Risk assessment of the application of tissue-tolerable plasma on human skin

Inactivation and sensitization of Pseudomonas aeruginosa by microplasma jet array for treating otitis media

Otitis media (OM), known as a middle ear infection, is the leading cause of antibiotic prescriptions for children. With wide-spread use of antibiotics in OM, resistance to antibiotics continues to decrease the efficacy of the treatment. Furthermore, as the presence of a middle ear biofilm has contributed to this reduced susceptibility to antimicrobials, effective interventions are necessary. A miniaturized 3D-printed microplasma jet array has been developed to inactivate Pseudomonas aeruginosa, a common bacterial strain associated with OM. The experiments demonstrate the disruption of planktonic and biofilm P. aeruginosa by long-lived molecular species generated by microplasma, as well as the synergy of combining microplasma treatment with antibiotic therapy. In addition, a middle ear phantom model was developed with an excised rat eardrum to investigate the antimicrobial effects of microplasma on bacteria located behind the eardrum, as in a patient-relevant setup. These results suggest the potential for microplasma as a new treatment paradigm for OM.

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.

Plasma Treatment Limits Cutaneous Squamous Cell Carcinoma Development In Vitro and In Vivo

Cutaneous squamous cell carcinoma (SCC) is the most prevalent cancer worldwide, increasing the cost of healthcare services and with a high rate of morbidity. Its etiology is linked to chronic ultraviolet (UV) exposure that leads to malignant transformation of keratinocytes. Invasive growth and metastasis are severe consequences of this process. Therapy-resistant and highly aggressive SCC is frequently fatal, exemplifying the need for novel treatment strategies. Cold physical plasma is a partially ionized gas, expelling therapeutic doses of reactive oxygen and nitrogen species that were investigated for their anticancer capacity against SCC in vitro and SCC-like lesions in vivo. Using the kINPen argon plasma jet, a selective growth-reducing action of plasma treatment was identified in two SCC cell lines in 2D and 3D cultures. In vivo, plasma treatment limited the progression of UVB-induced SSC-like skin lesions and dermal degeneration without compromising lesional or non-lesional skin. In lesional tissue, this was associated with a decrease in cell proliferation and the antioxidant transcription factor Nrf2 following plasma treatment, while catalase expression was increased. Analysis of skin adjacent to the lesions and determination of global antioxidant parameters confirmed the local but not systemic action of the plasma anticancer therapy in vivo.

Long-Term Risk Assessment for Medical Application of Cold Atmospheric Pressure Plasma

Despite increasing knowledge gained based on multidisciplinary research, plasma medicine still raises various questions regarding specific effects as well as potential risks. With regard to significant statements about in vivo applicability that cannot be prognosticated exclusively based on in vitro data, there is still a deficit of clinical data. This study included a clinical follow-up of five probands who had participated five years previously in a study on the influence of cold atmospheric pressure plasma (CAP) on the wound healing of CO2 laser-induced skin lesions. The follow-up included a complex imaging diagnostic involving dermatoscopy, confocal laser scanning microscopy (CLSM) and hyperspectral imaging (HSI). Hyperspectral analysis showed no relevant microcirculatory differences between plasma-treated and non-plasma-treated areas. In summary of all the findings, no malignant changes, inflammatory reactions or pathological changes in cell architecture could be detected in the plasma-treated areas. These unique in vivo long-term data contribute to a further increase in knowledge about important safety aspects in regenerative plasma medicine. However, to confirm these findings and secure indication-specific dose recommendations, further clinical studies are required.

Long-term Risk Assessment for Medical Application of Cold Atmospheric Pressure Plasma

Despite increasing knowledge gained based on multidisciplinary research, plasma medicine still raises various questions regarding specific effects as well as potential risks. With regard to significant statements about in vivo applicability that cannot be prognosticated exclusively based on in vitro data, there is still a deficit of clinical data. This study included a clinical follow-up of five probands who had participated five years previously in a study on the influence of cold atmospheric pressure plasma (CAP) on the wound healing of CO₂ laser-induced skin lesions. The follow-up included a complex imaging diagnostic involving dermatoscopy, confocal laser scanning microscopy (CLSM) and hyperspectral imaging (HSI). Hyperspectral analysis showed no relevant microcirculatory differences between plasma-treated and non-plasma-treated areas. In summary of all the findings, no malignant changes, inflammatory reactions or pathological changes in cell architecture could be detected in the plasma-treated areas. These unique in vivo long-term data contribute to a further increase in knowledge about important safety aspects in regenerative plasma medicine. However, to confirm these findings and secure indication-specific dose recommendations, further clinical studies are required.

