Abstract
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.
Cold Atmospheric Plasmas (CAPs) or Non Thermal Plasmas (NTPs) are increasingly used for biomedical applications. Herein, we studied the interactions of such CAPs, typically atmospheric ionization ...waves produced in a helium–nitrogen mixture (He/1% N
2
) with a commonly used physiological liquid in biology,
e.g.
Phosphate Buffered Saline solution (PBS) at pH 7.4. Optical Emission Spectroscopy (OES) of the plasma phase revealed the formation in the He/1% N
2
CAP of nitric oxide NO and hydroxyl HO˙ derivatives which can lead to numerous Reactive Oxygen and Nitrogen Species (RONS) after dissolution in the exposed PBS. Chemical changes in solution were first assessed by conductimetry and pHmetry; these experiments showed that an evaporation of the solution occurred under gas exposition and was amplified by the CAPs, being mostly related to the interaction between the ionization wave and the gas flow. Further, UV-visible absorption spectroscopy was used to identify and quantify long-lived RONS, namely nitrite (NO
2
−
), nitrate (NO
3
−
), as well as a short-lived species,
i.e.
peroxynitrite anion (ONOO
−
). The production in physiological solution of ONOO
−
under CAP exposure is demonstrated for the first time, based on experiments at two pH conditions (7.4 and 12) and on the analysis of decomposition kinetics of this unstable species. The combination of complementary physico-chemical techniques allows to decipher the complex reactivity of CAPs from the plasma phase to the liquid phase.
A semi-analytical model is presented for the determination of the electric field in reactors used for cold atmospheric pressure plasma (CAPP) jet production, based on the concept of dielectric ...barrier discharge (DBD). These systems are associated with various applications in contemporary engineering, ranging from material processing to biomedicine, and at the same time they provide many challenges for fundamental research. Here, we consider a simplified system configuration of a single driven electrode, surrounding a thin dielectric tube, which does not contribute to the electric field, since the potential variation is immediate due to its negligible size. By employing the cylindrical coordinate system that perfectly fits the present plasma jet reactor, we separate the area of electric activity into three distinct domains according to the imposed external conditions, while our analysis is restricted to the electrostatic limit of Maxwell’s equations. To this end, cylindrical harmonic field expansions are used for the potential, which produce the corresponding electric fields in each subdomain. Due to the imposed mixed-type boundary value problem, additional linear terms are incorporated, leading to three possible analytical solutions of the physical problem under consideration. The efficiency of the method is demonstrated by comparing the final formulae with a numerical solution, followed by the relevant discussion.
In the present work, a single dielectric barrier discharge (SDBD)-based actuator is developed and experimentally tested by means of various diagnostic techniques. Flexible dielectric barriers and ...conductive paint electrodes are used, making the design concept applicable to surfaces of different aerodynamic profiles. A technical drawing of the actuator is given in detail. The plasma is sustained by audio frequency sinusoidal high voltage, while it is probed electrically and optically. The consumed electric power is measured, and the optical emission spectrum is recorded in the ultraviolet–near infrared (UV–NIR) range. High-resolution spectroscopy provides molecular rotational distributions, which are treated appropriately to evaluate the gas temperature. The plasma-induced flow field is spatiotemporally surveyed with pitot-like tube and schlieren imaging. Briefly, the actuator consumes a mean power less than 10 W and shows a fair stability over one day, the average temperature of the gas above its surface is close to 400 K, and the fluid speed rises to 4.5 m s−1. A long, thin layer (less than 1.5 mm) of laminar flow is unveiled on the actuator surface. This thin layer is interfaced with an outspread turbulent flow field, which occupies a centimeter-scale area. Molecular nitrogen-positive ions appear to be part of the charged heavy species in the generated filamentary discharge, which can transfer energy and momentum to the surrounding air molecules.
This work is devoted to unbuffered and buffered water treatment by means of atmospheric pressure cold plasma of electrical discharges. The interest in the activation of these two liquids by ...plasma-induced, gaseous-phase chemistry ranges over a wide area of potential applications and interdisciplinary scientific fields. These include biology, medicine, sanitation, environmental restoration, agriculture, etc. Atmospheric pressure cold plasma is here produced in the form of a plasma jet and set into physical contact with the liquid specimens. The operational window of the treatment, in terms of plasma reactivity, is determined by means of UV-NIR optical emission spectroscopy, and the treated liquids are probed in a variety of respects. Evaporation rate, temperature, acidity and basicity, resistivity, and oxidation-reduction potential are measured as a function of the treatment time, either in-situ or ex-situ. The formation of principal reactive oxygen species, i.e., •OH, H2O2 and O2•−, with a plasma jet mean power lower than 400 mW, is eventually demonstrated and their concentration is measured with original methods borrowed from the biology field. The experimental results are linked to reports published over the last ten years, which are compiled in a brief but meaningful review.
