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Atmospheric pressure (AP) dielectric barrier discharges (DBDs) are increasingly used to treat thermally-sensitive materials. Reliable measurements of the kinetic gas temperature, T, are therefore of capital importance. Spectroscopically determined rotational temperatures, Trot, are often tacitly assumed to be equal to T. Here, we measured T with fibre-optic instrumentation that is a priori immune towards high voltages and high-frequency electromagnetic fields generally encountered in plasmas. Finding Trot > T in AP glow discharge (APGD) DBDs in He and Ne, we believe that Trot ≈ T only during the short (≈ µs) current peaks that characterize APGD. Therefore, T represents the time-averaged gas temperature; calorimetric measurements using a thermocouple buried in an electrode support this view. [ABSTRACT FROM AUTHOR]

Bone metastasis is a frequent occurrence following breast cancer. The bone‐tumor microenvironment is heterogeneous and complicated to recapitulate. The development of new chemotherapeutics is ineffective partly due to a lack of precise in vitro tissue models. We developed a three‐dimensional (3D) bone‐tumor interface model for customized chemotherapeutic screening. It comprises a plasma‐modified electrospun mat seeded with osteoblasts to mimic a bone tissue, with a cell‐seeded hydrogel layer containing more and less aggressive or noncancerous cells on top, mimicking the tumor compartment. By screening the model with doxorubicin, we observed different migratory behaviors, with IC50 values that were largely in accordance with those cell lines' characteristics. Our 3D model reproduces the bone microenvironment and has great potential as a drug screening tool for personalized medicine. [ABSTRACT FROM AUTHOR]

We report on a methodology for measuring the energy dissipated per AC high voltage cycle in a cold atmospheric pressure plasma jet (CAPJet). This method is adapted from research by Nisol et al. on plasma polymerization of hexamethyldisiloxane (HMDSO) organosilicon vapor in a large area planar dielectric barrier discharge (DBD) reactor. Here too, we measured ΔEg, the energy difference with and without small HMDSO vapor concentrations in the argon carrier gas flow. From ΔEg we then derived Em, the energy per molecule, and compared values with those of Nisol. Good agreements were found, including in film structures determined from attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra, thus suggesting that realistic Em values can be successfully obtained also for the CAPJet case. [ABSTRACT FROM AUTHOR]

The method we have developed for understanding energetic exchanges between precursor molecules and argon (Ar) carrier gas in a dielectric barrier discharge (DBD) has much‐proven merit. The present article focuses on hydrofluoromethanes, CHxFy. The precursors (‰ concentrations) were mixed with Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD. For each compound, Em, the energy absorbed per molecule, was plotted as a function of precursor flow rate. Besides the determination of Em, we have used optical emission spectroscopy as a diagnostic of the plasma physicochemistry. The influence of chemical structure has been investigated by depositing thin plasma polymer coatings; we have measured their deposition rates and water contact angles, which have been correlated with Em values and X‐ray photoelectron spectroscopy measurements. [ABSTRACT FROM AUTHOR]

Aging (or "hydrophobic recovery") of plasma‐modified polymer surfaces has been known and documented in the literature over several decades; to the best of our knowledge, the present study appears to be the first in which this is done for two vastly different rough surface structures: (i) electrospun nanofibrous (NF) mats, and (ii) flat films (FF), for three polymers of well‐documented interest in biotechnological applications: poly(lactic acid); poly(urethane); and poly(caprolactone). Two different plasma treatments are applied: low‐pressure (LP) radio‐frequency (rf) glow discharges in flows of O2 and NH3 under mild power conditions. Measured time‐dependent surface compositions (from X‐ray photoelectron spectroscopy survey spectra) and water contact angles (WCA) were found to tend toward asymptotic limiting values after ca. 30 days of storage in clean air, as previously reported by these and other authors. An entirely novel aspect of this work is to examine and compare time‐dependent WCA behaviors of NF and FF samples in terms of Wenzel (W) and Cassie‐Baxter (C‐B) model behaviors, including possible transitions from C‐B to W and their interpretation. [ABSTRACT FROM AUTHOR]

Thiol (SH)-terminated surfaces have been progressively gaining interest over the past years as a consequence of their widespread potential applications. Here, SH-terminated thin films have been prepared by 'co-polymerizing' gas mixtures comprising ethylene (C2H4) or butadiene (C4H6) with hydrogen sulfide (H2S). This has been accomplished by either vacuum-ultraviolet (VUV) irradiation of the flowing gas mixtures with near-monochromatic radiation from a Kr lamp, or by low-pressure r.f. plasma-enhanced chemical vapor deposition (PECVD). Varying the gas mixture ratio, R, allows one to control the films' sulfur content as well as the thiol concentration [SH]. The deposits were characterized by X-ray photoelectron spectroscopy (XPS), before and after chemical derivatization with N-ethylmaleimide, and by ATR FTIR. VUV- and plasma-prepared coatings were found to possess very similar structures and characteristics, showing chemically bonded sulfur concentrations, [S], up to 48 at% and [SH] up to 3%. All coatings remained essentially unchanged in thickness after immersion in water for 24 h. [ABSTRACT FROM AUTHOR]

