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Synthesis of PMMA/ZnO nanoparticles composite used for resin teeth
Danica Popović, Rajko Bobovnik, Silvester Bolka, Miroslav Vukadinovič, Vojkan Lazić, Rebeka Rudolf, 2017, izvirni znanstveni članek

Opis: Wear resistance is one of the most important physical properties of the artificial teeth used in acrylic dentures. The goal of this research was to synthesize a new composite material made of matrix Poly-(methyl methacrylate)-PMMA with different percentages (2 % and 3 % of volume fractions) of zinc-oxide nanoparticles (ZnO NPs) as reinforcing elements, to improve its mechanical properties. The dynamic mechanical behaviour of this composite was studied through the DMA method in comparison to the pure PMMA supported by the characterization of their microstructures. Then the wear resistance was analysed on the samples, which were prepared in the form of teeth. In this context their vertical height loss was measured after 100,000 chewing cycles on a chewing simulator, before and after the artificial thermal ageing. Investigations showed that the PMMA/ZnO NP composites dampened the vibrations better than the pure PMMA, which could be assigned to the homogenous distribution of ZnO NPs in the PMMA matrix. It was found that the mean vertical height loss for the pure PMMA teeth was significantly higher (more than 4 times) compared to composite teeth made with ZnO NPs. Introducing the thermal artificial ageing led to the finding that there was no effect on the height loss by the composite material with 3 % of volume fractions of ZnO NPs. Based on this it was concluded that PMMA/ZnO NPs composites showed improved in-vitro wear resistance compared to acrylic-resin denture teeth, so this new composite material should be preferred when occlusal stability is considered to be of high priority.
Ključne besede: poly-methyl methacrylate, PMMA, zinc-oxide nanoparticles, composite, resin teeth
Objavljeno: 12.12.2017; Ogledov: 797; Prenosov: 345
.pdf Celotno besedilo (1,55 MB)
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Effect of peptides' binding on the antimicrobial activity and biocompatibility of ‎protein-based substrates ‎
Maja Kaisersberger Vincek, 2017, doktorska disertacija

Opis: This work reveals the effect of coupling approach (chemical by using carbodiimide chemistry ‎and grafting-to vs. grafting-from synthesis routes, and enzymatic by using transglutaminase) ‎of a hydrophilic ε-poly-L-lysine (εPL) and an amphiphilic oligo-acyl-lysyl (OAK) derivative (K-7α12-OH) to wool fibers and gelatine (GEL) macromolecules, respectively, and substrates ‎antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria ‎after 1–24 h of exposure, as well as their cytotoxicity. Different spectroscopic (ultraviolet-‎visible, infrared, fluorescence and electron paramagnetic resonance) and separation ‎techniques (size-exclusion chromatography and capillary zone electrophoresis) as well as ‎zeta potential and potentiometric titration analysis, were performed to confirm the covalent ‎coupling of εPL/OAK, and to determine the amount and orientation of its immobilisation.‎ The highest and kinetically the fastest level of bacterial reduction was achieved with ‎wool/GEL functionalised with εPL/OAK by chemical grafting-to approach. This effect ‎correlated with both the highest grafting yield and conformationally the highly-flexible ‎(brush-like) orientation linkage of εPL/OAK, implicating on the highest amount of accessible ‎amino groups interacting with bacterial membrane. However, OAK`s amphipathic structure, ‎the cationic charge and the hydrophobic moieties, resulted to relatively high reduction of S. ‎aureus for grafting-from and the enzymatic coupling approaches using OAK-functionalised ‎GEL. ‎ The εPL/OAK-functionalised GEL did not induce toxicity in human osteoblast cells, even at ‎‎~25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of ‎εPL/OAK, supporting their potential usage in biomedical applications.‎ It was also shown that non-ionic surfactant adsorbs strongly onto the wool surface during ‎the process of washing, thereby blocking the functional sites of immobilized εPL and ‎decreases its antibacterial efficiency. ‎ ‎
Ključne besede: wool, gelatine, antimicrobial peptides, ε-poly-L-lysine, oligo-acyl-lysyl, grafting chemistry, ‎grafting approach, peptide orientation, antibacterial activity, cytotoxicity‎
Objavljeno: 17.08.2017; Ogledov: 969; Prenosov: 94
.pdf Celotno besedilo (3,98 MB)

Covalent binding of heparin to functionalized PET materials for improved haemocompatibility
Metod Kolar, Miran Mozetič, Karin Stana-Kleinschek, Mirjam Fröhlich, Boris Turk, Alenka Vesel, 2015, izvirni znanstveni članek