This report gives prominence to the importance of the traditional Cockcroft-Walton voltage multiplier to the design of pulsed power supplies for dielectric barrier discharge (DBD) applications. ...Following an inventive concept, a simple Cockcroft-Walton generator is combined with a MOSFET-based switch (in either "push" or "pull" mode). Thus, the to-be-chopped stabilized dc high voltage is produced by a compact, transformer-less, modular unit, having high flexibility in terms of engineering. This approach leads to well-defined, square, high-voltage pulses of variable amplitude, frequency, and duty cycle. Design, implementation, and proof test of such a prototype are here demonstrated. The prototype yields square pulses as high as 10 kV (plateau value), as narrow as 350 ns (variable pulsewidth up to millisecond, depending on the frequency), rising or falling time close to 20 ns, pulse repetition rates up to 4 kHz, and output mean power up to 150 W. The functionality of the system is demonstrated by driving coaxial, ambient air DBDs of variable lengths, while principal electrical and optical parameters are recorded. Peak power values higher than 70 kW are measured on the DBD side, while the voltage multiplier power efficiency factor remains close to 95%.
Laser-induced fluorescence diagnostic technique is applied here to probe xenon neutrals and single-charged ions in an ambipolar plasma source. A single tunable diode laser is employed for pumping ...both following transitions: <inline-formula> <tex-math notation="LaTeX">6s{~}^{\mathrm {2}} {{1/2}}_{\mathrm {1}}^{\mathrm {0}} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">6p{~}^{2} {{3/2}}_{\mathrm {1}}^{\mathrm {0}} </tex-math></inline-formula> (centered at 834.68 nm; air) and <inline-formula> <tex-math notation="LaTeX">5d{\mathrm {{4}}}_{\mathrm {7/2}} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">6p{\mathrm {{3}}}_{\mathrm {5/2}} </tex-math></inline-formula> (centered at 834.72 nm; air), for Xe I and Xe II detection, respectively. The corresponding decay states are <inline-formula> <tex-math notation="LaTeX">6s{\mathrm {{3/2}}}_{\mathrm {1}}^{\mathrm {0}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">6s{\mathrm {{2}}}_{\mathrm {3/2}} </tex-math></inline-formula> leading to fluorescence signal at 473.415 and 541.915 nm, respectively. A detailed description of the experimental setup along with time-averaged fluorescence signals are presented, demonstrating the possible application of the above adjacent pumping wavelengths in xenon ambipolar plasmas for probing both ions and neutrals under various operating conditions. A comprehensible discussion to what extent the registered laser-induced fluorescence signals mirror velocity distribution functions is realized, following hyperfine splitting and isotopic shift analysis.
This paper is devoted to the design, implementation, and test of a low cost, modular, and reliable pulsed high-voltage (HV) converter (dc chopper). The distinct characteristics of the present ...prototype refer to: adjustable voltage amplitude up to 7 kV, amplitude drop less than 4‰ for <inline-formula> <tex-math notation="LaTeX">2 \times 10 </tex-math></inline-formula> A output peak current at 5 kHz, adjustable pulse frequency up to 5 kHz, adjustable duty cycle between 1% and 10%, rising/falling time around 100 ns, and jitter about 10 ns. In principle, 1-kV modules based on a fast MOSFET each are combined in series to form a completely modular push-pull switch configuration. Contrary to sophisticated optical fiber-based insulation techniques, the driving low-voltage stage of the power supply is magnetically coupled to the HV stage. The low-voltage stage defines and schedules the HV pulses by means of a microcontroller. The 7 kV is equally distributed along MOSFETs due to balancing networks of passive components. Zener diodes in parallel with MOSFETs provide sufficient protection against overvoltages. The power supply has been successfully tested on dielectric-barrier discharge-based plasmas which have nowadays continuous technological interest.
Abstract
The impact of titanium dioxide (TiO
2
) on the physical properties of poly(lactic acid) (PLA) is explored, along with the combined effect of Atomic Layer Deposition of zinc oxide (ZnO) on ...the nanocomposite films' surface. PLA/TiO
2
bionanocomposites are prepared via melt‐extrusion and characterized in terms of their morphological, thermal, and mechanical properties. Homogeneous dispersion of the filler offers enhanced mechanical performance for samples up to 5 wt% in TiO
2
content. Thermal stability of PLA is also slightly improved upon increasing TiO
2
content. This work also demonstrates that surface modification of PLA/TiO
2
films employing Atomic Layer Deposition of zinc oxide enhances hydrophobicity, while antimicrobial activity, although mild, appears enhanced for coated samples. Water vapor permeability is retained in both coated and uncoated nanocomposites. Surface characterization of the studied specimens, by x‐ray photoelectron spectroscopy and scanning electron microscopy, reveals subsurface diffusion and reaction of the depositing compounds within PLA, leading to a different surface chemistry involving Zn(OH)
2
. This study gives valuable insights on the parameters affecting the atomic layer deposition of inorganic coatings on a polymeric substrate in the presence of nanoinclusions and, therefore, on the physical properties of the coated films, providing the pathway for their exploitation in food packaging applications.
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