at a temperature T < 42°C. In these regimes, the CAPJ appreciably suppresses the viability of the cancerous cells. It was shown that adding gold nanoparticles increases the cytotoxic effect of the plasma jet and decreases the viability of the NCI‑H23 epithelioid lung adenocarcinoma, the A549 lung adenocarcinoma, the BrCCh4e-134 mammary adenocarcinoma, and the cells of the uMel1 uveal melanoma. The polyethylenglycol-modified gold nanoparticles with fluorescent labels were used to visualize the absorption of the nanoparticles by the cells. It was shown that the CAPJ stimulated the penetration of the nanoparticles into the cells when they were applied to the medium immediately before the CAPJ treatment or immediately after, which indicates a short-time increase in the permeability of the cell membrane.

In this work the optimal operating modes of the atmospheric pressure cold plasma jet generation source were determined for applications involving biological objects, ensuring maximum suppression of cancer cell viability. A comparative study was conducted on the survival of cancer cells after treatment with a cold plasma helium jet under various voltage supply modes, the frequency of current contact with the surface of a biological object, and the different duration of voltage initiation pulses. The conditions ensuring the maximum reduction in the viability of cancer cells have been determined. In the course of the work, it was established that cold plasma treatment of cancer cells with a plasma jet, initiated by different modes, but providing the same intensity levels of OH radical release in the contact zone, leads to the same levels of decreased viability. The obtained results are important for the development of standardized plasma therapy protocols in oncology and other areas of medicine.

The characteristics of a low-temperature plasma jet at atmospheric pressure generated by sinusoidal voltage initiation have been investigated. The influence of the auxiliary electrode with a hole through which the plasma formation propagates to the target has been analyzed at different polarities and values of the applied voltage. The character of change in the current registered in the interaction zone of the plasma jet with the biotarget in the presence of an auxiliary electrode has been studied. The change of current touching frequency in the zone of plasma contact with the biotarget has been investigated. Spectral analysis of the interaction areas of the plasma jet and the culture liquid at different values of voltage at the auxiliary electrode with a hole was carried out. It is shown that the presence of an auxiliary electrode under negative potential results in an enhancement of the frequency of current touching the targets and an increase of the generation intensity of active radicals in the interaction zone. The presence of a positive potential on the electrode with a hole leads to a sharp decrease in the current amplitude and a decrease in the frequency of current contact with the target.

The intensity of the interaction between a helium cold atmospheric plasma jet (CAPJ) and a dielectric surface or animal skin is compared in experiment and numerical simulation. A cold plasma jet at atmospheric pressure is generated by a sinusoidal or positive pulsed voltage with different pulse durations in optimal modes. The impact effect is estimated on the basis of measured and calculated currents, line intensities in the CAPJ spectrum and temperature fields. The measured CAPJ characteristics show that the pulsed voltage for the CAPJ excitation is preferable compared to the sinusoidal mode. Varying the pulse duration of the periodic pulsed voltage makes it possible to obtain the maximum current and electric field strength at the surface within the permissible temperature in the contact area of the CAPJ with the skin of mice (<42°C). It is shown that the results of the CAPJ study obtained in physical experiments using a dielectric plate are applicable for tumor-bearing mice treatment.

Efficient and biologically safe mode of cold atmospheric plasma jet (CAPJ) is crucial for the development of CAPJ-based anticancer therapy. In the experiment and numerical simulations, by changing the pulse duration of a positive-pulsed voltage, we found the optimal CAPJ mode with regular streamer propagation. CAPJ regimes with a maximum discharge current at a temperature T<42 C substantially suppressed the viability of cancer cells. To enhance cell killing, gold nanoparticles (NPs) were added to the cells before and after the CAPJ exposure. Combination of CAPJ, generated with positive pulsed voltage, and gold nanoparticles decreased viability of NCI-H23 epithelial-like lung adenocarcinoma, A549 lung adenocarcinoma, BrCCh4e-134 breast adenocarcinoma and uMel1 uveal melanoma cells. Polyethylene glycol-modified nanoparticles with attached fluorescent label were used to visualize the uptake of NPs. We demonstrated that NPs efficiently entered the cells when were added to the cells just before CAPJ exposure or up to two hours afterwards. The efficiency ofNPs penetration into cells positively correlated with the induced cytotoxic effect: it was maximal when NPs was added to cells right before or immediately after CAPJ exposure. Summarizing, the treatment with optimal CAPJ modes in combination with modified NPs, bearing the cancer-addressed molecules and therapeutics may be next strategy of strengthening the CAPJ-based antitumor approaches.