Bone is a frequent site of tumor metastasis. The bone–tumor microenvironment is heterogeneous and complex in nature. Such complexity is compounded by relations between metastatic and bone cells influencing their sensitivity/resistance to chemotherapeutics. Standard chemotherapeutics may not show efficacy for every patient, and new therapeutics are slow to emerge, owing to the limitations of existing 2D/3D models. We previously developed a 3D interface model for personalized therapeutic screening, consisting of an electrospun poly lactic acid mesh activated with plasma species and seeded with stromal cells. Tumor cells embedded in an alginate-gelatin hydrogel are overlaid to create a physiologic 3D interface. Here, we applied our 3D model as a migration assay tool to verify the migratory behavior of different patient-derived bone metastasized cells. We assessed the impact of two different chemotherapeutics, Doxorubicin and Cisplatin, on migration of patient cells and their immortalized cell line counterparts. We observed different migratory behaviors and cellular metabolic activities blocked with both Doxorubicin and Cisplatin treatment; however, higher efficiency or lower IC50 was observed with Doxorubicin. Gene expression analysis of MDA-MB231 that migrated through our 3D hybrid model verified epithelial–mesenchymal transition through increased expression of mesenchymal markers involved in the metastasis process. Our findings indicate that we can model tumor migration in vivo, in line with different cell characteristics and it may be a suitable drug screening tool for personalized medicine approaches in metastatic cancer treatment. [ABSTRACT FROM AUTHOR]

Atmospheric pressure (AP) dielectric barrier discharges are frequently of interest for treating delicate substrates such as polymers or biological materials. In spite of its capital importance, thermometry in AP plasmas is subject to much uncertainty. We report temperature measurements in noble gases, nitrogen, and air using sensitive, accurate fibre-optic instrumentation that is a priori immune towards high voltages and high-frequency electromagnetic fields generally encountered in plasma environments. [ABSTRACT FROM AUTHOR]

Thin organic films with oxygen-bearing functional groups (hydroxyl, carboxyl, ...) were prepared by 'co-polymerizing' gas mixtures of ethylene (C2H4) and one of several O-containing oxidizer molecules, O2, CO2, or N2O. This was done either by vacuum-ultraviolet (VUV) photo-polymerization or by low-pressure r.f. plasma-assisted CVD. The gas mixture ratio, R, permits one to control total oxygen concentration, [O], as well as the relative proportions of the various functionalities. Analyses were performed by XPS (with or without chemical derivatization using TFAA to determine [OH] content), and IRRAS-FTIR. Temporal and structural stability (mass change) of deposits under exposure to air or water was examined; altogether, data confirmed different reaction pathways for VUV and PECVD. [ABSTRACT FROM AUTHOR]

We present precision measurements of the energy, Eg, dissipated per period of the applied ac voltage at kHz frequencies (4 ≤ f ≤ 32 kHz) by atmospheric-pressure glow discharges (APGD) in flows of helium and neon. Such data are important for determining the efficiency of excimer light sources, for example. We report the methodology and specific steps taken to achieve the desired degrees of precision and reproducibility, and compare our results with data published in the literature. [ABSTRACT FROM AUTHOR]

Abstract: We report the use of dielectrophoresis (DEP) to position U-937 monocytes within a non-uniform electric field, prior to electroporation (EP) for gene delivery. DEP positioning and EP pulsing were both accomplished using a common set of inert planar electrodes, micro-fabricated on a glass substrate. A single-shell model of the cell''s dielectric properties and finite-element modeling of the electric field distribution permitted us to predict the major features of cell positioning. The extent to which electric pulses increased the permeability of the cell membranes to florescent molecules and to pEGFPLuc DNA plasmids were found to depend on prior positioning. For a given set of pulse parameters, EP was either irreversible (resulting in cytolysis), reversible (leading to gene delivery), or not detectable, depending on where cells were positioned. Our results clearly demonstrate that position-dependent EP of cells in a non-uniform electric field can be controlled by DEP. [Copyright &y& Elsevier]

Phosphorylcholine (PC) groups were grafted onto ammonia plasma-treated biaxiallyoriented polypropylene (BOPP) surfaces, via (a) reductive amination of phosphorylcholine glyceraldehyde and (b) a two-step procedure involving the chemical amplification of surface amine groups with tris(2-aminoethyl amine) and subsequent reductive amination of phosphorylcholine glyceraldehyde. The occurrence of grafting was ascertained by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier-transform infrared (ATR–FT-IR) spectroscopy. The wettability of PC-modified surfaces was assessed by dynamic contact-angle measurements using the Wilhelmy plate method. Human U937 macrophages adhered and proliferated to a significantly larger extent on PC-modified surfaces, compared to unmodified or ammonia plasma-modified BOPP. [ABSTRACT FROM AUTHOR]

The pseudoglow and glow discharge behavior of a 0.5-mm metallic-dielectric electrode gap in helium under atmospheric pressure was examined as a function of ac voltage between 0.3 and 32 kHz. The number of discharge current pulses per half-cycle within the pseudoglow was found to diminish with rising frequency, as opposed to the increase observed with rising voltage. The reduction in the rise time and the quasi-monotonic decreases in amplitude of the successive discrete current pulses within the pseudoglow were attributed to the enhanced Penning ionization due to an increase in the number of energetic precursors (metastables and dimers) over the first quadrant in each half cycle. The interruption in the discharge pulse sequence, caused by a change in polarity of the ac field, greatly reduced the precursors' concentration and resulted in the first incipient pulse of the pseudoglow having the shortest rise time and width in the pulse sequence. The increase in frequency at constant voltage caused a gradual decrease in the number of discharge current pulses within the pseudoglow, until at ca. 10 kHz and beyond only a single pulse glow discharge took place. The influence of argon, nitrogen, hydrogen, and oxygen impurities was studied and interpreted in terms of Penning ionization and electron attachment. [ABSTRACT FROM AUTHOR]

Presents a study that examined the influence of surface charges upon the partial discharge behavior of a short metallic-dielectric plane-parallel electrode gap in an air-like mixture at atmospheric pressure. Form of charge distribution at the dielectric electrode surface; Application of a simulation model; Results and discussion.

