Development and characterization of a spark plasma device designed for medical and aesthetic applications

Cold atmospheric plasma devices have shown high potential to be useful for different medical applications. In this study, it has been tried to develop and characterize a cold atmospheric spark plasma device that can be used safely as a tool for medical and aesthetic applications. The schematic of the device is presented in the paper, and the signals of each block are also tested. A special handpiece for this device is designed to make the device as safe as possible. The device's properties that can impose a risk to users' health have been under consideration. The device's electrical properties have been tested, and results show that the electrical current of the device is below the safety thresholds and can be used safely. The radiation power of the device also has been tested. It is shown that the time needed for the radiation power to reach the danger threshold is much longer than the treatment time. The device will not impose any risk regarding radiation from the UV spectrum. Optical emission spectroscopy is also used to investigate the neutral and charged species that are the by-products of electrical discharge. The presence of NOx and OH locally in the discharge can be helpful for various medical applications. This paper presents one of the first studies conducted to investigate the engineering aspect and the immunometry of the spark plasma that can be used in medicine and other purposes.

Plasma-liquid interactions in the presence of organic matter-A perspective

As investigations in the biomedical applications of plasma advance, a demand for describing safe and efficacious delivery of plasma is emerging. It is quite clear that not all plasmas are "equal" for all applications. This Perspective discusses limitations of the existing parameters used to define plasma in context of the need for the "right plasma" at the "right dose" for each "disease system." The validity of results extrapolated from in vitro studies to preclinical and clinical applications is discussed. We make a case for studying the whole system as a single unit, in situ. Furthermore, we argue that while plasma-generated chemical species are the proposed key effectors in biological systems, the contribution of physical effectors (electric fields, surface charging, dielectric properties of target, changes in gap electric fields, etc.) must not be ignored.

Combined effect of heat and corona charge on molecular delivery to a T cell line in vitro

With the rapid increase of gene and immunotherapies for treating cancer, there is a need to efficiently transfect cells. Previous studies suggest that electrotransfer can provide a non-viral method for gene delivery. Electrotransfer traditionally relies upon the application of direct current pulses to the cells of interest. Corona charge was investigated in this study as an alternative to traditional methods as a means of creating the electric field necessary to deliver materials via electrotransfer. The goal was to determine if there was an increase in molecular delivery across the membrane of a human T cell line used as a model system. In a novel dish created for the study, the effects of elevated temperatures (37, 40, 43, and 45°C) during the treatment process were also examined in combination with corona charge application. Results showed that treating cells with corona charge at room temperature (~23°C) caused a statistically significant increase in molecular delivery while maintaining viability. Heat alone did not cause a statistically significant effect on molecular delivery. Combined corona charge treatment and heating resulted in a statistically significant increase on molecular delivery compared to controls that were only heated. Combined corona charge treatment and heating to all temperatures when compared to controls treated at room temperature, showed a statistically significant increase in molecular delivery.

Basic research and clinical exploration of cold atmospheric plasma for skin wounds

Skin wounds, such as burns, diabetic foot ulcers, pressure sores, and wounds formed after laser or surgical treatment, comprise a very high proportion of dermatological disorders. Wounds are treated in a variety of ways; however, some wounds are greatly resistant, resulting in delayed healing and an urgent need to introduce new alternatives. Our previous studies have shown that cold atmospheric plasma (CAP) has antibacterial activity and promotes cell proliferation, differentiation, and migration in vitro. To further advance the role of CAP in wound healing, we evaluated the safety and efficacy of CAP in vitro by irradiation of common refractory bacteria on the skin, irradiation of normal skin of rats and observing reactions, treatment of scald wounds in rats, and treating clinically common acute wounds. Our findings revealed that CAP can eliminate refractory skin bacteria in vitro; CAP positively affected wound healing in a rat scalding wound model; and direct CAP irradiation of low intensity and short duration did not lead to skin erythema or edema. CAP promises to be a new, economical, and safe means of wound treatment.

Atmospheric pressure plasma treatment of skin: penetration into hair follicles

Sterilization of skin prior to surgery is challenged by the reservoir of bacteria that resides in hair follicles. Atmospheric pressure plasma jets (APPJs) have been proposed as a method to treat and deactivate these bacteria as atmospheric plasmas are able to penetrate into structures and crevices with dimensions similar to those found in hair follicles. In this paper, we discuss results from a computational investigation of an APPJ sustained in helium flowing into ambient air, and incident onto a layered dielectric similar to human skin in which there are idealized hair follicles. We found that, depending on the location of the follicle, the bulk ionization wave (IW) incident onto the skin, or the surface IW on the skin, are able to launch IWs into the follicle. The uniformity of treatment of the follicle depends on the location of the first entry of the plasma into the follicle on the top of the skin. Typically, only one side of the follicle is treated on for a given plasma pulse, with uniform treatment resulting from rastering the plasma jet across the follicle over many pulses. Plasma treatment of the follicle is sensitive to the angle of the follicle with respect to the skin, width of the follicle pocket, conductivity of the dermis and thickness of the underlying subcutaneous fat layer, the latter due to the change in capacitance of the tissue.

