Molecular Mechanisms of the Efficacy of Cold Atmospheric Pressure Plasma (CAP) in Cancer Treatment

Synergistic effect of plasma-activated medium and novel indirubin derivatives on human skin cancer cells by activation of the AhR pathway

Due to the increasing number of human skin cancers and the limited effectiveness of therapies, research into innovative therapeutic approaches is of enormous clinical interest. In recent years, the use of cold atmospheric pressure plasma has become increasingly important as anti-cancer therapy. The combination of plasma with small molecules offers the potential of an effective, tumour-specific, targeted therapy. The synthesised glycosylated and non glycosylated thia-analogous indirubin derivatives KD87 and KD88, respectively, were first to be investigated for their pharmaceutical efficacy in comparison with Indirubin-3'-monoxime (I3M) on human melanoma (A375) and squamous cell carcinoma (A431) cells. In combinatorial studies with plasma-activated medium (PAM) and KD87 we determined significantly decreased cell viability and cell adhesion. Cell cycle analyses revealed a marked G2/M arrest by PAM and a clear apoptotic effect by the glycosylated indirubin derivative KD87 in both cell lines and thus a synergistic anti-cancer effect. I3M had a pro-apoptotic effect only in A431 cells, so we hypothesize a different mode of action of the indirubin derivatives in the two skin cancer cells, possibly due to a different level of the aryl hydrocarbon receptor and an activation of this pathway by nuclear translocation of this receptor and subsequent activation of gene expression.

Cold atmospheric plasma differentially affects cell renewal and differentiation of stem cells and APC-deficient-derived tumor cells in intestinal organoids

Cold atmospheric plasma (CAP) treatment has been proposed as a potentially innovative therapeutic tool in the biomedical field, notably for cancer due to its proposed toxic selectivity on cancer cells versus healthy cells. In the present study, we addressed the relevance of three-dimensional organoid technology to investigate the biological effects of CAP on normal epithelial stem cells and tumor cells isolated from mouse small intestine. CAP treatment exerted dose-dependent cytotoxicity on normal organoids and induced major transcriptomic changes associated with the global response to oxidative stress, fetal-like regeneration reprogramming, and apoptosis-mediated cell death. Moreover, we explored the potential selectivity of CAP on tumor-like Apc-deficient versus normal organoids in the same genetic background. Unexpectedly, tumor organoids exhibited higher resistance to CAP treatment, correlating with higher antioxidant activity at baseline as compared to normal organoids. This pilot study suggests that the ex vivo culture system could be a relevant alternative model to further investigate translational medical applications of CAP technology.

H2A.X Phosphorylation in Oxidative Stress and Risk Assessment in Plasma Medicine

At serine₁₃₉-phosphorylated gamma histone H2A.X (γH2A.X) has been established over the decades as sensitive evidence of radiation-induced DNA damage, especially DNA double-strand breaks (DSBs) in radiation biology. Therefore, γH2A.X has been considered a suitable marker for biomedical applications and a general indicator of direct DNA damage with other therapeutic agents, such as cold physical plasma. Medical plasma technology generates a partially ionized gas releasing a plethora of reactive oxygen and nitrogen species (ROS) simultaneously that have been used for therapeutic purposes such as wound healing and cancer treatment. The quantification of γH2A.X as a surrogate parameter of direct DNA damage has often been used to assess genotoxicity in plasma-treated cells, whereas no sustainable mutagenic potential of the medical plasma treatment could be identified despite H2A.X phosphorylation. However, phosphorylated H2A.X occurs during apoptosis, which is associated with exposure to cold plasma and ROS. This review summarizes the current understanding of γH2A.X induction and function in oxidative stress in general and plasma medicine in particular. Due to the progress towards understanding the mechanisms of H2A.X phosphorylation in the absence of DSB and ROS, observations of γH2A.X in medical fields should be carefully interpreted.

Low-Temperature Atmospheric Pressure Plasma Processes for the Deposition of Nanocomposite Coatings

Low-temperature atmospheric pressure (AP) plasma technologies have recently proven to offer a range of interesting opportunities for the preparation of a variety of nanocomposite (NC) coatings with different chemical compositions, structures, and morphologies. Since the late 2000s, numerous strategies have been implemented for the deposition of this intriguing class of coatings by using both direct and remote AP plasma sources. Interestingly, considerable progress has been made in the development of aerosol-assisted deposition processes in which the use of either precursor solutions or nanoparticle dispersions in aerosol form allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. This review summarizes the research published on this topic so far and, specifically, aims to present a concise survey of the developed plasma processes, with particular focus on their optimization as well as on the structural and functional properties of the NC coatings to which they provide access. Current challenges and opportunities are also briefly discussed to give an outlook on possible future research directions.

Effect of Cold Atmospheric Plasma on Epigenetic Changes, DNA Damage, and Possibilities for Its Use in Synergistic Cancer Therapy

Cold atmospheric plasma has great potential for use in modern medicine. It has been used in the clinical treatment of skin diseases and chronic wounds, and in laboratory settings it has shown effects on selective decrease in tumour-cell viability, reduced tumour mass in animal models and stem-cell proliferation. Many researchers are currently focusing on its application to internal structures and the use of plasma-activated liquids in tolerated and effective human treatment. There has also been analysis of plasma's beneficial synergy with standard pharmaceuticals to enhance their effect. Cold atmospheric plasma triggers various responses in tumour cells, and this can result in epigenetic changes in both DNA methylation levels and histone modification. The expression and activity of non-coding RNAs with their many important cell regulatory functions can also be altered by cold atmospheric plasma action. Finally, there is ongoing debate whether plasma-produced radicals can directly affect DNA damage in the nucleus or only initiate apoptosis or other forms of cell death. This article therefore summarises accepted knowledge of cold atmospheric plasma's influence on epigenetic changes, the expression and activity of non-coding RNAs, and DNA damage and its effect in synergistic treatment with routinely used pharmaceuticals.

From Toxicity to Selectivity: Coculture of the Fluorescent Tumor and Non-Tumor Lung Cells and High-Throughput Screening of Anticancer Compounds

For the search of anticancer compounds in modern large chemical libraries, new approaches are of great importance. Cocultivation of the cells of tumor and non-tumor etiology may reveal specific action of chemicals on cancer cells and also take into account some effects of the tumor cell's microenvironment. The fluorescent cell cocultivation test (FCCT) has been developed for screening of substances that are selectively cytotoxic on cancerous cells. It is based on the mixed culture of lung carcinoma cells A549'_EGFP and noncancerous fibroblasts of lung VA13_Kat, expressing different fluorescent proteins. Analysis of the cells was performed with the high-resolution scanner to increase the detection rate. The combination of cocultivation of cells with scanning of fluorescence reduces the experimental protocol to three steps: cells seeding, addition of the substance, and signal detection. The FCCT analysis does not disturb the cells and is compatible with other cell-targeted assays. The suggested method has been adapted for a high-throughput format and applied for screening of 2,491 compounds. Three compounds were revealed to be reproducibly selective in the FCCT although they were invisible in cytotoxicity tests in individual lines. Six structurally diverse indole, coumarin, sulfonylthiazol, and rifampicin derivatives were found and confirmed with an independent assay (MTT) to be selectively cytotoxic to cancer cells in the studied model.

