Vanessa Sarron

ROS implication in a new antitumor strategy based on non-thermal plasma

Non‐thermal plasma (NTP) is generated by ionizing neutral gas molecules/atoms leading to a highly reactive gas at ambient temperature containing excited molecules, reactive species and generating transient electric fields. Given its potential to interact with tissue or cells without a significant temperature increase, NTP appears as a promising approach for the treatment of various diseases including cancer. The aim of our study was to evaluate the interest of NTP both in vitro and in vivo. To this end, we evaluated the antitumor activity of NTP in vitro on two human cancer cell lines (glioblastoma U87MG and colorectal carcinoma HCT‐116). Our data showed that NTP generated a large amount of reactive oxygen species (ROS), leading to the formation of DNA damages. This resulted in a multiphase cell cycle arrest and a subsequent apoptosis induction. In addition, in vivo experiments on U87MG bearing mice showed that NTP induced a reduction of bioluminescence and tumor volume as compared to nontreated mice. An induction of apoptosis was also observed together with an accumulation of cells in S phase of the cell cycle suggesting an arrest of tumor proliferation. In conclusion, we demonstrated here that the potential of NTP to generate ROS renders this strategy particularly promising in the context of tumor treatment.

Characterization of pulsed atmospheric-pressure plasma streams (PAPS) generated by a plasma gun

An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107?108?cm?s?1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications.

Rare gas flow structuration in plasma jet experiments

Modifications of rare gas flow by plasma generated with a plasma gun (PG) are evidenced through simultaneous time-resolved ICCD imaging and schlieren visualization. The geometrical features of the capillary inside which plasma propagates before in-air expansion, the pulse repetition rate and the presence of a metallic target are playing a key role on the rare gas flow at the outlet of the capillary when the plasma is switched on. In addition to the previously reported upstream offset of the laminar to turbulent transition, we document the reverse action leading to the generation of long plumes at moderate gas flow rates together with the channeling of helium flow under various discharge conditions. For higher gas flow rates, in the l min−1 range, time-resolved diagnostics performed during the first tens of ms after the PG is turned on, evidence that the plasma plume does not start expanding in a laminar neutral gas flow. Instead, plasma ignition leads to a gradual laminar-like flow build-up inside which the plasma plume is generated. The impact of such phenomena for gas delivery on targets mimicking biological samples is emphasized, as well as their consequences on the production and diagnostics of reactive species.

Atmospheric-pressure plasma transfer across dielectric channels and tubes

Atmospheric-pressure plasma transfer refers to producing an ionization wave (IW) in a tube or channel by impingement of a separately produced IW onto its outer surface. In this paper, we report on numerical and experimental investigations of this plasma transfer phenomenon. The two tubes, source and transfer, are perpendicular to each other in ambient air with a 4 mm separation with both tubes being flushed with Ne or a Ne/Xe gas mixture at 1 atmosphere pressure. The primary IW is generated in the source tube by ns to µs pulses of ±25 kV, while the transfer tube is electrodeless, not electrically connected to the first and at a floating potential. The simulations are conducted using a two-dimensional (2D) plasma hydrodynamics model with radiation transport, where the three-dimensional tubes in the experiments are represented by 2D channels. Simulations and experiments show that the primary IW propagates across the inter-tube gap and upon impingement induces two secondary IWs propagating in opposite directions in the transfer tube. Depending on the polarity of the primary IW in the source tube, the secondary IW in the transfer tube can have polarities either the same or opposite to that of the primary IW. The speed and strength of both the primary and secondary IWs depend on the rate of rise of the voltage pulse in the source tube. The modelling results were found to agree well with the behaviour of plasma transfer observed using nanosecond intensified charge-coupled device imaging.

Splitting and Mixing of High-Velocity Ionization-Wave-Sustained Atmospheric-Pressure Plasmas Generated With a Plasma Gun

The nanosecond imaging of high-velocity ionization-wave-generated plasmas using a plasma gun is presented. A circular glass pipe is used to study the splitting, the propagation, and the mixing of atmospheric-pressure plasma streams ensuing from a single dielectric-barrier-discharge reactor.

Pulsed atmospheric pressure plasma streams: Characterization and role of critical experimental parameters

Summary form only given. This work reports on the investigation of neon and helium atmospheric pressure plasma generation and propagation in high aspect ratio capillaries, either in straight or branched assemblies. ICCD imaging on ns and sub-ns time scales, together with measurement of the speed of the plasma ionization front reveal the specific features of such plasmas. The plasmas are ignited with DBD electrodes and launched into a tube flushed with a moderate flow (a few sccm) of rare gas and powered with high voltage pulses delivered in single shot or repetitive mode up to a few kHz. The plasma expands in a wall hugging mode in the vicinity of the DBD electrodes gradually switching to a much more homogenous plasma volume during its propagation before inducing a plasma plume in ambient air at the outlet of the capillary. This plasma pattern is associated with two ionization front velocity regimes during which the plasma experiences an order of magnitude deceleration from a few 108 cm/s to a few 107 cm/s in the wall hugging mode and then gradually slows over distances of up to a few tens of cm in the homogenous mode. The influence of pulse repetition rate, dielectric wall permittivity, voltage rising front (either µs or ns) and voltage polarity, will be discussed, while accounting for the roles of the impedance of plasma tail behind the ionization front region and the wall charging processes. For our conditions, photoionization appears to be of minor importance.

Abstract 2839: Antitumor activity on colorectal and pancreatic tumors of a new strategy based on ROS generation by non-thermal plasma

Background. Local treatments of tumors are mainly based on surgical resection and/or treatment such as photodynamic therapy (PDT) or ionizing radiation (IR). Action mechanisms of IR and PDT are based on the generation of ROS in the vicinity of the cells. In this context, cold or Non Thermal Plasma (NTP), a new technology which can generate in situ ROS, is currently under investigations. NTP is a cold ( Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2839. doi:1538-7445.AM2012-2839