Metrology of Ar-N2/O2 Mixture Atmospheric Pressure Pulsed DC Jet Plasma and its Application in Bio-Decontamination

Atmospheric pressure plasma jets are gaining a lot of attention due to their widespread applications in the field of bio-decontamination, polymer modification, material processing, deposition of thin film, and nanoparticle fabrication. Herein, we are reporting the disinfection of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli bacteria using plasma jet. In this regard, Ar-O₂, Ar-N₂, and Ar-O₂-N₂ mixture plasma is generated and characterized using optical and electrical characterization. Variation in plasma parameters like electron temperature, electron density, and reactive species production is monitored with discharge parameters such as applied voltage and feed gas concentration. Results show that the peak average power consumed in Ar-O₂, Ar-N₂, and Ar-O₂-N₂ mixture plasma is found to be 4.45, 2.93, and 4.35 W respectively, at 8 kV. Moreover, it is noted that by increasing applied voltage, the electron temperature, electron density, and reactive species production also increases. It is worth noting that electron temperature increases with increase in oxygen concentration in the mixture (, while it decreases with increase in nitrogen concentration in the mixture (Ar-N₂). Similarly, a decreasing trend in electron temperature is noted for Ar-O₂-N₂ mixture plasma. On the other hand, a decreasing trend in electron density is noted for all the mixtures. Reduction in viable colonies of Pseudomonas aeruginosa, Staphylococcus Aureus, and Escherichia coli were confirmed by the serial dilution method. The inactivation efficiency of pulsed DC plasma generated, in the Ar-N₂ mixture at 8 kV and 6 KHz, was evaluated against P. aeruginosa, S. aureus and E. coli bacteria by measuring the number of surviving cells versus plasma treatment time. Results showed that after 240 s of plasma treatment, the number of survival colonies of the mentioned bacteria was reduced to less than 30 CFU/mL.

Portable Cold Atmospheric Plasma Patch-Mediated Skin Anti-Inflammatory Therapy

Although plasma is a promising technology in various fields, its clinical application is restricted by several limitations. A cold atmospheric plasma (CAP) patch is fabricated to help overcome hurdles, especially when treating skin diseases. This patch has surface dielectric barrier discharge, which generates reactive oxygen species (ROS) and reactive nitrogen species (RNS) on a flexible polymer film surface on which the embedded electrode induces a locally strong electric field. The effect of the CAP patch on psoriasis is also evaluated. The distinct characteristics of psoriasis between the lesion and non-lesion area allow the CAP patch to be suitable for only lesion area for its treatment. The CAP patch induces the opening of calcium channels in keratinocytes, thereby restoring abnormal keratinocyte differentiation and the collapse of the tight junction; thus, alleviating psoriatic symptoms. In addition, the favorable effect is due to the induction of ROS/RNS by the CAP patch, not the electric field generated during plasma generation. The findings indicate that the proposed portable CAP patch can help treat inflammatory skin disorders, especially psoriasis. As this can be used easily as a combination therapy with existing drugs, it may help reduce side effects caused by existing drugs.

The Effect of Plasma on Bacteria and Normal Cells in Infected Wound

Infected wound is one of the most common and serious problem in wound management. Cold atmospheric plasma (CAP) is considered to have a good effect in wound healing as a new type medicine. However, there is a key issue that has not been addressed in the treatment of infected wounds by plasma. Bacteria are always found in the deep region of the wound. When plasma is used to treat wounds, it also acts on normal tissue cells while decontaminating. What is the difference between the same dose of plasma acting on bacteria and normal cells? In this study, the most common bacteria (S. aureus, P. aeruginosa, and E. coli) in infected wound and two kinds of normal skin cells (human keratinocyte and human skin fibroblasts (HSF)) were selected to study the difference of the effects of the same dose of plasma on bacteria and cells. The results reveal that three kinds of 10⁶ CFU mL bacteria could be effectively inactivated by 5 order after plasma treatment 3 min, and P. aeruginosa was more sensitive to plasma (could be inactivated 5 order after 2 min treatment). The 10⁴ mL keratinocyte and HSF were treated with the same dose of plasma; keratinocyte can maintain over 90% of the activity and HSF cells can maintain over 70% of the activity. Moreover, the level of collagen I secreted by HSF increased. Therefore, cells can remain a high activity when a plasma dose capable of inactivating bacteria is applied to them.

