Interactions of the directed plasma from a cathodic arc withelectrodes and magnetic fields

Curved magnetic ducts are frequently used to remove macroscopic-sized droplets from the plasma stream of cathodic vacuum arcs. The plasma of a cathodic vacuum arc in a magnetic filter is characterized by a strongly directional ion velocity (corresponding to 20-100 eV) and magnetized electrons. In the first section of this paper the effects of these features on the I-V characteristic curves of planar probes are identified and explained using a simple model. This is then used to interpret the interaction of the plasma with the walls of a biased quarter torus duct. Two small electrodes placed on the outer and inner sections of the curved duct wall show that the I-V characteristic is determined primarily by the electron-ion current balance at the wall on the outside of the curve. The application of a bias to a planar electrode on the outer wall section was found to give the same increase in throughput as a positive bias applied to the entire duct with the advantage of a much smaller electron current being drawn by the biasing power supply. The improvement in duct throughput achievable with positive-biasing of the duct wall was found to depend on both the configuration and strength of the magnetic field in the quarter torus filter. The plasma density profile and potential were unaffected by the application of the bias     

Characterization of rhinovirus subviral A particles via capillary electrophoresis, electron microscopy and gas-phase electrophoretic mobility molecular analysis: Part I

During infection, enteroviruses, such as human rhinoviruses (HRVs), convert from the native, infective form with a sedimentation coefficient of 150S to empty subviral particles sedimenting at 80S (B particles). B particles lack viral capsid protein 4 (VP4) and the single-stranded RNA genome. On the way to this end stage, a metastable intermediate particle is observed in the cell early after infection. This subviral A particle still contains the RNA but lacks VP4 and sediments at 135S. Native (150S) HRV serotype 2 (HRV2) as well as its empty (80S) capsid have been well characterized by capillary electrophoresis. In the present paper, we demonstrate separation of at least two forms of subviral A particles on the midway between native virions and empty 80S capsids by CE. For one of these intermediates, we established a reproducible way for its preparation and characterized this particle in terms of its electrophoretic mobility and its appearance in transmission electron microscopy (TEM). Furthermore, the conversion of this intermediate to 80S particles was investigated. Gas-phase electrophoretic mobility molecular analysis (GEMMA) yielded additional insights into sample composition. More data on particle characterization including its protein composition and RNA content (for unambiguous identification of the detected intermediate as subviral A particle) will be presented in the second part of the publication.     

Plasma‐Activated Substrate with a Tropoelastin Anchor for the Maintenance and Delivery of Multipotent Adult Progenitor Cells

Conventional wound therapy utilizes wound coverage to prevent infection, trauma, and fluid and thermal loss. However, this approach is often inadequate for large and/or chronic wounds, which require active intervention via therapeutic cells to promote healing. To address this need, a patch which delivers multipotent adult progenitor cells (MAPCs) is developed. Medical‐grade polyurethane (PU) films are modified using plasma immersion ion implantation (PIII), which creates a radical‐rich layer capable of rapidly and covalently attaching biomolecules. It is demonstrated that a short treatment duration of 400 s maximizes surface activation and wettability, minimizes reduction in gas permeability, and preserves the hydrolytic resistance of the PU film. The reactivity of PIII‐treated PU is utilized to immobilize the extracellular matrix protein tropoelastin in a functional conformation that stably withstands medical‐grade ethylene oxide sterilization. The PIII‐treated tropoelastin‐functionalized patch significantly promotes MAPC adhesion and proliferation over standard PU, while fully maintaining cell phenotype. Topical application of the MAPC‐seeded patch transfers cells to a human skin model, while undelivered MAPCs repopulate the patch surface for subsequent cell transfer. The potential of this new wound patch as a reservoir for the sustained delivery of therapeutic MAPCs and cell‐secreted factors for large and/or non‐healing wounds is indicated in the findings.     

Electric probe measurements of high-voltage sheath collapse in cathodic arc plasmas due to surface charging of insulators

High-voltage sheath dynamics near a negatively biased substrate in cathodic arc plasmas are investigated using a biased electrical probe. Since the sheath is devoid of electrons, the sheath boundary can be inferred from the position where a positively biased probe draws no electron current. The extent of the sheath is primarily dependent on the plasma density, the ion velocity and the applied voltage. Using insulating substrates, the sheath boundary eventually retracts due to a dynamic reduction in the applied voltage. This reduction is caused by positive charge accumulation on the insulator surface. The collapse time of the sheath is dependent on the plasma density and the substrate characteristics. We believe this to be the first direct observation of the reduction in the width of the high-voltage sheath when implanting an electrical insulator using plasma-based ion implantation (PBII). This information is important when determining the optimal parameters for plasma-based ion implantation of insulators. Our measurements are compared with theoretical predictions based on the Child-Langmuir equations for high-voltage sheaths. By choosing appropriate values for the secondary electron coefficient the theory could be made to fit the experimental data. A discussion of the validity of the choice of secondary electron coefficients is presented.     

