Pieter Cools

Antimicrobial nano-silver non-woven polyethylene terephthalate fabric via an atmospheric pressure plasma deposition process

An antimicrobial nano-silver non-woven polyethylene terephthalate (PET) fabric has been prepared in a three step process. The fabrics were first pretreated by depositing a layer of organosilicon thin film using an atmospheric pressure plasma system, then silver nano-particles (AgNPs) were incorporated into the fabrics by a dipping-dry process, and finally the nano-particles were covered by a second organosilicon layer of 10-50 nm, which acts as a barrier layer. Different surface characterization techniques like SEM and XPS have been implemented to study the morphology and the chemical composition of the nano-silver fabrics. Based on these techniques, a uniform immobilization of AgNPs in the PET matrix has been observed. The antimicrobial activity of the treated fabrics has also been tested using P. aeruginosa, S. aureus and C. albicans. It reveals that the thickness of the barrier layer has a strong effect on the bacterial reduction of the fabrics. The durability and stability of the AgNPs on the fabrics has also been investigated in a washing process. By doing so, it is confirmed that the barrier layer can effectively prevent the release of AgNPs and that the thickness of the barrier layer is an important parameter to control the silver ions release.

Effects of different sterilization methods on the physico-chemical and bioresponsive properties of plasma-treated polycaprolactone films

For most tissue engineering applications, surface modification and sterilization of polymers are critical aspects determining the implant success. The first part of this study is thus dedicated to modifying polycaprolactone (PCL) surfaces via plasma treatment using a medium pressure dielectric barrier discharge, while the second part focuses on the sterilization of plasma-modified PCL. Chemical and physical surface changes are examined making use of water contact angle goniometry (WCA), x-ray photoelectron spectroscopy and atomic force microscopy. Bioresponsive properties are evaluated by performing cell culture tests. The results show that air and argon plasmas decrease the WCA significantly due to the incorporation of oxygen-containing functionalities onto the PCL surface, without modifying its morphology. Extended treatment times lead to PCL degradation, especially in the case of air plasma. In addition to surface modification, the plasma potential to sterilize PCL is studied with appropriate treatment times, but sterility has not been achieved so far. Therefore, plasma-modified films are subjected to UV, H2O2 plasma (HP) and ethylene oxide (EtO) sterilizations. UV exposure of 3 h does not alter the PCL physico-chemical properties. A decreased wettability is observed after EtO sterilization, attributable to the modification of PCL chain ends reacting with EtO molecules. HP sterilization increases the WCA of the plasma-treated samples, presumably due to the scission of the hydrophilic bonds generated during the prior plasma treatments. Moreover, HP modifies the PCL surface morphology. For all the sterilizations, an improved cell adhesion and proliferation is observed on plasma-treated films compared to untreated ones. EtO shows the lowest proliferation rate compared to HP and UV. Overall, of the three sterilizations, UV is the most effective, since the physical alterations provoked by HP might interfere with the structural integrity when it comes to 3D scaffolds, and the chemical modifications caused by EtO, in addition to its toxicity, interfere with PCL bioactivity.

Surface Treatment of PEOT/PBT (55/45) with a Dielectric Barrier Discharge in Air, Helium, Argon and Nitrogen at Medium Pressure

This work describes the surface modification of 300PEO-PEOT/PBT 55/45 thin films using a medium pressure dielectric barrier discharge system operated in argon, helium, nitrogen or dry air to improve cell-surface interactions of this established biomaterial. The first part of the paper describes the optimization of the plasma processing parameters using water contact angle goniometry. The optimized samples are then characterized for changes in surface topography and surface chemical composition using atomic force microscopy (AFM) and X-ray fluorescence spectroscopy (XPS) respectively. For all plasma treatments, a pronounced increase in surface wettability was observed, of which the extent is dependent on the used plasma discharge gas. Except for dry air, only minor changes in surface topography were noted, while XPS confirmed that the changes in wettability were mainly chemical in nature with the incorporation of 5–10% of extra oxygen as a variety of polar groups. Similarly, for the nitrogen plasma, 3.8% of nitrogen polar groups were additionally incorporated. Human foreskin fibroblast (HFF) in vitro analysis showed that within the first 24 h after cell seeding, the effects on cell-surface interactivity were highly dependent on the used discharge gas, nitrogen plasma treatment being the most efficient. Differences between untreated and plasma-treated samples were less pronounced compared to other biodegradable materials, but a positive influence on cell adhesion and proliferation was still observed.