Singlet-Oxygen-Induced Phospholipase A2 Inhibition: A Major Role for Interfacial Tryptophan Dioxidation

Several studies have revealed that various diseases such as cancer have been associated with elevated phospholipase A2 (PLA2 ) activity. Therefore, the regulation of PLA2 catalytic activity is undoubtedly vital. In this study, effective inactivation of PLA2 due to reactive species produced from cold physical plasma as a source to model oxidative stress is reported. We found singlet oxygen to be the most relevant active agent in PLA2 inhibition. A more detailed analysis of the plasma-treated PLA2 identified tryptophan 128 as a hot spot, rich in double oxidation. The significant dioxidation of this interfacial tryptophan resulted in an N-formylkynurenine product via the oxidative opening of the tryptophan indole ring. Molecular dynamics simulation indicated that the efficient interactions between the tryptophan residue and phospholipids are eliminated following tryptophan dioxidation. As interfacial tryptophan residues are predominantly involved in the attaching of membrane enzymes to the bilayers, tryptophan dioxidation and indole ring opening leads to the loss of essential interactions for enzyme binding and, consequently, enzyme inactivation.

Evaluation of cold atmospheric-pressure plasma against burn wound infections and gene silencing

Background and Objectives

Non-thermal atmospheric-pressure plasma or cold plasma is defined as an ionized gas. This study aimed to investigate the effect of cold plasma on Pseudomonas aeruginosa strains. Also, the expression level of the alp virulence gene before and after treatment with cold plasma was compared with the Housekeeping gene gyrA.

Materials and Methods

P. aeruginosa isolates recovered from hospitalized burn patients at Shahid Motahari Burns Hospital, Tehran, Iran. The Kirby Bauer disk diffusion method was used to determine the antimicrobial susceptibility test. Then, the antibacterial effect of atmospheric non-thermal plasma was evaluated on P. aeruginosa in as in vitro and in vivo studies at different times on Muller Hinton agar and in mouse model (treated by plasma every day/ 90 sec). The histopathological study was evaluated by Hematoxylin-Eosin staining. Data were analyzed using SPSS software by the Chi-square test and Pvalues less than 0.05 considered as statistically significant.

Results

Results indicated that non-thermal atmospheric plasma inhibited the growth of P. aeruginosa. The non-thermal helium plasma accelerates wound healing for 6 days. Results showed that cold plasma decreased virulence gene expression alp after treatment. Therefore, cold plasma can be suggested as a complementary therapeutic protocol to reduce bacterial infection and accelerate wound healing and reduce the expression of virulence genes of pathogens.

Conclusion

Cold plasma showed pathogen inhibitory properties of P. aeruginosa and virulence alkaline protease and wound healing properties in animal models, so this inexpensive and suitable method can be presented to the medical community to disinfect burn wounds and improve wound healing.

[Wound therapy with cold atmospheric plasma in severe recessive dystrophic epidermolysis bullosa : A pilot study]

BACKGROUND

Cold atmospheric pressure plasma (CAP) has antimicrobial and wound-healing properties. Patients affected by severe autosomal recessive dystrophic epidermolysis bullosa (RDEB) suffer from widespread, difficult-to-treat wounds, which require complex wound management.

OBJECTIVE

In a pilot project, we investigated over a period of 5 months the response and tolerability of a CAP wound therapy in a 21-year-old and a 28-year-old female patient with severe generalized RDEB and following cutaneous squamous cell cancer (cSSC) in the older patient.

MATERIALS AND METHODS

In both patients, diagnosis of RDEB was confirmed by molecular genetics. Individual- and patient-specific wound therapy was continued during the study period, and additionally CAP therapy with a dielectric barrier discharge (DBE) device was initiated. CAP treatment was performed for 90 s per wound and could be applied every day or every other day. Clinical evaluation included photographic documentation and regular interviews of patients and parents.

RESULTS

CAP-treated wounds largely demonstrated improved wound healing and signs of a reduced bacterial contamination. Furthermore, CAP proved to prevent wound chronification. When applied on a polyester mesh, it was well-tolerated on most body sites.

CONCLUSION

The introduction of CAP could improve the wound management of EB patients and should be evaluated in clinical studies. The effect of CAP on cSSC development should be particularly studied.

Canady Helios Cold Plasma Induces Breast Cancer Cell Death by Oxidation of Histone mRNA

Breast cancer is the most common cancer among women worldwide. Its molecular receptor marker status and mutational subtypes complicate clinical therapies. Cold atmospheric plasma is a promising adjuvant therapy to selectively combat many cancers, including breast cancer, but not normal tissue; however, the underlying mechanisms remain unexplored. Here, four breast cancer cell lines with different marker status were treated with Canady Helios Cold Plasma™ (CHCP) at various dosages and their differential progress of apoptosis was monitored. Inhibition of cell proliferation, induction of apoptosis, and disruption of the cell cycle were observed. At least 16 histone mRNA types were oxidized and degraded immediately after CHCP treatment by 8-oxoguanine (8-oxoG) modification. The expression of DNA damage response genes was up-regulated 12 h post-treatment, indicating that 8-oxoG modification and degradation of histone mRNA during the early S phase of the cell cycle, rather than DNA damage, is the primary cause of cancer cell death induced by CHCP. Our report demonstrates for the first time that CHCP effectively induces cell death in breast cancer regardless of subtyping, through histone mRNA oxidation and degradation during the early S phase of the cell cycle.

Epithelial-to-Mesenchymal Transition Enhances Cancer Cell Sensitivity to Cytotoxic Effects of Cold Atmospheric Plasmas in Breast and Bladder Cancer Systems

Cold atmospheric plasma (CAP) has emerged as a highly selective anticancer agent, most recently in the form of plasma-activated medium (PAM). Since epithelial-mesenchymal transition (EMT) has been implicated in resistance to various cancer therapies, we assessed whether EMT status is associated with PAM response. Mesenchymal breast cancer cell lines, as well as the mesenchymal variant in an isogenic EMT/MET human breast cancer cell system (PMC42-ET/LA), were more sensitive to PAM treatment than their epithelial counterparts, contrary to their responses to other therapies. The same trend was seen in luminal muscle-invasive bladder cancer model (TSU-Pr1/B1/B2) and the non-muscle-invasive basal 5637 bladder cancer cell line. Three-dimensional spheroid cultures of the bladder cancer cell lines were less sensitive to the PAM treatment compared to their two-dimensional counterparts; however, incrementally better responses were again seen in more mesenchymally-shifted cell lines. This study provides evidence that PAM preferentially inhibits mesenchymally-shifted carcinoma cells, which have been associated with resistance to other therapies. Thus, PAM may represent a novel treatment that can selectively inhibit triple-negative breast cancers and a subset of aggressive bladder cancers, which tend to be more mesenchymal. Our approach may potentially be utilized for other aggressive cancers exhibiting EMT and opens new opportunities for CAP and PAM as a promising new onco-therapy.