A versatile pilot‐scale reactor has been designed in such a way that it can be readily converted from a dielectric barrier discharge "PECVD" operating mode into a photoinitiated "PICVD" one; in the latter, low‐pressure mercury (Hg) lamps replace the high‐voltage glow discharge plasma. Both processes operate at ambient temperature and atmospheric pressure, 100 kPa, using acetylene (C2H2) monomer. In both sets of experiments, it was found that efficient gas‐to‐solid conversion can occur in the form of a nanoparticulate amorphous hydrocarbon polymer‐like material. It was found that in the PICVD case, great care was required to exclude even traces of O2 contamination, because it not only reduced the growth rate of solid, but the latter then became highly oxidized ([O] ~50 at.%) and water‐soluble. [ABSTRACT FROM AUTHOR]

Two dielectric barrier discharge (DBD) reactors, one small, the other about 40 times larger, associated equipment, and a dedicated MATLAB code have been used to carry out precise determinations of electrical energy, $E_{g}$ , dissipated per discharge cycle of the applied a.c. voltage, $V_{a}$. In the smaller reactor, this was done over the frequency range $5 \le f\le 50$ kHz and using twin pairs of several different insulating materials (2.54-cm-diameter disks) with relative permittivities between $2.1 \le \kappa _{\text {die}}^{\prime }\le 9.5$ as dielectric barriers in DBDs for four different gases: He, Ne, Ar, and N2. In the large reactor, $f$ was restricted to 20 kHz in Ar and He; this latter system primarily serves for plasma polymerization experiments in which organic “monomers” are admixed with the flow of Ar as carrier gas. We report the method for exactly evaluating $E_{g}$ , and then present and compare values measured under different conditions. To the extent possible, these are compared between the small and large reactors, and with results published in the literature. The reliability of the method is confirmed, for example, by reproducing published breakdown fields of the gases examined, and by several other original results. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microparticle-depleted blood plasma failed to coagulate in plastic cups. • Polyethylene-carboxylate L-PPE:O nanocoatings were created by glow-discharge plasma. • Hydroxyapatite particles, glass microbeads, and L-PPE:O coatings had anionic surfaces. • Anionic surfaces induced burst coagulation of microparticle-depleted plasma via FXII. • Microparticles and anionic surfaces can activate thrombin without platelet activation. Abstract Biomaterials are frequently evaluated for pro-coagulant activity but usually in the presence of microparticles (MPs), cell-derived vesicles in blood plasma whose phospholipid surfaces allow coagulation factors to set up as functional assemblies. We tested the hypothesis that synthetic anionic surfaces can catalyze burst thrombin activation in human blood plasma in the absence of MPs. In a thromboelastography (TEG) assay with plastic sample cups and pins, recalcified human citrated platelet-poor plasma spontaneously burst-coagulated but with an unpredictable clotting time whereas plasma depleted of MPs by ultracentrifugation failed to coagulate. Coagulation of MP-depleted plasma was restored in a dose-dependent manner by glass microbeads, hydroxyapatite nanoparticles (HA NPs), and carboxylic acid-containing anionic nanocoatings of TEG cups and pins (coated by glow-discharge plasma-polymerized ethylene containing oxygen, L-PPE:O with 4.4 and 6.8 atomic % [COOH]). Glass beads lost their pro-coagulant activity in MP-depleted plasma after their surfaces were nanocoated with hydrophobic plasma-polymerized hexamethyl disiloxane (PP-HMDSO). In FXII-depleted MP-depleted plasma, glass microbeads failed to induce coagulation, however, FXIa was sufficient to induce coagulation in a dose-dependent manner, with no effect of glass beads. These data suggest that anionic surfaces of crystalline, organic, and amorphous solid synthetic materials catalyze explosive thrombin generation in MP-depleted plasma by activating the FXII-dependent intrinsic contact pathway. The data also show that microparticles are pro-coagulant surfaces whose activity has been largely overlooked in many coagulation studies to-date. These results suggest a possible mechanism by which anionic biomaterial surfaces induce bone healing by contact osteogenesis, through fibrin clot formation in the absence of platelet activation. [ABSTRACT FROM AUTHOR]

Thiol (SH)‐terminated surfaces have gained interest over the past years due to their potential applications, especially in the biomedical field. In this work, SH‐terminated films have been prepared by “co‐polymerizing” gas mixtures of acetylene (C2H2) and hydrogen sulfide (H2S) using low‐pressure r.f. plasma‐enhanced chemical vapor deposition. R.f. power greatly influences the deposition rate, sulfur content, [S], and thiol concentration, [SH], of the films, as confirmed by XPS (both before and after chemical derivatization), FTIR, and mass spectrometry measurements. These data are compared with those obtained in a similar discharge by using a single molecule precursor, propanethiol. Among other differences, it is demonstrated that [SH] is higher when using binary gas mixtures compared to the single molecule precursor. [ABSTRACT FROM AUTHOR]

