Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session ET4: Biological and Biomedical Applications of Plasmas II |
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Chair: Mounir Laroussi, Old Dominion University Room: Petit Amphitheatre |
Tuesday, October 5, 2010 4:00PM - 4:30PM |
ET4.00001: Blood-biocompatible materials via plasma processing Invited Speaker: Biocompatible materials, e.g. vascular grafts made of polymers have successfully replaced large-diameter blood vessels, but the long-term performance of small-diameter ($<$ 6 mm) vascular grafts is still disappointing. The main problem is insufficient biocompatibility of polymer surface with blood, which causes complications after implementation; such as thrombosis or restenosis. These complications immediately lead to an additional surgical procedure, which is expensive and unpleasant (or sometimes even fatal)~for the patient. Many efforts have been done to improve surface biocompatibility of vascular grafts, mainly by coating the surface with bioactive substances such as gelatin, albumin, collagen and heparin. However, successful results have not yet been reported for small-diameter vascular grafts. A promising way to modify surface properties of vascular grafts is by plasma treatment, as this method enables modification of surface properties in terms of surface roughness, surface chemistry, wettability and crystallinity, without alternating the bulk attributes. Because these surface properties play a key role in biocompatibility of materials, we studied effects of plasma processing on polymer surfaces and correlated them with proliferation of endothelia cells and adhesion of platelets in order to achieve direct protection of vascular grafts with self-controlled bio-surface. The \textit{in vitro} biological response of plasma processed polymers showed that more significant changes in biological response can be obtained on oxygen treated surfaces. These surfaces enabled improved proliferation of endothelia cells and reduced adhesion of platelets. This can mainly be attributed to newly formed oxygen functional groups, which seem to have remarkable influence on adhesion of platelets. And more, the platelet adhesion is also a function of polymer crystallinity, since as much lower platelet adhesion is observed on semicrystalline polymers in comparison to amorphous. Interestingly there is no significant correlation between platelet adhesion and surface wettability. So, we can conclude that low temperature oxygen plasma processing is promising method to improve proliferation of endothelia cells and to reduce adhesion of platelets from blood, and improve hemocompatibile properties of vascular grafts made of polymers like PET. [Preview Abstract] |
Tuesday, October 5, 2010 4:30PM - 4:45PM |
ET4.00002: Novel Plasma Surface Texturing of Metals for Biomedical Applications Eunsung Park A novel plasma process for creating nano- and micron-scale textures was investigated on several alloys using radio-frequency (RF) inert gas plasmas. Various morphologies with high aspect ratio as well as 3-dimensionally interconnected porous structures have evolved on metal surfaces. The morphologies were found to be varied with alloy composition and/or plasma processes. In this plasma texturing process, metal samples were placed directly on the substrate holder that was electrically connected to an RF electrode. Typical process parameters included power of 200W to 800W, pressures of 20 mTorr to 80 mTorr, and process time of 8 min to 10 min. The resulting microstructures were believed to be formed by the combination of ion sputtering and subsequent materials diffusion due to heating of the metal surfaces. Process variables, including RF energy and pressure, as well as properties of the material to be textured (thermal and electrical transport properties and sample geometry) were all found to affect the degree of texturing and type of microstructure formed. This texturing process provides several advantages over other coating-based texturing processes. A major advantage with this surface modification process is the elimination of concern regarding coating delamination and loose particulates, which would cause serious problems in some biomedical applications. Possible applications of the textured surfaces include drug reservoirs, surfaces that promote tissue or bone in-growth, and other applications benefited by high surface areas. [Preview Abstract] |
Tuesday, October 5, 2010 4:45PM - 5:00PM |
ET4.00003: Development of an Air Plasma Driven by Energy Controlled DC Pulse Chang-Seung Ha, Dong-Hyun Kim, Hae June Lee, Ho-Jun Lee, Sang Rye Park, Gyoo Cheon Kim An atmospheric pressure plasma jet driven by energy controlled DC pulse has been developed. In the previous study, we showed that Ar and He plasma jet was successfully generated and well controlled by proposed method with relatively low DC voltage ($\sim $800 V)(1). In this study, the DC pulse is raised to 2 kV using DC-DC converter and switching device, and the plasma is generated under air flow condition. This air jet plasma device adopt dielectric-free metal electrode with externally controllable ballast capacitor. The plasma can stably and precisely be controlled by voltage and capacitance of ballast capacitor. It is shown that operation regime of the air plasma jet can be varied from the glow mode to the near-arc. The electro-optical characteristics such as voltage and current waveforms, optical emission spectra, and ICCD images were investigated. As an application of proposed plasma source, study on the cancer cell treatment was performed. It is observed that the death of oral squamous cell carcinoma (SCC25) cell is caused by exposure of air plasma jet. This result demonstrates the potential of the proposed plasma source for skin or oral cancer treatment. (1) C-S Ha \textit{et al.}, Proceedings of 37$^{th}$ ICOPS, 20-24 June 2010 [Preview Abstract] |