Cold Atmospheric Plasma (CAP) for the Treatment of Actinic Keratosis and Skin Field Cancerization: Clinical and High-Frequency Ultrasound Evaluation

INTRODUCTION

Cold atmospheric plasma (CAP) has been clinically demonstrated to be an effective treatment for actinic keratosis (AK) in a number of case series. In this study, we evaluated the efficacy of CAP in the treatment of multiple AKs and assessed morphological changes induced on the skin field of cancerization both clinically and by high-frequency ultrasound (HFUS).

METHODS

Patients with multiple grade I-II AKs of the scalp and/or face who were resistant or intolerant to conventional field-directed treatments were enrolled. CAP treatments were performed using a microwave-driven argon plasma jet. At baseline and 3 months after the last CAP session, performance indexes were determined using three-dimensional digital pictures and HFUS investigations were performed on a representative Olsen grade II AK and a small spot of clinically unaffected skin within the test area.

RESULTS

Twelve patients were enrolled in the study. All clinical variables showed a statistically significant reduction after CAP. HFUS evaluation revealed that the total, epidermal and dermal thicknesses of the target AKs had not changed with treatment. CAP therapy significantly increased dermal density in both the target AK and the surrounding photodamaged skin and signficantly decreased the thickness of the subepidermal low-echogenic band in the perilesional skin, which is an ultrasound sign of photodamage.

CONCLUSIONS

Cold atmospheric plasma was found to be an effective treatment for patients with multiple AKs. CAP was not followed by skin atrophy. HFUS examiniation showed the CAP improved features of chronic photodamage of the dermis of the skin underlying and surrounding the AK spots.

Aquaporin 4 and brain-related disorders: Insights into its apoptosis roles

Brain-related disorders are leading global health problems. Various internal and external factors are involved in the progression of brain-related disorders. Inflammatory pathways, oxidative stresses, apoptosis, and deregulations of various channels are critical players in brain-related disorder pathogenesis. Among these players, aquaporins (AQP) have critical roles in various physiological and pathological conditions. AQPs are water channel molecules that permit water to cross the hydrophobic lipid bilayers of cellular membranes. AQP4 is one of the important members of AQP family. AQPs are involved in controlling apoptosis pathways in brain-related disorders. In this regard, several reports have evaluated the pathological effects of AQP4 by targeting the apoptosis-related processes in brain-related disorders. Here, for the first time, we highlight the impact of AQP4 on apoptosis-related processes in brain-related disorders.

Differential Effect of Non-Thermal Plasma RONS on Two Human Leukemic Cell Populations

Simple Summary

As the number of investigations into the use of non-thermal plasma (NTP) for cancer treatment expands, it is becoming apparent that susceptibility of different cancer cells to NTP varies. We hypothesized that such differences could be attributed to the cell type-dependent interactions between NTP-generated reactive oxygen and nitrogen species (RONS) and the target cells. To test this hypothesis, we examined how two different human leukemic cell lines—Jurkat T lymphocytes and THP-1 monocytes—influence hydrogen peroxide and nitrite content in media after NTP exposure. We also assessed the potential of NTP to enhance immunogenicity in these cells and assayed phagocytosis of NTP-exposed leukemic cells by macrophages. Our results highlight the significance of target-mediated modulation of plasma chemical species in the development and clinical use of protocols involving plasma sources for use in cancer therapeutic application.

Abstract

Non-thermal plasma application to cancer cells is known to induce oxidative stress, cytotoxicity and indirect immunostimulatory effects on antigen presenting cells (APCs). The purpose of this study was to evaluate the responses of two leukemic cell lines—Jurkat T lymphocytes and THP-1 monocytes—to NTP-generated reactive oxygen and nitrogen species (RONS). Both cell types depleted hydrogen peroxide, but THP-1 cells neutralized it almost immediately. Jurkat cells transiently blunted the frequency-dependent increase in nitrite concentrations in contrast to THP-1 cells, which exhibited no immediate effect. A direct relationship between frequency-dependent cytotoxicity and mitochondrial superoxide was observed only in Jurkat cells. Jurkat cells were very responsive to NTP in their display of calreticulin and heat shock proteins 70 and 90. In contrast, THP-1 cells were minimally responsive or unresponsive. Despite no NTP-dependent decrease in cell surface display of CD47 in either cell line, both cell types induced migration of and phagocytosis by APCs. Our results demonstrate that cells modulate the RONS-mediated changes in liquid chemistry, and, importantly, the resultant immunomodulatory effects of NTP can be independent of NTP-induced cytotoxicity.

Plasma-Treated Solutions (PTS) in Cancer Therapy

Simple Summary

Cold physical plasma is a partially ionized gas generating various reactive oxygen and nitrogen species (ROS/RNS) simultaneously. ROS/RNS have therapeutic effects when applied to cells and tissues either directly from the plasma or via exposure to solutions that have been treated beforehand using plasma processes. This review addresses the challenges and opportunities of plasma-treated solutions (PTSs) for cancer treatment.

Abstract

Cold physical plasma is a partially ionized gas generating various reactive oxygen and nitrogen species (ROS/RNS) simultaneously. ROS/RNS have therapeutic effects when applied to cells and tissues either directly from the plasma or via exposure to solutions that have been treated beforehand using plasma processes. This review addresses the challenges and opportunities of plasma-treated solutions (PTSs) for cancer treatment. These PTSs include plasma-treated cell culture media in experimental research as well as clinically approved solutions such as saline and Ringer’s lactate, which, in principle, already qualify for testing in therapeutic settings. Several types of cancers were found to succumb to the toxic action of PTSs, suggesting a broad mechanism of action based on the tumor-toxic activity of ROS/RNS stored in these solutions. Moreover, it is indicated that the PTS has immuno-stimulatory properties. Two different routes of application are currently envisaged in the clinical setting. One is direct injection into the bulk tumor, and the other is lavage in patients suffering from peritoneal carcinomatosis adjuvant to standard chemotherapy. While many promising results have been achieved so far, several obstacles, such as the standardized generation of large volumes of sterile PTS, remain to be addressed.