Non-thermal Plasma Technology for the Improvement of Scaffolds for Tissue Engineering and Regenerative Medicine - A Review

Non-thermal plasma technology is one of those techniques that suffer relatively little from diffusion limits, slow kinetics and complex geometries compared to more traditional liquid-based chemical surface modification techniques. Combined with a lack of solvents, preservation of the bulk properties and fast treatment times, it is a well-liked technique for the treatment of materials for biomedical applications. In this book chapter, a review will be given on what the scientific community determined to be essential to obtain appropriate scaffolds for tissue engineering and how plasma scientists have used non-thermal plasma technology to accomplish this. A distinction will be made depending on the scaffold fabrication technique, as each technique has its own set of specific problems that need to be tackled. Fabrication techniques will include traditional fabrication methods, rapid prototyping and electrospinning. As for the different plasma techniques, both plasma activation, grafting and polymerization will be included in the review and linked to the in-vitro/in-vivo response to these treatments. The literature review itself is preceded by a more general overview on cell communication, giving useful insights on how surface modification strategies should be developed.

Influence of non-thermal TiCl4/Ar + O2 plasma-assisted TiOx based coatings on the surface of polypropylene (PP) films for the tailoring of surface properties and cytocompatibility

The superior bulk properties (corrosion resistance, high strength to weight ratio, relatively low cost and easy processing) of hydrocarbon based polymers such as polypropylene (PP) have contributed significantly to the development of new biomedical applications such as artificial organs and cell scaffolds. However, low cell affinity is one of the main draw backs for PP due to its poor surface properties. In tissue engineering, physico-chemical surface properties such as hydrophilicity, polar functional groups, surface charge and morphology play a crucial role to enrich the cell proliferation and adhesion. In this present investigation TiOx based biocompatible coatings were developed on the surface of PP films via DC excited glow discharge plasma, using TiCl4/Ar+O2 gas mixture as a precursor. Various TiOx-based coatings are deposited on the surface of PP films as a function of discharge power. The changes in hydrophilicity of the TiOx/PP film surfaces were studied using contact angle analysis and surface energy calculations by Fowkes approximation. X-ray photo-electron spectroscopy (XPS) was used to investigate the surface chemical composition of TiOx/PP films. The surface morphology of the obtained TiOx/PP films was investigated by scanning electron and transmission electron microscopy (SEM &TEM). Moreover, the surface topography of the material was analyzed by atomic force microscopy (AFM). The cytocompatibility of the TiOx/PP films was investigated via in vitro analysis (cell viability, adhesion and cytotoxicity) using NIH3T3 (mouse embryonic fibroblast) cells. Furthermore the antibacterial activities of TiOx/PP films were also evaluated against two distinct bacterial models namely Gram positive Staphylococcus aureus (S.aureus) and Gram negative Escherichia coli DH5α. (E.coli) bacteria. XPS results clearly indicate the successful incorporation of TiOx and oxygen containing polar functional groups on the surface of plasma treated PP films. Moreover the surface of modified PP films exhibited nano structured morphology, as confirmed by SEM, TEM and AFM. The physico-chemical changes have improved the hydrophilicity of the PP films. The in-vitro analysis clearly confirms that the TiOx coated PP films performs as good as the standard tissue culture plates and also are unlikely to impact the bacterial cell viability.

Plasma Modified Textiles for Biomedical Applications

In the textile market industry, technical textiles are one of the fastest growing businesses. Part of that industry consists of textiles for medical and healthcare applications and are responsible for a continuous increase in its market potential [1]. Next to their need in hospital environ‐ ments, there is a growing demand in other sectors such as the food and hotel industry, due to stricter hygiene regulations. In most cases biomedical textile meets a well-defined set of requirements such as minimizing non-specific protein adsorption, drug delivery coatings or the presence of active functional coatings and most importantly excellent biocompatibility (blood-, tissue-or cyto-compatibility) [2]. In general there are very few materials meeting all these characteristics, while at the same time offering the needed structural and mechanical properties. Furthermore, depending on the application, the production process has to be costeffective and approved by local legislation.

