Nitric Oxide Releasing Coronary Stent: A New Approach Using Layer‐by‐Layer Coating and Liposomal Encapsulation

The sustained or controlled release of nitric oxide (NO) can be the most promising approach for the suppression or prevention of restenosis and thrombosis caused by stent implantation. The aim of this study is to investigate the feasibility in the potential use of layer‐by‐layer (LBL) coating with a NO donor‐containing liposomes to control the release rate of NO from a metallic stent. Microscopic observation and surface characterizations of LBL‐modified stents demonstrate successful LBL coating with liposomes on a stent. Release profiles of NO show that the release rate is sustained up to 5 d. In vitro cell study demonstrates that NO release significantly enhances endothelial cell proliferation, whereas it markedly inhibits smooth muscle cell proliferation. Finally, in vivo study conducted with a porcine coronary injury model proves the therapeutic efficacy of the NO‐releasing stents coated by liposomal LBL technique, supported by improved results in luminal healing, inflammation, and neointimal thickening except thrombo‐resistant effect. As a result, all these results demonstrate that highly optimized release rate and therapeutic dose of NO can be achieved by LBL coating and liposomal encapsulation, followed by significantly efficacious outcome in vivo.     

Electrografting of a biodegradable layer as a primer adhesion coating onto a metallic stent: in vitro and in vivo evaluations

Drug-eluting stents have been developed to reduce the risk of restenosis after angioplasty. To facilitate the adhesion of a poly(lactic acid) (PLA) overlayer loaded with rapamycin (20 wt%), a biodegradable macromonomer based on poly(lactic acid) (HEMA-PLA) was grafted onto the metallic stent by electrografting in a one-step reaction involving the immobilization of aryl diazonium onto the metal followed by an in situ surface electro-polymerization. The HEMA-PLA coating was chemically characterized. Mechanical performance during stent expansion was tested. Morphology examinations showed a strong adhesion of PLA topcoat in the presence of the electrografted layer. Biocompatibility and degradation of the coating were studied in vitro and in vivo in rabbit iliac arteries. These 28 days implantations resulted in a minimal inflammatory process with a partial degradation of the coating. These results suggest that this kind of anchoring of a biodegradable layer shows great potential for drug-eluting stents.     

The Impact of Plasma‐modified Films with Sulfur Dioxide,Sodium Oxide on Food Pathogenic Microorganisms

In this study, plasma modification was carried out in barrier discharge under atmospheric pressure. Sulfur dioxide and/or sodium oxide was used as the coating precursor. The results show that the films treated with a mixture of argon and sulfur dioxide inhibited microbial growth considerably better than those with coatings containing argon and sodium oxide. The highest levels of growth inhibition, of 86% for Staphylococcus aureus and 82% for Escherichia coli, were achieved with films carrying a sulfur‐containing coating (1.4% SO₂). Copyright © 2014 John Wiley & Sons, Ltd.     

Combined vacuum plasma surface treatment for increase of durability of face milling cutters from high‐speed steel

The article deals with the influence of the vacuum plasma surface treatment on the life of the face milling cutter of high‐speed steel R6M5 (analog M2 (USA, AISI/ASTM)). Such processing combines ion nitriding in gas plasma and the deposition of the wear‐resistant TiAlN layer in the metal gas plasma of the vacuum‐arc discharge. Research verifies that the use of vacuum plasma treatment combining the formation of the transition nitrided layer in the gas plasma and the subsequent deposition of TiAlN coating in metal gas plasma created by a vacuum‐arc discharge is an effective way to improve the tool life of high‐speed steel face milling cutters.     

Development of an optimized electrochemical process for subsequent coating of 316 stainless steel for stent applications

