Plasma-based surface modification of polystyrene microtiter plates for covalent immobilization of biomolecules

In recent years, polymer surfaces have become increasingly popular for biomolecule attachment because of their relatively low cost and desirable bulk physicochemical characteristics. However, the chemical inertness of some polymer surfaces poses an obstacle to more expansive implementation of polymer materials in bioanalytical applications. We describe use of argon plasma to generate reactive hydroxyl moieties at the surface of polystyrene microtiter plates. The plates are then selectively functionalized with silanes and cross-linkers suitable for the covalent immobilization of biomolecules. This plasma-based method for microtiter plate functionalization was evaluated after each step by X-ray photoelectron spectroscopy, water contact angle analysis, atomic force microscopy, and bioimmobilization efficacy. We further demonstrate that the plasma treatment followed by silane derivatization supports direct, covalent immobilization of biomolecules on microtiter plates and thus overcomes challenging issues typically associated with simple physisorption. Importantly, biomolecules covalently immobilized onto microtiter plates using this plasma-based method retained functionality and demonstrated attachment efficiency comparable to commercial preactivated microtiter plates.     

Current trends in biomaterial surface functionalization—nitrogen-containing plasma assisted processes with enhanced selectivity

Low-pressure gas-discharge plasmas are widely used for polymer surface functionalization on industrial scale. For biomaterial applications, the density and selectivity of the functionalization are of particular importance, because functional groups control the immobilization of biomolecules. Therefore, surface modification of biomaterials is a challenging task for low-pressure plasma technique. Plasma processes have been successfully applied to various polymer types in order to generate multifunctional surfaces. This paper discusses the present state and the prospects of non-coating plasma processes to generate mono functional surfaces of controlled amino group density. Such surfaces appear most desirable for many applications. The results of various microwave- and radio-frequency- excited plasma processes reported in the literature are reviewed and compared to a sequence of experiments that was conducted in a UHV reaction environment. Non-thermal plasmas are especially well suited for thermally damageable polymers. The effect of hydrogen admixture to discharges in nitrogen and ammonia is discussed in detail. The optimization of process parameters lead to highly selective amino functionalization of high density. The selectivity reached 100% -NH₂/N at a surface density of amino groups of 3% -NH₂/C.     

Efficient decomposition of NO by ammonia radical-injection method using an intermittent dielectric barrier discharge

Although many NO decomposition systems have been developed using plasmas such as dielectric barrier discharges (DBDs), corona discharges, surface discharges, glow discharges, and microwave discharges, the present system is unique on the viewpoint of the use of an intermittent one-cycle sinusoidal power source to generate DBD plasma. There are several features of the system: (1) easy control of the electric power consumed in the DBD plasma, and (2) DBD-plasma generation used only for the production of ammonia radicals. The system employs a radical injection system, where the radicals are produced in a separate discharge chamber, called radical injector, from NO flow field. This enables an efficient production of ammonia radicals being appropriate for DeNOx. It is shown from the temperature dependence of NO removal (DeNOx) characteristics that the present system is a low-temperature DeNOx system compared to a conventional thermal DeNOx system, and NO decomposition is performed over a wide range of gas temperature containing NO. Surveying parametric characteristics of DeNOx, the energy efficiency is improved by a factor of 30% compared to the previously obtained result.     

用于超光滑表面加工的常压低温等离子体抛光系统设计

介绍了一种新型超光滑表面加工方法及其系统的设计．该方法主要基于低温等离子体化学作用,通过活性反应原子与工件表面原子间的化学反应实现原子级的材料去除,避免了表层和亚表层损伤．该常压低温等离子体抛光系统首次引入了电容耦合式射频等离子体炬,并根据装置的实际特性进行了良好的阻抗匹配．原子发射光谱分析结果表明,该系统实现了稳定的大气压等离子体放电,并有效地激发出高密度的活性反应原子．针对单晶硅片的加工试验结果,也证明了该系统可高效稳定地工作,并实现了约1．46mm^3/min的材料去除速率和0．6nm（Ra）的表面粗糙度．     

Ein plasmagestütztes Hochfrequenzverfahren zum niederenergetischen Ionenbeschuß von Isolatorwerkstoffen,insbesondere von Gläsern

A novel plasma based radio frequency method for low energy charge compensated ion bombardment of dielectric surfaces is described. As a practical example, this technique is applied for a controlled removal of undefined leached surface layers on glass samples.     