We have studied “PEG‐like” plasma‐deposited coatings of poly(ethylene glycol), some of which prevent protein adsorption and cellular adhesion. This enables inhibition of possible inflammatory reactions or rejection of an implant following its insertion into living tissue. Our approach, based on electrical measurements in atmospheric pressure Ar dielectric barrier discharges, enables precise measurements of E m, the energy absorbed per monomer molecule. Here, we demonstrate the importance of E m in preparing PEG‐like coatings for biomedical applications, for example by highlighting the great importance of molecular weight of monoglyme (1G) or diglyme (2G) monomers, and by obtaining anti‐fouling layers, “PP‐2G,” only with the diglyme. We demonstrate resistance to protein adsorption and cell adhesion of PP‐2G surfaces prepared with optimized F d (and E m) values. [ABSTRACT FROM AUTHOR]

We report dielectric barrier discharge (DBD)-based atmospheric pressure (AP) plasma polymerization (PP) experiments using argon carrier gas and a wide variety of hydrocarbon molecules as the precursors ('monomers'). As in our preceding research with other reagents, unprecedented precision and reproducibility in energy measurements is again demonstrated. Measurements based on various aliphatic and aromatic hydrocarbon compounds have yielded values of Em, the energy absorbed from the plasma by each monomer molecule. Systematic differences among families of compounds enabled us to draw several important conclusions about fragmentation and polymerization in the DBD plasma environment, observations which are in fair qualitative agreement with low-pressure radio-frequency PP data by Yasuda and Hirotsu from the 1970s. [ABSTRACT FROM AUTHOR]

Surface modifications are often required to enhance cell adhesion and growth around implanted biomaterials. This study compares various functionalization processes in their ability to create high densities of oxygen- and/or nitrogen-containing functional groups, mostly on a polymeric biomaterial, polyethylene terephthalate (PET). Primary amine (NH2)-rich surfaces were prepared by low-pressure plasma-polymerization (L-PPE:N), plasma modification (functionalized PET, 'PETf'), chemical vapour deposition (Parylene diX AM), and grafting of polyallylamine (PAAm). Plasma polymerization was also used to obtain oxygen-rich (L-PPE:O) as well as hybrid (L-PPE:O,N) films, which were respectively compared to oxygen-rich tissue culture polystyrene (TCP) and hybrid (Primaria™) culture plates. Compositions and bond types were studied by X-ray photoelectron spectroscopy. Finally, the effect of each surface on cell adhesion and growth was assessed using human umbilical vein endothelial cells (HUVECs). Amine-containing surfaces manifested a wide [NH2] range, up to 8.9%. Hybrid surfaces, Primaria™ and L-PPE:O,N, showed lower [NH2] in spite of high [N], suggesting more varied and complex functionalities. Except for Parylene, all O- and NH2-rich surfaces promoted HUVEC adhesion and growth similarly, despite differing chemical compositions. Primaria™ showed the best cell behavior, but L-PPE:O,N did not reproduce this apparent synergistic effect. To conclude, both N- and O-rich surfaces displayed good cell-colonization properties, particularly plasma polymers, while 'hybrid' surfaces appear somewhat ambiguous and call for further investigation. [ABSTRACT FROM AUTHOR]

The patency of small-diameter (<6 mm) synthetic vascular grafts (VGs) is still limited by the absence of a confluent, blood flow-resistant monolayer of endothelial cells (ECs) on the lumen and of vascular smooth muscle cell (VSMC) growth into the media layer. In this research, electrospinning has been combined with bioactive coatings based on chondroitin sulfate (CS) to create scaffolds that possess optimal morphological and bioactive properties for subsequent cell seeding. We fabricated random and aligned electrospun poly(ethylene terephthalate), ePET, mats with small pores (3.2 ± 0.5 or 3.9 ± 0.3 μm) and then investigated the effects of topography and bioactive coatings on EC adhesion, growth, and resistance to shear stress. Bioactive coatings were found to dominate the cell behavior, which enabled creation of a near-confluent EC monolayer that resisted physiological shear-flow conditions. CS is particularly interesting since it prevents platelet adhesion, a key issue to avoid blood clot formation in case of an incomplete EC monolayer or partial cell detachment. Regarding the media layer, circumferentially oriented nanofibers with larger pores (6.3 ± 0.5 μm) allowed growth, survival, and inward penetration of VSMCs, especially when the CS was further coated with tethered, oriented epithelial growth factor (EGF). In summary, the techniques developed here can lead to adequate scaffolds for the luminal and media layers of small-diameter synthetic VGs. [ABSTRACT FROM AUTHOR]

We report dielectric barrier discharge (DBD)-based atmospheric pressure (AP) plasma enhanced chemical vapor deposition (PECVD) experiments using argon carrier gas and ethyl lactate (EL) as the precursor molecule ('monomer'). As in our preceding research with other monomers, unprecedented precision and reproducibility is again demonstrated, here to create plasma polymerized (PP-EL) deposits. PP-EL is thought to be an excellent candidate for bio-medical applications on account of the non-toxic nature of resulting PP-EL deposits. We have shown that a narrow range of energy values absorbed from the plasma, Em, between roughly 21 and 42 eV/molecule, lead to PP-EL coatings of widely varying structural and physical properties, ones with controlled retention of chemical features of the EL monomer, and a predictable rate of degradation in aqueous media. [ABSTRACT FROM AUTHOR]