Metallic endovascular stents are used as medical devices to scaffold biological lumen, most often diseased arteries, after balloon angioplasty. They are commonly made of 316L stainless steel or Nitinol, two alloys containing nickel, an element classified as potentially toxic and carcinogenic by the International Agency for Research on Cancer. Although they are largely implanted, the long-term safety of such metallic elements is still controversial, since the corrosion processes may lead to the release of several metallic ions, including nickel ions in diverse oxidation states. To avoid metallic ion release in the body, the strategy behind this work was to develop a process aiming the complete isolation of the stainless steel device from the body fluids by a thin, cohesive and strongly adherent coating of RF-plasma-polymerized fluoropolymer. Nevertheless, prior to the polymer film deposition, an essential aspect was the development of a pre-treatment for the metallic substrate, based on the electrochemical polishing process, aiming the removal of any fragile interlayer, including the native oxide layer and the carbon contaminated layer, in order to obtain a smooth, defect-free surface to optimize the adhesion of the plasma-deposited thin film. In this work, the optimized parameters for electropolishing, such as the duration and the temperature of the electrolysis, and the complementary acid dipping were presented and accurately discussed. Their effects on roughness as well as on the evolution of surface topography were investigated by Atomic Force Microscopy, stylus profilometry and Scanning Electron Microscopy. The modifications induced on the surface atomic concentrations were studied by X-ray Photoelectron Spectroscopy. The improvements in terms of the surface morphology after the pre-treatment were also emphasized, as well as the influence of the original stainless steel surface finish.     

The effect of electron beam sterilization on the physical properties of the bioresorbable polymer coatings on the titanium 6-aluminum 4-vanadium substrate

The aim of the work is to determine the physical properties of titanium 6-aluminum 4-vanadium alloy with poly (glycolide-ϵ-caprolactone) coating after electron beam sterilization. First, the metal substrate is machined with grade 120 and 320 grinding papers. Some of the samples are subjected to anodic oxidation. Then, the samples are coated with a biodegradable polymer layer of poly (glycolide-ϵ-caprolactone). Samples with polymer coatings are subjected to electron beam sterilization. To evaluate the effect of sterilization on physical properties of modified titanium alloy the scanning electron microscopy and atomic force microscopy, adhesion studies of the polymer coating to the metal substrate and wettability tests are applied. On the basis of the obtained results, an increase of the contact angle value is found both after applying the polymer coating to the surface of the tested titanium 6-aluminium 4-vanadium alloy as well as after electron beam sterilization. In addition, a slight increase of the adhesion in sterilized samples comparted to non-sterilized is observed. In scanning electron microscopic observations, traces of machining on the surface of the metal substrate and the continuity of the polymer coatings before and after sterilization are found. In the atomic force microscopic studies in relation to the initial state, a very good mapping of the surface topography of the samples with a homogeneous coating is found.     

Coating process and early stage adhesion evaluation of poly(2-hydroxy-ethyl-methacrylate) hydrogel coating of 316L steel surface for stent applications

In this study, a spray-coating method has been set up with the aim to control the coating of poly(2-hydroxy-ethyl-methacrylate) (pHEMA), an hydrophilic polymeric hydrogel, onto the complex surface of a 316L steel stent for percutaneous coronary intervention (PCI). By varying process parameters, tuneable thicknesses, from 5 to 20 μm, have been obtained with uniform and homogeneous surface without crack or bridges. Surface characteristics of pHEMA coating onto metal surface have been investigated through FTIR-ATR, contact angle measurement, SEM, EDS and AFM. Moreover, results from Single-Lap-Joint and Pull-Off adhesion tests as well as calorimetric analysis of glass transition temperature suggested that pHEMA deposition is firmly adhered on metallic surface. The pHEMA coating evaluation of roughness, wettability together with its morphological and chemical stability after three cycles of expansion-crimping along with preliminary results after 6 months demonstrates the suitability of the coating for surgical implantation of stent.     

Tribochemical structuring and coating of implant metal surfaces with titanium oxide and hydroxyapatite layers

The sandblasting process with corundum is used for cleaning, roughening and activating of metal surfaces in dentistry and orthopaedics. The high local energy transfer at the impact point originates the displacement of particles in the surface. In principle, this method can be used for coating surfaces by sandblasting. In this work, we present a newly developed technique, which allows the coating of metal surfaces with titanium dioxide (TiO₂) and hydroxyapatite (HA) using a sandblasting process. The blasting material is a composite ceramic consisting of an alumina core (carrier material) covered with a porous shell of titanium dioxide or hydroxyapatite. The technique is applied to titanium substrates; the surface roughness, morphology and composition of the samples are analysed. The procedure results in an averaged surface roughness of 10–15 μm. Energy dispersive X-ray analysis (EDX) indicates the formation of a thin layer consisting of coating material on the metal surface. Furthermore, the traces of corundum crystals, which are inevitable by using the common technique, i.e. sandblasting with single-component grains, are clearly decreased. X-ray diffraction analysis (XRD) indicates mainly the existence of crystalline rutile and hydroxyapatite/β-tricalcium phosphate (β-TCP) on the surface. Therefore, the presented method would be suitable for simultaneously roughening, coating and optimizing the biocompatibility of metal implant surfaces in dentistry and endoprosthetics.     

