Plasma Polymer Matrix Research Articles

Antibacterial, highly hydrophobic and semi transparent Ag/plasma polymer nanocomposite coating on cotton fabric obtained by plasma based co-deposition

This study aims at deposition and characterization of antibacterial, hydrophobic and semitransparent metal/plasma polymer nanocomposite coating, containing Ag nanoparticles, onto cotton fabrics intended to be used in medical applications. The nano composite coatings were obtained via a simple, one step and ecofriendly plasma based co-deposition approach where silver was magnetron sputtered simultaneously with plasma polymerization of hexamethyldisiloxane (HMDSO) monomer. The nanocomposite thin films containing different concentration of silver were deposited either by varying silver sputter rate or thickness of the plasma polymer matrix to obtain a good balance between optical properties of the coated fabric and its long term antibacterial performance. The obtained coatings were investigated in detail with respect to their composition, morphology, optical properties, nanoparticle size distribution, silver ion release efficiency, antibacterial performance, water contact angle and washing stability of the coating. The thickness of the plasma matrix was found to be more important in controlling the release of silver ions as well as affecting the optical properties of the coating. The water contact angle on the coated fabric was up to 145°, close to super hydrophobicity. The coating showed effective antibacterial efficacy against Staphylococcus epidermidis (a Gram positive bacterium) which was present even when fabric was subjected to 10 repeated washing cycles indicating good washing stability of the coating.

Distribution of metal nanoparticles in a plasma polymer matrix according to the structure of the polymer and the nature of the metal

The amount and distribution of metal nanoparticles in a plasma polymer matrix are studied according to the chemical structure of the polymer and the nature of the metal. The structure of the polymer (polyallylalcohol) is modified by varying the plasma parameters such as polymerization time, input power and discharge time. This study, done with silver, shows that when the polymer contains a lot of functional groups (here hydroxyl ones) with a rough surface, a high amount of silver, homogeneously distributed is inserted into the polymer. Moreover, three metals are studied: Ag, Cu and Sn. A higher quantity of silver and tin ions is inserted into the matrix compared to copper. Finally, two routes for the incorporation of silver nanoparticles are studied where the impregnation with the metallic salt and its reduction are done either in two stages or in one step with a single solution containing both the metallic salt and the reducing agent. The first method allows obtaining a higher amount of loaded silver with a homogeneous dispersion in the matrix.

Structure and Stability of C:H:O Plasma Polymer Films Co-Polymerized Using Dimethyl Carbonate

C:H:O plasma polymer films (PPFs) were deposited by means of plasma-enhanced chemical vapour deposition using the non-toxic, biodegradable organic compound dimethyl carbonate (DMC) at various plasma powers and pressures in order to control the degradation properties related to the carbonate ester group. Coating properties using pure DMC monomer vapours were compared to co-polymerized films from gaseous mixtures of DMC with either ethylene (C2H4) or carbon dioxide (CO2) affecting deposition rate and chemical composition. C:H:O film properties were found to depend primarily on the amount of oxygen in the plasma. To investigate the PPF stability during aging, changes in the composition and properties were studied during their storage both in air and in distilled water over extended periods up to 5 months. It was shown that aging of the films is mostly due to oxidation of the plasma polymer matrix yielding slow degradation and decomposition. The aging processes and their rate are dependent on the intrinsic amount of oxygen in the as-prepared C:H:O films which in turn depends on the experimental conditions and the working gas mixture. Adjustable film properties were mainly attained using a pure DMC plasma considering both gas phase and surface processes. It is thus possible to prepare C:H:O PPFs with controllable degradability both in air and in water.

