Persistent effectivity of gas plasma-treated, long time-stored liquid on epithelial cell adhesion capacity and membrane morphology

Subcytotoxic transepidermal delivery using low intensity cold atmospheric plasma

Cold atmospheric plasma (CAP) has been utilized in various medical devices using its oxidative nature. Recent studies have provided evidence that CAP can facilitate the delivery of large, hydrophilic molecules through the epidermis to the dermis. On the other hand, a new approach called low-intensity CAP (LICAP) has been developed, allowing the plasma level to be controlled within a subtoxic range, thereby demonstrating various biological benefits without tissue damage. However, the ability of LICAP to enhance transepidermal delivery in sub-cytotoxic conditions has not been fully investigated. This study aims to determine the sub-cytotoxic range of exposure time for LICAP and, within the range, to investigate the effects of LICAP treatment on transepidermal drug delivery (TED) and mechanisms using human keratinocytes and a mouse model. For the in vitro studies, LICAP treatment was evaluated in human keratinocyte (HaCaT) cells by assessing reactive species production, DNA damage, and cytotoxicity profiles. Within the determined safety range, mechanistic analyses were conducted to examine LICAP-enhanced delivery pathways. mRNA expression and protein levels of tight and adherens junction genes were quantified, and changes in ultramicroscopic morphology of HaCaT monolayers were investigated. Intracellular delivery of fluorescein isothiocyanate (FITC)-dextran was also assessed. For the in vivo studies, E-cadherin expression and the transepidermal delivery (TED) of human epidermal growth factor (hEGF) were analyzed in LICAP-treated mouse dorsal skin. The upper safety range of LICAP exposure time, reducing cell viability by 70% (IC70 or LD30), was estimated at 34.3 s. Within the safety range, LICAP treatment downregulated multiple tight and adherens junction genes in HaCaT cells. Consistent with the in vitro results, the epidermal E-cadherin expression was reduced, and human epidermal growth factor (hEGF) was infiltrated in the dermis of the LICAP-treated mouse skin. Intercellular clefts were detected in the HaCaT cell monolayer immediately following LICAP treatment and intracellular delivery of FITC-dextran was confirmed after LICAP exposure. This study demonstrated that LICAP treatment enhances transepidermal permeation of hEGF, apparently via both paracellular and transcellular routes. Under our study conditions, LICAP treatment seems to be a novel approach to facilitate TED with low safety concerns in vitro. Further translational studies are needed for clinical evaluation.

Interplay of Cellular Nrf2/NF-κB Signalling after Plasma Stimulation of Malignant vs. Non-Malignant Dermal Cells

Skin cancer is one of the most common malignancies worldwide. Cold atmospheric pressure Plasma (CAP) is increasingly successful in skin cancer therapy, but further research is needed to understand its selective effects on cancer cells at the molecular level. In this study, A431 (squamous cell carcinoma) and HaCaT (non-malignant) cells cultured under identical conditions revealed similar ROS levels but significantly higher antioxidant levels in unstimulated A431 cells, indicating a higher metabolic turnover typical of tumour cells. HaCaT cells, in contrast, showed increased antioxidant levels upon CAP stimulation, reflecting a robust redox adaptation. Specifically, proteins involved in antioxidant pathways, including NF-κB, IκBα, Nrf2, Keap1, IKK, and pIKK, were quantified, and their translocation level upon stimulation was evaluated. CAP treatment significantly elevated Nrf2 nuclear translocation in non-malignant HaCaT cells, indicating a strong protection against oxidative stress, while selectively inducing NF-κB activation in A431 cells, potentially leading to apoptosis. The expression of pro-inflammatory genes like IL-1B, IL-6, and CXCL8 was downregulated in A431 cells upon CAP treatment. Notably, CAP enhanced the expression of antioxidant response genes HMOX1 and GPX1 in non-malignant cells. The differential response between HaCaT and A431 cells underscores the varied antioxidative capacities, contributing to their distinct molecular responses to CAP-induced oxidative stress.

Selective adhesion inhibition and hyaluronan envelope reduction of dermal tumor cells by cold plasma-activated medium

The sensitivity to cold plasma is specific to tumor cells while leaving normal tissue cells unaffected. This is the desired challenge in cancer therapy. Therefore, the focus of this work was a comparative study concerning the plasma sensitivity of dermal tumor cells (A-431) versus non-tumorigenic dermal cells (HaCaT) regarding their adhesion capacity. We found a selective inhibiting effect of plasma-activated medium on the adhesion of tumor cells while hardly affecting normal cells. We attributed this to a lower basal gene expression for the adhesion-relevant components CD44, hyaluronan synthase 2 (HAS2), HAS3, and the hyaluronidases in A431. Noteworthy, after plasma exposure, we revealed a significantly higher expression and synthesis of the hyaluronan envelope, the HAS3 gene, and the transmembrane adhesion receptors in non-tumorigenic HaCaTs.