High-performance organic optoelectronic devices enhanced by surface plasmon resonance

The surface plasmon effect on polymer solar cells and polymer light-emitting diodes is demonstrated by using metal nanoparticles prepared from block copolymer templates. Light absorption of the polymer thin layer is increased with the incorporation of metallic nanostructures, resulting in a significant surface plasmon effect in the optoelectronic devices.     

等离子体浸没离子注入及表面强化工艺的进展

等离子体浸没离子注入 (PIII)消除了传统束线离子注入 (IBII)固有的视线限制 ,是一种更适合于处理复杂形状工件的手段 .近十年来 ,PIII及其工业应用在国内外得到了迅速发展 .然而 ,随着PIII的研究与开发的深入 ,发现仍有若干重要的物理与技术问题 ,诸如浅的注入层、离子注入不均匀性、气体 (氮 )等离子体的有限应用范围等等 ,阻碍了PIII工业应用的发展 .目前 ,这些问题已成为国内外学者关注的焦点 .我实验室近年来在注入过程鞘层动力学的计算机理论模拟、离子注入剂量不均匀性改善、圆筒内表面注入研究、新型长射程阴极弧金属等离子体源研制、气体及金属等离子体的综合性表面改性工艺研究、以及低能高温PIII新工艺研究等方面进行了研究工作 .     

Keramik-Polymer Kombinationsschichten

Ceramic Polymer Composite Coatings The tribological properties of ceramic-polymer composite coatings which consist of thermal sprayed oxide ceramics coated with polymer lacquers for numerous industrial applications are discussed in this paper. The surface of these coatings match the requirements of high wear resistance and low coefficient of friction which is desired for many industrial applications. For experimental evaluation, samples were fabricated by coating aluminum substrates with titanium dioxide by means of atmospheric plasma spraying (APS). This oxide ceramic surface was successively coated by means of air spraying with a polymer lacquer containing molybdenum disulphide (MoS₂) and polytetrafluor ethylene (PTFE) as solid lubricants. The tribological properties (coefficient of friction and wear) of this combination layer were determined using a tribometer under oscillating sliding movement.     

Improving conversion efficiency of dye-sensitized solar cells by metal plasma ion implantation of ruthenium ions

Dye-sensitized solar cells (DSSC) are based on the concept of photosensitization of wide-band-gap mesoporous oxide semiconductors. At present, DSSC have ventured into advanced development and pilot production. Our current research emphasizes on improvements on titanium dioxide (TiO₂) photosensitivity under visible light irradiation by using metal plasma ion implantation (MPII). The anatase TiO₂ electrode was prepared via a sol-gel process and deposited onto indium-tin oxide glass substrates. Subsequently, the as-deposited TiO₂ films were subjected to MPII at 20 keV in order to incorporate ruthenium (Ru) atoms onto the TiO₂ surface layer. The Ru-implanted TiO₂ thin film possessed nanocrystalline Ru clusters of 20 nm in diameter and distributed in near surface layer of TiO₂ films. The Ru clusters showed effective in both prohibiting electron-hole recombination and generating additional Ru-O impurity levels for the TiO₂ band gap structure. A significant reduction of TiO₂ band gap energy from 3.22 to 3.11 eV was achieved, which resulted in the extension of photocatalysis of TiO₂ from UV to Vis regime. A small drop of photoelectric performance of 8% was obtained due to the incorporation of Ru atoms in the surface layer of TiO₂, a similar side effect as observed in the Fe-implanted TiO₂. However, the overall retention of the photocatalysis capability is as high as 92% when switch from UV to Vis irradiation. The improvement of the photosensitivity of TiO₂ DSSC by means of metal plasma ion implantation is promising.     