Development of a biodegradable plasma polymer matrix by dielectric barrier discharge

Event Abstract Back to Event Development of a biodegradable plasma polymer matrix by dielectric barrier discharge Morgane Laurent1, 2, 3*, Julia Köhler1*, Gad Sabbatier2, 3*, Corinne Hoesli2, 3*, Nicolas Gherardi1* and Gaétan Laroche2, 3* 1 Université de Toulouse - CNRS, LAPLACE, France 2 Université Laval, Dep. of Materials Engineering, Canada 3 Centre de recherche du CHU de Québec, Laboratoire d’Ingénierie de Surface, Canada Introduction: Most strategies aiming at developing biocompatible arterial prostheses target the recruitment of endothelial cells (EC) to reproduce a native artery intima. In practice, the implantation of arterial prostheses leads to neointimal hyperplasia, which is characterized by the obstruction of blood vessels due to the proliferation of smooth muscle cells (SMC) on the prosthesis wall. In vitro experiments already demonstrated the potential of some drugs to inhibit SMC proliferation while somewhat promoting EC ability to proliferate[1]. Plasma based technologies were successfully used in the past to coat biomedical devices to improve their biocompatibility[2]. The strategy consists in using plasma energy to polymerize a gaseous precursor. By selecting appropriate precursor and plasma conditions, one can build up a plasma polymer (PP) with tailored properties. In this context, we exploited a dielectric barrier discharge (DBD) to build up a biodegradable PP to be used as drug delivery system (DDS). Materials and Methods: Ethyl lactate was used as precursor due to its potential to form a PP resembling to poly(lactic acid). The influence of plasma power, deposition time, and carrier gas was correlated to the in vitro degradation rate of the coating. Layers were characterized by FTIR and XPS spectroscopies, while surface profilometry was used to follow the PP degradation under aqueous conditions. Cell viability experiments were carried out on EC to ascertain the applicability of this plasma based DDS. Results: XPS showed that layers deposited under nitrogen (N2 layers) contained about 50% carbon, and up to 45% nitrogen, with the remaining consisting of oxygen. The IR spectrum (Figure 1; in red) showed the presence of nitrile, amine, and amide functionalities (through both C=O and N-H modes). Coatings synthesized under argon (Ar layers) were made of 75% C, and 25% O, as analyzed by XPS. Ester and CH2/CH3 groups were observed through IR analyses (Figure 1; in blue). In buffer, all coatings degraded faster at the entrance of the plasma region (Figure 2). The degradation rate seemed to decrease with great increase of the plasma power and when using Ar as carrier gas. Viability cell tests showed that the layers are nontoxic to EC. Discussion: N2 coatings contained mainly hydrophilic functionalities, and only a few hydrocarbon groups, which explain their fast degradation in buffer. In agreement with the formation of a more conventional polymer structure, Ar layers’ hydrocarbon structure, coupled with some hydrolysable moieties, led to a slower degradation behavior. Moreover, all layers seemed to enable the growth of EC, therefore showing the potential of plasma deposited films for vascular applications. Conclusion: By selecting the appropriate carrier gas and adjusting the plasma power input, it is possible to adapt the deposited layer’s chemistry, and hence its degradation upon aqueous environment. This study shows the potential of DBD for the development of DDS. Conseil franco-québécois de coopération universitaire; Pascale Chevallier (U. Laval) and Andrée-Anne Guay-Béguin (U. Laval)

Long-term aging of Ag/a-C:H:O nanocomposite coatings in air and in aqueous environment

Nanocomposite coatings of silver particles embedded in a plasma polymer matrix possess interesting properties depending on their microstructure. The film microstructure is affected among others also by the RF power supplied during the deposition, as shown by transmission electron microscopy. The optical properties are characterized by UV–vis–NIR spectroscopy. An anomalous optical absorption peak from the Ag nanoparticles is observed and related to the microstructure of the nanocomposite films. Furthermore, a long-term aging of the coatings is studied in-depth in ambient air and in aqueous environments. It is shown that the studied films are not entirely stable. The deposition conditions and the microstructure of the films affect the processes taking place during their aging in both environments.