Argon Plasma Exposure Augments Costimulatory Ligands and Cytokine Release in Human Monocyte-Derived Dendritic Cells

Cold physical plasma is a partially ionized gas expelling many reactive oxygen and nitrogen species (ROS/RNS). Several plasma devices have been licensed for medical use in dermatology, and recent experimental studies suggest their putative role in cancer treatment. In cancer therapies with an immunological dimension, successful antigen presentation and inflammation modulation is a key hallmark to elicit antitumor immunity. Dendritic cells (DCs) are critical for this task. However, the inflammatory consequences of DCs following plasma exposure are unknown. To this end, human monocyte-derived DCs (moDCs) were expanded from isolated human primary monocytes; exposed to plasma; and their metabolic activity, surface marker expression, and cytokine profiles were analyzed. As controls, hydrogen peroxide, hypochlorous acid, and peroxynitrite were used. Among all types of ROS/RNS-mediated treatments, plasma exposure exerted the most notable increase of activation markers at 24 h such as CD25, CD40, and CD83 known to be crucial for T cell costimulation. Moreover, the treatments increased interleukin (IL)-1α, IL-6, and IL-23. Altogether, this study suggests plasma treatment augmenting costimulatory ligand and cytokine expression in human moDCs, which might exert beneficial effects in the tumor microenvironment.

Oxidative stress in bladder cancer: an ally or an enemy?

Bladder cancer (BC) is the most common cancer of the urinary tract and despite all innovations, remains a major challenge due to high morbidity and mortality. Genomic and epigenetic analyses allowed the discovery of new genes and pathways involved in the pathogenesis and regulation of BC. However, the effect on mortality has been modest and the development of new targets for BC treatment are needed. Recent evidence suggests that cancer cells are under increased stress associated with oncogenic transformation, with changes in metabolic activity and increased generation of reactive oxygen species (ROS). The increased amounts of ROS in cancer cells are associated with stimulation of cellular proliferation, promotion of mutations and genetic instability, as well as alterations in cellular sensitivity to anticancer agents. Since these mechanisms occur in cancer cells, there is a close link between oxidative stress (OS) and BC with implications in prevention, carcinogenesis, prognosis, and treatment. We address the role of OS as an enemy towards BC development, as well as an ally to fight against BC. This review promises to expand our treatment options for BC with OS-based therapies and launches this approach as an opportunity to improve our ability to select patients most likely to respond to personalized therapy.

Plasma Treatment of Fish Cells: The Importance of Defining Cell Culture Conditions in Comparative Studies

The present study provides the fundamental results for the treatment of marine organisms with cold atmospheric pressure plasma. In farmed fish, skin lesions may occur as a result of intensive fish farming. Cold atmospheric plasma offers promising medical potential in wound healing processes. Since the underlying plasma-mediated mechanisms at the physical and cellular level are yet to be fully understood, we investigated the sensitivity of three fish cell lines to plasma treatment in comparison with mammalian cells. We varied (I) cell density, (II) culture medium, and (III) pyruvate concentration in the medium as experimental parameters. Depending on the experimental setup, the plasma treatment affected the viability of the different cell lines to varying degrees. We conclude that it is mandatory to use similar cell densities and an identical medium, or at least a medium with identical antioxidant capacity, when studying plasma effects on different cell lines. Altogether, fish cells showed a higher sensitivity towards plasma treatment than mammalian cells in most of our setups. These results should increase the understanding of the future treatment of fish.

Atmospheric Pressure Plasma Irradiation Facilitates Transdermal Permeability of Aniline Blue on Porcine Skin and the Cellular Permeability of Keratinocytes with the Production of Nitric Oxide

The transdermal delivery system of nutrients, cosmetics, and drugs is particularly attractive for painless, noninvasive delivery and sustainable release. Recently, atmospheric pressure plasma techniques have been of great interest to improve the drug absorption rate in transdermal delivery. Currently, plasma-mediated changes in the lipid composition of the stratum corneum are considered a possible mechanism to increase transdermal permeability. Nevertheless, its molecular and cellular mechanisms in transdermal delivery have been largely confined and still veiled. Herein, we present the effects of cold plasma on transdermal transmission on porcine skin and the cellular permeability of keratinocytes and further demonstrate the production of nitric oxide from keratinocytes. Consequently, argon plasma irradiation for 60 s resulted in 2.5-fold higher transdermal absorption of aniline blue dye on porcine skin compared to the nontreated control. In addition, the plasma-treated keratinocytes showed an increased transmission of high-molecular-weight molecules (70 and 150 kDa) with the production of nitric oxide. Therefore, these findings suggest a promoting effect of low-temperature plasma on transdermal absorption, even for high-molecular-weight molecules. Moreover, plasma-induced nitric oxide from keratinocytes is likely to regulate transdermal permeability in the epidermal layer.

Applications of Cold Atmospheric Pressure Plasma in Dentistry

Plasma is an electrically conducting medium that responds to electric and magnetic fields. It consists of large quantities of highly reactive species, such as ions, energetic electrons, exited atoms and molecules, ultraviolet photons, and metastable and active radicals. Non-thermal or cold plasmas are partially ionized gases whose electron temperatures usually exceed several tens of thousand degrees K, while the ions and neutrals have much lower temperatures. Due to the presence of reactive species at low temperature, the biological effects of non-thermal plasmas have been studied for application in the medical area with promising results. This review outlines the application of cold atmospheric pressure plasma (CAPP) in dentistry for the control of several pathogenic microorganisms, induction of anti-inflammatory, tissue repair effects and apoptosis of cancer cells, with low toxicity to healthy cells. Therefore, CAPP has potential to be applied in many areas of dentistry such as cariology, periodontology, endodontics and oral oncology.

Cold Atmospheric Plasma: A New Strategy Based Primarily on Oxidative Stress for Osteosarcoma Therapy

Osteosarcoma is the most common primary bone tumor, and its first line of treatment presents a high failure rate. The 5-year survival for children and teenagers with osteosarcoma is 70% (if diagnosed before it has metastasized) or 20% (if spread at the time of diagnosis), stressing the need for novel therapies. Recently, cold atmospheric plasmas (ionized gases consisting of UV-Vis radiation, electromagnetic fields and a great variety of reactive species) and plasma-treated liquids have been shown to have the potential to selectively eliminate cancer cells in different tumors through an oxidative stress-dependent mechanism. In this work, we review the current state of the art in cold plasma therapy for osteosarcoma. Specifically, we emphasize the mechanisms unveiled thus far regarding the action of plasmas on osteosarcoma. Finally, we review current and potential future approaches, emphasizing the most critical challenges for the development of osteosarcoma therapies based on this emerging technique.