The generation parameters of a cold plasma jet produced by sinusoidal excitation were studied. Irradiation parameters for effective reduction of cancer cell viability and optimized conditions for use in animal experiments were determined.

The treatment of solid tumors by a cold atmospheric plasma (CAP) jet is an innovative approach that has been actively developed only in the last decade. As a result, studies aimed at identifying the conditions for selective effect on tumor cells, including as parts of 3D models that mimic malignant neoplasms are pertinent. It is known that the main cytotoxic effects of a CAP are caused by reactive oxygen and nitrogen species in the plasma jet. Their availability for cells in classical 2D and 3D models of cell cultivation may be different. Here, we used multicellular spheroids of MCF7–EGFR cells with overexpression of the epidermal growth-factor receptor (EGFR), cells of parental breast adenocarcinoma MCF7 cell line, and nontransformed human breast cells MCF10A. Irradiation of MCF7–EGFR spheroids induced destruction of multicellular 3D structures into individual cells and activated cell death. It has been shown that the cells of irradiated spheroids undergo phagocytosis by activated macrophages. Comparison of a direct CAP irradiation of MCF7–EGFR spheroids and indirect treatment with plasma-activated medium (PAM) revealed a higher content of reactive oxygen and nitrogen species in spheroid cells cultivated in the irradiated medium. It produced a higher cytotoxic effect than direct irradiation. It has been shown that the cytotoxic properties of PAM are better preserved when such a medium is stored at 4° than at –20°C. Thus, the death of tumor cells in spheroids was more effective with addition of the culture medium irradiated with a CAP than direct irradiation of cells.

In the paper, the characteristics of a cold atmospheric plasma jet generated by non-contact and contact methods of initiating a gas discharge with a pulsed voltage are investigated. The parameters of current detectabled in the contact zone of the plasma jet touching the object, depending on the amplitude and duration of unipolar positive pulses for contact and non-contact initiation of the discharge, have been studied. The frequency of touching of the plasma jet current with the object under different durations of initiating voltage pulses and pulse repetition frequencies has been investigated. The spectral analysis of the plasma jet interaction zone with object has been carried out. The modes providing the highest intensity of OH radical emission were determined. The temperature increment in the cold plasma jet interaction zone with the object at different parameters of voltage and speed of gas pumped through the device has been investigated. Comparative research of the characteristics of cold plasma jets initiated by contact and non-contact excitation by unipolar positive pulses has been carried out. It is established that the amplitude of the current registered on the object surface is several times higher for the plasma jet initiated by contact excitation of the gas medium. It is shown that at non-contact method of discharge ignition by unipolar positive pulses the frequency of current touching the object of influence matches with the repetition frequency of voltage pulses.

The interaction of cold atmospheric plasma (CAP) with biotargets is accompanied by chemical reactions on their surfaces and insides, and it has great potential as an anticancer approach. This study discovers the molecular mechanisms that may explain the selective death of tumor cells under CAP exposure. To reach this goal, the transcriptional response to CAP treatment was analyzed in A549 lung adenocarcinoma cells and in lung-fibroblast Wi-38 cells. We found that the CAP treatment induced the common trend of response from A549 and Wi-38 cells—the p53 pathway, KRAS signaling, UV response, TNF-alpha signaling, and apoptosis-related processes were up-regulated in both cell lines. However, the amplitude of the response to CAP was more variable in the A549 cells. The CAP-dependent death of A549 cells was accompanied by DNA damage, cell-cycle arrest in G2/M, and the dysfunctional response of glutathione peroxidase 4 (GPx4). The activation of the genes of endoplasmic reticulum stress and ER lumens was detected only in the A549 cells. Transmission-electron microscopy confirmed the alteration of the morphology of the ER lumens in the A549 cells after the CAP exposure. It can be concluded that the responses to nuclear stress and ER stress constitute the main differences in the sensitivity of tumor and healthy cells to CAP exposure.