Discrimination between the effects of pulsed electrical stimulation and electrochemically conditioned medium on human osteoblasts

BACKGROUND

Electrical stimulation is used for enhanced bone fracture healing. Electrochemical processes occur during the electrical stimulation at the electrodes and influence cellular reactions. Our approach aimed to distinguish between electrochemical and electric field effects on osteoblast-like MG-63 cells. We applied 20 Hz biphasic pulses via platinum electrodes for 2 h. The electrical stimulation of the cell culture medium and subsequent application to cells was compared to directly stimulated cells. The electric field distribution was predicted using a digital twin.

RESULTS

Cyclic voltammetry and electrochemical impedance spectroscopy revealed partial electrolysis at the electrodes, which was confirmed by increased concentrations of hydrogen peroxide in the medium. While both direct stimulation and AC-conditioned medium decreased cell adhesion and spreading, only the direct stimulation enhanced the intracellular calcium ions and reactive oxygen species.

CONCLUSION

The electrochemical by-product hydrogen peroxide is not the main contributor to the cellular effects of electrical stimulation. However, undesired effects like decreased adhesion are mediated through electrochemical products in stimulated medium. Detailed characterisation and monitoring of the stimulation set up and electrochemical reactions are necessary to find safe electrical stimulation protocols.

The effect of low-intensity cold atmospheric plasma jet on photoaging-induced hyperpigmentation in mouse model

BACKGROUND

Cold atmospheric plasma (CAP) produces reactive oxygen/nitrogen species (RONS) in the target and can induce cytoprotective effects by activating hormesis-related pathways when its intensity is in the low range.

OBJECTIVES

The aim of this study is to evaluate the effect of low-intensified CAP (LICAP) on skin with photoaging-induced hyperpigmentation in an animal model.

METHODS

Changes in cell viability and RONS production following LICAP treatment were measured. For the in vivo study, 30 hairless mice underwent antecedent photoaging induction followed by the allocated therapy (i.e., LICAP, topical ascorbic acid (AA), or both). During the first 4 weeks of the treatment period (8 weeks), ultraviolet (UV)-B irradiation was concurrently administered. Visual inspection and measurement of the melanin index (MI) were performed to assess the change in skin pigmentation at Weeks 0, 2, 4, 6, and 8.

RESULTS

RONS production increased linearly until the saturation point. Cell viability was not significantly affected by LICAP treatment. At Week 8, MI was significantly decreased in every treatment group compared with the values at Week 0 and Week 4. The treatment effect of the concurrent therapy group was superior to that of the LICAP and AA groups.

CONCLUSION

LICAP appears to be a novel modality for photoprotection and pigment reduction in photodamaged skin. LICAP treatment and topical AA application seem to exert a synergistic effect.

Pulsed Electrical Stimulation Affects Osteoblast Adhesion and Calcium Ion Signaling

An extensive research field in regenerative medicine is electrical stimulation (ES) and its impact on tissue and cells. The mechanism of action of ES, particularly the role of electrical parameters like intensity, frequency, and duration of the electric field, is not yet fully understood. Human MG-63 osteoblasts were electrically stimulated for 10 min with a commercially available multi-channel system (IonOptix). We generated alternating current (AC) electrical fields with a voltage of 1 or 5 V and frequencies of 7.9 or 20 Hz, respectively. To exclude liquid-mediated effects, we characterized the AC-stimulated culture medium. AC stimulation did not change the medium’s pH, temperature, and oxygen content. The H2O2 level was comparable with the unstimulated samples except at 5 V_7.9 Hz, where a significant increase in H2O2 was found within the first 30 min. Pulsed electrical stimulation was beneficial for the process of attachment and initial adhesion of suspended osteoblasts. At the same time, the intracellular Ca2+ level was enhanced and highest for 20 Hz stimulated cells with 1 and 5 V, respectively. In addition, increased Ca2+ mobilization after an additional trigger (ATP) was detected at these parameters. New knowledge was provided on why electrical stimulation contributes to cell activation in bone tissue regeneration.

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.

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.

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.