Protective Role of Sphingomyelin in Eye Lens Cell Membrane Model against Oxidative Stress

In the eye lens cell membrane, the lipid composition changes during the aging process: the proportion of sphingomyelins (SM) increases, that of phosphatidylcholines decreases. To investigate the protective role of the SMs in the lens cell membrane against oxidative damage, analytical techniques such as electrochemistry, high-resolution mass spectrometry (HR-MS), and atomic force microscopy (AFM) were applied. Supported lipid bilayers (SLB) were prepared to mimic the lens cell membrane with different fractions of PLPC/SM (PLPC: 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine). The SLBs were treated with cold physical plasma. A protective effect of 30% and 44% in the presence of 25%, and 75% SM in the bilayer was observed, respectively. PLPC and SM oxidation products were determined via HR-MS for SLBs after plasma treatment. The yield of fragments gradually decreased as the SM ratio increased. Topographic images obtained by AFM of PLPC-bilayers showed SLB degradation and pore formation after plasma treatment, no degradation was observed in PLPC/SM bilayers. The results of all techniques confirm the protective role of SM in the membrane against oxidative damage and support the idea that the SM content in lens cell membrane is increased during aging in the absence of effective antioxidant systems to protect the eye from oxidative damage and to prolong lens transparency.

Role of Short- and Long-Lived Reactive Species on the Selectivity and Anti-Cancer Action of Plasma Treatment In Vitro

Simple Summary

One fundamental feature that has emerged from in vitro application of cold plasmas in cancer treatment is the key role of the liquid phase covering the cells. In the present work, we investigated the effect of direct and indirect plasma treatments on two cancer and three normal cell lines to assess the benefits of one treatment over the other in terms of death of tumor versus healthy cells. Our results demonstrate that indirect plasma treatment is as efficient at killing tumor cells as an appropriate combination of H₂O₂, NO₂⁻ and acidic pH in ad hoc solutions, while sparing normal cells. However, direct plasma treatment is far more efficient at killing normal than tumor cells, and we provide evidence that short- and long-lived reactive species contribute synergistically to kill normal cells, while having an additive effect regarding tumor cell death. Collectively, our results call the use of plasma-activated liquid in cancer treatment into question.

Abstract

(1) Plasma-activated liquids (PAL) have been extensively studied for their anti-cancer properties. Two treatment modalities can be applied to the cells, direct and indirect plasma treatments, which differ by the environment to which the cells are exposed. For direct plasma treatment, the cells covered by a liquid are present during the plasma treatment time (phase I, plasma ON) and the incubation time (phase II, plasma OFF), while for indirect plasma treatment, phase I is cell-free and cells are only exposed to PAL during phase II. The scope of this work was to study these two treatment modalities to bring new insights into the potential use of PAL for cancer treatment. (2) We used two models of head and neck cancer cells, CAL27 and FaDu, and three models of normal cells (1Br3, NHK, and RPE-hTERT). PBS was used as the liquid of interest, and the concentration of plasma-induced H₂O₂, NO₂⁻ and NO₃⁻, as well as pH change, were measured. Cells were exposed to direct plasma treatment, indirect plasma treatment or reconstituted buffer (PBS adjusted with plasma-induced concentrations of H₂O₂, NO₂⁻, NO₃⁻ and pH). Metabolic cell activity, cell viability, lipid peroxidation, intracellular ROS production and caspase 3/7 induction were quantified. (3) If we showed that direct plasma treatment is slightly more efficient than indirect plasma treatment and reconstituted buffer at inducing lipid peroxidation, intracellular increase of ROS and cancer cell death in tumor cells, our data also revealed that reconstituted buffer is equivalent to indirect plasma treatment. In contrast, normal cells are quite insensitive to these two last treatment modalities. However, they are extremely sensitive to direct plasma treatment. Indeed, we found that phase I and phase II act in synergy to trigger cell death in normal cells and are additive concerning tumor cell death. Our data also highlight the presence in plasma-treated PBS of yet unidentified short-lived reactive species that contribute to cell death. (4) In this study, we provide strong evidence that, in vitro, the concentration of RONS (H₂O₂, NO₂⁻ and NO₃⁻) in combination with the acidic pH are the main drivers of plasma-induced PBS toxicity in tumor cells but not in normal cells, which makes ad hoc reconstituted solutions powerful anti-tumor treatments. In marked contrast, direct plasma treatment is deleterious for normal cells in vitro and should be avoided. Based on our results, we discuss the limitations to the use of PAL for cancer treatments.

Cold Atmospheric Plasma, a Novel Approach against Bladder Cancer, with Higher Sensitivity for the High-Grade Cell Line

Simple Summary

Bladder cancer has a high incidence and mortality. Besides this, currently available therapies for this type of cancer have low efficacy and show considerable adverse effects, urging the need of new therapeutic approaches. Cold Atmospheric Plasma treatment presents itself as a promising alternative, having demonstrated antitumor effects against several types of cancer. The present work arises from a multidisciplinary team, namely, medical doctors and researchers, in an attempt to find new therapeutic strategies to fight bladder cancer. Therefore, our main objective is to evaluate Cold Atmospheric Plasma effects against bladder cancer, as well as the mechanisms by which it exerts its effects. The results obtained demonstrate that Cold Atmospheric Plasma treatment has a promising antitumor effect on bladder cancer, with higher sensitivity for the high-grade cell line. This new approach using Cold Atmospheric Plasma for the treatment of bladder cancer presents enormous clinical benefits, since it is able to selectively treat the tumor tissue, sparing the normal urothelium, with an additional glaring positive economic impact, since it entails a decrease in the cost of therapy in comparison with conventional therapeutic options.

Abstract

Antitumor therapies based on Cold Atmospheric Plasma (CAP) are an emerging medical field. In this work, we evaluated CAP effects on bladder cancer. Two bladder cancer cell lines were used, HT-1376 (stage III) and TCCSUP (stage IV). Cell proliferation assays were performed evaluating metabolic activity (MTT assay) and protein content (SRB assay). Cell viability, cell cycle, and mitochondrial membrane potential (Δψ_m) were assessed using flow cytometry. Reactive oxygen and nitrogen species (RONS) and reduced glutathione (GSH) were evaluated by fluorescence. The assays were carried out with different CAP exposure times. For both cell lines, we obtained a significant reduction in metabolic activity and protein content. There was a decrease in cell viability, as well as a cell cycle arrest in S phase. The Δψ_m was significantly reduced. There was an increase in superoxide and nitric oxide and a decrease in peroxide contents, while GSH content did not change. These results were dependent on the exposure time, with small differences for both cell lines, but overall, they were more pronounced in the TCCSUP cell line. CAP showed to have a promising antitumor effect on bladder cancer, with higher sensitivity for the high-grade cell line.