低温等离子体对生物材料表面改性固定生物分子的研究进展

概述了等离子体技术在固定生物分子领域的应用.介绍了低温等离子体技术,包括等离子体直接处理、聚合、刻蚀、以及对生物材料表面改性以固定生物分子的方法、原理、影响因素及其发展趋势.     

Experimental and Numerical Study of Material Removal in Electrochemical Discharge Machining (ECDM)

In this paper a novel approach is proposed to investigate the characteristics of the plasma channel and material removal in electrochemical discharge machining (ECDM) of glass. For this purpose, a specific pulsed voltage was applied to the ECDM process to perform single discharging on the glass workpiece. In this way, a voltage slightly lower than the critical voltage was applied as the offset voltage. Meanwhile the working voltages above the critical voltage were applied to the process in a specific period of time to produce single sparks. The signatures of the single sparks on the workpiece surface were used to determine the characteristics of the plasma channel. According to the results, the average diameter of 260 µm was achieved for the plasma channel in the glass machining conditions. This paper also reports a thermophysical model for material removal in ECDM process based on the finite element method (FEM) and plasma channel diameter achieved in this study. The amount of the removed material as well as the diameter and depth of the crater, achieved by the FEM, was measured and compared with the experimental outcomes. The results demonstrate the consistency of the proposed model with the experimental observations.     

Atomic oxygen generation by in-situ plasma and post-plasma in dielectric barrier discharges for surface treatment

Atomic oxygen (AO) generation is experimentally and numerically investigated for in-situ plasma and post-plasma produced by dielectric barrier discharges (DBDs) for surface treatment. The AO generation in in-situ plasma inside a DBD reactor is closely related to the plasma characteristics depending on the applied voltage and O₂ additive concentration, while the AO density distribution along the post-plasma ejected outside the reactor exit is influenced by the AO generation in the in-situ plasma, gas flow rate, and effluent distance. Contact angle measurements show that the metal surface characteristics, which are treated by in-situ plasma and post-plasma, respectively, are distinctive from each other depending on the AO densities.     

An investigation of the treatment of particulate matter from gasoline engine exhaust using non-thermal plasma

A plasma reactor with catalysts was used to treat exhaust gas from a gasoline engine in order to decrease particulate matter (PM) emissions. The effect of non-thermal plasma (NTP) of the dielectric discharges on the removal of PM from the exhaust gas was investigated experimentally. The removal efficiency of PM was based on the concentration difference in PM for particle diameters ranging from 0.3 to 5.0 microm as measured by a particle counter. Several factors affecting PM conversion, including the density of plasma energy, reaction temperature, flow rate of exhaust gas, were investigated in the experiment. The results indicate that PM removal efficiency ranged approximately from 25 to 57% and increased with increasing energy input in the reactor, reaction temperature and residence time of the exhaust gas in the reactor. Enhanced removal of the PM was achieved by filling the discharge gap of the reactor with Cu-ZSM-5 catalyst pellets. In addition, the removal of unburned hydrocarbons was studied. Finally, available approaches for PM conversion were analyzed involving the interactions between discharge and catalytic reactions.     

Investigation of the processes of periodic plasma structure formation in transverse nanosecond discharge with a slotted cathode

A periodic standing-like plasmic striation in inert gases has been observed and investigated under transversal nanosecond electric discharges. The pressure limits relevant for formation of a periodic plasma structure have been established, and the critical values for the voltage amplitude and discharge current have been found corresponding to the upper boundary of the range in which the plasma structure is formed. The external magnetic field effect on the parameters of the periodic plasma structure has been studied. It is stated that the plasma structure is formed at the stage of steady-state discharge and that the lifetime of the periodic structure considerably increases when the transversal magnetic field is applied.     

