Influence of aerosol injection on the liquid chemistry induced by an RF argon plasma jet

A radio-frequency driven plasma jet in annular geometry coupled with an aerosol injection into the effluent is proposed for the controllable reactive oxygen species (ROS)/reactive nitrogen species (RNS) production and delivery on biological targets in the context of plasma medicine, e.g. wound care. The role of the aqueous aerosol in modulating the reactive species production is investigated by combining physical and chemical analytics. Optical emission spectroscopy, electron paramagnetic resonance spectroscopy, and a biochemical model based on cysteine as a tracer molecule have been applied, revealing that aerosol injection shifts the production of ROS from atomic and singlet oxygen toward hydroxyl radicals, which are generated in the droplets. Species generation occurred mainly at the droplets boundary layer during their transport through the effluent, leading to a limited cysteine turnover upon introduction into the aerosol solution. The subsequent delivery of unmodified cysteine molecules at a target suggested the application of the plasma source for the topical delivery of drugs, expanding the potential applicability and effectiveness. The presence of RNS was negligible regardless of aerosol injection and only traces of the downstream products nitrate and nitrate were detected. In summary, the aerosol injection into the effluent opens new avenues to control UV radiation and reactive species output for the biomedical applications of non-thermal plasma sources, reaching out toward the regulation, safety, and efficacy of targeted applications

Quantification of the ozone and singlet delta oxygen produced in gas and liquid phases by a non-thermal atmospheric plasma with relevance for medical treatment

In the field of plasma medicine, the identification of relevant reactive species in the liquid phase is highly important. To design the plasma generated species composition for a targeted therapeutic application, the point of origin of those species needs to be known. The dominant reactive oxygen species generated by the plasma used in this study are atomic oxygen, ozone, and singlet delta oxygen. The species density changes with the distance to the active plasma zone, and, hence, the oxidizing potential of this species cocktail can be tuned by altering the treatment distance. In both phases (gas and liquid), independent techniques have been used to determine the species concentration as a function of the distance. The surrounding gas composition and ambient conditions were controlled between pure nitrogen and air-like by using a curtain gas device. In the gas phase, in contrast to the ozone density, the singlet delta oxygen density showed to be more sensitive to the distance. Additionally, by changing the surrounding gas, admixing or not molecular oxygen, the dynamics of ozone and singlet delta oxygen behave differently. Through an analysis of the reactive species development for the varied experimental parameters, the importance of several reaction pathways for the proceeding reactions was evaluated and some were eventually excluded

Influence of aerosol injection on the liquid chemistry induced by an RF argon plasma jet

A radio-frequency driven plasma jet in annular geometry coupled with an aerosol injection into the effluent is proposed for the controllable reactive oxygen species (ROS)/reactive nitrogen species (RNS) production and delivery on biological targets in the context of plasma medicine, e.g. wound care. The role of the aqueous aerosol in modulating the reactive species production is investigated by combining physical and chemical analytics. Optical emission spectroscopy, electron paramagnetic resonance spectroscopy, and a biochemical model based on cysteine as a tracer molecule have been applied, revealing that aerosol injection shifts the production of ROS from atomic and singlet oxygen toward hydroxyl radicals, which are generated in the droplets. Species generation occurred mainly at the droplets boundary layer during their transport through the effluent, leading to a limited cysteine turnover upon introduction into the aerosol solution. The subsequent delivery of unmodified cysteine molecules at a target suggested the application of the plasma source for the topical delivery of drugs, expanding the potential applicability and effectiveness. The presence of RNS was negligible regardless of aerosol injection and only traces of the downstream products nitrate and nitrate were detected. In summary, the aerosol injection into the effluent opens new avenues to control UV radiation and reactive species output for the biomedical applications of non-thermal plasma sources, reaching out toward the regulation, safety, and efficacy of targeted applications

Non-touching plasma–liquid interaction – where is aqueous nitric oxide generated?

Mass transport through graphene is receiving increasing attention due to the potential for molecular sieving. Experimental studies are mostly limited to the translocation of protons, ions, and water molecules, and results for larger molecules through graphene are rare. Here, we perform controlled radical polymerization with surface-anchored self-assembled initiator monolayer in a monomer solution with single-layer graphene separating the initiator from the monomer. We demonstrate that neutral monomers are able to pass through the graphene (via native defects) and increase the graphene defects ratio (Raman ID/IG) from ca. 0.09 to 0.22. The translocations of anionic and cationic monomers through graphene are significantly slower due to chemical interactions of monomers with the graphene defects. Interestingly, if micropatterned initiator-monolayers are used, the translocations of anionic monomers apparently cut the graphene sheet into congruent microscopic structures. The varied interactions between monomers and graphene defects are further investigated by quantum molecular dynamics simulations

Oxygen atoms are critical in rendering THP-1 leukaemia cells susceptible to cold physical plasma-induced apoptosis

Cold physical plasma has been suggested as a powerful new tool in oncology. However, some cancer cells such as THP-1 leukaemia cells have been shown to be resistant towards plasma-induced cell death, thereby serving as a good model for optimizing plasmas in order to foster pro-apoptotic anticancer effects. A helium/oxygen radio frequency driven atmospheric plasma profoundly induced apoptosis in THP-1 cells whereas helium, humidified helium, and humidified helium/oxygen plasmas were inefficient. Hydrogen peroxide – previously shown as central plasma-derived agent – did not participate in the killing reaction but our results suggest hypochlorous acid to be responsible for the effect observed. Proteomic analysis of THP-1 cells exposed to He/O2 plasma emphasized a prominent growth retardation, cell stress, apoptosis, and a pro-immunogenic profile. Altogether, a plasma setting that inactivates previously unresponsive leukaemia cells is presented. Crucial reactive species in the plasma and liquid environment were identified and discussed, deciphering the complexity of plasma from the gas phase into the liquid down to the cellular response mechanism. These results may help tailoring plasmas for clinical applications such as oxidation-insensitive types of cancer