Plasma-activated water: Physicochemical properties, microbial inactivation mechanisms, factors influencing antimicrobial effectiveness, and applications in the food industry

Novel nonthermal inactivation technologies have been increasingly popular over the traditional thermal food processing methods due to their capacity in maintaining microbial safety and other quality parameters. Plasma-activated water (PAW) is a cutting-edge technology developed around a decade ago, and it has attracted considerable attention as a potential washing disinfectant. This review aims to offer an overview of the fundamentals and potential applications of PAW in the agri-food sector. A detailed description of the interactions between plasma and water can help to have a better understanding of PAW, hence the physicochemical properties of PAW are discussed. Further, this review elucidates the complex inactivation mechanisms of PAW, including oxidative stress and physical effect. In particular, the influencing factors on inactivation efficacy of PAW, including processing factors, characteristics of microorganisms, and background environment of water are extensively described. Finally, the potential applications of PAW in the food industry, such as surface decontamination for various food products, including fruits and vegetables, meat and seafood, and also the treatment on quality parameters are presented. Apart from decontamination, the applications of PAW for seed germination and plant growth, as well as meat curing are also summarized. In the end, the challenges and limitations of PAW for scale-up implementation, and future research efforts are also discussed. This review demonstrates that PAW has the potential to be successfully used in the food industry.

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.

Physical plasma-treated saline promotes an immunogenic phenotype in CT26 colon cancer cells in vitro and in vivo

Metastatic colorectal cancer is the fourth most common cause of cancer death. Current options in palliation such as hyperthermic intraperitoneal chemotherapy (HIPEC) present severe side effects. Recent research efforts suggested the therapeutic use of oxidant-enriched liquid using cold physical plasma. To investigate a clinically accepted treatment regimen, we assessed the antitumor capacity of plasma-treated saline solution. In response to such liquid, CT26 murine colon cancer cells were readily oxidized and showed cell growth with subsequent apoptosis, cell cycle arrest, and upregulation of immunogenic cell death (ICD) markers in vitro. This was accompanied by marked morphological changes with re-arrangement of actin fibers and reduced motility. Induction of an epithelial-to-mesenchymal transition phenotype was not observed. Key results were confirmed in MC38 colon and PDA6606 pancreatic cancer cells. Compared to plasma-treated saline, hydrogen peroxide was inferiorly toxic in 3D tumor spheroids but of similar efficacy in 2D models. In vivo, plasma-treated saline decreased tumor burden in Balb/C mice. This was concomitant with elevated numbers of intratumoral macrophages and increased T cell activation following incubation with CT26 cells ex vivo. Being a potential adjuvant for HIPEC therapy, our results suggest oxidizing saline solutions to inactivate colon cancer cells while potentially stimulating antitumor immune responses.

Hmox1 Upregulation Is a Mutual Marker in Human Tumor Cells Exposed to Physical Plasma-Derived Oxidants

Increasing numbers of cancer deaths worldwide demand for new treatment avenues. Cold physical plasma is a partially ionized gas expelling a variety of reactive oxygen and nitrogen species, which can be harnesses therapeutically. Plasmas and plasma-treated liquids have antitumor properties in vitro and in vivo. Yet, global response signatures to plasma treatment have not yet been identified. To this end, we screened eight human cancer cell lines to investigate effects of low-dose, tumor-static plasma-treated medium (PTM) on cellular activity, immune-modulatory properties, and transcriptional levels of 22 redox-related genes. With PTM, a moderate reduction of metabolic activity and modest modulation of chemokine/cytokine pattern and markers of immunogenic cell death was observed. Strikingly, the Nuclear factor (erythroid-derived 2)-like 2 (nrf2) target heme oxygenase 1 (hmox1) was upregulated in all cell lines 4 h post PTM-treatment. nrf2 was not changed, but its baseline expression inversely and significantly correlated with hmox1 expression after exposure to PTM. Besides awarding hmox1 a central role with plasma-derived oxidants, we present a transcriptional redox map of 22 targets and chemokine/cytokine secretion map of 13 targets across eight different human tumor cell lines of four tumor entities at baseline activity that are useful for future studies in this field.

Cold atmospheric plasma causes a calcium influx in melanoma cells triggering CAP-induced senescence

Cold atmospheric plasma (CAP) is a promising approach in anti-cancer therapy, eliminating cancer cells with high selectivity. However, the molecular mechanisms of CAP action are poorly understood. In this study, we investigated CAP effects on calcium homeostasis in melanoma cells. We observed increased cytoplasmic calcium after CAP treatment, which also occurred in the absence of extracellular calcium, indicating the majority of the calcium increase originates from intracellular stores. Application of previously CAP-exposed extracellular solutions also induced cytoplasmic calcium elevations. A substantial fraction of this effect remained when the application was delayed for one hour, indicating the chemical stability of the activating agent(s). Addition of ryanodine and cyclosporin A indicate the involvement of the endoplasmatic reticulum and the mitochondria. Inhibition of the cytoplasmic calcium elevation by the intracellular chelator BAPTA blocked CAP-induced senescence. This finding helps to understand the molecular influence and the mode of action of CAP on tumor cells.

