The aim of the present study was to investigate combined effects of cold atmospheric plasma (CAP) and the chemotherapeutic drug doxorubicin (DOX) on murine and human melanoma cells, and normal cells. In addition to free drug, the combination of CAP with a liposomal drug (DOX-LIP) was also studied for the first time. Thiazolyl blue tetrazolium bromide (MTT) and Trypan Blue exclusion assays were used to evaluate cell viability; the mechanism of cell death was evaluated by flow cytometry. Combined treatment effects on the clonogenic capability of melanoma cells, was also tested with soft agar colony formation assay. Furthermore the effect of CAP on the cellular uptake of DOX or DOX-LIP was examined. Results showed a strong synergistic effect of CAP and DOX or DOX-LIP on selectively decreasing cell viability of melanoma cells. CAP accelerated the apoptotic effect of DOX (or DOX-LIP) and dramatically reduced the aggressiveness of melanoma cells, as the combination treatment significantly decreased their anchorage independent growth. Moreover, CAP did not result in increased cellular uptake of DOX under the present experimental conditions. In conclusion, CAP facilitates DOX cytotoxic effects on melanoma cells, and affects their metastatic potential by reducing their clonogenicity, as shown for the first time.

The Stratum corneum is the outermost layer of the skin, acting as a protective barrier of the epidermis, and its surface properties are directly related to the spreading of topically applied drugs and cosmetics. Numerous works have been devoted to the wettability of this layer over the past 70 years, but, despite the extensive application of atmospheric-pressure plasmas to dermatology, stratum corneum wettability with respect to plasma-induced species has never been considered. The present report assesses the treatment of human stratum corneum epidermidis by atmospheric-pressure pulsed cold plasma-jets for various time intervals and both chemical and morphological modifications are probed. The increase and saturation of the surface free energy due to functionalization are demonstrated, whereas prolonged treatment leads to tissue local disruption (tissue integrity is lost, and stratum corneum looks exfoliated, porous, and even thermally damaged). The latter point arises skepticism about the common practice of contacting atmospheric-pressure plasmas with skin without any previous precautions since the lost skin surface integrity may allow the penetration of pathogenic microorganisms.

Acinetobacter baumannii is a typically short, almost round, rod-shaped (coccobacillus) Gram-negative bacterium. It can be an opportunistic pathogen in humans, affecting people with compromised immune systems, and it is becoming increasingly important as a hospital-associated (nosocomial) infection. It has also been isolated from environmental soil and water samples. In this work, unlike conventional medical methods like antibiotics, the influence of atmospheric-pressure cold plasma on this bacterium is evaluated by means of a colony count technique and scanning electron microscopy. The plasma used here refers to streamers axially propagating into a helium channel penetrating the atmospheric air. The plasma is probed with high resolution optical emission spectroscopy and copious reactive species are unveiled under low-temperature conditions. Based on the experimental results, post-treatment (delayed) biochemical effects on Acinetobacter baumannii and morphological modifications appear dominant, leading to complete deactivation of this bacterium.

In the present work, a capillary dielectric-barrier discharge of the coaxial electrode configuration, commonly employed to atmospheric-pressure cold plasma jet production, is studied in terms of thermal effects. The discharge is driven by sinusoidal high voltage in the kHz range and operates with helium gas channeled into a capillary dielectric tube having one end opened to the atmospheric air. The voltage amplitude and frequency, gas flow rate, and discharge volume are varied independently, and thermal effects are investigated by experimentally acquired results coupled with numerically determined data. The experiments refer to electrical power measurements, time-resolved temperature measurements, infrared imaging, and high resolution optical emission spectroscopy. The numerical modelling incorporates an electro-hydrodynamic force in the governing equations to take into account the helium-air interplay and uses conjugate heat transfer analysis. The comparison between experimental and numerical data shows that power is principally consumed in the dielectric barrier-helium interface resulting in the dielectric heating. A linear relation between steady state temperatures and supplied power, independent of the designing and operating conditions, is experimentally established. However, the gas flow rate affects the thermal effects differently compared to the other parameters, supporting the idea of a twofold nature of these systems, i.e., electrical and hydrodynamic. The main claim states the possibility of correlating (both experimentally and numerically) designing and operating parameters for evaluating heat distribution and gas temperature in capillary dielectric-barrier discharges used for plasma jet production. This is of high importance for processing temperature-sensitive materials, including bio-specimens.

The operation of an ECR-driven (2.45 GHz) hydrogen negative ion source is studied. Electron densities and temperatures are investigated with electrostatic probes and negative ion densities are measured with laser photodetachment. Vacuum ultraviolet irradiance measurements are focused on molecular transitions to the ground state while high-resolution visible emission spectroscopy is used to study the transitions between excited states for both molecules and atoms. The standalone operation of the source is found to be more efficient in higher pressures (12 mTorr) where negative ion densities are as high as 4 × 10 ⁹ cm ⁻³ . Further investigation on the operation of the source reveals a rich vibrational spectrum. On the other hand, a limitation on the production of negative ions which is attributed to a lack of low-energy electrons becomes apparent. The underlying mechanisms that lead to this behavior are discussed along with possible solutions to this issue. Finally, the rates of different negative ion destruction processes are estimated and compared.