A large research reactor for dielectric barrier discharge (DBD) experiments at atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant plasma conditions ( f = 20 kHz, Va( f) = 8 kVp-p = 2.8 kVrms). Five esters, acrylates with differing number of unsaturations were used as 'monomers'; monomer flows, Fd, were at ‰ concentrations in the F = 10 standard liters per minute (slm) of argon. We earlier perfected and reported a method for measuring Eg, the energy dissipated per cycle of the applied a.c. voltage, and Δ Eg, the energy difference with and without monomer in the Ar flow. The latter, combined with Fd enable calculation of Em, the average energy absorbed from the plasma per monomer molecule. Plots of Em versus Fd and 1/ Fd yield much valuable information, for example about the role of CC and CC bonds in fragmentation and polymerization reactions. Fourier-transform infrared (FTIR) spectroscopy, spectroscopic ellipsometry (SE), and scanning electron microscopy (FEG-SEM) further enhance and complement data interpretation. [ABSTRACT FROM AUTHOR]

In the plasma polymerization literature, there has been an interest since at least the 1970s to correlate the structure of plasma polymer (PP) deposits with plasma parameters during deposition, most particularly with the energy input per monomer molecule, Em. In our two laboratories, we have developed methods for measuring Em (or somewhat equivalent, Ea) in low- (LP) and atmospheric-pressure (AP) discharge plasmas. In this article we propose a new parameter, the so-called energy conversion efficiency, ECE, which permits direct comparison of LP and AP experiments. This is done for the case of three model monomer compounds, ethane, acetylene, and acrylic acid (AAc). 'Critical' energy values that demarcate ECE regimes separating different fragmentation/reaction mechanisms agree remarkably well for all three monomers examined; resulting Em (or Ea) values are correlated with specific mechanisms, and the numerical results are convincingly supported by data from the chemical literature. [ABSTRACT FROM AUTHOR]

It has come to the authors’ attention that Figure in the article by B. Nisol et al. ( https://doi.org/10.1002/ppap.201500161, published in Plasma Process. Polym. 2016, 13, 557) displayed an erroneous result. An error occurred in the Matlab® code while carrying out the transfer of the energy measurement methodology to a larger DBD reactor. This erratum is published to correct this. [ABSTRACT FROM AUTHOR]

A large research reactor for performingdielectric barrier discharge (DBD) experiments at atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant plasma conditions ( f = 20 kHz, Va( f) = 8 kVp-p = 2.8 kVrms). Various permanent gases (H2, O2, N2, light hydrocarbons) and some heavier organic molecules were introduced as reactive 'dopant' flows, Fd, at ‰ concentrations in the F = 10 standard liters per minute (slm) flow of argon. We have earlier perfected and reported a method for measuring Eg, the energy dissipated per cycle of the applied a.c. voltage, and Δ Eg, the energy difference with and without reactive dopant in the Ar flow. The latter and Fd permit calculation of Em, the energy absorbed from the plasma by each dopant molecule. Plots of Em versus Fd and 1/ Fd yield much valuable information about excitation, fragmentation, and polymerization in the DBD plasma environment. Optical emission (OES) and Fourier-transform infrared (FTIR) spectroscopies help to further enhance and complement interpretation of measured data. [ABSTRACT FROM AUTHOR]

We present results on the deposition of plasma polymer (PP) films in a dielectric barrier discharge system fed with mixtures of argon or nitrogen carrier gas plus different hydrocarbon precursors, where the latter possess different carbon-to-hydrogen ratios: CH 4 < C 2 H 6 < C 2 H 4 = C 3 H 6 < C 2 H 2 . The influence of precursor gas mixture and flow rate, excitation frequency, and absorbed power on PP film compositions and properties has been investigated. The discharge was characterized by electrical measurements, while the chemical compositions and structures of coatings were analysed by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, total combustion, and elastic recoil detection analyses, the latter two for determining carbon-to-hydrogen ratios. Scanning electron microscopy was used to study the coatings' morphology, and profilometry for evaluating deposition rates. [ABSTRACT FROM AUTHOR]

A large reactor for performing dielectric barrier discharges (DBD) experiments at atmospheric pressure (AP) has been built and tested. The area of electrodes is more than 40 times greater than that of a small DBD cell, in which we have perfected a method formeasuring Eg, the energy dissipated per cycle of the applied a.c. high voltage, Va( f). This methodology has been successfully applied to plasma polymerization experiments on the larger system, using volatile organic precursors (dopants) at ‰ concentrations in 10 standard liters per minute of argon (Ar). We measured Δ Eg, the energy difference with and without dopant, for Va( f) ∼ 3 kVrms (20 ≤ f ≤ 40 kHz). From Δ Eg we then derived Etot/ N, the energy per molecule, and observed surprisingly good agreement with data published in the literature relating to low-pressure (LP) plasmas. [ABSTRACT FROM AUTHOR]

Plasma polymerized coatings (PP) are increasingly used for biomedical applications in contact with body fluids. We optimized and studied the stability, mechanical properties, and adhesion in air and aqueous media of amine (NH2)-rich PP in low-pressure r.f. plasma from [NH3/C2H4] mixtures (L-PPE:N). Quartz crystal microbalance with dissipation monitoring (QCM-D) revealed partial dissolution or water-uptake (swelling) in real-time in various solutions, which helped identify the best gas mixture ratio for compromise between stability and high concentration of (NH2) groups. Nanoindention revealed strong decrease of Young's modulus and hardness in water. Finally, a Cross-Hatch peel test was used to optimize L-PPE:N adhesion on poly(tetrafluoroethylene) (PTFE): plasma pre-treatment prevented both dry and wet delamination. [ABSTRACT FROM AUTHOR]