В эксперименте и численном моделировании проводится сравнение интенсивности взаимодействия гелиевой холодной плазменной струи (ХПС) с диэлектрической поверхностью и с кожей животных. ХПС при атмосферном давлении генерируется синусоидальным или положительным импульсным напряжением с различной длительностью импульса в оптимальных режимах. Эффект воздействия оценивается на основе измеренных и рассчитанных токов, интенсивностей линий в спектре ХПС и температурных полей. Измеренные характеристики ХПС показывают, что импульсный характер возбуждения ХПС является предпочтительным по сравнению с синусоидальным режимом. Варьирование длительности импульсов периодического импульсного напряжения позволяет получить максимальные ток и напряженность электрического поля у поверхности в рамках допустимой температуры в зоне контакта ХПС с кожей мышей (<42°C). Показано, что результаты исследования ХПС полученные в физических экспериментах с использованием диэлектрической пластины применимы для воздействия на мышей-опухоленосителей.

Comparative studies of the generation of a cold plasma jet atmospheric pressure in helium excited by a sinusoidal voltage with different methods of its initiation have been carried out. The frequency and temperature ranges of the plasma jet, acceptable for exposure to biological objects, were determined.

Low-temperature plasma jets at atmospheric pressure generated by sinusoidal and positive pulsed voltages interact differently with the treated surface. In the experiment and in numerical simulations, we compare the operating modes of helium plasma jets for these types of operating voltages. The discharge current on the treated surface over time and the surface heating are studied for different discharge parameters acceptable for anticancer therapy. The intensity of the emission spectrum is analyzed to improve the effectiveness of the plasma jet. Surface heating is controlled in order to meet the safety conditions of plasma exposure to biological objects. For the case of pulsed voltage the effect of voltage pulse duration on the intensity of plasma-surface interaction is discussed. The results on cancer cells A549 and MCF-7 demonstrate the high efficiency of the cold plasma jet generated at found optimal modes.

Cold atmospheric plasma (CAP) is an intensively-studied approach for the treatment of malignant neoplasms. Various active oxygen and nitrogen compounds are believed to be the main cytotoxic effectors on biotargets; however, the comprehensive mechanism of CAP interaction with living cells and tissues remains elusive. In this study, we experimentally determined the optimal discharge regime (or semi-selective regime) for the direct CAP jet treatment of cancer cells, under which lung adenocarcinoma A549, A427 and NCI-H23 cells demonstrated substantial suppression of viability, coupled with a weak viability decrease of healthy lung fibroblasts Wi-38 and MRC-5. The death of CAP-exposed cancer and healthy cells under semi-selective conditions was caspase-dependent. We showed that there was an accumulation of lysosomes in the treated cells. The increased activity of lysosomal protease Cathepsin D, the transcriptional upregulation of autophagy-related MAPLC3B gene in cancer cells and the changes in autophagy-related proteins may have indicated the activation of autophagy. The addition of the autophagy inhibitor chloroquine (CQ) after the CAP jet treatment increased the death of A549 cancer cells in a synergistic manner and showed a low effect on the viability of CAP-treated Wi-38 cells. Downregulation of Drp1 mitochondrial protein and upregulation of PINK1 protein in CAP + CQ treated cells indicated that CQ increased the CAP-dependent destabilization of mitochondria. We concluded that CAP weakly activated pro-survival autophagy in irradiated cells, and CQ promoted CAP-dependent cell death due to the destabilization of autophagosomes formation and mitochondria homeostasis. To summarize, the combination of CAP treatment with CQ could be useful for the development of cold plasma-based antitumor approaches for clinical application.