Beschichtung und Reinigung von Oberflächen mit Atmosphärendruck‐Plasmen. Coating and cleaning of surfaces with atmospheric pressure plasmas

Since long time dielectric barrier discharges have been in use for technical applications such as ozone synthesis and surface activation treatment of polymers for subsequent printing, pasting, or laquering. A new field of applications for these discharges is opened by their use for plasma‐based coating and cleaning processes at atmospheric pressure. By introducing gaseous monomers (like hydrocarbons, fluorocarbons, silicon‐organic compounds) into the discharge zone, coatings can be deposited on electrically conductive or insulating substrates. Barrier discharges in oxygen containing gases can also be used for the degreasing of surfaces. Owing to the possibility, to sustain barrier discharges in very small volumes, new perspectives are opened for the geometrically structured modification of chemical and physical properties of surfaces as well as for the modification or coating of internal surfaces in microfluidic devices.     

Comparison of two methods for removal of arsenic from potable water

Arsenic, well known of its toxicity, is present in potable water in many areas in the world, as well as in underground water used for water supply in Vojvodina, a region in Serbia. Its removal from raw water is necessary before distribution. In this work two methods of arsenic removal from water are compared. First method is water ozonation by introducing ozone in water and then filtration. Second method is treatment of water in plasma reactor and then filtration. High efficiency of the second method was confirmed by low concentration of arsenic in filtrate (below detection limit).     

Surface and bioproperties of nanocrystalline diamond/amorphous carbon nanocomposite films

Nanocrystalline diamond/amorphous carbon (NCD/a-C) nanocomposite films have been deposited by microwave plasma chemical vapour deposition from CH₄/N₂ mixtures. In order to investigate their suitability as templates for the immobilization of biomolecules, e.g. for applications in biosensors, four differently prepared surfaces, namely as-grown, hydrogen plasma treated, oxygen plasma treated, and chemically treated with aqua regia, have been thoroughly characterized by methods such as XPS, TOF-SIMS, AFM, and contact angle measurements. In addition, in order to investigate the affinity of these surface to non-specific bonding of biomolecules, they have been exposed to bovine serum albumin (BSA). It turned out that already the as-grown surface is hydrogen terminated; the degree of the termination is even slightly improved by the hydrogen plasma treatment. Reaction with aqua regia, on the other hand, led to a partial destruction of the H-termination. The oxygen plasma treatment, finally, causes a termination by O and OH, rather than by carboxylic acid groups. In addition, an increase of sp² bonded carbon is observed. All surfaces were found to be susceptible to attachment of BSA proteins, but the coverage of the hydrogen terminated was lower than that of the O-terminated film. The highest BSA concentrations were found for the aqua regia sample where the H-termination has been removed partially. Finally, our results show that even minor surface contaminations have a great influence on the BSA coverage.     

Enhanced processing of coatings on glass surfaces

In this contribution, basic technically usable interactions of atmospheric pressure plasmas (APP), laser irradiation and solids as well as a technique which combines such plasmas and laser irradiation are introduced. Two examples for plasma‐enhanced laser processing of coatings on glass surfaces are presented in more detail. First, APP‐assisted annealing of amorphous silicon layers is discussed. It is shown that the crystallised area is notably increased by assisting plasmas where the particular improvement factor depends on the particularly applied type of plasma. Second, the impact of assisting plasmas on laser removal of lacquers and varnishes from glass surfaces is presented. By introducing a plasma jet to the laser removal process, the laser energy required for cleaning or delamination is notably reduced.     

PECVD mit der Bandhohlkathode

Plasma‐enhanced High Rate Surface Treatment of Steel Sheet by Means of the Strip Hollow Cathode Method Low pressure glow discharges are of strong interest for the development of new technologies for steel strip surface treatment for different applications. The challenge of the integration of plasma processes into existing continuous steel sheet coating processes consists in the requirements of a very high deposition rate combined with minimal loss due to parasitic oatings. Regarding these requirements a novel strip hollow cathode process (SHC) for surface treatment based on the hollow cathode effect between two flat and parallel cathodes has been developed. This method has significant potential for surface treatment of large area metal strips in continuous technological processes.     