金刚石单晶真空蒸镀铬的工业化应用

应用真空蒸镀处理技术，在金刚石单晶表面蒸镀金属铬层，并在真空高温条件下，部分铬与金刚石键合生成Cr7C3，有效地提高金刚石表面对金属粘结剂的粘结力。该蒸镀技术工艺简单、经济，可以在工业化生产中应用。结果表明，经真空蒸镀处理后，金刚石制品的寿命提高了50％～100％。     

Synthesis and characterization of composite membrane by deposition of acrylic acid plasma polymer onto pre-treated polyethersulfone support

The plasma techniques were explored to deposit a layer of hydrophilic polymer on asymmetric porous membranes used as support material. Microporous membranes were synthesized by the phase inversion technique from polyethersulfone (PES) and submitted to a surface treatment with RF-plasma of non-polymerizable gas. Carbon dioxide (CO₂) was selected to generate this plasma and to increase the surface energy. Further plasma treatment proceeded with acrylic acid (AA) in vapor phase as source for the permanent surface hydrophilic functionalization. The infrared spectra with horizontal attenuated total reflectance (HATR) show that the deposited plasma polymer provides a high concentration of carbonyl and hydroxyl groups. The hydrophilic polymer layer was evenly deposited, with good adhesion to the support, as was observed by electronic microscopy (SEM). The surface free energy (γ_S) was increased through plasma treatments and confirmed by the decrease of contact angle (θ) measurements and increase of adhesion work (W _a). The nitrogen permeability decreased 650 times; after that a dense thin film was deposited by plasma treatment during 40 min (at 5 W and 8 Pa). Final composite membranes show stability, high surface hydrophilicity, and a surface chemical nature very stable with time.     

NiTi superelastic orthodontic archwires with polyamide coating

Twenty orthodontic archwires with 55.2 % Ni and 44.8 % Ti (% weight) were subjected to a dipping treatment to coat the NiTi surface by a polyamide polymer. It has been selected a Polyamide 11 due to its remarkable long lasting performance. The transformation temperatures as well as the transformation stresses of the NiTi alloy were determined in order to know whether the coating process can alter its properties. The adhesive wear tests have been demonstrated that the wear rates as well as the dynamic friction coefficients μ of polymer coated wires are much lower than metallic wires. The corrosion studies have shown that the use of this polymer, as coating, seals the NiTi surface to prevent corrosion and the release of nickel ions. The average decrease of Ni ions release due to this coating is around 85 %.     

Self-assembled monolayer of 3-aminopropyltrimethoxysilane for improved adhesion between aluminum alloy substrate and polyurethane coating

A good adhesion between a polymer coating and a metal or metal alloy substrate such as Al 2024-T3 plays a critical role in corrosion protection of metal substrates. In our study, a self-assembled monolayer film of 3-aminopropyltrimethoxysilane was formed on Al 2024-T3 substrate by covalent bonding. The adhesion property of a self-priming polyurethane coating was evaluated by pull-off adhesion test, wet tape test and thermal cycling test. All the testing results indicate that both dry and wet adhesion properties of the polyurethane coating were improved significantly after APS treatment of Al 2024-T3 in polar solvents such as methanol and acetone. In nonpolar solvents such as hexane, the APS treatment led to inconsistent improvement or sometime decreased adhesion of polyurethane coating. X-ray photoelectron spectroscopic study revealed that while a monolayer film was formed on the aluminum alloy surface after treating the substrate with APS in methanol and acetone, a multilayer film was formed on the substrate surface when the treatment was conducted in hexane. The APS monolayer film served as a covalent bond linkage between polymer coating and aluminum alloy substrates, which led to the increased adhesion property of polymer coating and corrosion resistance of the metal alloy substrate.     

Rational design of phosphonate/quaternary amine block polymer as an high-efficiency antibacterial coating for metallic substrates

Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates.Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments(repeat units of 15)but varied cationic segments(repeat units of 8,45,and 70)were precisely prepared.Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate.Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations.Results showed that the antibacterial rate of the modified TC4 surface were 95.8%of S.aureus and 92.9%of E.coli cells attached.Interestingly,unlike the cationic free polymer or cationic hydrogels,the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity.In addition,the phosphonate/quate rnary amine block polymers can be easily constructed on titanium,stainless steel,and Ni/Cr alloy with significantly improved antibacterial property,indicating the generality of the block polymer for surface antibacterial modification of bio-metals.     

