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International audience; Cold Atmospheric Plasmas (CAPs) are now currently used for numerous applications concerning the surface treatment of solid materials at the macro-, micro- and nano- scales. Surface modifications produced lead to new functionnalities induced by the interactions of the materials with the different energy components (electrons, ions, photons, reactive species) of these partially ionised gases, produced at atmospheric pressure and temperature closed to the room one. Another large area of applications is related to the treatment of liquids in which it is possible to increase the chemical reactivity, thus allowing nanoparticles synthetisis or bacterial decontamination. In this presentation we will first discuss on the physical and chemical properties of these specific plasmas. Their principles of manufacturing will be summarized and particular attentions will be indicated on the environment around the plasma-surface interaction zone. A non-exhaustive state of the art will provide a better understanding of the physical mechanisms associated with their propagation up to the material to be treated. A large biological applications field will be then shown, illustrated by the analyses of modifications produced on steels, polymers but also on physiological liquids and living cells. Methods of the interactions characterizations are numerous and we will present some known techniques but with an innovative approach as for instance the IR-ATR spectroscopy for tracking of modifications of polymers surface. The insitu electrochemistry1 has been also developed during the plasma exposure of liquids and results obtained will be given, showing that it is possible to measure very low current in the nA range and in the presence of high electric fields used for the plasma formation. Bio-chemically Reactive Oxygen and Nitrogen Species (RONS) production (H2O2, NO2-) can thus be followed and quantified, as well as the detection of short-living species.

International audience

International audience; Compelling evidence suggests that Cold Atmospheric Pressure Plasma (CAPPs) has potential as a new cancer therapy. However, knowledge about cellular signaling events and toxicity subsequent to plasma treatment of is still poorly documented. The aim of this study was to focus on the interaction between 3 different types of plasma (He, He-O2, He-N2) and human epithelial cell lines to gain better insight into plasma-cell interaction. We choose epithelial cell lines (human keratinocytes, human fibroblasts, human colorectal carcinoma and skin melanoma) to gain insight into plasma-cell interaction and to determine which cellular pathways are induced by CAPP treatment in normal and malignant cells. We provide evidence that the proteasome, a major intracellular proteolytic system which is important for tumor cell growth and survival, is a target for (He or He-N2) CAPP. This is accompanied by apoptosis, DNA damage, mitochondrial dysfunction and mild oxidative protein damage. By differential label-free quantitative proteomic analysis we found that CAPP triggers antioxidant and cellular defense but also seen cancerous processes in keratinocytes. Moreover we found that malignant cells are more resistant to CAPP treatment than normal cells. However, reactiveoxygen and nitrogen species (RONS) are not the only actors involved in cell death; electric field and charged particles could play a significant role especially for He-O2 CAPP. Particular attention was paid to the contribution of the electric field (EF) and RONS in cellular response to plasma treatment. Taken together, our findings provide insight into potential mechanisms of CAPP-induced cell death.

International audience

The thermal behaviors of cetyl (C16OH) and stearyl (C18OH) alcohols, alone or in mixture (C16/18OH), or flooded with water in the absence or presence of cetyl trimetyl ammonium chloride (CTAC), have been investigated using differential scanning calorimetry and X-ray scattering. Additional endothermic temperature transitions were observed at 16.9, 58.8, and 70.7 A degrees C and also an unusual exothermic transition at 63.5 A degrees C, when C16/18OH is in the presence of CTAC. The two first transitions at 16.9 and 58.8 A degrees C seems to be, respectively, linked to the hydration mechanism and the melting of long-chain alcohols, while the exothermic one at 63.5 A degrees C is corresponding to the crystallization of a swollen lamellar phase L (beta) . The crystallized swollen lamellar phase L (beta) melts at 70.7 A degrees C into a L (alpha) swollen liquid lamellar mesomorph phase, inducing an endothermic transition. This L (beta) -> L (alpha) transition is reversible upon cooling and reheating. Those data are key information to control the dispersion state of swollen lamellar crystals of long-chain alcohols.

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National audience

International audience; Today, it is necessary to better understand the role of reactive species in plasmas on biological objects in order to use plasma processes for biomedical applications. Even when well-known plasma set-ups producing one main reactive species in a controlled environment are used, it is still difficult to understand reactive species interaction processes with biological systems. In this study, nanoimaging with the most sensitive mass spectrometry technology, and the use of isotopic 15N2 or/and 18O2 containing-Ar gas mixtures to produce the plasma is proposed in order to obtain isotopic and elemental data on microwave late afterglow treated Escherichia coli bacteria. By this way, new data dealing with reactive species binding processes on plasma treated bacteria by using NanoSIMS50 mass spectrometer are obtained.

International audience; This work presents a primary experimental study of a custom-made coaxial DBD reactor driven by a bipolar pulsed High Voltage supply. The reactor is fed by nitrogen or air at atmospheric pressure conditions and uses a dielectric coating on the HV electrode. The High Voltage generator delivers a "pulse-like" bipolar signal in the 10-50 kHz frequency range. This set-up has been conceived for surface treatment applications in afterglow conditions. Electrical and optical diagnostics are employed for the investigation of the nitrogen and air DBD while varying the frequency of the HV bipolar signal and the maximum applied voltage. Current and voltage oscillogrammes are used in order to derive the mean plasma power injected in the gap. Photomultiplier scans reveal the discharge's filamentary character whereas Optical Emission Spectroscopy (OES) shows the excited species present in such conditions. Comparisons between electrical and OES results show a correlation between the mean plasma power and the production of active species.

International audience; The formation and propagation of ionization waves (streamers) in the filamentary mode of a barrier discharge in Nitrogen at atmospheric pressure is examined. The role of photoemission as well as of photoionization is analysed via a two dimensional finite element flux corrected transport (FEM-FCT) [1] model. Numerical investigations show how the photoemission coefficient influences the formation and propagation of ionization waves into the gas gap. In addition, an attempt is made to elucidate the way the streamer interacts with the dielectric basically by considering the surface charge accumulation in the dielectric material.

International audience; no abstract