Nitrogen‐Doped TiO2 Nanoparticles and Their Composites with Plasma Polymer as Deposited by Atmospheric Pressure DBD

TiO2 nanoparticles and nitrogen‐doped TiO2−xNx nanoparticles dispersed in plasma polymer phase are produced by atmospheric pressure DBD in titanium tetraisopropoxide with dry air, mixture of N2 and O2, and 100% N2 used as carrier gases. Energy supply per monomer molecule (the Yasuda parameter) is found to be an important parameter describing the deposition process in N2. In the monomer deficient regime, spherical TiO2 particles are produced with an average size varying from 30 to 80 nm. In the power deficient regime, composite films are deposited consisting of TiO2−xNx nanoparticles embedded in nitrogen‐rich plasma polymer matrix, particulates being larger than 100 nm.

Deposition of Al nanoparticles and their nanocomposites using a gas aggregation cluster source

The study describes the preparation and properties of Al/Al x O y nanoparticles and their nanocomposites with hydrocarbon plasma polymer. The nanoparticles were deposited using a simple gas aggregation cluster source based on a planar magnetron. The influence of deposition parameters on size distribution was studied. It was found that Al nanoparticles may be deposited with mean diameter ranging from 30 to 60 nm by varying magnetron current from 0.4 to 0.2 A. Attention was also paid to the investigation of the charge of the nanoparticles. It is shown that a large portion of Al x O y nanoparticles leave the gas aggregation source as negatively charged. The nanoparticles were also embedded into the plasma polymer matrix by their simultaneous co-deposition with plasma-polymerized n-hexane. Morphology and chemical composition of such fabricated nanocomposites were determined. It was shown that Al x O y nanoparticles embedded into the polymeric matrix exhibit localized surface plasmon resonances in the deep ultraviolet region of the electromagnetic spectrum and the position of the plasmon peak is strongly correlated with nanoparticle size.

Tailor-Made Silver Release Properties of Silver-Containing Functional Plasma Polymer Coatings Adjusted Through a Macroscopic Kinetics Approach

Combining a functional plasma polymer matrix with antibacterially active silver (Ag) within a nanocomposite structure allows secure production and applications in various fields, especially in the medical sector. Therefore, nitrogen or oxygen containing hydrocarbon plasma polymers and Ag nanoparticles were simultaneously deposited. Functional groups such as amino or carboxylic groups as well as an adjusted amount of Ag can be incorporated into the growing films by controlling the plasma deposition properties. For this purpose, macroscopic kinetics were used to characterise the deposition behaviour also as a base for possible industrial up-scaling. XPS and ICP-OES were used to analyse the chemical composition of the polymer–Ag nanocomposites and the Ag content which could be incorporated depending on the plasma process conditions. Finally, the Ag release was determined in bi-distilled water for classification and comparison with the antibacterial properties. The antibacterial effect of the polymer–Ag nanocomposites was proofed with the gram− strain Pseudomonas aeruginosa PAO1 and the gram+ strain Staphylococcus aureus (ST12 Group) showing a clear efficacy dependence on the amount of released Ag and the possibility for tailor-made antibacterial active plasma films.

Nanocomposite and nanostructured films with plasma polymer matrix

Nanocomposite and nanostructured films have been studied for several decades mainly due to their unique physical, chemical or bioresponsive properties. The main attention has been paid to metal/plasma polymer nanocomposites prepared by simultaneous plasma polymerization and metal co-sputtering or evaporation. These nanocomposite films are concisely reviewed. More complex composites that are prepared by metal oxide incorporation into plasma polymer matrices using RF sputtering are discussed. Recently emerged utilization of beams of nanoclusters for the deposition of these nanocomposites and preparation of nanostructured surfaces of plasma polymers by various plasma based methods is described.