Antimicrobial effects of microwave-induced plasma torch (MiniMIP) treatment on Candida albicans biofilms

The susceptibility of Candida albicans biofilms to a non-thermal plasma treatment has been investigated in terms of growth, survival and cell viability by a series of in vitro experiments. For different time periods, the C. albicans strain SC5314 was treated with a microwave-induced plasma torch (MiniMIP). The MiniMIP treatment had a strong effect (reduction factor (RF) = 2.97 after 50 s treatment) at a distance of 3 cm between the nozzle and the superior regions of the biofilms. In addition, a viability reduction of 77% after a 20 s plasma treatment and a metabolism reduction of 90% after a 40 s plasma treatment time were observed for C. albicans. After such a treatment, the biofilms revealed an altered morphology of their cells by atomic force microscopy (AFM). Additionally, fluorescence microscopy and confocal laser scanning microscopy (CLSM) analyses of plasma-treated biofilms showed that an inactivation of cells mainly appeared on the bottom side of the biofilms. Thus, the plasma inactivation of the overgrown surface reveals a new possibility to combat biofilms.

Risk Assessment of kINPen Plasma Treatment of Four Human Pancreatic Cancer Cell Lines with Respect to Metastasis

Cold physical plasma has limited tumor growth in many preclinical models and is, therefore, suggested as a putative therapeutic option against cancer. Yet, studies investigating the cells' metastatic behavior following plasma treatment are scarce, although being of prime importance to evaluate the safety of this technology. Therefore, we investigated four human pancreatic cancer cell lines for their metastatic behavior in vitro and in chicken embryos (in ovo). Pancreatic cancer was chosen as it is particularly metastatic to the peritoneum and systemically, which is most predictive for outcome. In vitro, treatment with the kINPen plasma jet reduced pancreatic cancer cell activity and viability, along with unchanged or decreased motility. Additionally, the expression of adhesion markers relevant for metastasis was down-regulated, except for increased CD49d. Analysis of 3D tumor spheroid outgrowth showed a lack of plasma-spurred metastatic behavior. Finally, analysis of tumor tissue grown on chicken embryos validated the absence of an increase of metabolically active cells physically or chemically detached with plasma treatment. We conclude that plasma treatment is a safe and promising therapeutic option and that it does not promote metastatic behavior in pancreatic cancer cells in vitro and in ovo.

Deionized water can substitute common bleaching agents for nonvital tooth bleaching when treated with non-thermal atmospheric plasma

The bleaching efficacy of common bleaching agents and deionized water treated with non-thermal atmospheric pressure plasma in the pulp chamber for nonvital tooth bleaching was evaluated. A total of 120 extracted human maxillary first incisors were stained using human blood. Teeth were randomly divided into eight groups (n = 15). In the first four groups, teeth were bleached using 35% hydrogen peroxide gel, 37% carbamide peroxide gel, 2:1 (w/v) sodium perborate paste, and deionized water for 30 min. In the remaining groups, bleaching agents were treated with non-thermal atmospheric plasma for 5 min inside the pulp chamber. Overall color changes (∆E) were determined using Commission Internationale de L'Eclairage Lab Colour System. The plasma-assisted tooth bleaching has not increased tooth temperature beyond 37°C. Bleaching efficacies of bleaching agents were significantly improved when treated with non-thermal atmospheric plasma compared to their application (P < 0.05). A remarkable bleaching effect was obtained when bleaching agents were substituted with water and when treated with non-thermal atmospheric plasma. Non-thermal atmospheric plasma treatment could be a novel tool for activation of bleaching agents in the pulp chamber for nonvital tooth bleaching procedure. Moreover, water could be used as a novel bleaching agent when treated with the non-thermal atmospheric plasma to eliminate possible risks which might arise from peroxide-containing agents.