Opis: The hemocompatibility of vascular grafts made from poly(ethylene terephthalate) (PET) is insufficient due to the rapid adhesion and activation of blood platelets that occur upon incubation with whole blood. PET polymer was treated with NHx radicals created by passing ammonia through gaseous plasma formed by a microwave discharge, which allowed for functionalization with amino groups. X-ray photoelectron spectroscopy characterization using derivatization with 4-chlorobenzaldehyde indicated that approximately 4% of the –NH2 groups were associated with the PET surface after treatment with the gaseous radicals. The functionalized polymers were coated with an ultra-thin layer of heparin and incubated with fresh blood. The free-hemoglobin technique, which is based on the haemolysis of erythrocytes, indicated improved hemocompatibility, which was confirmed by imaging the samples using confocal optical microscopy. A significant decrease in number of adhered platelets was observed on such samples. Proliferation of both human umbilical vein endothelial cells and human microvascular endothelial cells was enhanced on treated polymers, especially after a few hours of cell seeding. Thus, the technique represents a promising substitute for wet-chemical modification of PET materials prior to coating with heparin.
Ključne besede: poly(ethylene terephthalate), vascular graft, biocompatibility, heparin, plasma, functionalization, haemolysis, platelet adhesion, endothelization
Objavljeno: 21.06.2017; Ogledov: 592; Prenosov: 276
.pdf Celotno besedilo (1,70 MB)
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Modification of PET-polymer surface by nitrogen plasma
Rok Zaplotnik, Metod Kolar, Aleš Doliška, Karin Stana-Kleinschek, 2011, izvirni znanstveni članek

Opis: Low pressure weakly nitrogen plasma was applied for incorporation of nitrogen-containing functional groups onto poly(ethylene terephthalate) - PET polymer. Nitrogen plasma was created in an electrode-less radiofrequency discharge at the nominal power of 200 W and the frequency of 27.12 MHz. Nitrogen molecules entered the discharge region were highly excited, partially dissociated and weakly ionized. Transformation into the state of plasma allowed for creation of chemically reactive particles with a high potential energy while the kinetic energy remained close to the value typical for room temperature. The chemical reactivity allowed for rapid functionalization with nitrogen-rich functional groups. The appearance of these groups was monitored by X-ray photoelectron spectroscopy - XPS. The polymer surface was quickly saturated with nitrogen indicating that the modification was limited to an extremely thin surface film.
Ključne besede: poly(ethylene terephthalate), nitrogen plasma, surface modification, functional groups, X-ray photoelectron spectroscopy
Objavljeno: 17.03.2017; Ogledov: 540; Prenosov: 79
.pdf Celotno besedilo (150,48 KB)
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Microvoid system in fibres
Majda Sfiligoj-Smole, Diana Gregor-Svetec, 2002, izvirni znanstveni članek

Opis: The macrovoid system of poly(ethylene terephthalate) (PET) and poly(propylene) (PP) fibres was studied by small-angle x-ray scattering (SAXS). Commercial PET textile fibres were treated in different media and the influence on fibre homogeneity was followd by SAXS. PP technical fibres were manufactured on a laboratory spin-drawing device and subsequently drawn at different drawing conditions on a laboratory drawing device. The influence of drawing on the pore system was followed.
Ključne besede: textile industry, textile fibres, morphology, structure, investigations, SAXS, poly(ethylene terephtalate), PET, poly(propylene), PP, voids, microvoids
Objavljeno: 10.07.2015; Ogledov: 745; Prenosov: 68
.pdf Celotno besedilo (284,24 KB)
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Tuning of poly(ethylene terephtalate)(PET)surface properties by oxygen plasma treatment
Aleš Doliška, Metod Kolar, 2011, izvirni znanstveni članek

Opis: Modification of surface properties of poly(ethyleneterephtalate) (PET) thin films by treatment with weakly ionized oxygen plasma was studied by contact angles of water and diiodomethane (DIM) drops. Samples were exposed to oxygen plasma with the ion density of 5 x 1015/m[sup]3 and the neutral oxygen atom density of 3 x 1021/m[sup]3. Just after the treatment they were characterized by contact angle measurements. Results showed a quick decrease of the water contact angle in the first few seconds of plasma treatment, while prolonged treatment did not cause any substantiated modification. The contact angles of DIM, on the other hand, remained rather constant for the first several secondsof plasma treatment, and increased after prolonged treatment. It was found that the dispersion component of the surface free energy decreased with increasing treatment time, while the polar component increased with treatment time. The results were explained by surface functionalization as well as by roughness effects.
Ključne besede: poly(ethylene terephtalante), PET, oxygen plasma, contact angle, hydrophilic, functionalization
Objavljeno: 01.06.2012; Ogledov: 1433; Prenosov: 43
.pdf Celotno besedilo (329,87 KB)
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UV polymerization of poly (N-isopropylacrylamide) hydrogel
Manja Kurečič, Majda Sfiligoj-Smole, Karin Stana-Kleinschek, 2012, izvirni znanstveni članek