Gas plasma irradiation of breast cancers promotes immunogenicity, tumor reduction, and an abscopal effect in vivo

While many new and emerging therapeutic concepts have appeared throughout the last decades, cancer still is fatal in many patients. At the same time, the importance of immunology in oncotherapy is increasingly recognized, not only since the advent of checkpoint therapy. Among the many types of tumors, also breast cancer has an immunological dimension that might be exploited best by increasing the immunogenicity of the tumors in the microenvironment. To this end, we tested a novel therapeutic concept, gas plasma irradiation, for its ability to promote the immunogenicity and increase the toxicity of breast cancer cells in vitro and in vivo. Mechanistically, this emerging medical technology is employing a plethora of reactive oxygen species being deposited on the target cells and tissues. Using 2D cultures and 3D tumor spheroids, we found gas plasma-irradiation to drive apoptosis and immunogenic cancer cell death (ICD) in vitro, as evidenced by an increased expression of calreticulin, heat-shock proteins 70 and 90, and MHC-I. In 4T1 breast cancer-bearing mice, the gas plasma irradiation markedly decreased tumor burden and increased survival. Interestingly, non-treated tumors injected in the opposite flank of mice exposed to our novel treatment also exhibited reduced growth, arguing for an abscopal effect. This was concomitant with an increase of apoptosis and tumor-infiltrating CD4⁺ and CD8⁺ T-cells as well as dendritic cells in the tissues. In summary, we found gas plasma-irradiated murine breast cancers to induce toxicity and augmented immunogenicity, leading to reduced tumor growth at a site remote to the treatment area.

On the Liquid Chemistry of the Reactive Nitrogen Species Peroxynitrite and Nitrogen Dioxide Generated by Physical Plasmas

Cold physical plasmas modulate cellular redox signaling processes, leading to the evolution of a number of clinical applications in recent years. They are a source of small reactive species, including reactive nitrogen species (RNS). Wound healing is a major application and, as its physiology involves RNS signaling, a correlation between clinical effectiveness and the activity of plasma-derived RNS seems evident. To investigate the type and reactivity of plasma-derived RNS in aqueous systems, a model with tyrosine as a tracer was utilized. By high-resolution mass spectrometry, 26 different tyrosine derivatives including the physiologic nitrotyrosine were identified. The product pattern was distinctive in terms of plasma parameters, especially gas phase composition. By scavenger experiments and isotopic labelling, gaseous nitric dioxide radicals and liquid phase peroxynitrite ions were determined as dominant RNS. The presence of water molecules in the active plasma favored the generation of peroxynitrite. A pilot study, identifying RNS driven post-translational modifications of proteins in healing human wounds after the treatment with cold plasma (kINPen), demonstrated the presence of in vitro determined chemical pathways. The plasma-driven nitration and nitrosylation of tyrosine allows the conclusion that covalent modification of biomolecules by RNS contributes to the clinically observed impact of cold plasmas.

Nonenzymatic post-translational modifications in peptides by cold plasma-derived reactive oxygen and nitrogen species

Cold physical plasmas are emerging tools for wound care and cancer control that deliver reactive oxygen species (ROS) and nitrogen species (RNS). Alongside direct effects on cellular signaling processes, covalent modification of biomolecules may contribute to the observed physiological consequences. The potential of ROS/RNS generated by two different plasma sources (kINPen and COST-Jet) to introduce post-translational modifications (PTMs) in the peptides angiotensin and bradykinin was explored. While the peptide backbone was kept intact, a significant introduction of oxidative PTMs was observed. The modifications cluster at aromatic (tyrosine, histidine, and phenylalanine) and neutral amino acids (isoleucine and proline) with the introduction of one, two, or three oxygen atoms, ring cleavages of histidine and tryptophan, and nitration/nitrosylation predominantly observed. Alkaline and acidic amino acid (arginine and aspartic acid) residues showed a high resilience, indicating that local charges and the chemical environment at large modulate the attack of the electron-rich ROS/RNS. Previously published simulations, which include only OH radicals as ROS, do not match the experimental results in full, suggesting the contribution of other short-lived species, i.e., atomic oxygen, singlet oxygen, and peroxynitrite. The observed PTMs are relevant for the biological activity of peptides and proteins, changing polarity, folding, and function. In conclusion, it can be assumed that an introduction of covalent oxidative modifications at the amino acid chain level occurs during a plasma treatment. The introduced changes, in part, mimic naturally occurring patterns that can be interpreted by the cell, and subsequently, these PTMs allow for prolonged secondary effects on cell physiology.

Advances in Plasma Oncology toward Clinical Translation

This Special Issue on "Advances in Plasma Oncology Toward Clinical Translation" aims to bring together cutting-edge research papers within the field in the context of clinical translation and application [...].

A combination of electrochemistry and mass spectrometry to monitor the interaction of reactive species with supported lipid bilayers

Reactive oxygen and nitrogen species (RONS), e.g. generated by cold physical plasma (CPP) or photodynamic therapy, interfere with redox signaling pathways of mammalian cells, inducing downstream consequences spanning from migratory impairment to apoptotic cell death. However, the more austere impact of RONS on cancer cells remains yet to be clarified. In the present study, a combination of electrochemistry and high-resolution mass spectrometry was developed to investigate the resilience of solid-supported lipid bilayers towards plasma-derived reactive species in dependence of their composition. A 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer was undisturbed by 200 µM H2O2 (control) but showed full permeability after CPP treatment and space-occupying oxidation products such as PoxnoPC, PAzePC, and POPC hydroperoxide were found. Electron paramagnetic resonance spectroscopy demonstrated the presence of hydroxyl radicals and superoxide anion/hydroperoxyl radicals during the treatment. In contrast, small amounts of the intramembrane antioxidant coenzyme Q10 protected the bilayer to 50% and LysoPC was the only POPC derivative found, confirming the membrane protective effect of Q10. Such, the lipid membrane composition including the presence of antioxidants determines the impact of pro-oxidant signals. Given the differences in membrane composition of cancer and healthy cells, this supports the application of cold physical plasma for cancer treatment. In addition, the developed model using the combination of electrochemistry and mass spectrometry could be a promising method to study the effect of reactive species or mixes thereof generated by chemical or physical sources.

Cold Atmospheric Pressure Plasma (CAP) as a New Tool for the Management of Vulva Cancer and Vulvar Premalignant Lesions in Gynaecological Oncology

Vulvar cancer (VC) is a specific form of malignancy accounting for 5–6% of all gynaecologic malignancies. Although VC occurs most commonly in women after 60 years of age, disease incidence has risen progressively in premenopausal women in recent decades. VC demonstrates particular features requiring well-adapted therapeutic approaches to avoid potential treatment-related complications. Significant improvements in disease-free survival and overall survival rates for patients diagnosed with post-stage I disease have been achieved by implementing a combination therapy consisting of radical surgical resection, systemic chemotherapy and/or radiotherapy. Achieving local control remains challenging. However, mostly due to specific anatomical conditions, the need for comprehensive surgical reconstruction and frequent post-operative healing complications. Novel therapeutic tools better adapted to VC particularities are essential for improving individual outcomes. To this end, cold atmospheric plasma (CAP) treatment is a promising option for VC, and is particularly appropriate for the local treatment of dysplastic lesions, early intraepithelial cancer, and invasive tumours. In addition, CAP also helps reduce inflammatory complications and improve wound healing. The application of CAP may realise either directly or indirectly utilising nanoparticle technologies. CAP has demonstrated remarkable treatment benefits for several malignant conditions, and has created new medical fields, such as “plasma medicine” and “plasma oncology”. This article highlights the benefits of CAP for the treatment of VC, VC pre-stages, and postsurgical wound complications. There has not yet been a published report of CAP on vulvar cancer cells, and so this review summarises the progress made in gynaecological oncology and in other cancers, and promotes an important, understudied area for future research. The paradigm shift from reactive to predictive, preventive and personalised medical approaches in overall VC management is also considered.