Conductivity augments ROS and RNS delivery and tumor toxicity of an argon plasma jet

Gas plasma jet technology was recently identified as a potential adjuvant in the palliation of cancer patients. However, a practical point raised is if higher therapeutic efficacy is achieved with the gas plasma applied in direct contact to the tumor tissue (conducting) or during treatment with the remote cloud of reactive oxygen and nitrogen species (ROS/RNS) being expelled. In a bedside-to-bench study, this clinical question was translated into studying these two distinct treatment modalities using a three-dimensional tumor cell-matrix-hydrogel assay with subsequent quantitative confocal imaging. Z-resolved fluorescence analysis of two cancer cell lines revealed greater toxicity of the conducting mode. This result was re-iterated in the growth analysis of vascularized tumor tissue cultured on chicken embryos' CAM using in ovo bioluminescence imaging. Furthermore, for conducting compared to free mode, optical emission spectroscopy revealed stronger RNS signal lines in the gas phase, while both ROS/RNS deposition in the liquid was drastically exacerbated in the conducting mode. Altogether, our results are vital in understanding the importance of standardized treatment distances on the therapeutic efficacy of gas plasma exposure in clinical oncology and will help to give critical implications for clinicians involved in plasma onco-therapy in the future.

Patient-Derived Human Basal and Cutaneous Squamous Cell Carcinoma Tissues Display Apoptosis and Immunomodulation following Gas Plasma Exposure with a Certified Argon Jet

Reactive oxygen species (ROS) have been subject of increasing interest in the pathophysiology and therapy of cancers in recent years. In skin cancer, ROS are involved in UV-induced tumorigenesis and its targeted treatment via, e.g., photodynamic therapy. Another recent technology for topical ROS generation is cold physical plasma, a partially ionized gas expelling dozens of reactive species onto its treatment target. Gas plasma technology is accredited for its wound-healing abilities in Europe, and current clinical evidence suggests that it may have beneficial effects against actinic keratosis. Since the concept of hormesis dictates that low ROS levels perform signaling functions, while high ROS levels cause damage, we investigated herein the antitumor activity of gas plasma in non-melanoma skin cancer. In vitro, gas plasma exposure diminished the metabolic activity, preferentially in squamous cell carcinoma cell (SCC) lines compared to non-malignant HaCaT cells. In patient-derived basal cell carcinoma (BCC) and SCC samples treated with gas plasma ex vivo, increased apoptosis was found in both cancer types. Moreover, the immunomodulatory actions of gas plasma treatment were found affecting, e.g., the expression of CD86 and the number of regulatory T-cells. The supernatants of these ex vivo cultured tumors were quantitatively screened for cytokines, chemokines, and growth factors, identifying CCL5 and GM-CSF, molecules associated with skin cancer metastasis, to be markedly decreased. These findings suggest gas plasma treatment to be an interesting future technology for non-melanoma skin cancer topical therapy.

Impact of electrical grounding conditions on plasma-liquid interactions using Thomson scattering on a pulsed argon jet

The interaction between an argon plasma jet excited using microsecond duration voltage pulses and a liquid target was examined using Thomson scattering to quantify the temporal evolution of the electron density and temperature. The electrical resistance between a liquid target and the electrical ground was varied from 1 to [Formula: see text] to mimic different conductivity liquids while the influence of the varying electrical properties on the electron dynamics within the plasma were examined. It was demonstrated that the interaction between the plasma jet and a liquid target grounded via a high resistance resulted in typical dielectric barrier discharge behaviour, with two discharge events per applied voltage pulse. Under such conditions, the electron density and temperature reached a peak of [Formula: see text] and 3.4 eV, respectively; with both rapidly decaying over several hundreds of nanoseconds. For liquid targets grounded via a low resistance, the jet behaviour transitioned to a DC-like discharge, with a single breakdown event being observed and sustained throughout the duration of each applied voltage pulse. Under such conditions, electron densities of [Formula: see text] were detected for several microseconds. The results demonstrate that the electron dynamics in a pulsed argon plasma jet are extremely sensitive to the electrical characteristics of the target, which in the case of water, can evolve during exposure to the plasma.