Plasma treated polyethylene grafted with adhesive molecules for enhanced adhesion and growth of fibroblasts

The cell–material interface plays a crucial role in the interaction of cells with synthetic materials for biomedical use. The application of plasma for tailoring polymer surfaces is of abiding interest and holds a great promise in biomedicine. In this paper, we describe polyethylene (PE) surface tuning by Ar plasma irradiating and subsequent grafting of the chemically active PE surface with adhesive proteins or motives to support cell attachment. These simple modifications resulted in changed polymer surface hydrophilicity, roughness and morphology, which we thoroughly characterized. The effect of our modifications on adhesion and growth was tested in vitro using mouse embryonic fibroblasts (NIH 3T3 cell line). We demonstrate that the plasma treatment of PE had a positive effect on the adhesion, spreading, homogeneity of distribution and moderately on proliferation activity of NIH 3T3 cells. This effect was even more pronounced on PE coated with biomolecules.     

Electrochemical treatment of deproteinated whey wastewater and optimization of treatment conditions with response surface methodology

Electrochemical treatment of deproteinated whey wastewater produced during cheese manufacture was studied as an alternative treatment method for the first time in literature. Through the preliminary batch runs, appropriate electrode material was determined as iron due to high removal efficiency of chemical oxygen demand (COD), and turbidity. The electrochemical treatment conditions were optimized through response surface methodology (RSM), where applied voltage was kept in the range, electrolyte concentration was minimized, waste concentration and COD removal percent were maximized at 25 degrees C. Optimum conditions at 25 degrees C were estimated through RSM as 11.29 V applied voltage, 100% waste concentration (containing 40 g/L lactose) and 19.87 g/L electrolyte concentration to achieve 29.27% COD removal. However, highest COD removal through the set of runs was found as 53.32% within 8h. These results reveal the applicability of electrochemical treatment to the deproteinated whey wastewater as an alternative advanced wastewater treatment method.     

Interactions between neural stem cells and biomaterials combined with biomolecules

Neural repair and regeneration have been a tough problem in clinical studies. Tissue engineering using biomaterials along with neural stem cells (NSCs) have shown great potential for treatment, especially along with the biomolecules to regulate the NSCs can get more promising results. The biomolecules in the materials have a favorable impact on cell adhes ion, expansion, and differentiation. Thus, the interactions between biomaterials loading biomolecules and NSCs also receive particular attention. In this review, recent progresses of modified biomaterials by such biomolecules for neural injury and their impact on NSCs behavior will be discussed.     

Modeling of high frequency atmospheric pressure Ar/H2/SiH4 glow discharges

In this paper, a one-dimensional self-consistent fluid model is applied to simulate high frequency atmospheric pressure glow discharges. The results show that the plasma density and current density depend strongly on the excitation frequency. When the excitation frequency is below 13.56 MHz, the discharge operates in the α mode, and when the excitation frequency is above 13.56 MHz, the discharge operates in a γ-like mode. The densities of species including SiH₃⁺, SiH₃⁻, SiH₃, SiH₂, H, Ar⁺, Ar^? and electron are enhanced with the frequency increasing from 6.78 to 27.12 MHz. Similar discharge mode transition was observed experimentally in radio frequency atmospheric pressure He glow discharges. The effects of excitation frequency on plasma characteristics and densities of precursors for μc-Si:H film are further discussed. This study reveals that an appropriate excitation frequency is important for the growth of μc-Si:H film.     

Frequency-selective rotation of two-particle nanoactuators for rapid and sensitive detection of biomolecules

We describe an optomagnetic bionanotechnology for rapid and sensitive solution-based affinity assays. Nanoactuators made from bioactive magnetic nanoparticles undergo rotational motion in the volume of a fluid under frequency-controlled magnetic actuation. The nanoactuators show a time-dependent scattering cross-section to an incoming light beam. We demonstrate that the temporal behavior of the scattered light intensity relates to the number, the magnetic properties and the size distribution of the nanoactuators, independently revealing the average value and variation in the magnetic properties of the nanoparticles as well as the concentration of nanoactuators. The method is applied to detect biomolecules in fluid by interparticle binding. In a total assay time of less than 3 min, we demonstrate a limit of detection lower than 400 fM in buffer and 5 pM in human plasma.