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

Cold atmospheric plasma-activated medium for potential ovarian cancer therapy

Cold atmospheric plasma (CAP) has emerged as an innovative tool with broad medical applications, including ovarian cancer (OC) treatment. By bringing CAP in close proximity to liquids such as water or cell culture media, solutions containing reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated, called plasma-activated media (PAM). In this systematic review, we conduct an in-depth analysis of studies focusing on PAM interactions with biological substrates. We elucidate the diverse mechanisms involved in the activation of different media and the complex network of chemical reactions underlying the generation and consumption of the prominent reactive species. Furthermore, we highlight the promises of PAM in advancing biomedical applications, such as its stability for extended periods under appropriate storage conditions. We also examine the application of PAM as an anti-cancer and anti-metastatic treatment for OC, with a particular emphasis on its ability to induce apoptosis via distinct signaling pathways, inhibit cell growth, suppress cell motility, and enhance the therapeutic effects of chemotherapy. Finally, the future outlook of PAM therapy in biomedical applications is speculated, with emphasis on the safety issues relevant to clinical translation.

Toxicity study of rats treated by plasma-activated solution

Background

Cold atmospheric plasma (CAP) is an effective treatment for various skin diseases. Plasma-activated solution (PAS) is an indirect method of CAP treatment that produces biological effects similar to those of direct treatment with plasma devices. The anticancer and bacteriostatic effects of PAS have been demonstrated in vitro experiments; however, on the basis of the lack of toxicological studies on PAS, its effects on living mammals when administered by subcutaneous injection is poorly known.

Purpose

The purpose of this study was to evaluate the effects of PAS on local skin tissue cells, blood system, heart, liver, lungs, kidneys and other vital organs of the rat when injected subcutaneously.

Methods

PAS was prepared by CAP irradiation of phosphate-buffered saline (PBS). PBS and different PBS groups (CAP irradiation for 1, 3, or 5 min) were injected subcutaneously once every 48 h. The rats were euthanized immediately after 10 cycles of therapy.

Results

No adverse effects were observed during the entire period of the experiment. Histopathological examination of organs and tissues revealed no structural changes. Moreover, no obvious structural changes were observed in skin tissue. DNA damage and cancerous proliferative changes were not detected in skin tissue treated with PAS. Subsequently, RNA sequencing and western blotting were performed. The results showed that PAS increased the expression of growth factors like transforming growth factor beta (TGF-β) and vascular endothelial growth factor A (VEGFA). These results might be directly linked to the role of PAS in stimulating TGF-β receptor signaling pathway and angiogenesis.

Conclusion

The results showed that multiple subcutaneous injections of PAS did not show significant toxic side effects on local skin tissues and some vital organs in rats, providing a scientific basis to support the future treatment of skin diseases with PAS.

Combined Effect of Plasma-Activated Water and Topotecan in Glioblastoma Cells

The increase in cancer diagnoses and cancer deaths, severe side effects of existing treatments and resistance to traditional treatments have generated a need for new anticancer treatments. Glioblastoma multiforme (GBM) is the most common, malignant and aggressive brain cancer. Despite many innovations regarding GBM treatment, the final outcome is still very poor, making it necessary to develop new therapeutic approaches. Cold atmospheric plasma (CAP) as well as plasma-activated liquids (PAL) are being studied as new possible approaches against cancer. The anticancer activity of PAL such as "plasma-activated water" (PAW) is dependent on the reactive chemical compounds present in the solution. Possible combinatory effects with conventional therapies, such as chemotherapeutics, may expand the potential of PAL for cancer treatment. We aim to explore the therapeutic properties of a combination of PAW and topotecan (TPT), an antineoplastic agent with major cytotoxic effects during the S phase of the cell cycle, on a GBM cancer cell line (U-251mg). Combined treatments with PAW and TPT showed a reduction in the metabolic activity and cell mass, an increase in apoptotic cell death and a reduction in the long-term survival. Single applications of PAW+TPT treatments showed a cytotoxic effect in the short term and an antiproliferative effect in the long term, warranting future exploration of combining PAW with chemotherapeutic agents as new therapeutic approaches.