Nanocomposite gold/poly(ethylene oxide)-like plasma polymers prepared by plasma-assisted vacuum evaporation and magnetron sputtering

A new method of deposition of nanocomposite gold/poly(ethylene oxide)-like thin films was investigated where gold was sputtered from an r. f. magnetron and poly(ethylene oxide)-like plasma polymer was simultaneously deposited via vacuum evaporation of conventional poly(ethylene oxide). Such method allows formation of the plasma polymer matrix with composition very close to that of precursor, a feature difficult to obtain in plasma polymerization processes. The films with different content of gold were prepared by varying the evaporation rate of poly(ethylene oxide) at constant power of the magnetron discharge. Chemical composition and cross-linking density of polymeric phase as well as the size distribution of gold nanoparticles were shown to be strongly dependent on the discharge power conditions. Stability of resultant nanocomposites in water was also studied. Such films are perspective for use in biomedical applications.

Formation and Distribution of Silver Nanoparticles in a Functional Plasma Polymer Matrix and Related Ag+ Release Properties

AbstractPlasma polymer coatings with embedded Ag nanoparticles were deposited in a low pressure RF plasma reactor using an asymmetrical setup with an Ag electrode. The plasma polymer was deposited from a reactive gas/monomer mixture of CO2/C2H4 yielding a functional hydrocarbon matrix. In addition, Ar was simultaneously used to sputter Ag atoms from the Ag electrode, forming nanoparticles within the growing polymer matrix. The influence of the power input, gas ratio and coating thickness on both, the Ag content and the Ag nanoparticle morphology, as well as the distribution in the polymer matrix were investigated. It was found that both increasing the power input and the CO2 ratio result in a higher incorporation of Ag into the matrix.magnified image

Properties of tin/plasma polymer nanocomposites

Thin composite layers (tin in plasma polymer matrix) were prepared in a stainless steel vacuum chamber. An RF powered magnetron with tin target was used to excite the discharge and to activate the monomer species ( n-hexane). The gas mixture introduced comprised Ar and n-hexane vapours. The properties of the films and chemical composition were characterized by AFM (surface morphology), TEM and Electron tomography (bulk structure characterization), XPS and FTIR spectroscopy (chemical composition analyses). Current–voltage characteristics were measured to examine the electrical properties of the layers and their dependence on the deposition parameters.

Nanocomposite Ti/hydrocarbon plasma polymer films from reactive magnetron sputtering as growth support for osteoblast‐like and endothelial cells

Nanocomposite Ti/hydrocarbon plasma polymer (Ti/ppCH) films were deposited by DC magnetron sputtering of titanium target in n-hexane, argon, or a mixture of these two gases. The resultant films were heterogeneous, with inorganic regions of nanometer scale distributed within a plasma polymer matrix. The titanium content was controlled by adjusting the argon/n-hexane ratio in the working gas. In the pure n-hexane atmosphere, the Ti concentration was found to be below 1 at %, whereas in pure argon it reached 20 at %, as measured by Rutherford backscattering spectroscopy and elastic recoil detection analysis (RBS/ERDA). A high level of titanium oxidation is detected with TiO(2), substoichiometric titania, and titanium carbide, composing an inorganic phase of the composite films. In addition, high hydrogen content is detected in films rich with titanium. Ti-deficient and Ti-rich films proved equally good substrates for adhesion and growth of cultured human osteoblast-like MG 63 cells. In these cells, the population densities on days 1, 3, and 7 after seeding, spreading area on day 1, formation of talin-containing focal adhesion plaques as well as concentrations of talin and osteocalcin (per mg of protein) were comparable to the values obtained in cells on the reference cell culture materials, represented by microscopic glass coverslips or a polystyrene dish. An interesting finding was made when the Ti/ppCH films were seeded with calf pulmonary artery endothelial cells of the line CPAE. The cell population densities, the spreading area and also the concentration of von Willebrand factor, a marker of endothelial cell maturation, were significantly higher on Ti-rich than on Ti-deficient films. On Ti-rich films, these parameters were also higher or similar in comparison with the reference cell culture materials. Thus, both types of films could be used for coating bone implants, of which the Ti-rich film remains effective in enhancing the endothelialization of blood contacting artificial materials.

