A method for growing carbon nanowalls on a substrate of an implantable medical device by means of a processing chamber is provided, said method comprising: providing said substrate in said processing chamber, evacuating said processing chamber to a processing pressure, entering a gas mixture inside the processing chamber, providing radicals inside said chamber and adsorbing said radicals on said substrate leading to growing of carbon nanowalls on said substrate.
Persin, Zdenka
Ravber, Matej
Kleinschek, Karin Stana
Knez, Zeljko
Skerget, Mojca
Kurecic, Manja
Considering the increasing resistance of numerous bacteria to antibiotics, a novel wound dressing material was developed with naturally acquired olive leaf extract, which shows not only good antimicrobial activity, but also very good antioxidant activity. Besides that, the leaves are treated as waste in agriculture, giving an impact on waste management. An environmentally friendly procedure, electrospinning, was used for the first time to prepare polysaccharide nanofibrous mats with incorporated olive leaf extract, with the unique property of releasing the active phenolic components in a prolonged manner over 24 hours. The developed electrospun mats were characterized using scanning electron microscopy, high-performance liquid chromatography and ultraviolet-visible spectroscopy for determination of free radical scavenging activity by 2,2-diphenyl-1-picrylhydrazyl, antimicrobial testing and release kinetics. Antimicrobial tests have shown that electrospun mats with olive leaf extract achieve reduction towards the tested microorganisms: Staphylococcus aureus (G+), Escherichia coli (G-), Enterococcus faecalis (G+) and Pseudomonas aeruginosa (G-), while the high antioxidant activity of olive leaf extract was preserved during the electrospinning procedure. Release of olive leaf extract from electrospun mats was mathematically modeled, and the release kinetics evaluation indicates the appropriateness of the Korsmeyer-Peppas model for fitting the obtained results of release ability due to erosion of polysaccharide nanofiber mats.
Maver, Uros
Gradisnik, Lidija
Smrke, Dragica Maja
Kleinschek, Karin Stana
Maver, Tina
The potential of alginate/carboxymethyl cellulose based thin films was demonstrated as a testing platform for evaluation of the influence of in situ incorporated growth factors into formulations intended for 3D bio-printed wound healing materials. Actual formation of blend films with and without included growth factors was analysed using ATR-IR spectroscopy. Surface morphology and topography were evaluated by atomic force and scanning electron microscopies, whereas the hydrophilicity of all tested materials was determined using the water contact angle measurement method. The inclusion of growth factors into blend films did not affect the films' formation, nor their morphology, whereas their highly hydrophilic character was even slightly enhanced by the added growth factors. Further, several aspects (viability, proliferation and cell morphology), in regard to the blend films included growth factors' influence on both of the most abundant skin cell types (keratynocytes and fibroblasts) were tested. A significantly improved cell viability was detected for films with incorporated growth factors. The prepared thin film-based testing platform could present an important tool to aid the development of novel printable (bio)inks.
Kargl, Rupert
Mohan, Tamilselvan
Ribitsch, Volker
Saake, Bodo
Puls, Juergen
Kleinschek, Karin Stana
The solution properties of cellulose, dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc), were analysed using rheology and turbidity measurements. The influence of dimethylsulfoxide addition and temperature change on the viscosity of these solutions was studied in detail. Subsequently, crystallinity measurements of precipitated powders from EMIMAc solutions were conducted. Additionally, the stability of cellulose during storage in the ionic liquid solution was proven by molecular weight analysis. Thin films of cellulose were prepared by spin coating from EMIMAc/DMSO mixtures and subsequent precipitation on silicon wafers and quartz crystal microbalance gold coated sensors. Atomic force microscopy and profilometry gave insights into the morphology and thickness of the prepared films and their possible application in the study of surface properties of cellulose.