Acrylic Acid Plasma Coated 3D Scaffolds for Cartilage tissue engineering applications

The current generation of tissue engineered additive manufactured scaffolds for cartilage repair shows high potential for growing adult cartilage tissue. This study proposes two surface modification strategies based on non-thermal plasma technology for the modification of poly(ethylene oxide terephthalate/poly(butylene terephthalate) additive manufactured scaffolds to enhance their cell-material interactions. The first, plasma activation in a helium discharge, introduced non-specific polar functionalities. In the second approach, a carboxylic acid plasma polymer coating, using acrylic acid as precursor, was deposited throughout the scaffolds. Both surface modifications were characterized by significant changes in wettability, linked to the incorporation of new oxygen-containing functional groups. Their capacity for chondrogenesis was studied using ATDC5 chondroblasts as a model cell-line. The results demonstrate that the carboxylic acid-rich plasma coating had a positive effect on the generation of the glucoaminoglycans (GAG) matrix and stimulated the migration of cells throughout the scaffold. He plasma activation stimulated the formation of GAGs but did not stimulate the migration of chondroblasts throughout the scaffolds. Both plasma treatments spurred chondrogenesis by favoring GAG deposition. This leads to the overall conclusion that acrylic acid based plasma coatings exhibit potential as a surface modification technique for cartilage tissue engineering applications.

Functionalized, biocompatible, and impermeable nanoscale coatings for PEEK

Biologically compatible coatings that provide hermetic seal could resolve a major technological hurdle in the attempt to replace metals with polymers for biochips and active medical implants. The use of amorphous carbon/diamond like carbon (a-C:H) coatings to hermetically seal and biologically enhance polyether-ether-ketone (PEEK) for biomedical device integration in the human body was investigated. The PEEK coating functionality (sp3/sp2 ratio), hardness and thickness (70-200nm) were controlled, by varying H2 and N2 concentration during the plasma operation with CH4. a-C:H coatings having the highest indentation modulus of 13.5GPa, originate out of a CH4 (90%) rich composition. Even in a mixture of 70/30 H2/CH4 the hardness is 4.76GPa, corresponding to hard and dense coatings. In all tested conditions of deposition coatings hardens was sufficient for the purpose of PEEK implants modification. The synthesized (a-C:H) nanoscale coatings were not water permeable as measured by the hydrolysis test, resolving the traditional challenge of swelling in wet environment. The hardness of the coatings showed strong correlations with the thickness, surprisingly however, with no correlations with the sp3/sp2 ratio. Selected non water permeable nanoscale coating on PEEK showed strong bioactivity by being viable for human osteoblast (hFOB) and human fibroblast (hGF) cells without toxicity issues. No correlation was observed between the coatings sp3/sp2 ratio and biological performance.

Covalent Fluorination Strategies for the Surface Modification of Polydienes

Nonreactive additives are widely applied to enhance polymer properties but can leach out of the material over time. In this work, two essentially different fluorinated additives bearing a triazolinedione moiety are synthesized and grafted on several polydiene backbones (acrylonitrile-butadiene-styrene, styrene-butadiene, and styrene-isoprene-styrene (SIS) copolymers), either by dip-coating or by reaction in solution. The resulting polymers are analyzed by contact angle goniometry, size exclusion chromatography, and NMR, infrared, and X-ray photoelectron spectroscopy. Independent of the modification procedure, the fluorophilic perfluoroalkyl additive is found at the material surface, thereby yielding a more hydrophobic surface. For SIS thermoplastic elastomers, for example, contact angles up to 125° can be obtained.

75 A single clone of Achromobacter xylosoxidans colonizes Belgian cystic fibrosis patients from different centres

Objective Several major infection problems with Achromobacter xylosoxidans were observed for CF patients in Belgium. We tried to assess the epidemiology. Methods We typed 50 strains from 24 CF patients – from Ghent University Hospital (UZG, n=17) and from the University of Antwerp Hospital (UZA, n=7), most of which (14 from Ghent and 5 from Antwerp) had stayed at the rehabilitation centre. CF-related strains had been collected over a period of 10 years. We also included 8 unrelated strains: 7 clinical strains from non-CF patients and the type strain. McRAPD (arbitrarily primed PCR in combination with melting curve analysis)(Deschaght et al. 2011. Res Microbiol 162: 386–392), nrdA gene sequencing (Spilker et al. 2013. J Cystic Fibrosis 12: 298–301) and MALDI-TOF typing (newly developed) were used for typing. Results Typing revealed that most isolates from CF patients were indistinguishable by any of the three approaches. Only 6 CF patients had invididual types of A. xylosoxidans . Non-CF strains, including the one isolated from a non-CF patient at the rehabilitation centre, belonged to separate genotypes. The major clone observed in this study had previously been recognized as a major cluster (10 patients) in the rehabilitation centre of De Haan and its distinctness from a previously established minor cluster in De Haan (4 patients, Van Daele et al. 2005. J Clin Microbiol 43: 2998–3002) was confirmed in this study. Conclusion These data indicate that most CF patients from different CF centres in Belgium are colonized by a single clone of genuine A. xylosoxidans , that is spreading since at least 10 years. We thank the MucoVereniging Belgium