Multifunctional Nanocomposite Plasma Coatings: Enabling New Biomaterials Applications

ABSTRACTDue to the increasing prevalence of resistance of bacteria to antibiotics and antiseptic methods, new strategies to prevent colonization of biomaterials are needed. Due to its high antimicrobial activity and relatively low toxicity to human cells, we are evaluating silver (Ag) releasing plasma polymers as a strategy to prevent bacterial colonization. Such Ag/plasma polymer nanocomposite materials, consisting of nano-scaled metal clusters embedded within a plasma-polymer matrix can be deposited using a mixed, plasma polymerization /sputtering process. For example, Ag containing plasma polymer nanocomposites are deposited employing an Ag cathode, an appropriate monomer to yield the desired material properties of the matrix (biocompatibility) and an asymmetric reactor design. The focus of this paper is a new development at Empa: a multi-functional Ag/amino-hydrocarbon (Ag/a-C:H:N) nanocomposite that can enhance cell growth and simultaneously prevent bacterial colonization at surfaces. Ag/a-C:H:N coatings containing 4.0% Ag have been demonstrated to reduce bacterial adhesion of E. coli by up to 95%, as compared to an external polyester fabric control in a static assay. Likewise, these coatings demonstrated a bacterial toxic effect both at the surface and in the surrounding media due to the release of Ag ions. XPS characterization of various nanocomposites has shown that the Ag quantity and matrix characteristics of the films can be tailored to specific requirements by altering deposition parameters such as power input, pressure and gas feed ratio. Although the surface chemistry has been characterized, open questions remain to the amount and the kinetics of the release of Ag and the subsequent effect on bacteria and cells. Since Ag release profiles will ultimately determine the antimicrobial efficacy of the coatings, as well as duration of the effect, these dosing issues must be quantified and clarified. Ag release kinetics of the various Ag/a-C:H:N as measured by atomic absorption spectroscopy has been evaluated and the relationships to biological assays, including bacterial and cellular adhesion are clarified. A range of Ag/a-C:H:N coatings having various Ag content are tested in two biological assays, bacterial toxicity and cytoxicity. Bacterial growth tests using the pathogen, P. aeruginosa wild type (PAO1), were performed according to the method of Tiller et al. The method is based on the bacterial deposition from aerosols, thus, it mimics bacterial exposure through airways such as intubation tubes. Secondly, cytotoxicity assays of the nanocomposites has been performed using a murine fibroblast cell line 3T3 testing protocol, and the proliferation of the cultures was measured taking the DNA amount per well as an index (Bruinink 2001). We will answer questions regarding what is the fundamental Ag content and Ag release profile under static bacterial testing environments which allow a maximum bacterial-toxic effect with a minimum amount of Ag.

Rf sputtering of composite SiO x/plasma polymer films and their basic properties

Composite SiO x /PTFE films were deposited by rf sputtering in argon using balanced magnetron equipped with a PTFE/SiO 2 target. The composition of deposited films, found by XPS and FTIR, ranged from fluorocarbon plasma polymers with very small SiO x content up to coatings with a greater incorporation of SiO x . The hardness of fluorocarbon polymer films with increased concentration of SiO x was 2400 N/mm 2. This is between two to three times higher than in the case of fluorocarbon plasma polymers with very low SiO x content. The static contact angle of water ranges from 112 to 95° and the refractive index from 1.49 to 1.43, when incorporation of SiO x into fluorocarbon plasma polymer matrix decreases.