Tuesday, October 5, 2010 5:00PM - 5:15PM |
ET4.00004: A new design of dielectric barrier discharge for self surface sterilization Yangfang Li, Tetsuji Shimizu, Julia Zimmermann, Gregor Morfill We present a new design of the electrode for dielectric barrier discharge. In this new development, electrodes are encapsulated inside a dielectric surface so that no naked metal electrode is exposed to the air. The plasma is ignited on the surface of the device by applying low-frequency ($\sim$1 kHz) high voltage ($\sim$10 kV) signal between the electrodes and the surface can then be sterilized by the plasma. We tried the different encapsulating materials, for example, epoxy, optical glass, and glass ceramic. And also different arrangements of the electrodes were tested for the bactericidal effect and for the plasma ignition on the surface. The results show that the surface can be sterilized within 30 seconds for typical operating conditions. In the end, we will discuss the possible applications of this new device for a regular disinfection of the kitchen tables, laboratory benches, and so on. [Preview Abstract] |
Tuesday, October 5, 2010 5:15PM - 5:30PM |
ET4.00005: Reduced-pressure ($\sim $1 torr) argon discharges for sterilization: influence of the type of materials subjected to the discharge Pierre Levif, Jacynthe Seguin, Michel Moisan, Jean Barbeau Noble gases, as argon, for sterilization purposes in plasma discharges at reduced pressure, is very promising. As compared to molecular discharges (N$_{2})$, absorbed power density in argon is relatively low, which allows processing thermally-sensitive materials through plasma immersion. Noble gases discharges for sterilization purposes is safe for operator: no toxic residues, therefore no need to vent medical devices processed, in contrast to low-temperature chemical sterilization. The system designed to generate adequate reduced-pressure argon plasma sterilizer is described. Results of effects of nature of substrates subjected to argon discharge are analyzed through optical emission spectroscopy. The discharge spectrum in empty chamber is similar to that obtained when adding metal and glass substrates. In contrast, presence of polymers strongly modifies the spectrum. Influence of this ``contamination effect'' of gaseous phase on inactivation efficiency of exposed bacterial spores is examined through survival curves of microorganisms. Our results bring new insight into time evolution of inactivation mechanisms when different materials are being subjected to argon discharge for sterilization purposes. [Preview Abstract] |
Tuesday, October 5, 2010 5:30PM - 5:45PM |
ET4.00006: Damages on Bacteria Irradiated by Microwave-excited Atmospheric Pressure Plasmas Tatsuya Ogawa, Kazuo Takahashi, Takuya Urayama, Shinji Aoki The sterilization mechanism was analyzed in atmospheric microwave-excited plasmas. The bacteria on stainless steel were exposed to plasmas. The effect of plasma on sterilization was evaluated by colony counting method. The XPS was employed to analyze chemical bond composition changing with killing bacteria. The surviving bacteria decreased with plasma exposure time. On the bacteria surface, the -C-H-, --C-C-, -C=O- and -NH-C=O bonds decreased, and the -C-O-, -C-N-, -C-N$^{+}$- and COOH bonds increased with the time. Changing in the chemical composition on the bacteria surface corresponds to damage of cell wall resulting in killing of bacteria. [Preview Abstract] |
Tuesday, October 5, 2010 5:45PM - 6:00PM |
ET4.00007: Effect of Anode-Cathode Gap on Microhollow Cathode Discharges J. Greenan, C.M.O. Mahony, P.D. Maguire, D. Mariotti A high pressure hollow cathode (HC) plasma source was designed and fabricated for thin film deposition of bio-compatible coatings on coronary artery stent interiors. We investigate the electrical {\&} optical characteristics of a 10 mm long solid-wall hollow cylinder ($\sim $2~mm ID), as a stent substitute, with precision control of the anode -- cathode (cylinder) gap dimension (to 12 micron). We present VI, Paschen curves and other derived scaling characteristics while OES was employed to determine the effective electron temperature via a collisional-radiative model [1]. An analytical radial sheath model is used to estimate the sheath width and electron density within the cylinder. We observe in the VI characteristics, a number of modes not associated with expansion over the cathode exterior but indicating current-dependent discharge progression along the interior of the cathode cylinder. We also observe deviation from standard pd and j/p$^{2}$ scaling.\\[4pt] [1] Mariotti D et. al., \textit{J. Appl. Phys} \textbf{101} (2007) 013307 [Preview Abstract] |
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