Opis: This contribution is focused on the determination of polymerization and crosslinking mechanism of poly (N-isopropyl- acralymide) hydrogel and its swelling properties. Hydrogels were synthesized by environmental friendly UV polymerization method, from monomer N-isopropylacrylamide (NIPAM) and crosslinker N,N´-methylenebisacrylamide (BIS) of different concentrations. UV polymerization was performed in an UV chamber using UVA light with the wave length 350 nm. Surface morphology and pore structure analysis was carried out using SEM microscopy. The polymerization and crosslinking mechanism was determined by Fourier Transform Infrared spectroscopy (FT-IR). It was confirmed that crosslinker concentration influences the hydrogel structure and swelling properties. By increasing the crosllinker concentration the hydrogel structure changes from homogen to heterogen and the equilibrium degree of swelling decreases.
Ključne besede: poly (N-isopropylacrylamide) hydrogel, UV polymerization, FTIR, polymerization mechanism, swelling properties, SEM
Objavljeno: 01.06.2012; Ogledov: 1369; Prenosov: 81
.pdf Celotno besedilo (599,31 KB)
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Heparin adsorption onto model poly(ethylene terephtalate) (PET) surfaces monitored by QCM-D
Aleš Doliška, Simona Strnad, Karin Stana-Kleinschek, 2012, izvirni znanstveni članek

Opis: The adsorption of anticoagulant heparin onto model poly(ethylene terephtalate) (PET) film was monitored using a quartz crystal microbalance with a dissipation unit (QCM-D). Synthetic vascular grafts are usually made from PET, a material with appropriate mechanical properties but moderate haemocompatibility. Therefore anticoagulant heparin is usually used to improve haemocompatibility of PET surfaces. Heparin possesses a high negative charge and as such does not adsorb directly onto hydrophobic PET, which is also negatively charged. To increase heparin adsorption different cationic polymers were investigated as spacers and the highest adsorption was achieved using polyethyleneimine (PEI) as an anchoring agent. The heparin was adsorbed from water solution as well as from phosphate buffer saline (PBS). Heparin dissolved in PBS adsorb better onto PET than heparin from water solution. The results were characterized using Sauerbrey equation and Voigt based viscoelastic model. We found out that heparin adsorbed onto PET formed a thin and rigid film and that Sauerbrey equation is appropriate for characterization of heparin adsorption onto PET.
Ključne besede: poly(ethyleneterephtalate), PET, heparin, QCM-D, haemocompatibility
Objavljeno: 01.06.2012; Ogledov: 1352; Prenosov: 50
.pdf Celotno besedilo (416,79 KB)
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The plasma polymerisation process for the deposition of amino-containing film on the poly(ethylene terephthalate) dressing-layer for safe wound-healing
Zdenka Peršin, Adolf Jesih, Karin Stana-Kleinschek, 2012, izvirni znanstveni članek

Opis: This article presents a new approach for preparing antimicrobial layer as a part of multi-composite dressing for safe and efficient wound - healing within a moist environment. Plasma polymerisation using a mixture of argon, ammonia, and hexane gases was used for preparing a thin polymer film on the poly(ethylene terephthalate) (PET) surface. The plasma deposition efficiency, regarding the amount of nitrogen, was evaluated by the Kjeldahl method, whilst the absorption of C.I. Acid Orange 7 dye onto accessible amino groups was monitored within the UV/VIS spectral region. The quantitative amount of charged surface groups was determined by potencometric titration. The results obtained using Kjeldahl method indicated the presence of a substantial amount of nitrogen within the deposited film. Furthermore, mono - azo acidic dye was absorbed onto the polymerised sample, pointing to the formation of an ionic bond between the sulphuric and amino groups. The plasma deposited PET samples resulted in inhibitions regarding all the pathogen microorganisms used, mostly those present in the infected wound.
Ključne besede: plasma polymerisation, argon, ammonia, hexane, poly(ethylene terephthalate), antimicrobial properties, wound dressing
Objavljeno: 01.06.2012; Ogledov: 1368; Prenosov: 84
.pdf Celotno besedilo (75,93 KB)
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