Redox for Repair: Cold Physical Plasmas and Nrf2 Signaling Promoting Wound Healing

Chronic wounds and ulcers are major public health threats. Being a substantial burden for patients and health care systems alike, better understanding of wound pathophysiology and new avenues in the therapy of chronic wounds are urgently needed. Cold physical plasmas are particularly effective in promoting wound closure, irrespective of its etiology. These partially ionized gases deliver a therapeutic cocktail of reactive oxygen and nitrogen species safely at body temperature and without genotoxic side effects. This field of plasma medicine reanimates the idea of redox repair in physiological healing. This review compiles previous findings of plasma effects in wound healing. It discusses new links between plasma treatment of cells and tissues, and the perception and intracellular translation of plasma-derived reactive species via redox signaling pathways. Specifically, (i) molecular switches governing redox-mediated tissue response; (ii) the activation of the nuclear E2-related factor (Nrf2) signaling, together with antioxidative and immunomodulatory responses; and (iii) the stabilization of the scaffolding function and actin network in dermal fibroblasts are emphasized in the light of wound healing.

Transport and accumulation of plasma generated species in aqueous solution

The interaction between cold atmospheric pressure plasma and liquids is receiving increasing attention for various applications. In particular, the use of plasma-treated liquids (PTL) for biomedical applications is of growing importance, in particular for sterilization and cancer treatment. However, insight into the underlying mechanisms of plasma-liquid interactions is still scarce. Here, we present a 2D fluid dynamics model for the interaction between a plasma jet and liquid water. Our results indicate that the formed reactive species originate from either the gas phase (with further solvation) or are formed at the liquid interface. A clear increase in the aqueous density of H₂O₂, HNO₂/NO₂^- and NO₃^- is observed as a function of time, while the densities of O₃, HO₂/O₂^- and ONOOH/ONOO^- are found to quickly reach a maximum due to chemical reactions in solution. The trends observed in our model correlate well with experimental observations from the literature.

Inactivation of dermatophyte infection by nonthermal plasma on animal model

Superficial fungal infections are a major epidemiological issue with increasing prevalence and are a common global problem. This article describes experimental therapy of superficial fungal skin infection using low-temperature plasma. Groups of guinea pigs were artificially infected with Trichophyton mentagrophytes SK 3286 dermatophyte and treated with plasma produced by a DC cometary discharge with an inserted grid. The course of infection was a week shorter and milder in animals treated by plasma than that in nontreated animals, the significant lowering of dermatophytic germs also occurred in the treated group. The exposure to plasma causes no harm to experimental animals. The results allow for the development of a new dermatophytoses therapy by low temperature plasma treatment.

Cutaneous alternariosis in an immunocompromised dog successfully treated with cold plasma and cessation of immunosuppressive medication

A cutaneous infection with Alternaria spp. was diagnosed in a 2-year-old male intact Irish setter dog, presenting with multifocal papules, plaques and ulcerations involving all four distal limbs, shoulder blades, scrotum, pinnae and nasal mucous membranes. The dog had been treated for inflammatory bowel disease and lymphangiectasia with immunosuppressive doses of cyclosporine and prednisolone for approximately 3 months. The diagnosis was based on clinical signs, the demonstration of fungal elements within skin biopsies, deep fungal culture and fungal PCR from a formalin-fixed tissue specimen. Complete clinical remission was achieved by tapering and cessation of the immunosuppressive medication, treatment with cold atmospheric-pressure plasma (CAPP) and topical enilconazole within 8 weeks.

Evolutionary clade affects resistance of Clostridium difficile spores to Cold Atmospheric Plasma

Clostridium difficile is a spore forming bacterium and the leading cause of colitis and antibiotic associated diarrhoea in the developed world. Spores produced by C. difficile are robust and can remain viable for months, leading to prolonged healthcare-associated outbreaks with high mortality. Exposure of C. difficile spores to a novel, non-thermal atmospheric pressure gas plasma was assessed. Factors affecting sporicidal efficacy, including percentage of oxygen in the helium carrier gas admixture, and the effect on spores from different strains representing the five evolutionary C. difficile clades was investigated. Strains from different clades displayed varying resistance to cold plasma. Strain R20291, representing the globally epidemic ribotype 027 type, was the most resistant. However all tested strains displayed a ~3 log reduction in viable spore counts after plasma treatment for 5 minutes. Inactivation of a ribotype 078 strain, the most prevalent clinical type seen in Northern Ireland, was further assessed with respect to surface decontamination, pH, and hydrogen peroxide concentration. Environmental factors affected plasma activity, with dry spores without the presence of organic matter being most susceptible. This study demonstrates that cold atmospheric plasma can effectively inactivate C. difficile spores, and highlights factors that can affect sporicidal activity.