Organic pollutants degradation using plasma with simultaneous ammonification assisted by electrolytic two-cell system

Atmospheric non-thermal dielectric barrier discharge (DBD) plasma has gained considerable attention due to its cost-efficiency, environmental friendliness, and simplicity. However, certain deficiencies restrict its broad application. Herein, the DBD plasma was used to disrupt three model pharmaceutically active compounds (PhACs), sulfamethoxazole (SMX), ibuprofen (IBP), and norfloxacin (NFX), by varying parameters, such as gas type (Ar, N2, O2, and air) and flow rate (1-4 L min-1). The air plasma discharge had the highest degradation efficiency, and the air flow rate was optimized at 2 L min-1. However, only 10% of IBP was removed by the sole plasma, whereas NFX and SMX were entirely removed after 30 min. Since the air plasma discharge generates reactive oxygen and nitrogen species in a chained reaction, the remaining NO2- and NO3- in the aqueous phase were problematic. Therefore, by coupling plasma with electrolysis using Cu/reduced Cu nanowire (R-CuNw) as the anode/cathode, all three PhACs were removed within 30 min, and NO2- and NO3- were completely reduced to NH3 with cathodic reduction. Moreover, the electrical energy per order (EEO, 0.04 kWh L-1) and treatment cost (0.003 USD L-1) were much lower than those of the single system. This system demonstrates great potential for water remediation, and the production of NH3 as a value-added by-product remarkably improves its practicality and is of great importance in agriculture and energy-related industries.

Comparison of the Biological Properties of Plasma-Treated Solution and Solution of Chemical Reagents

Presently, plasma-treated solutions (PTS) are widely introduced into medicine. Plasma-activated solutions contain various reactive forms of oxygen and nitrogen which provide the desired biological effects. Yet it remains unclear exactly which components of the treated solution are the most important and what the difference is between the plasma-treated solution and a chemically prepared solution composed of the same components. In this work, we show that the chemically prepared mixture of nitrites, nitrates, and hydrogen peroxide with concentrations similar to the plasma-treated solution exerts a fundamentally different effect on a cell culture. The chemically prepared solution has higher cyto- and genotoxicity and causes necrosis, while under the action of the plasma-treated solution, apoptotic processes develop in the cells slowly.

Protective effects of low-temperature plasma on cisplatin-induced nephrotoxicity

The application of atmospheric pressure low-temperature plasma (LTP) in medical treatment has received extensive attention owing to its redox regulatory and anti-inflammatory properties. Nephrotoxicity due to oxidative stress and inflammation is the main adverse effect of cisplatin. In the present study, rats with cisplatin-induced nephrotoxicity were treated with LTP to investigate its potential protective effect. The results showed that LTP treatment has multiple protective effects on cisplatin-induced nephrotoxicity. It significantly improved clinical indicators such as survival rate, water intake, food intake, body weight, and mobility, as well as physiological indexes such as reduced renal index and levels of serum urea, creatinine, and total bilirubin; pathological indicators such as reduced tubular injury, inflammatory infiltration, tubulointerstitial fibrosis, and apoptosis; cell survival indicators such as decreased protein levels of Caspase-3 and Bax and increased Bcl-2; anti-oxidation status such as reduced malondialdehyde content and increased activities of catalase, superoxide dismutase, and glutathione peroxidase; and reduced inflammatory factors such as TNF-α in kidney tissues. Specially, LTP treatment did not influence the anticancer effect of cisplatin as observed in the solid tumor mouse model established by subcutaneously inoculating H22 cells. Moreover, LTP did not influence the physiological and pathological indicators of normal rats, suggesting its biological safety. In conclusion, LTP can protect against cisplatin-induced nephrotoxicity through its anti-oxidation, anti-inflammation, and anti-apoptosis effects, without influencing the anticancer effect of cisplatin.