Enhanced Generation of Reactive Species by Cold Plasma in Gelatin Solutions for Selective Cancer Cell Death

Atmospheric pressure plasma jets generate reactive oxygen and nitrogen species (RONS) in liquids and biological media, which find application in the new area of plasma medicine. These plasma-treated liquids were demonstrated recently to possess selective properties on killing cancer cells and attracted attention toward new plasma-based cancer therapies. These allow for local delivery by injection in the tumor but can be quickly washed away by body fluids. By confining these RONS in a suitable biocompatible delivery system, great perspectives can be opened in the design of novel biomaterials aimed for cancer therapies. Gelatin solutions are evaluated here to store RONS generated by atmospheric pressure plasma jets, and their release properties are evaluated. The concentration of RONS was studied in 2% gelatin as a function of different plasma parameters (treatment time, nozzle distance, and gas flow) with two different plasma jets. Much higher production of reactive species (H₂O₂ and NO₂^-) was revealed in the polymer solution than in water after plasma treatment. The amount of RONS generated in gelatin is greatly improved with respect to water, with concentrations of H₂O₂ and NO₂^- between 2 and 12 times higher for the longest plasma treatments. Plasma-treated gelatin exhibited the release of these RONS to a liquid media, which induced an effective killing of bone cancer cells. Indeed, in vitro studies on the sarcoma osteogenic (SaOS-2) cell line exposed to plasma-treated gelatin led to time-dependent increasing cytotoxicity with the longer plasma treatment time of gelatin. While the SaOS-2 cell viability decreased to 12%-23% after 72 h for cells exposed to 3 min of treated gelatin, the viability of healthy cells (hMSC) was preserved (∼90%), establishing the selectivity of the plasma-treated gelatin on cancer cells. This sets the basis for designing improved hydrogels with high capacity to deliver RONS locally to tumors.

Cold Atmospheric Pressure Plasma in Wound Healing and Cancer Treatment

Plasma medicine is gaining increasing attention and is moving from basic research into clinical practice. While areas of application are diverse, much research has been conducted assessing the use of cold atmospheric pressure plasma (CAP) in wound healing and cancer treatment—two applications with entirely different goals. In wound healing, a tissue-stimulating effect is intended, whereas cancer therapy aims at killing malignant cells. In this review, we provide an overview of the latest clinical and some preclinical research on the efficacy of CAP in wound healing and cancer therapy. Furthermore, we discuss the current understanding of molecular signaling mechanisms triggered by CAP that grant CAP its antiseptic and tissue regenerating or anti-proliferative and cell death-inducing properties. For the efficacy of CAP in wound healing, already substantial evidence from clinical studies is available, while evidence for therapeutic effects of CAP in oncology is mainly from in vitro and in vivo animal studies. Efforts to elucidate the mode of action of CAP suggest that different components, such as ultraviolet (UV) radiation, electromagnetic fields, and reactive species, may act synergistically, with reactive species being regarded as the major effector by modulating complex and concentration-dependent redox signaling pathways.

Inhibition of Angiogenesis by Treatment with Cold Atmospheric Plasma as a Promising Therapeutic Approach in Oncology

Background: Cold atmospheric plasma (CAP) is increasingly used in the field of oncology. Many of the mechanisms of action of CAP, such as inhibiting proliferation, DNA breakage, or the destruction of cell membrane integrity, have been investigated in many different types of tumors. In this regard, data are available from both in vivo and in vitro studies. Not only the direct treatment of a tumor but also the influence on its blood supply play a decisive role in the success of the therapy and the patient’s further prognosis. Whether the CAP influences this process is unknown, and the first indications in this regard are addressed in this study. Methods: Two different devices, kINPen and MiniJet, were used as CAP sources. Human endothelial cell line HDMEC were treated directly and indirectly with CAP, and growth kinetics were performed. To indicate apoptotic processes, caspase-3/7 assay and TUNEL assay were used. The influence of CAP on cellular metabolism was examined using the MTT and glucose assay. After CAP exposure, tube formation assay was performed to examine the capillary tube formation abilities of HDMEC and their migration was messured in separate assays. To investigate in a possible mutagenic effect of CAP treatment, a hypoxanthine-guanine-phosphoribosyl-transferase assay with non malignant cell (CCL-93) line was performed. Results: The direct CAP treatment of the HDMEC showed a robust growth-inhibiting effect, but the indirect one did not. The MMT assay showed an apparent reduction in cell metabolism in the first 24 h after CAP treatment, which appeared to normalize 48 h and 72 h after CAP application. These results were also confirmed by the glucose assay. The caspase 3/7 assay and TUNEL assay showed a significant increase in apoptotic processes in the HDMEC after CAP treatment. These results were independent of the CAP device. Both the migration and tube formation of HDMEC were significant inhibited after CAP-treatment. No malignant effects could be demonstrated by the CAP treatment on a non-malignant cell line.

Cold atmospheric pressure (physical) plasma in dermatology: where are we today?

Cold atmospheric pressure plasma is physical plasma (essentially ionized gas) created at room temperature and atmospheric pressure, and it has complex effects on cells, tissues, and living organisms. These effects are studied extensively for medical and dermatological use. This article reviews current achievements and new trends in clinical dermatological cold plasma research, discusses the basics of plasma physics and plasma engineering, and describes the most important areas of laboratory plasma research to provide a well-rounded understanding of the nature, present applications, and future promise of this exciting, emerging technology.

Cancer treatment with gas plasma and with gas plasma-activated liquid: positives, potentials and problems of clinical translation

Gas plasmas, created in atmospheric pressure conditions, both thermal (hot) and non-thermal (cold) are emerging as useful tools in medicine. During surgery, hot gas plasmas are useful to reduce thermal damage and seal blood vessels. Gas plasma pens use cold gas plasma to produce reactive chemical species with selective action against cancers, which can be readily exposed in surgery or treated from outside of the body. Solutions activated by cold gas plasma have potential as a novel treatment modality for treatment of less readily accessible tumours, or those with high metastatic potential. This review summarises the preclinical and clinical trial evidence currently available, as well as the challenges for translation of direct gas plasma and gas plasma-activated solution treatment into regular practice.