Investigating the Mutagenicity of a Cold Argon-Plasma Jet in an HET-MN Model

OBJECTIVE

So-called cold physical plasmas for biomedical applications generate reactive oxygen and nitrogen species and the latter can trigger DNA damage at high concentrations. Therefore, the mutagenic risks of a certified atmospheric pressure argon plasma jet (kINPen MED) and its predecessor model (kINPen 09) were assessed.

METHODS

Inner egg membranes of fertilized chicken eggs received a single treatment with either the kINPen 09 (1.5, 2.0, or 2.5 min) or the kINPen MED (3, 4, 5, or 10 min). After three days of incubation, blood smears (panoptic May-Grünwald-Giemsa stain) were performed, and 1000 erythrocytes per egg were evaluated for the presence of polychromatic and normochromic nuclear staining as well as nuclear aberrations and binucleated cells (hen's egg test for micronuclei induction, HET-MN). At the same time, the embryo mortality was documented. For each experiment, positive controls (cyclophosphamide and methotrexate) and negative controls (NaCl-solution, argon gas) were included. Additionally, the antioxidant potential of the blood plasma was assessed by ascorbic acid oxidation assay after treatment.

RESULTS

For both plasma sources, there was no evidence of genotoxicity, although at the longest plasma exposure time of 10 min the mortality of the embryos exceeded 40%. The antioxidant potential in the egg's blood plasma was not significantly reduced immediately (p = 0.32) or 1 h (p = 0.19) post exposure to cold plasma.

CONCLUSION

The longest plasma treatment time with the kINPen MED was 5-10 fold above the recommended limit for treatment of chronic wounds in clinics. We did not find mutagenic effects for any plasma treatment time using the either kINPen 09 or kINPen MED. The data provided with the current study seem to confirm the lack of a genotoxic potential suggesting that a veterinary or clinical application of these argon plasma jets does not pose mutagenic risks.

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.

Treatment of a Superficial Mycosis by Low-temperature Plasma: A Case Report

A case of dermatomycosis caused by zoophilic strain of Trichophyton interdigitale was treated by low-temperature plasma produced by direct current (DC) cometary discharge. The shortening of skin lesion persistence along with suppression of subjective discomfort and etiological agent was observed.

Differential influence of components resulting from atmospheric-pressure plasma on integrin expression of human HaCaT keratinocytes

Adequate chronic wound healing is a major problem in medicine. A new solution might be non-thermal atmospheric-pressure plasma effectively inactivating microorganisms and influencing cells in wound healing. Plasma components as, for example, radicals can affect cells differently. HaCaT keratinocytes were treated with Dielectric Barrier Discharge plasma (DBD/air, DBD/argon), ozone or hydrogen peroxide to find the components responsible for changes in integrin expression, intracellular ROS formation or apoptosis induction. Dependent on plasma treatment time reduction of recovered cells was observed with no increase of apoptotic cells, but breakdown of mitochondrial membrane potential. DBD/air plasma increased integrins and intracellular ROS. DBD/argon caused minor changes. About 100 ppm ozone did not influence integrins. Hydrogen peroxide caused similar effects compared to DBD/air plasma. In conclusion, effects depended on working gas and exposure time to plasma. Short treatment cycles did neither change integrins nor induce apoptosis or ROS. Longer treatments changed integrins as important for influencing wound healing. Plasma effects on integrins are rather attributed to induction of other ROS than to generation of ozone. Changes of integrins by plasma may provide new solutions of improving wound healing, however, conditions are needed which allow initiating the relevant influence on integrins without being cytotoxic to cells.