Applications of Plasma-Activated Liquid in the Medical Field

Much progress has been made since plasma was discovered in the early 1900s. The first form of plasma was thermal type, which was limited for medical use due to potential thermal damage on living cells. In the late 1900s, with the development of a nonthermal atmospheric plasma called cold plasma, profound clinical research began and ‘plasma medicine’ became a new area in the academic field. Plasma began to be used mainly for environmental problems, such as water purification and wastewater treatment, and subsequent research on plasma and liquid interaction led to the birth of ‘plasma-activated liquid’ (PAL). PAL is currently used in the fields of environment, food, agriculture, nanoparticle synthesis, analytical chemistry, and sterilization. In the medical field, PAL usage can be expanded for accessing places where direct application of plasma is difficult. In this review, recent studies with PAL will be introduced to inform researchers of the application plan and possibility of PAL in the medical field.

Antimicrobial Effect of Plasma-Activated Tap Water on Staphylococcus aureus, Escherichia coli, and Candida albicans

In this study, the potential antimicrobial activity of plasma-activated tap water (PAW) was evaluated against Staphylococcus aureus, Escherichia coli, and Candida albicans. For this, PAW was prepared in a gliding arc plasma system using two treatment conditions: stagnant water and water stirring by a magnetic stirrer, called moving water. Subsequently, their oxidation-reduction potential (ORP), pH, electrical conductivity (σ), and total dissolved solids (TDS) were monitored in different areas of the sample divided according to the depth of the beaker. It was observed that PAW obtained in dynamic conditions showed a more uniform acidity among the evaluated areas with pH 3.53 and ORP of 215 mV. Finally, standardized suspensions of Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10799), and Candida albicans (SC 5314) were treated with PAW, and the reduction of viable cells determined the antimicrobial effect. Our results indicate that the tap water, activated by plasma treatment using gliding arc, is an excellent inactivation agent in the case of Staphylococcus aureus and Escherichia coli. On the other hand, no significant antimicrobial activity was achieved for Candida albicans.

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.

Direct Exposure of Dry Enzymes to Atmospheric Pressure Non-Equilibrium Plasmas: The Case of Tyrosinase

The direct interaction of atmospheric pressure non-equilibrium plasmas with tyrosinase (Tyr) was investigated under typical conditions used in surface processing. Specifically, Tyr dry deposits were exposed to dielectric barrier discharges (DBDs) fed with helium, helium/oxygen, and helium/ethylene mixtures, and effects on enzyme functionality were evaluated. First of all, results show that DBDs have a measurable impact on Tyr only when experiments were carried out using very low enzyme amounts. An appreciable decrease in Tyr activity was observed upon exposure to oxygen-containing DBD. Nevertheless, the combined use of X-ray photoelectron spectroscopy and white-light vertical scanning interferometry revealed that, in this reactive environment, Tyr deposits displayed remarkable etching resistance, reasonably conferred by plasma-induced changes in their surface chemical composition as well as by their coffee-ring structure. Ethylene-containing DBDs were used to coat tyrosinase with a hydrocarbon polymer film, in order to obtain its immobilization. In particular, it was found that Tyr activity can be fully retained by properly adjusting thin film deposition conditions. All these findings enlighten a high stability of dry enzymes in various plasma environments and open new opportunities for the use of atmospheric pressure non-equilibrium plasmas in enzyme immobilization strategies.