N2 non-thermal atmospheric pressure plasma promotes wound healing in vitro and in vivo: Potential modulation of adhesion molecules and matrix metalloproteinase-9

Advances in physics and biology have made it possible to apply non-thermal atmospheric pressure plasma (NTP) in the biomedical field. Although accumulating evidence suggests that NTP has various medicinal effects, such as facilitating skin wound healing on exposed tissue while minimizing undesirable tissue damage, the underlying molecular mechanisms are not fully understood. In this study, NTP generated from N₂ optimized wound healing in the scratch wound healing assay. In addition, matrix metalloproteinase (MMP)-9 expression and enzyme activity increased and the urokinase-type plasminogen activator (uPA) system was activated after NTP treatment. We also showed that NTP treatment increased Slug and TCF8/ZEB1 expression and decreased that of E-cadherin, suggesting induction of the epithelial-to-mesenchymal transition (EMT). The effect of N₂ NTP was verified on rat wound model. Taken together, these results suggest that N₂ NTP promotes wound healing by inducing the EMT and activating the MMP-9/uPA system. These findings show the therapeutic potential of NTP for skin wound healing.

Formation of reactive nitrogen species including peroxynitrite in physiological buffer exposed to cold atmospheric plasma

Cold Atmospheric Plasmas (CAPs) are increasingly used for biomedical applications, their various reactive components must be then better determined. We demonstrate that peroxynitrite (ONOO⁻) is effectively a major reactive species generated by CAPs.

Aqueous Plasma Pharmacy: Preparation Methods, Chemistry, and Therapeutic Applications

Plasma pharmacy is a subset of the broader field of plasma medicine. Although not strictly defined, the term aqueous plasma pharmacy (APP) is used to refer to the generation and distribution of reactive plasma-generated species in an aqueous solution followed by subsequent administration for therapeutic benefits. APP attempts to harness the therapeutic effects of plasma-generated oxidant species within aqueous solution in various applications, such as disinfectant solutions, cell proliferation related to wound healing, and cancer treatment. The subsequent use of plasma-generated solutions in the APP approach facilitates the delivery of reactive plasma species to internal locations within the body. Although significant efforts in the field of plasma medicine have concentrated on employing direct plasma plume exposure to cells or tissues, here we focus specifically on plasma discharge in aqueous solution to render the solution biologically active for subsequent application. Methods of plasma discharge in solution are reviewed, along with aqueous plasma chemistry and the applications for APP. The future of the field also is discussed regarding necessary research efforts that will enable commercialization for clinical deployment.

Emerging applications of low temperature gas plasmas in the food industry

The global burden of foodborne disease due to the presence of contaminating micro-organisms remains high, despite some notable examples of their successful reduction in some instances. Globally, the number of species of micro-organisms responsible for foodborne diseases has increased over the past decades and as a result of the continued centralization of the food processing industry, outbreaks now have far reaching consequences. Gas plasmas offer a broad range of microbicidal capabilities that could be exploited in the food industry and against which microbial resistance would be unlikely to occur. In addition to reducing the incidence of disease by acting on the micro-organisms responsible for food spoilage, gas plasmas could also play a role in increasing the shelf-life of perishable foods and thereby reduce food wastage with positive financial and environmental implications. Treatment need not be confined to the food itself but could include food processing equipment and also the environment in which commercial food processing occurs. Moreover, gas plasmas could also be used to bring about the degradation of undesirable chemical compounds, such as allergens, toxins, and pesticide residues, often encountered on foods and food-processing equipment. The literature on the application of gas plasmas to food treatment is beginning to reveal an appreciation that attention needs also to be paid to ensuring that the key quality attributes of foods are not significantly impaired as a result of treatment. A greater understanding of both the mechanisms by which micro-organisms and chemical compounds are inactivated, and of the plasma species responsible for this is forming. This is significant, as this knowledge can then be used to design plasma systems with tailored compositions that will achieve maximum efficacy. Better understanding of the underlying interactions will also enable the design and implementation of control strategies capable of minimizing variations in plasma treatment efficacy despite perturbations in environmental and operational conditions.

Non-thermal atmospheric-pressure plasma possible application in wound healing

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out.