Низкотемпературные плазменные струи при атмосферном давлении, генерируемые синусоидальным и положительным импульсным напряжением, по-разному взаимодействуют с обрабатываемой поверхностью. В эксперименте и в численном моделировании сравниваются режимы работы струи гелиевой плазмы для этих типов рабочих напряжений. Ток разряда на обрабатываемой поверхности с течением времени, и нагрев поверхности изучены для различных параметров разряда, допустимых для противораковой терапии. Для повышения эффективности плазменной струи анализируется интенсивность спектра излучения. Нагрев поверхности контролируется для того, чтобы удовлетворить условиям безопасного плазменного воздействия на биологические объекты. Обсуждается влияние длительности импульса напряжения на интенсивность взаимодействия плазмы с поверхностью. Результаты воздействия на раковые клетки A549 и MCF-7 демонстрируют высокую эффективность холодной плазменной струи, генерируемой в оптимальных режимах.

The parameters of a cold plasma jet of atmospheric pressure generated in a non-contact method of gas discharge initiation have been studied. The character of changes in the amplitude of the registered current in the area of plasma jet contact with the target, depending on the sinusoidal voltage amplitude has been investigated. The change in the frequency of current touching in the interaction area of plasma jet with a target is investigated. The spectral analysis of interaction area and surface heating caused by plasma jet influence on a target at various generation parameters are carried out. A comparative analysis of parameters of cold plasma jets generated by contact and non-contact method of gas discharge initiation was performed. The results showed that the non-contact method of discharge excitation provides stable modes of operation in which the frequency of target current touching coincides with the frequency of voltage applied to the electrodes. The obtained results allow determining effective ranges of cold plasma jet functioning required for medical and biological investigations.

Cold plasma activates various processes when acting on biomolecules, including tumors. Сold plasma jet (CPJ) generates active forms of oxygen and nitrogen, and such species cause oxidative stress. This study shows an increase in active forms of nitrogen in irradiated A549 tumor cells compared to healthy Wi-38 cells. The action of CPJ on tumor cells causes cell cycle arrest, and suppresses their proliferation.

Research of the cold plasma jet atmospheric pressure generation parameters at different frequencies of the applied sinusoidal voltage was carried out. The modification in the contact frequency of the cold plasma jet depending on the amplitude of the applied sinusoidal voltage has been investigated. The modification in the contact frequency in the interaction zone of the plasma-target with the experimental conditions has been shown. The character of the modification in the current amplitude registered in the interaction zone of copper substrate with the plasma jet depending on the tuning of the resonant frequency of the applied voltage source has been investigated. The experimental results showed that a frequency modification in a small range can lead to a change in the amplitude of the current pulse by more than 3 times. The obtained results allow to determine the stable effective operating ranges of a cold plasma jet atmospheric pressure, which necessary for biomedical research.

Nowadays the low temperature atmospheric pressure plasma jets are widely used for the suppression of the malignant tumor growth. In this work, to maximize the effect of the CAPJ treatment on the different cancer cell lines, the optimization of the plasma jet device is reported for the sinusoidal initiation voltage. In experiments and in 2D fluid model simulations, we vary the discharge voltage amplitude from 3 kV to 5 kV with the frequency 13–50 kHz. The efficacy of plasma treatment is confirmed in our bio experiments with various cancer cell lines. A strong cytotoxic effect and selectivity of cells treated with the optimal CAP regimes are demonstrated on the A549 and MCF7 cancer cells and Wi-38 normal cells.

Comparative studies of cold plasma jet of generation at atmospheric pressure in helium excited by sinusoidal and unipolar positive pulses voltage at 2-6 kV for medical applications were carried out. It has been shown that the achieved parameters are identical, but the absence of the effect of frequency self-organization of streamer breakdown leading to irregularity in streamer propagation under pulse excitation makes it preferable in biophysical experiments. A limiting factor for plasma jet exposure is the achievable target temperature, which can be reduced by limiting the current duration. Keywords: cold plasma jet, excitation by sinusoidal and pulsed voltage, temperature.