Maver, Tina
Maver, Uros
Kleinschek, Karin Stana
Rascan, Irena Mlinaric
Smrke, Dragica Maja
The loss of tissue is still one of the most challenging problems in healthcare. Efficient laboratory expansion of skin tissue to reproduce the skins barrier function can make the difference between life and death for patients with extensive full-thickness burns, chronic wounds, or genetic disorders such as bullous conditions. This engineering has been initiated based on the acute need in the 1980s and today, tissue-engineered skin is the reality. The human skin equivalents are available not only as models for permeation and toxicity screening, but are frequently applied in vivo as clinical skin substitutes. This review aims to introduce the most important recent development in the extensive field of tissue engineering and to describe already approved, commercially available skin substitutes in clinical use. =20
Doliska, Ales
Willfor, Stefan
Strnad, Simona
Ribitsch, Volker
Kleinschek, Karin Stana
Eklund, Patrik
Xu, Chunlin
Galactoglucomannans (GGMs) are water-soluble polysaccharides released and accumulated in process waters in the production of thermomechanical pulp. The general trend in the forestry industry is moving towards bio-refineries, for example utilizing these hemicelluloses as bioactive substances. At present, there is no industrial use of wood-derived mannans. In this study, GGMs extracted from thermomechanical pulp, as well as further carboxymethylated galactoglucomannans (CM-GGMs), were sulfated to increase their antithrombotic properties. The products were characterized with Fourier transform infrared spectroscopy, nuclear magnetic resonance and capillary electrophoresis. The carbohydrate composition and sulfur amounts were determined. The products' total charges were determined by polyelectrolyte titrations and their antithrombotic effect was measured based on the activated partial thromboplastin time. The results showed a significant increase in the antithrombotic effect of the sulfated galactoglucomannans from spruce wood and thus a potential new use for wood-derived mannans.
The requirement of promoting a revolution in filtration technology has led to growing devotion in advanced functional materials such as electrospun membranes for filtering devices as a solution for providing water at lower energy costs. In this study, electrospun polyvinylidene fluoride membranes were fabricated by reinforcing 0.5 and 1 wt. % of chitin nanowhiskers in order to improve their thermal stability, mechanical properties, pure water flux and oil-water filtration performance for the possible application as filtration membranes. Morphological analysis revealed the porous and fibrous structure of membranes which confirmed by BET surface area analysis. Incorporation of chitin nanowhiskers improved the mechanical properties of the membranes such as elongation at break and tensile strength (specifically at 1 wt. % of chitin nanowhisker) while resulted in substantial enhancement of their thermal properties. Furthermore, polyvinylidene fluoride/chitin nanowhisker membranes showed enhanced oil-water separation ability, while reinforcement of chitin nanowhisker led to increase pure water flux rate, which measured as a crucial point in filtration membranes. The oil-water separation results compared with a commercial polyvinylidene fluoride membrane and the results signified the potential of electrospun polyvinylidene fluoride/chitin nanowhisker to be used for filtration application.
Elschner, Thomas
Reishofer, David
Kargl, Rupert
Griesser, Thomas
Heinze, Thomas
Kleinschek, Karin Stana
Reactive coatings of hydroxyethyl cellulose furoate in the form of thin films, suitable for the covalent immobilization of functional molecules, were developed and characterized in this work. The cellulose furoate derivatives were synthesized under homogeneous conditions by esterification of hydroxyethyl cellulose with 2-furoic acid. Reactive platform layers of these furoates were obtained by chemical surface modification of spin coated thin films with N, N'-carbonyldiimidazole. This chemistry allowed the covalent immobilization of functional molecules bearing primary and secondary amines on the films. The degree of substitution of the furoate thin films and their amino functionalized counterparts was determined gravimetrically by a quartz crystal microbalance (QCM-D) and correlated with infrared and X-ray photoelectron spectroscopy and zeta-potential measurements. Scanning electron-and atomic force microscopy showed changes in the morphologies that were influenced by the chemical reactions on the surface. The concept presented can be seen as a versatile method for immobilizing amine-containing (bio-) molecules to polysaccharide surfaces with the furoates having the potential for further reversible cross-linking in Diels-Alder reactions.