Aligned electrospun poly(ethylene terephthalate) (ePET) nanofiber mats have been fabricated, which mimic the media layer of arteries. We used three different plasma etching techniques to bring their mechanical and surface properties in line with those of natural blood vessels: (i) atmospheric pressure ('HP') corona discharge in air; (ii) low-pressure radio-frequency plasma ('LP') and (iii) microwave plasma asher, (ii) and (iii) in pure oxygen (O2), or O2 mixture with Ar or CF4. (iii) gave substantial reduction in Young's modulus after as little as 5 min. treatment in O2, without damage to the fibers. Changes in surface composition and drastic improvement in wettability/wicking were also observed, which resulted in promoting adhesion and growth of smooth muscle cells (SMCs). [ABSTRACT FROM AUTHOR]

Thromboelastography uses cups and pins made of Cyrolite® plastic to analyze the rate of fibrin clot formation in blood samples. In this study, TEG cups and pins were modified by 4 distinct coating types using plasma-enhanced chemical vapor deposition (PECVD): carboxylated, amine-rich, hydrophobic, SiO2, and analyzed for surface chemistry and wettability. We tested the hypothesis that the coagulation kinetics of recalcified citrated blood plasma is controlled by surface chemistry, in the absence of clot activator. Only carboxylated surfaces became negatively charged upon wetting, and accelerated clot formation in a highly reproducible manner, whereas Cyrolite® and the other coatings had delayed and unpredictable clotting times. These data are consistent with a model whereby carboxylated surfaces selectively adsorb and activate factor XII while repelling other more abundant anionic blood proteins, resulting in reproducible clot kinetics. [ABSTRACT FROM AUTHOR]

Low-temperature plasma (LTP) science and technology are rapidly establishing their place in agriculture, with already existing or envisaged future commercial applications in (i) sustainable fertilizer production, (ii) food safety "from farm to fork", and (iii) in reducing pollution and pathogens. On-demand local fertilizer production or pathogen inactivation at the farm by LTP technology will reduce the need for complex logistics. This current S.I. consists of one review article and 14 original research papers, focusing on state-of-the-art LTP applications in agricultural and food-related fields, ranging from the basics of activating air and water by electrical discharges and the treatment and decontamination of seeds and plants, to LTP use as a food processing technology. [Extracted from the article]

Abstract: The mechanical properties of mammalian cells are largely determined by their cytoskeletons (CSKs), which comprise several distinct but interacting cytoplasmic molecular networks. To examine the influence of the CSK on cell mechanical properties, we deformed several mammalian cell-types (L929, CHO, HEK293, and U937) in suspension using time-varying non-uniform electric fields. Confocal fluorescent microscopy was also used to visualize and semi-quantitatively analyze CSK dimensions. We found mechanical properties of individually deformed cells to depend on cortical actin (CA) thickness. U937 and HEK293 cells with thin CA were more easily deformed than CHO and L929 cells, which bore thicker CA. In additional experiments, we treated U937 cells with latrunculin-A (Lat-A) and acrylamide (ACR), drugs that disrupt microfilaments (MF) and intermediate-filaments (IF), respectively, in order to assess their effects on the CSK and on the cell mechanical properties. We fit strain data using either a power-law or a viscoelasticity model of compliance. Our results demonstrated that maximal strain values observed under identical loading conditions were determined by the structural integrity and thickness of CA in suspended cells. Young''s modulus values of individually deformed cells that were estimated using a power-law model showed a linear dependence on cortical actin thickness. [Copyright &y& Elsevier]

Background: Recent evidence indicates that osteoarthritis (OA) may be a systemic disease since mesenchymal stem cells (MSCs) from OA patients express type X collagen, a marker of late stage chondrocyte hypertrophy (associated with endochondral ossification). We recently showed that the expression of type X collagen was suppressed when MSCs from OA patients were cultured on nitrogen (N)-rich plasma polymer layers, which we call "PPE:N" (N-doped plasma-polymerized ethylene, containing up to 36 atomic percentage (at.% ) of N. Methods: In the present study, we examined the expression of type X collagen in fetal bovine growth plate chondrocytes (containing hypertrophic chondrocytes) cultured on PPE:N. We also studied the effect of PPE:N on the expression of matrix molecules such as type II collagen and aggrecan, as well as on proteases (matrix metalloproteinase-13 (MMP-13) and molecules implicated in cell division (cyclin B2). Two other culture surfaces, "hydrophilic" polystyrene (PS, regular culture dishes) and nitrogen-containing cation polystyrene (Primaria®), were also investigated for comparison. Results: Results showed that type X collagen mRNA levels were suppressed when cultured for 4 days on PPE:N, suggesting that type X collagen is regulated similarly in hypertrophic chondrocytes and in human MSCs from OA patients. However, the levels of type X collagen mRNA almost returned to control value after 20 days in culture on these surfaces. Culture on the various surfaces had no significant effects on type II collagen, aggrecan, MMP-13, and cyclin B2 mRNA levels. Conclusion: Hypertrophy is diminished by culturing growth plate chondrocytes on nitrogen-rich surfaces, a mechanism that is beneficial for MSC chondrogenesis. Furthermore, one major advantage of such "intelligent surfaces" over recombinant growth factors for tissue engineering and cartilage repair is potentially large cost-saving. [ABSTRACT FROM AUTHOR]

