Atmospheric pressure plasma as CO source for biomedical applications

International audienceIn this work we developed a plasma source based on a Plasma Gun reactor able to generate small quantities of CO. The production fraction of CO molecules has been measured ex-situ by means of gas chromatography. We showed that the density is in the 100-10000 ppm range. The CO concentration can be controlled by varying the gas mixture and by tuning the applied voltage. In CO clinical application, the typical dose used is in the range of 100-1000 ppm. It means that this plasma reactor is suitable as CO source for biological applications

Enhanced generation of reactive species by cold plasma in gelatin solutions for selective cancer cell death

Atmospheric pressure plasma jets generate reactive oxygen and nitrogen species (RONS) in liquids and biological media, which find application in the new area of plasma medicine. These plasma-treated liquids were demonstrated recently to possess selective properties on killing cancer cells and attracted attention toward new plasma-based cancer therapies. These allow for local delivery by injection in the tumor but can be quickly washed away by body fluids. By confining these RONS in a suitable biocompatible delivery system, great perspectives can be opened in the design of novel biomaterials aimed for cancer therapies. Gelatin solutions are evaluated here to store RONS generated by atmospheric pressure plasma jets, and their release properties are evaluated. The concentration of RONS was studied in 2% gelatin as a function of different plasma parameters (treatment time, nozzle distance, and gas flow) with two different plasma jets. Much higher production of reactive species (H2O2 and NO2–) was revealed in the polymer solution than in water after plasma treatment. The amount of RONS generated in gelatin is greatly improved with respect to water, with concentrations of H2O2 and NO2– between 2 and 12 times higher for the longest plasma treatments. Plasma-treated gelatin exhibited the release of these RONS to a liquid media, which induced an effective killing of bone cancer cells. Indeed, in vitro studies on the sarcoma osteogenic (SaOS-2) cell line exposed to plasma-treated gelatin led to time-dependent increasing cytotoxicity with the longer plasma treatment time of gelatin. While the SaOS-2 cell viability decreased to 12%–23% after 72 h for cells exposed to 3 min of treated gelatin, the viability of healthy cells (hMSC) was preserved (~90%), establishing the selectivity of the plasma-treated gelatin on cancer cells. This sets the basis for designing improved hydrogels with high capacity to deliver RONS locally to tumors.Peer ReviewedPreprin

Études expérimentales et modélisation de la combustion des nuages de particules micrométriques et nanométriques d'aluminium.

The numerous new projects for ambitious space missions have revived the interest for the investigation of solid-state rocket engines. Among others, aluminum particles are one of the main compounds of a solid-propellant propulsion unit. However, incomplete combustion and agglomerate formation are remaining issues. A proposed solution to avoid them is to use nanometric particles instead of commonly employed micrometric-size particles.The objective of this work was to experimentally characterize the combustion in air of both micrometric and nanometric aluminum particle clouds for strong richnesses and under standard conditions for temperature and pressure. In order to achieve our goals, a specific test bench was developed and various diagnostic techniques were used to gain knowledge in the physical mechanisms at work during combustion of tiny aluminum particles. Moreover, computer simulations were carried out to support experimental outcomes. The study reveals that the speed of flame increases with the particle concentration. For an identical concentration, combustion propagates faster throughout clouds of nano-particles. The temperature of the gas phase and the condensed phase are lower for nano-particle clouds than for micro-particle clouds. A physical model based on fitted parameters allows to obtain combustion times in good agreement with experimental outcomes. Two power-laws relations in which the combustion time varies as either D0,25 or D0,49 are derived when considering nanometric particles that are not agglutinated.Le regain d'intérêt actuel pour les missions spatiales a donné un nouvel essor aux études sur les systèmes de propulsion solide. Les particules d'aluminium constituent un élément indispensable à ce type de propulseur. Cependant des problèmes de combustion incomplète et d'agglomération des particules subsistent. Une solution envisagée pour les résoudre est d'utiliser des particules nanométriques en remplacement des particules micrométriques utilisées communément.L'objectif de ce travail a été de caractériser expérimentalement la combustion dans l'air d'un nuage de particules d'aluminium micrométrique et nanométrique pour de fortes richesses dans les conditions normales de température et de pression. Un outil de simulation numérique a été élaboré sur cette base expérimentale. Pour répondre aux besoins de l'étude, un dispositif expérimental spécifique a été développé et de multiples techniques d'analyse ont été utilisées afin de comprendre les mécanismes physiques mis en jeu lors de la combustion des particules d'aluminium. Il en ressort que la vitesse de flamme augmente avec la concentration et que pour la même concentration globale, la combustion se propage plus rapidement dans les nuages de nanoparticules que dans les nuages de microparticules. Les températures de la phase gazeuse et de la phase condensée pour le nuage de particules nanométriques sont inférieures à celles du nuage de particules micrométriques. L'élaboration d'un modèle à partir des paramètres expérimentaux permet d'obtenir des temps de combustion qui concordent avec l'expérience. Deux lois en D 0,25 et D 0,49 peuvent être estimées en considérant des particules nanométriques non agglutinées

Etudes expérimentales et modélisation de la combustion des nuages de particules micrométriques et nanométriques d'aluminium

ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

Studies on the burning of micro-and nano-aluminum particle clouds

International audienceThe aim of the present work is to reduce the burning time of aluminum particles with the ultimate goal to improve the performances of solid propellants. Aluminium nanoparticles have gained importance because of their increased reactivity as compared with traditional micro-sized particle. Decreasing the size of Al particles increases their specific surface area, and hence decreases the burning time of the same mass of particles. Nevertheless another consequence of decreasing the particle size is an increase of alumina mass fraction in the reactant powders passivated in air. An experimental program is initiated to determine flame propagation velocities of micro-sized (around 6 µm) and nano-sized (around 250 nm) aluminum particle clouds. Another goal of this study is to estimate the gas phase temperature from AlO molecular spectra and the temperature of condensed phase emitters in the flame using emission spectroscopy. To this end, an experimental setup is developed to investigate the flame characteristics of particle clouds ignited by an electric spark in a glass tube. The present results show that nano-sized Al particle clouds burn faster than micro-sized particle clouds for the same global particle mass concentration in air. The cloud flame propagation velocity depends also on the particle concentration. The temperature measurements indicate a consistent value around 2900 K for all nano-Al particle burning clouds and 3300 K for micro-Al particle clouds. The results of the condensed phase temperature show, first a stable temperature and then a decreasing trend along the axis of the flame

Production of carbon monoxide from a He/CO 2 plasma jet as a new strategy for therapeutic applications

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Plasma jet as a source of carbon monoxide (CO) for biomedical applications

International audienceCarbon monoxide (CO) has a bad reputation due to the potentially lethal consequences when inhaled at high concentrations. However, at low doses CO appears to have many beneficial effects for human health and has a broad spectrum of biological activities such as anti-inflammatory, vasodilatory, anti-apoptotic, and anti-proliferative effects [1]. Plasma can generate CO from the dissociation of CO2, and in this context, non-equilibrium plasma at atmospheric pressure is an attractive in situ CO source, since it is able to create CO at low doses from CO2 [2]. Moreover, plasma can be used for biomedical applications and intense research is now being conducted on the potential therapeutic use of plasma for the treatment of different pathologies including cancer and skin wounds. Plasmas are very versatile as they possess the capacity to generate large amounts of reactive species combined with electric field, photons and charged particles. However, the combination of plasma and CO for biomedical applications remains to be fully explored. This presentation will focus on the challenge to develop a plasma reactor to generate controlled quantities of CO that can be used for therapeutic purposes. The reactor is based on plasma jet configuration where the discharge is produced in a coaxial dielectric barrier discharge (DBD) reactor equipped with a quartz capillary tube [3]. Helium with small addition of CO2 goes through the device. To assess and quantify the production of CO from plasma, we developed a system whereby mouse blood hemoglobin, a strong scavenger of CO, interacted with the plasma reaction. Once CO binds to hemoglobin, it forms carboxyhemoglobin (COHb), which can be precisely quantified by light absorption. We will present the first results showing that an indirect and a direct plasma treatment have a different influence on the production of CO and its binding to hemoglobin. [1]B. E. Mann and R. Motterlini, Chem. Commun., no. 41, p. 4197, 2007.[2]E. Carbone and C. Douat, Plasma Med., vol. 8, no. 1, pp. 93–120, 2018.[3]T. Darny, J.-M. Pouvesle, V. Puech, C. Douat, S. Dozias, and E. Robert, Plasma Sources Sci. Technol., vol. 26, no. 4, p. 045008, Mar. 2017

Low Temperature Reactivity of Aluminum Nanopowders with Liquid Water

International audienceIn this paper, we present an experimental study of the isothermal reaction of aluminum nanoparticles with liquid water in the temperature range [45 – 95°C]. Gas phase chromatography and X-ray diffraction analyses have revealed that the reaction Al + H 2 O yields to a solid aluminum oxyhydroxide (AlOOH) and to hydrogen (H 2). Hence, in order to describe the macrokinetics of the oxyhydroxidation of aluminum, the H 2 gas release was measured as a function of time and temperature. Furthermore, the effect of salt water (3% NaCl or KCl in mass) compared to pure water was investigated. It is shown that the hydrogen release is preceded by an induction period corresponding to the destruction of the oxide film initially covering the Al particles. The induction and the maximal hydrogen flow rate follow an Arrhenius law. Activation energies are calculated. In opposition to the works about the corrosion of salt water, the kinetics of reactions are slowed down by the addition of chloride ions

Studies on the burning of micro- and nanoaluminum particle clouds in air

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Ignition of single nickel-coated aluminum particles

International audienceA thin coating of nickel on the surface of aluminum particles can prevent their agglomeration and at the same time facilitate their ignition, thus increasing the efficiency of aluminized propellants. In this work, ignition of single nickel-coated aluminum particles is investigated using an electrodynamic levitation setup (heating by laser) and a tube reactor (heating by high-temperature gas). The levitation experiments are usedfor measurements of the ignition delay time at different Ni contents in the particles. The high-temperature gas experiments are used to measure the critical ignition temperature. It is reported that the Ni coating dramatically decreases both the ignition delay time of laser-heated Al particles and the critical ignition temperature of gas-heated Al particles. A heat balance analysis of the levitated particles shows that the lower ignition temperature of Ni-coated Al particles is the most probable reason for the observed reduction in the ignition delay time. Exothermic intermetallic reactions between liquid Al and solid Ni are considered as the main reason for the lowered ignition temperature of Ni-coated Al particles