镁合金表面处理的发展现状

综述了镁合金的表面处理方法的现状，主要有化学转化膜，化学氧化，阳极氧化，表面渗层处理，金属涂层，激光表面处理，有机物涂层等，还展望了今后的发展趋势。     

Plasma processing of PDMS based spinal implants for covalent protein immobilization,cell attachment and spreading

PDMS is widely used for prosthetic device manufacture. Conventional ion implantation is not a suitable treatment to enhance the biocompatibility of poly dimethyl siloxane (PDMS) due to its propensity to generate a brittle silicon oxide surface layer which cracks and delaminates. To overcome this limitation, we have developed new plasma based processes to balance the etching of carbon with implantation of carbon from the plasma source. When this carbon was implanted from the plasma phase it resulted in a surface that was structurally similar and intermixed with the underlying PDMS material and not susceptible to delamination. The enrichment in surface carbon allowed the formation of carbon based radicals that are not present in conventional plasma ion immersion implantation (PIII) treated PDMS. This imparts the PDMS surfaces with covalent protein binding capacity that is not observed on PIII treated PDMS. The change in surface energy preserved the function of bound biomolecules and enhanced the attachment of MG63 osteosarcoma cells compared to the native surface. The attached cells, an osteoblast interaction model, showed increased spreading on the treated over untreated surfaces. The carbon-dependency for these beneficial covalent protein and cell linkage properties was tested by incorporating carbon from a different source. To this end, a second surface was produced where carbon etching was balanced against implantation from a thin carbon-based polymer coating. This had similar protein and cell-binding properties to the surfaces generated with carbon inclusion in the plasma phase, thus highlighting the importance of balancing carbon etching and deposition. Additionally, the two effects of protein linkage and bioactivity could be combined where the cell response was further enhanced by covalently tethering a biomolecule coating, as exemplified here with the cell adhesive protein tropoelastin. Providing a balanced carbon source in the plasma phase is applicable to prosthetic device fabrication as illustrated using a 3-dimensional PDMS balloon prosthesis for spinal implant applications. Consequently, this study lays the groundwork for effective treatments of PDMS to selectively recruit cells to implantable PDMS fabricated biodevices.

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Balancing the corrosion resistance and through-plane electrical conductivity of Cr coating via oxygen plasma treatment

Developing an electrically conductive and corrosion-resistant coating is essential for metal bipolar plates of polymer electrolyte membrane fuel cells(PEMFCs). Although enhanced corrosion resistance was seen for Cr coated stainless steel(Cr/SS) bipolar plates, they experience a quick decrease of through-plane electrical conductivity due to the formation of a porous and low-conductive corrosion product layer at the plate surface, thus leading to an increase in interfacial contact resistance(ICR). To tackle this issue, the multilayer Cr coatings were deposited using the magnetron sputtering with a remote inductively coupled oxygen plasma(O-ICP) in the present study. After the O-ICP treatment, a Cr oxide layer(Cr O*) is formed on the specimen surface. The Cr O*/Cr/SS has a remarkably lower stable corrosion rate(iss) than that of the native Cr oxides(Cr On/Cr/SS). Compared with Cr On/Cr/SS, the excellent performance of Cr O*/Cr/SS is attributed to a denser and thicker surface layer of Cr O* with Cr being oxidized to its highest valence state,Cr(VI). More importantly, the through-plane electrical conductivity of the specimens treated by the optimized O-ICP decreases much slowly than Cr On/Cr/SS and thus, the increament of ICR of Cr O*/Cr/SS after the potentiostatic polarization test is considerably smaller than that of Cr On/Cr/SS, which is benefited from the reduced issthat mitigates the deposition of corrosion products and hinders further oxidation of Cr coating. Therefore, Cr O*/Cr/SS proves to be a well balanced trade-off between corrosion resistance and through-plane electrical conductivity. The results of this study demonstrate that O-ICP treatment on a conductive metal coating is an effective strategy to improve the corrosion resistance and suppress the increase of ICR over the long-term polarization. The technique reported herein exhibits its promising potential application in preparing corrosion resistant and electrically conductive coatings on metal bipolar plates to be used in PEMFCs.