Plasma Medicine: A Field of Applied Redox Biology

Plasma medicine comprises the application of physical plasma directly on or in the human body for therapeutic purposes. Three most important basic plasma effects are relevant for medical applications: i) inactivation of a broad spectrum of microorganisms, including multidrug-resistant pathogens, ii) stimulation of cell proliferation and angiogenesis with lower plasma treatment intensity, and iii) inactivation of cells by initialization of cell death with higher plasma treatment intensity, above all in cancer cells. Based on own published results as well as on monitoring of relevant literature the aim of this topical review is to summarize the state of the art in plasma medicine and connect it to redox biology. One of the most important results of basic research in plasma medicine is the insight that biological plasma effects are mainly mediated via reactive oxygen and nitrogen species influencing cellular redox-regulated processes. Plasma medicine can be considered a field of applied redox biology.

Biological and medical applications of plasma-activated media, water and solutions

Non-thermal atmospheric pressure plasma has been proposed as a new tool for various biological and medical applications. Plasma in close proximity to cell culture media or water creates reactive oxygen and nitrogen species containing solutions known as plasma-activated media (PAM) or plasma-activated water (PAW) - the latter even displays acidification. These plasma-treated solutions remain stable for several days with respect to the storage temperature. Recently, PAM and PAW have been widely studied for many biomedical applications. Here, we reviewed promising reports demonstrating plasma-liquid interaction chemistry and the application of PAM or PAW as an anti-cancer, anti-metastatic, antimicrobial, regenerative medicine for blood coagulation and even as a dental treatment agent. We also discuss the role of PAM on cancer initiation cells (spheroids or cancer stem cells), on the epithelial mesenchymal transition (EMT), and when used for metastasis inhibition considering its anticancer effects. The roles of PAW in controlling plant disease, seed decontamination, seed germination and plant growth are also considered in this review. Finally, we emphasize the future prospects of PAM, PAW or plasma-activated solutions in biomedical applications with a discussion of the mechanisms and the stability and safety issues in relation to humans.

Plasma-Activation of Larger Liquid Volumes by an Inductively-Limited Discharge for Antimicrobial Purposes

A new configuration of a discharge chamber and power source for the treatment of up to 1 L of liquid is presented. A leakage transformer, energizing two metal electrodes positioned above the liquid, limits the discharge current inductively by utilizing the weak magnetic coupling between the primary and secondary coils. No additional means to avoid arcing (electric short-circuiting), e.g., dielectric barriers or resistors, are needed. By using this technique, exceeding the breakdown voltage leads to the formation of transient spark discharges, producing non-thermal plasma (NTP). These discharges effected significant changes in the properties of the treated liquids (distilled water, physiological saline solution, and tap water). Considerable concentrations of nitrite and nitrate were detected after the plasma treatment. Furthermore, all tested liquids gained strong antibacterial efficacy which was shown by inactivating suspended Escherichia coli and Staphylococcus aureus. Plasma-treated tap water had the strongest effect, which is shown for the first time. Additionally, the pH-value of tap water did not decrease during the plasma treatment, and its conductivity increased less than for the other tested liquids.

Plasma-activated medium triggers cell death and the presentation of immune activating danger signals in melanoma and pancreatic cancer cells

Over the past decade, cold atmospheric plasmas have shown promising application in cancer therapy. The therapeutic use of plasma-activated media is a topic addressed in an emerging field known as plasma pharmacy. In oncology, plasma-activated media are  used to harness the therapeutic effects of oxidant species when they come in contact with cancer cells. Among several factors that contribute to the anticancer effect of plasma-activated liquid media (PALM), H₂O₂ and NO derivatives likely play a key role in the apoptotic pathway. Despite the significant amount of literature produced in recent years, a full understanding of the mechanisms by which PALM exert their activity against cancer cells is limited. In this paper, a sealed dielectric-barrier discharge was used to disentangle the effect of reactive nitrogen species (RNS) from that of reactive oxygen species (ROS) on cancer cells. Two cancers characterized by poor prognosis have been investigated: metastatic melanoma and pancreatic cancer. Both tumour models exposed to PALM rich in H₂O₂ showed a reduction in proliferation and an increase in calreticulin exposure and ATP release, suggesting the potential use of activated media as an inducer of immunogenic cell death via activation of the innate immune system.