Metal clusters in plasma polymer matrices Part II. Silver clusters

By means of an inert gas evaporation technique in combination with a simultaneous plasma polymerisation process silver clusters have been prepared within plasma polymer matrices from vinyltrimethylsilane (VTMS) with mean diameters between 1.3 and 4.5 nm and from tetraethoxysilane (TEOS) between 4.8 and 6.2 nm, respectively. The materials were characterised by transmission electron microscopy (TEM), electron diffraction (ED), X-ray photoelectron spectroscopy (XPS) and UV-visible spectrophotometry. From the decrease of the Ag-lattice parameter with decreasing size of the silver clusters a value of the surface stress coefficient fss=5.4±1.1 N m-1 could be deduced. UV-visible spectrophotometry of Ag–VTMS composites revealed a damping layer around the metal clusters, which prevents oxidation of the silver particles. A strong blue shift of the plasmon resonance frequency from λmax=557 nm to λmax=450 nm with decreasing filling factor could be observed for the Ag–TEOS composites. The plasma polymer matrix from tetraethoxysilane monomer shows a strong chemical damping of the surface plasmon resonance. The measured UV-visible spectra were fitted with the Maxwell-Garnett theory.

Optical response of thin plasma-polymer films with non-spherical silver nanoparticles

The size and shape of silver nanoparticles which are embedded in a plasma-polymer matrix were obtained by transmission electron microscopy and analyzed with optical image processing. We used a sample in which silver particles were present before and after reshaping caused by thermal annealing in adjacent regions. As most of the particles appeared as elongated rotational ellipsoids, the major and minor half axis were determined for each particle. We adopted the model of Gans in the Rayleigh approximation to calculate for each investigated particle the extinction spectra from 4000 cm-1 to 35000 cm-1 using the data from the image processing. The various spectra for 368 silver particles were added to get total extinction spectra for the sample as deposited and after reshaping, respectively. We found good agreement with the experimental spectra. The blue shift of the plasma-resonance absorption, which occurs due to the reshaping of the silver particles during thermal annealing, was also confirmed by using only changes in the particle sizes and shapes.

Determination of thermally induced microstructural changes of embedded metal nanoparticles by lateral and cross-sectional transmission electron microscopy

The size and shape of silver and indium nanoparticles embedded in a plasma polymer matrix formed from benzene or styrene monomer were determined by transmission electron microscopy (TEM) in lateral direction and by cross-sectional transmission electron microscopy (XTEM) in vertical direction. In multilayer assemblies consisting of plasma polymer/plasma polymer metal composite/plasma polymer [ABA], silver as well as indium nanoparticles were embedded only in one plane. XTEM micrographs on samples before and after appropriate thermal annealing (450 K) showed, that the multilayer [ABA] structure was not destroyed. At a higher annealing temperature and time (570 K, 3 h) only parts of the plasma polymer matrix were left. With all thermal annealed samples, reshapening and coalescence of the embedded silver particles was found. For multilayers with embedded indium particles, the second plasma polymer layer was formed mainly as a shell around the large particles. During thermal annealing in the electron microscope, the formation of indium oxide particles inside these shells was observed.

Optical properties of nonspherical silver nanoparticles embedded in a plasma polymer thin film matrix

ABSTRACTSilver nanoparticles which are embedded in a plasma polymer matrix were obtained by transmission electron microscopy. Their sizes and shapes were analyzed with optical image processing. As most of the particles appeared as elongated rotational ellipsoids, the major and minor half axes were determined for each particle. The model of Gans in the Rayleigh approximation was used to calculate the extinction spectra for each investigated particle using the data from the image processing. Various spectra for 1049 silver particles were added to get a total extinction spectrum which was in good agreement with the experimental spectrum.

Cross-sectional TEM investigations of plasmapolymer-metal composite films

Plasmapolymer-metal composite films were investigated by means of cross-sectional transmission electron microscopy (XTEM). Copper and silver were encapsulated as small particles in the plasmapolymer matrix. Size and shape of the silver particles depend on the polymerization power density. Within films deposited with low polymerization power density, the silver particles are almost spherical and a three-dimensional particle distribution was found in the polymer matrix. However, the shape of the particles in films deposited at higher power density is more elliptic and the particle distribution is two-dimensional. High resolution images demonstrate the structure of single silver particles. By lateral and cross-sectional transmission electron microscopy the size and shape of the encapsulated particles could be reconstructed three-dimensionally.