Studien über den Hofmannschen Abbau quartärer Ammoniumverbindungen

Ohne Zusammenfassung     

Protein immobilization capacity and covalent binding coverage of pulsed plasma polymer surfaces

Three carbon surfaces were deposited using pulsed plasma enhanced chemical vapour deposition method: a low and a high nitrogen-containing plasma polymer surfaces and a diamond-like carbon surface. The surfaces were analysed using both X-ray photoelectron spectroscopy (XPS) technique and the enzyme-linked immunosorbent assay (ELISA) method combining with sodium dodecyl sulphate (SDS) cleaning to investigate the capacity and covalent binding of the immobilized proteins. A good correlation was found on quantification of remaining protein after SDS cleaning using the ELISA method and the XPS technique. All surfaces had similar initial capacity of protein attachment but with large different resistance to SDS cleaning. The analysis showed that the high nitrogen-containing plasma polymer was the best biocompatible material due to its highest resistance to SDS cleaning, i.e. with the highest quantity (∼80%) of proteins bound covalently.     

Capillary electrophoresis of liposomes functionalized for protein binding

CE enabled assessing the attachment of hexa-histidine-tagged proteins to functionalized phospholipid liposomes. The liposomes were made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, phosphatidyl-ethanolamine, cholesterol and distearoyl-glycero-3-phosphoethanolamine-N-methoxy(polyethylene glycol) in a molar ratio of 29:26:40:5. The unilamellar vesicles, which had an average diameter of 170 nm, were labelled by inclusion of FITC-dextran for fluorescence detection. CE was carried out in poly(vinyl alcohol) (PVA)-coated capillaries at 25 degrees C with a BGE consisting of Tris-HCl (50 mM, pH 8.0). For conjugation of the liposomes with the proteins (soluble synthetic receptor fragments with molecular mass of 60 and 70 kDa, respectively), Ni(2+) was implanted into the vesicle surface by an anchor lipid containing a nitrilotriacetate acid (NTA) group as complexation agent for the metal ions. The difference in surface charge enabled the separation of the different species of interest by CE: plain vesicles, vesicles functionalised with Ni-NTA, vesicle-protein complexes and the species formed upon removal of the Ni-ions by complexation with EDTA. Loss of the Ni-ions resulted in the release of the proteins and the reappearance of the plain Ni-free NTA-liposome species in the electropherograms.     

Comparison of protein surface attachment on untreated and plasma immersion ion implantation treated polystyrene: protein islands and carpet

Surface attachment of the enzyme horseradish peroxidase (HRP) was studied on untreated and ion beam implanted polystyrene (PS) films. The PS films of 100 nm thickness on a silicon wafer were treated using the plasma immersion ion implantation (PIII) technique, with argon ions of energy 20 keV and fluences of up to 2 x 10(16) ions/cm2. Differential transmittance Fourier transform infrared (FTIR) spectra confirmed the presence of proteins on the PS surfaces by detection of the amide A, I, and II protein vibrations. Spectroscopic ellipsometry over the UV-vis spectral region provided the optical constants and thickness of the protein layer, while tapping mode atomic force microscopy (AFM) was used to image the protein distribution on the surface. The combination of AFM, ellipsometry, and FTIR analysis showed that, on the untreated PS surface, HRP formed islands 8 nm in height and 30 nm in lateral size, covering approximately 27% of the PS surface. After PIII modification of the PS surface, the protein covered 100% of the surface area.     

Influence of Gas Entry Point on Plasma Chemistry,Ion Energy and Deposited Alumina Thin Films in Filtered Cathodic Arc

The effect of gas entry point on the plasma chemistry, ion energy distributions and resulting alumina thin film growth have been investigated for a d.c. cathodic arc with an aluminum cathode operated in an oxygen/argon atmosphere. Ions of aluminum, oxygen and argon, as well as ions originating from the residual gas are investigated, and measurements for gas entry at both the cathode and close to the substrate are compared. The latter was shown to result in higher ion flux, lower levels of ionised residual gas, and lower ion energies, as compared to gas inlet at the cathode. These plasma conditions that apply when gas entry at the substrate is used result in a higher film deposition rate, less residual gas incorporation, and more stoichiometric alumina films. The results show that the choice of gas entry point is a crucial parameter in thin film growth using reactive PVD processes such as reactive cathodic arc deposition.