Abstract: The development of new strategies for protein immobilization to control cell adhesion, growth and differentiation is of prime interest in the field of tissue engineering. Here we propose a versatile approach based on the interaction between two de novo designed peptides, Ecoil and Kcoil, for oriented immobilization of epidermal growth factor (EGF) on polyethylene terephthalate (PET) films. After amination of PET surfaces by ammonia plasma treatment, Kcoil peptides were covalently grafted in an oriented fashion using succinimidyl 6-[30-(2-pyridyldithio)-propionamido] hexanoate (LC-SPDP) linker, and the Kcoil-functionalized films were characterized by X-ray photoelectron spectroscopy (XPS). Bioactivity of Ecoil-EGF captured on Kcoil-functionalized PET via coiled-coil interactions was confirmed by EGF receptor phosphorylation analysis following A-431 cell attachment. We also demonstrated cell biological effects where tethered EGF enhanced adhesion, spreading and proliferation of human corneal epithelial cells compared to EGF that was either physically adsorbed or present in solution. Tethered EGF effects were most likely linked to the prolonged activation of both mitogen-activated protein kinase and phosphoinositidine 3-kinase pathways. Taken together, our results indicate that coiled-coil-based oriented immobilization is a powerful method to specifically tailor biomaterial surfaces for tissue engineering applications. [Copyright &y& Elsevier]

Abstract: Nitrogen (N)- and oxygen (O)-rich organic thin films were deposited by vacuum-ultraviolet (VUV)-assisted photo-chemical polymerisation of flowing ethylene (C2H4)–ammonia (NH3) and C2H4–nitrous oxide (N2O) mixtures of varying ratios, R, respectively. The reaction mechanism of these binary gas mixtures was investigated as a function of the wavelength, λ, of two near-mono-chromatic VUV sources. Surface-near compositions of these “UV-PE:N” and “UV-PE:O” films were determined by X-ray photoelectron (XPS), and by Fourier transform (reflection–absorption) infrared (FTIR) spectroscopies. The two types of films were compared with plasma polymers deposited using low-pressure radio-frequency (r.f.) glow discharges in similar gas flow mixtures, “PPE:N” and “PPE:O”. VUV-photochemistry appears to be superior to plasma-chemistry in its capability to produce nearly “mono-functional” organic thin films, ones that are rich in primary amines, –NH2, and in carboxylic acid groups, –COOH, respectively. [Copyright &y& Elsevier]

Abstract: Low- and atmospheric-pressure plasma co-polymerisations of binary gas mixtures of C2H4 and NH3 or N2, respectively, were investigated for depositing N-rich plasma polymer coatings for biomedical applications. Deposition kinetics and relevant surface characteristics of resulting plasma polymerised ethylene enriched with nitrogen, “PPE:N”, coatings were investigated as a function of the gas mixture ratio, X =NH3(N2)/C2H4. Physico-chemical properties of the coatings were determined using a combination of complementary surface-sensitive techniques: for example, total nitrogen concentrations, [N], up to 40 at.% were measured by X-ray Photoelectron Spectroscopy, XPS, while those of primary amines, [–NH2], were determined by performing chemical derivatisation followed by XPS analyses. PPE:N films were further characterised by UV–VIS Ellipsometry, Near Edge X-ray Absorption Fine Structure Spectroscopy, IR Spectroscopy and by Contact Angle Goniometry measurements. The stability of the coatings was tested, both in terms of water solubility and of “ageing” in ambient atmosphere. For the latter, selected samples were stored in the laboratory for different durations, in order to assess possible changes in their chemical structures. [Copyright &y& Elsevier]

Abstract: Complications following endovascular aneurysm repair (EVAR) are related to deficient healing around the stent-graft (SG). New generations of SG with surface properties that foster vascular repair could overcome this limitation. Our goal was to evaluate the potential of a new nitrogen-rich plasma-polymerised biomaterial, designated PPE:N, as an external coating for polyethylene terephtalate (PET)- or polytetrafluoro-ethylene (PTFE)-based SGs, to promote healing around the implant. Thin PPE:N coatings were deposited on PET and PTFE films. Then, adhesion, growth, migration and resistance to apoptosis of vascular smooth muscle cells (VSMCs) and fibroblasts, as well as myofibroblast differentiation, were assessed in vitro. In another experimental group, chondroitin sulphate (CS), a newly described mediator of vascular repair, was added to normal culture medium, to search for possible additional benefit. PPE:N-coatings, especially on PET, increased and accelerated cell adhesion and growth, compared with control PET and with standard polystyrene culture plates (PCP). PPE:N was also found to increase the resistance to apoptosis in VSMC, an important finding as aneurysms are characterised by VMSC depletion caused by a pro-apoptotic phenotype. Addition of CS in solution further increased migration and resistance to apoptosis. In conclusion, PPE:N-coating and/or CS could promote vascular repair around SGs following EVAR. [Copyright &y& Elsevier]