The Emerging Role of Cold Atmospheric Plasma in Implantology: A Review of the Literature

In recent years, cold atmospheric plasma (CAP) technologies have received increasing attention in the field of biomedical applications. The aim of this article is to review the currently available literature to provide an overview of the scientific principles of CAP application, its features, functions, and its applications in systemic and oral diseases, with a specific focus on its potential in implantology. In this narrative review, PubMed, Medline, and Scopus databases were searched using key words like “cold atmospheric plasma”, “argon plasma”, “helium plasma”, “air plasma”, “dental implants”, “implantology”, “peri-implantitis”, “decontamination”. In vitro studies demonstrated CAP’s potential to enhance surface colonization and osteoblast activity and to accelerate mineralization, as well as to determine a clean surface with cell growth comparable to the sterile control on both titanium and zirconia surfaces. The effect of CAP on biofilm removal was revealed in comparative studies to the currently available decontamination modalities (laser, air abrasion, and chlorhexidine). The combination of mechanical treatments and CAP resulted in synergistic antimicrobial effects and surface improvement, indicating that it may play a central role in surface “rejuvenation” and offer a novel approach for the treatment of peri-implantitis. It is noteworthy that the CAP conditioning of implant surfaces leads to an improvement in osseointegration in in vivo animal studies. To the best of our knowledge, this is the first review of the literature providing a summary of the current state of the art of this emerging field in implantology and it could represent a point of reference for basic researchers and clinicians interested in approaching and testing new technologies.

The Hyaluronan Pericellular Coat and Cold Atmospheric Plasma Treatment of Cells

In different tumors, high amounts of hyaluronan (HA) are correlated with tumor progression. Therefore, new tumor therapy strategies are targeting HA production and degradation. In plasma medicine research, antiproliferative and apoptosis-inducing effects on tumor cells were observed using cold atmospheric plasma (CAP) or plasma-activated media (PAM). Until now, the influence of PAM on the HA pericellular coat has not been the focus of research. PAM was generated by argon-plasma treatment of Dulbecco’s modified Eagle’s Medium via the kINPen®09 plasma jet. The HA expression on PAM-treated HaCaT cells was determined by flow cytometry and confocal laser scanning microscopy. Changes in the adhesion behavior of vital cells in PAM were observed by impedance measurement using the xCELLigence system. We found that PAM treatment impaired the HA pericellular coat of HaCaT cells. The time-dependent adhesion was impressively diminished. However, a disturbed HA coat alone was not the reason for the inhibition of cell adhesion because cells enzymatically treated with HAdase did not lose their adhesion capacity completely. Here, we showed for the first time that the plasma-activated medium (PAM) was able to influence the HA pericellular coat.

Anticancer Effects of Cold Atmospheric Plasma in Canine Osteosarcoma Cells

Osteosarcoma is known to be one of the frequently occurring cancers in dogs. Its prognosis is usually very poor, with a high incidence of lung metastasis. Although radiation therapy has become a major therapeutic choice for canine osteosarcoma, the high costs and unexpected side effects prevent some patients from considering this treatment. Cold atmospheric plasma (CAP) is an ionized gas with high energy at low temperatures, and it produces reactive oxygen species that mediate many signaling pathways. Although many researchers have used CAP as an anticancer therapeutic approach in humans, its importance has been neglected in veterinary medicine. In this study, D-17 and DSN canine osteosarcoma cell lines were treated with CAP to observe its anticancer activity. By high-content screening and flow cytometry, CAP-treated cells showed growth arrest and apoptosis induction. Moreover, the osteosarcoma cells exhibited reduced migration and invasion activity when treated with CAP. Overall, CAP exerted an anticancer effect on canine osteosarcoma cell lines. CAP may have the potential to be used as a novel modality for treating cancer in veterinary medicine.

Large-Scale Image Analysis for Investigating Spatio-Temporal Changes in Nuclear DNA Damage Caused by Nitrogen Atmospheric Pressure Plasma Jets

The effective clinical application of atmospheric pressure plasma jet (APPJ) treatments requires a well-founded methodology that can describe the interactions between the plasma jet and a treated sample and the temporal and spatial changes that result from the treatment. In this study, we developed a large-scale image analysis method to identify the cell-cycle stage and quantify damage to nuclear DNA in single cells. The method was then tested and used to examine spatio-temporal distributions of nuclear DNA damage in two cell lines from the same anatomic location, namely the oral cavity, after treatment with a nitrogen APPJ. One cell line was malignant, and the other, nonmalignant. The results showed that DNA damage in cancer cells was maximized at the plasma jet treatment region, where the APPJ directly contacted the sample, and declined radially outward. As incubation continued, DNA damage in cancer cells decreased slightly over the first 4 h before rapidly decreasing by approximately 60% at 8 h post-treatment. In nonmalignant cells, no damage was observed within 1 h after treatment, but damage was detected 2 h after treatment. Notably, the damage was 5-fold less than that detected in irradiated cancer cells. Moreover, examining damage with respect to the cell cycle showed that S phase cells were more susceptible to DNA damage than either G1 or G2 phase cells. The proposed methodology for large-scale image analysis is not limited to APPJ post-treatment applications and can be utilized to evaluate biological samples affected by any type of radiation, and, more so, the cell-cycle classification can be used on any cell type with any nuclear DNA staining.

Combination Treatment with Cold Physical Plasma and Pulsed Electric Fields Augments ROS Production and Cytotoxicity in Lymphoma

New approaches in oncotherapy rely on the combination of different treatments to enhance the efficacy of established monotherapies. Pulsed electric fields (PEFs) are an established method (electrochemotherapy) for enhancing cellular drug uptake while cold physical plasma is an emerging and promising anticancer technology. This study aimed to combine both technologies to elucidate their cytotoxic potential as well as the underlying mechanisms of the effects observed. An electric field generator (0.9–1.0 kV/cm and 100-μs pulse duration) and an atmospheric pressure argon plasma jet were employed for the treatment of lymphoma cell lines as a model system. PEF but not plasma treatment induced cell membrane permeabilization. Additive cytotoxicity was observed for the metabolic activity and viability of the cells while the sequence of treatment in the combination played only a minor role. Intriguingly, a parallel combination was more effective compared to a 15-min pause between both treatment regimens. A combination effect was also found for lipid peroxidation; however, none could be observed in the cytosolic and mitochondrial reactive oxygen species (ROS) production. The supplementation with either antioxidant, a pan-caspase-inhibitor or a ferroptosis inhibitor, all partially rescued lymphoma cells from terminal cell death, which contributes to the mechanistic understanding of this combination treatment.

Special Issue “Plasma Technology for Biomedical Applications”

The use of plasmas for biomedical applications in encountering a growing interest, especially in the framework of so-called “plasma medicine”, which aims at exploiting the action of low-power, atmospheric pressure plasmas for therapeutic purposes [...]