Doliska, Ales
Strnad, Simona
Ribitsch, Volker
Kleinschek, Karin Stana
Willfor, Stefan
Saake, Bodo
The aim of this study was to setup a method for detection and quantification of monosaccharide components in technical galactoglucomannas (T-GGM) from spruce wood using capillary zone electrophoresis (CZE). CZE technique was optimised regarding borate buffer concentrations, EOF modifier application, and system pH. Aqueous solution of T-GGM was chemically hydrolysed by sulphuric acid, in an autoclave. In this way obtained monosaccharides were derivatized with 4-amino benzoic acid ethyl ester via reductive amination using sodium cyanoborohydride. The results of the optimisation procedure showed that the borate buffers at lowest concentrations (100 and 200 mM) with acetonitrile addition as EOF modifier gave the optimal measurement results, as it showed sufficient separation at relatively short migration times. The amounts of single monosaccharide components in the T-GGM samples obtained by the optimised CZE procedure were practically the same in comparison to the results of the well established HPLC-anion exchange chromatography. On the basis of this research, it was concluded that the capillary zone electrophoresis is an efficient analytical procedure for the characterisation of galactoglucomannans derived from softwoods.
Kargl, Rupert
Bracic, Matej
Resnik, Matic
Mozetic, Miran
Bauer, Wolfgang
Kleinschek, Karin Stana
Mohan, Tamilselvan
This work describes the preparation of spin-coated thin polymer films composed of cellulose (CE), ethyl cellulose (EC), and cellulose acetate (CA) in the form of bi- or mono-component coatings on sensors of a quartz crystal microbalance with dissipation monitoring (QCM-D). Depending on the composition and derivative, hydrophilicity can be varied resulting in materials with different surface properties. The surfaces of mono- and bi-component films were also analyzed by atomic force microscopy (AFM) and large differences in the morphologies were found comprising nano- to micrometer sized pores. Extended protein adsorption studies were performed by a QCM-D with 0.1 and 10 mg mL(-1) bovine serum albumin (BSA) and 0.1 and 1 mg mL(-1) fibrinogen from bovine plasma in phosphate buffered saline. Analysis of the mass of bound proteins was conducted by applying the Voigt model and a comparison was made with the Sauerbrey wet mass of the proteins for all films. The amount of deposited proteins could be influenced by the composition of the films. It is proposed that the observed effects can be exploited in biomaterial science and that they can be used to extent the applicability of bio-based polymer thin films composed of commercial cellulose derivatives.
Zemljic, Lidija Fras
Persin, Zdenka
Stenius, Per
Kleinschek, Karin Stana
The influence of peroxide bleaching and slack-mercerization on the amount of acidic groups in regenerated fibres (viscose, modal and lyocell) were studied. Conductometric titration was used to determine the total content of acidic carboxylic groups. Polyelectrolyte titration was used for surface and total charge determination, and to obtain information about the charge distribution and accessibilities of charged groups. Changes in fibre crystallinity to pre-treatment processes were characterized using iodine sorption (Schwertassek method) and correlated to treatments and the amount of carboxylic groups. For all three types of fibres the amount of accessible carboxyl groups was lowered by an increase in the degree of crystallinity. Bleaching with hydrogen peroxide causes some oxidative cellulose damage and, therefore, a larger amount of carboxyl groups (presumably formed at the end of cellulose chains). Slack-mercerization did not significantly change the total amount of acidic groups in the fibres, but their accessibility to cationic polyelectrolytes, in particular to polymers with high molecular weight was substantially lowered.
Smole, Majda Sfiligoj
Stakne, Kristina
Kleinschek, Karin Stana
Kurecic, Mania
Bele, Marjan
Svetec, Diana Gregor
Ribitsch, Volker
Nanocomposite fibers based on polypropylene (PP) polymer were prepared with different content of nanofiller. Filaments were spun from an isotactic iPP homopolymer. Montmorillonite modified by N,N-dimethyl-N,N dioctadecylammonium cations was used for preparation of PP nanocomposite fibers. A PP grafted with acrylic acid was added as a coupling agent. Nanocomposite fibers were characterized, i.e., the surface morphology of PP nanocomposite fibers was observed and surface properties were defined by electrokinetic properties determination by zeta potential measurements. For particle distribution observation the plasma etching was involved as a method for sample preparation. The addition of nanoparticles has an impact on ZP value of nanofilled fibers, however, isoelectric point IEP is not significantly influenced by different concentrations of nanofiller. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1276-1281, 2009
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