Background: The loss of the notochordal cells from the nucleus pulposus is associated with ageing and disc degeneration. However, understanding the mechanisms responsible for the loss of these cells has been hampered in part due to the difficulty of culturing and maintaining their phenotype. Furthermore, little is known about the influence of the substratum on the molecular markers of notochordal cells. Methods: Notochordal cells were isolated from lumbar spine of non-chondrodystrophoid dogs and cultured on N-rich plasma polymer layers, so-called "PPE:N" (N-doped plasma-polymerised ethylene, containing up to 36% [N]) surfaces, for 3, 7 or 14 days. Gene expression of vimentin (VIM), pleiotrophin (PTN), matrix Gla protein (MGP), cartilage oligomeric matrix protein (COMP), keratin 18 (KRT 18), aggrecan (AGG), collagen type 1 (COL1A2), collagen type 2 (COL2A1) was analyzed through semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Results: Notochordal cells were maintained in culture on PPE:N for up to 14 days with no loss in cell viability. Except for VIM, gene expression varied depending on the culture periods and [N] concentration of the substratum. Generally, PPE:N surfaces altered gene expression significantly when cells were cultured for 3 or 7 days. Conclusion: The present study has shown that notochordal cells from dogs can attach to and grow on PPE:N surfaces. Analysis of the expression of different genes in these cells cultured on different N-functionalized surfaces indicates that cellular behaviour is gene-specific and time-dependent. Further studies are required to better understand the roles of specific surface functionalities on receptor sites, and their effects on cellular phenotypes. [ABSTRACT FROM AUTHOR]

Abstract: Little is known of the effect of material surfaces on stem cell differentiation. The present study has addressed the hypothesis that the interaction of mesenchymal stem cells (MSCs) with material surfaces modified by glow discharge plasma is a major regulator of osteogenic differentiation. We found that biaxially oriented polypropylene (BOPP) plasma treated in ammonia significantly reduced up-regulation of expression of osteogenic marker genes, such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). In contrast, ALP expression was up-regulated when cultured on treated Nylon-6 polyamide (Ny-t) but was substantially reduced when cultured on its pristine counterpart (Ny-p) on day 3. On day 7, ALP expression was down-regulated with MSCs cultured on Ny-t although its expression level was up again on day 14. BSP was expressed weakly on day 3, but was up-regulated when cultured on Ny-t and Ny-p. Its expression reached its maximum on day 14 when cultured on a polystyrene control, while it was cyclically up-regulated on Ny-t. Similarly, there was a slight increase in OC expression when MSCs were cultured on Ny-t and Ny-p on day 3, when compared to control. Thus, the nature of the surface can directly influence MSCs differentiation, ultimately affecting the quality of new tissue formation with BOPP-t suppressing osteogenic differentiation. [Copyright &y& Elsevier]

Surface chemical micropatterns have been created by both low-pressure “cold” plasma, and by vacuum ultraviolet (VUV) photochemical modification of biaxially oriented polypropylene (BOPP). Oxygen, nitrogen and ammonia plasma, and ammonia-VUV treatments have been performed, including through metal masks with micrometer-sized openings. Surface analysis by X-ray photoelectron spectroscopy (XPS) has been used to characterise the modified surfaces. Imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS) of partially masked regions has demonstrated the ability to produce micrometer scale chemical patterns of oxygen and nitrogen-containing functionalities, for example, hydroxyl and amine groups, contrasted with untreated hydrocarbon regions. Nitrogen and ammonia plasma patterned surfaces, and ammonia-VUV patterned surfaces have been used to control the immobilisation and growth of foetal bovine cerebellar neurons and growth plate chondrocytes cells in culture. [Copyright &y& Elsevier]

Presents a study that investigated the atmospheric pressure glow discharges in a dielectric barrier discharge rector. Background on scientific investigation of gas discharges at atmospheric pressure; Methodology; Examination of the discharges in different noble gases under varying experimental conditions.

The electrical discharge characteristics of a large‐area experimental dielectric barrier discharge in argon–hexamethyldisiloxane mixtures containing up to about 1,600 ppm of the monomer is analysed by means of electrical measurements and numerical modelling. A time‐dependent, spatially one‐dimensional fluid model is employed, taking into account the spatial variation of the discharge plasma between the two plane‐parallel dielectrics covering the electrodes. Reasonable agreement between electrical measurements and modelling results is generally found for the gap voltages and discharge currents. Remaining differences between the measured and calculated electrical energy dissipated in the plasma per period are discussed. [ABSTRACT FROM AUTHOR]

Plasma-assisted microfabrication has been a topic of capital importance in the evolution of plasma science and technology, especially since the 1970s. To a large extent, one can associate this trend of growth with "Moore's Law", the observation that the number of transistors in a dense integrated circuit doubles about every 2 years. Currently, the overall performance of computer chips is limited by energy consumption and data communication speeds among the CPUs, caches, memories, and storage devices. [Extracted from the article]

An introduction is presented in which the editor discusses various topics within the issue including article on Innovative Analytical Techniques for Plasma Polymers, Plasma Processing and Moore's Law, and Plasma-based Decontamination.

The method developed for fundamental understanding of energetic exchanges between monomer molecules and argon carrier gas in a dielectric barrier discharge (DBD) has previously proven merit. In this seventh article related to this methodology, research has been extended to a new family of precursors: anhydrides. Monomers (typically ‰) were mixed with 10 slm of Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD corresponding to an energy per cycle of 1600 μJ for pure Ar. For each of the investigated monomers Em, the energy absorbed per molecule was plotted as a function of precursor flow rate. The influence of chemical structure (C/O ratio, unsaturation) has been investigated and compared with previous data for other types of precursors. Thin plasma polymer coatings were deposited; in addition to measuring deposition rates, we also present relationships between Em values, spectro‐ellipsometric and FTIR measurements. [ABSTRACT FROM AUTHOR]