Atmospheric Pressure Plasma Systems and Applications

Atmospheric-pressure plasmas have a wide variety of potential industrial applications. They are used in extractive metallurgy; metal recovery; novel nanomaterial synthesis; refractory and wear-resistant coatings deposition; chemical synthesis; energy conversion; industrial, medical, and nuclear waste destruction; engine combustion enhancement; and exhaust gas pollutants clean up. Atmospheric plasmas are produced by applying DC or AC high voltage between two electrodes designed as cylindrical in shape for jets and planar for the dielectric barrier discharge systems. This review presents an overview of the use of atmospheric-pressure plasma devices and industrial processes carried out in several of these areas.

A Novel Method for Estimating the Dosage of Cold Atmospheric Plasmas in Plasma Medical Applications

Cold atmospheric plasmas (CAPs) used in plasma medicine have shown great potential in various aspects including wound healing, dermatology, cancer therapy, etc. It is one of the important issues to determine the plasma dosage in plasma medicine because it dominates the specific plasma treatment results. However, the multi-process interactions between CAPs and biological materials make it rather challenging to give an accurate and versatile definition for plasma dosage. In this study, the ratio of the discharge energy to the number of the treated in vitro kidney cells (mJ/cell) was employed as the unit of the plasma dosage. Additionally, inspired by basic knowledge of pharmacy, the median lethal dose (LD50) was employed to help estimate the plasma dosage. The experimental results show that the value of LD50 using the newly designed CAP Bio-Med Platform for the kidney cells is 34.67 mJ/cell. This biology-based method has the advantages of easy operation, independence of specific CAP sources, and also independence of complex interactions between CAPs and the treated biological targets, and consequently, may provide a new direction to quantitatively define the plasma dosage in various plasma medical applications.

An innovative strategy to rapidly inactivate 8.2-log Enterococcus faecalis in fresh pineapple juice using cold atmospheric plasma

Enterococcus faecalis is a life-threatening bacterium that resists high levels of antibiotics or chemical preservatives. In this study, we aimed to investigate the inactivation of E. faecalis in fresh pineapple juice (FPJ) with two different cold atmospheric plasmas (CAP) reinforced by H2O2/H2O cold vapor: a plasma jet and a surface dielectric barrier discharge (SDBD). CAP treatments for 300 s with plasma jet and 420 s with SDBD caused an 8.2 log reduction of E. faecalis. The concentration of reactive oxygen and nitrogen species induced in FPJ by plasmas was also evaluated. In terms of quality attributes of FPJ, no noticeable color changes (ΔE) were observed. Furthermore, a trifle of loss of organic content such as sugars and organic acids was observed after treatments. These results suggest that our rapid CAP strategy effectively inactivated E. faecalis in FPJ with no change of color and negligible effects on other physicochemical properties.

Recent Advances in the Plasma-Assisted Synthesis of Zinc Oxide Nanoparticles

An overview of recent work on the low-temperature plasma-assisted synthesis of zinc oxide (ZnO) nanoparticles is presented and interpreted in terms of gas-phase and surface reactions with illustrated examples. The thermodynamical nonequilibrium conditions allow the formation of chemically reactive species with a potential energy of several eV, which readily interact with the Zn precursors and initiate reactions leading to the formation of nanoparticles or nanowires. The high-quality nanowires were synthesized from Zn powders only upon interaction with moderately ionized plasma in a narrow range of plasma parameters. This technique is promising for the synthesis of large quantities of nanowires with aspect ratios well above 10, but the exact range of parameters remains to be determined. Apart from the ex situ techniques, the ZnO nanoparticles can be synthesized by depositing a film of precursors (often Zn salts or Zn-containing organometallic compounds) and exposing them to oxygen plasma. This technique is useful for the synthesis of well-adherent ZnO nanoparticles on heat-sensitive objects but requires further scientific validation as it often leads to the formation of a semicontinuous ZnO film rather than nanoparticles. Both low-pressure and atmospheric plasmas are useful in converting the precursor film into ZnO nanoparticles despite completely different mechanisms.

Cold Atmospheric Plasma: A New Strategy Based Primarily on Oxidative Stress for Osteosarcoma Therapy

Osteosarcoma is the most common primary bone tumor, and its first line of treatment presents a high failure rate. The 5-year survival for children and teenagers with osteosarcoma is 70% (if diagnosed before it has metastasized) or 20% (if spread at the time of diagnosis), stressing the need for novel therapies. Recently, cold atmospheric plasmas (ionized gases consisting of UV–Vis radiation, electromagnetic fields and a great variety of reactive species) and plasma-treated liquids have been shown to have the potential to selectively eliminate cancer cells in different tumors through an oxidative stress-dependent mechanism. In this work, we review the current state of the art in cold plasma therapy for osteosarcoma. Specifically, we emphasize the mechanisms unveiled thus far regarding the action of plasmas on osteosarcoma. Finally, we review current and potential future approaches, emphasizing the most critical challenges for the development of osteosarcoma therapies based on this emerging technique.