Nitrosylation vs. oxidation – How to modulate cold physical plasmas for biological applications

Thiol moieties are major targets for cold plasma-derived nitrogen and oxygen species, making CAPs convenient tools to modulate redox-signaling pathways in cells and tissues. The underlying biochemical pathways are currently under investigation but especially the role of CAP derived RNS is barely understood. Their potential role in protein thiol nitrosylation would be relevant in inflammatory processes such as wound healing and improving their specific production by CAP would allow for enhanced treatment options beyond the current application. The impact of a modified kINPen 09 argon plasma jet with nitrogen shielding on cysteine as a thiol-carrying model substance was investigated by FTIR spectroscopy and high-resolution mass spectrometry. The deposition of short-lived radical species was measured by electron paramagnetic resonance spectroscopy, long-lived species were quantified by ion chromatography (NO2-, NO3-) and xylenol orange assay (H2O2). Product profiles were compared to samples treated with the so-called COST jet, being introduced by a European COST initiative as a reference device, using both reference conditions as well as conditions adjusted to kINPen gas mixtures. While thiol oxidation was dominant under all tested conditions, an Ar + N2/O2 gas compositions combined with a nitrogen curtain fostered nitric oxide deposition and the desired generation of S-nitrosocysteine. Interestingly, the COST-jet revealed significant differences in its chemical properties in comparison to the kINPen by showing a more stable production of RNS with different gas admixtures, indicating a different •NO production pathway. Taken together, results indicate various chemical properties of kINPen and COST-jet as well as highlight the potential of plasma tuning not only by gas admixtures alone but by adjusting the surrounding atmosphere as well

Plasma-liquid interactions: a review and roadmap

Plasma-liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas

Generation of highly reactive species by plasma-liquid interaction

Because of the vital role of the liquid as interface in plasma medicine, this work is focused on the elucidation of the interaction of plasmas with biologically relevant liquids. The results of this thesis are an important step in the direction of the applications to real biological liquids such as blood and wound secretion ex vivo as well as in vivo. In this thesis the following questions are investigated and answered with the special focus on the free radicals as highly reactive and, therefore, hard to detect relevant group of chemical species: What is the impact of the atmospheric-pressure argon plasma jet on biologically relevant solutions? Which species are generated due to the plasma treatment of liquids? What is an appropriate detection procedure for the qualification and quantification of the short-lived species? Does the surrounding conditions influence the formation of liquid-phase reactive species and can this influence be used to tailor a desired liquid composition? What is the influence of the plasma surroundings? What is the influence of feed gas manipulation regarding the reactive species generation? Can these impacts be used for a selected reactive species composition generation? Does the treated liquid medium affect the plasma-generated reactive species output and in what way? Which are the underlying mechanisms and origins of the plasma-caused chemical changes in the solutions? Do reactive species exist, which origin is located in the gaseous phase? What is the impact of the plasma jet radiation?Auf Grund der wichtigen Rolle der Flüssigkeit als Grenzfläche in der Plasmamedizin ist diese Doktorarbeit auf die Aufklärung der Wechselwirkung des Plasmas mit biologisch relevanten Flüssigkeiten fokussiert. Die Ergebnisse dieser Arbeit sind ein wichtiger Schritt in Richtung der Anwendung von Plasmen zur Behandlung realer biologischer Flüssigkeiten wie beispielsweise Blut und Wundsekret ex vivo wie auch in vivo. In dieser Doktorarbeit wurden die folgenden Fragestellungen mit dem speziellen Fokus auf den hochreaktiven freien Radikalen untersucht und beantwortet: Welchen Einfluss hat der Atmosphärendruckplasmajet auf biologisch relevante Flüssigkeiten? Welche Spezies werden durch die Plasmabehandlung in der Flüssigkeit erzeugt? Welche Methode ist für den qualitativen und quantitativen Nachweis der kurzlebigen Spezies geeignet? Haben die den Plasmajet umgebenden Bedingungen einen Einfluss auf die Bildung der reaktiven Spezies in der Flüssigkeit und kann dieser Einfluss für eine gezielte Spezieszusammensetzung in der Flüssigkeit genutzt werden? Welchen Einfluss hat die Umgebungsluft auf das Plasma? Welchen Einfluss hat die Variation des Arbeitsgases hinsichtlich der Erzeugung reaktiver Spezies in der Flüssigkeit? Kann dieser Einfluss für eine gezielte Spezieskomposition genutzt werden? Beeinflusst das Plasma-behandelte flüssige Medium die Ausbeute der durchs Plasma erzeugten reaktiven Spezies? Welche Mechanismen liegen der Spezieserzeugung zu Grunde und wo liegt der Ursprung der durch das Plasma verursachten chemischen Änderungen in der Flüssigkeit? Existieren reaktive Spezies in der Flüssigkeit, deren Ursprung in der Gasphase liegt? Welchen Einfluss hat die Strahlung des Plasmajets auf die Speziesbildung in der Flüssigkeit

LIF spectroscopy on cold Plasma Jets for Plasma Medicine

Invited oralInternational audienc

Dynamics of filamentary plasma jets used in plasma medicine

oralInternational audienc