Effects of O2 Addition on the Discharge Parameters and Production of Reactive Species of a Transferred Atmospheric Pressure Plasma Jet

The therapeutic effects of atmospheric pressure plasma jets (APPJs) have been associated with the presence of reactive species, mainly the reactive oxygen and nitrogen ones, generated in this kind of plasmas. Due to that, many studies attempting to enhance the production of reactive species in APPJs have been performed. The employment of gas admixtures, usually mixing a noble gas with oxygen (O2) or water vapor, is one of the most common methods to achieve such goal. This work presents a study of how the addition of small amounts of O2 affects the electrical parameters and the production of reactive species in a transferred APPJ produced at the tip of a long and flexible plastic tube. The study was carried out employing helium (He) as the working gas and applying a high voltage (HV) in the form of amplitude-modulated sine waveform (burst mode). With this configuration it was possible to verify that the O2 addition reduces the discharge power and effective current, as a result of late ignition and shorter discharge duration. It was also found that the addition of O2 to a certain content in the gas admixture makes the light emission from oxygen atoms increase, indicating an increment in oxygen related reactive species in the plasma jet. However, at the same time the light emitted from hydroxyl (OH) and nitric oxide (NO) exhibits the opposite behavior, i.e., decrease, indicating a reduction of such species in the APPJ. For these reasons, the addition of O2 to the working gas seems to be useful for increasing the effectiveness of the plasma treatment only when the target modification effect is directly dependent on the content of atomic oxygen.

The emerging potential of cold atmospheric plasma in skin biology

The maintenance of skin integrity is crucial to ensure the physiological barrier against exogenous compounds, microorganisms and dehydration but also to fulfill social and aesthetic purposes. Besides the development of new actives intended to enter a formulation, innovative technologies based on physical principles have been proposed in the last years. Among them, Cold Atmospheric Plasma (CAP) technology, which already showed interesting results in dermatology, is currently being studied for its potential in skin treatments and cares. CAP bio-medical studies gather several different expertise ranging from physics to biology through chemistry and biochemistry, making this topic hard to pin. In this review we provide a broad survey of the interactions between CAP and skin. In the first section, we tried to give some fundamentals on skin structure and physiology, related to its essential functions, together with the main bases on cold plasma and its physicochemical properties. In the following parts we dissected and analyzed each CAP parameter to highlight the already known and the possible effects they can play on skin. This overview aims to get an idea of the potential of cold atmospheric plasma technology in skin biology for the future developments of dermo-cosmetic treatments, for example in aging prevention.

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.

Cell Electropermeabilisation Enhancement by Non-Thermal-Plasma-Treated PBS

The effectiveness of electrochemotherapy (ECT) in local eradication of tumours in human and veterinary medicine has been proven. ECT consists of increasing the uptake of cytotoxic drugs by means of pulsed electric fields (PEFs) that transiently permeabilise the cell membrane. Still, this tumour treatment includes some drawbacks that are linked to the characteristics of the intense electric pulses (EPs) used. Meanwhile, the emerging field of cancer therapies that are based on the application of non-thermal plasmas (NTP) has recently garnered interest because of their potentialities as rich sources of reactive species. In this work, we investigated the potential capabilities of the combined application of indirect NTP treatment and microsecond PEFs (µsPEFs) to outperform in vitro cell electropermeabilisation, the basis of ECT. Thus, phosphate-buffered saline (PBS) was plasma-treated (pPBS) and used afterwards to explore the effects of its combination with µsPEFs. Analysis of two different cell lines (DC-3F Chinese hamster lung fibroblasts and malignant B16-F10 murine melanoma cells), by flow cytometry, revealed that this combination resulted in significant increases of the level of cell membrane electropermeabilisation, even at very low electric field amplitude. The B16-F10 cells were more sensitive to the combined treatment than DC-3F cells. Importantly, the percentage of permeabilised cells reached values similar to those of cells exposed to classical electroporation field amplitude (1100 V/cm) when the cells were treated with pPBS before and after being exposed only to very low PEF amplitude (600 V/cm). Although the level of permeabilisation of the cells that are treated by the pPBS and the PEFs at 600 V/cm is lower than the level reached after the exposure to µsPEFs alone at 1100 V/cm, the combined treatment opens the possibility to reduce the amplitude of the EPs used in ECT, potentially allowing for a novel ECT with reduced side-effects.

Experimental Investigation on the Influence of Target Physical Properties on an Impinging Plasma Jet

The present work aims to investigate the interaction between a plasma jet and targets with different physical properties. Electrical, morphological and fluid-dynamic characterizations were performed on a plasma jet impinging on metal, dielectric and liquid substrates by means of Intensified Charge-Coupled Device (ICCD) and high-speed Schlieren imaging techniques. The results highlight how the light emission of the discharge, its time behavior and morphology, and the plasma-induced turbulence in the flow are affected by the nature of the target. Surprisingly, the liquid target induces the formation of turbulent fronts in the gas flow similar to the metal target, although the dissipated power in the former case is lower than in the latter. On the other hand, the propagation velocity of the turbulent front is independent of the target nature and it is affected only by the working gas flow rate.