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Hemicelluloses application for synthetic polymer surfaces functionalisation
Nena Dimitrušev, 2016, doktorska disertacija

Opis: The main aim of this thesis was development of thin functional layers from hemicelluloses xylans on the polyethylene terephthalate (PET) surfaces. Hemicelluloses, xylans, as renewable polymers, were chemically modified in order to introduce anionic and cationic functional groups. Two types of chemical modifications were performed: carboxymethylation in order to increase anionic nature of xylans and improve their hydrophilic character and cationization for introducing of amino groups and antimicrobial characteristics. Both types of modifications were successful, which was proved by ATR FTIR and raman techniques, elemental analysis, total bound nitrogen determination, size exclusion chromatography and polyelectrolyte titrations. Polyelectrolyte titration results showed increased amounts of deprotonated carboxyl groups in carboxymethylated xylans as well as increased amounts of protonated groups in cationized xylans. Antimicrobial activity of xylans was investigated by the determination of minimal inhibitory concentration (MIC) against S. aureus, E. coli, and C. albicans and it was found out that the samples with higher amounts of active amino groups showed lower MIC. Cationised glucuronoxylan showed significantly higher antimicrobial activities against S. aureus in comparison to cationised arabinoxylan and nonmodified xylan samples. However, none of xylan samples was active against fungi. In order to analyze surface properties of solid surfaces, films from xylan (nonmodified and modified) water solution was formed by casting method. The surface chemical composition of films were investigated by x-ray photoelectron spectroscopy (XPS), and the results showed that films made from carboxymethylated xylans had significantly higher amounts of carbon fraction involved in O=C-O bonds, compared to nonmodified xylans. Such surface chemical structure caused higher surface free energy with higher electron-donor contribution and thus high hydrophilicity of these films. Films made by cationized xylans had higher amount of carbon involved in C-C and C-H bonds compared to nonmodified and lower surface free energy with increase of dispersive Lifshitz Van der Waals contribution. In order to thoroughly investigate the adsorption of xylans onto synthetic surfaces Quartz crystal microbalance with dissipation unit (QCM-D) was used. For these measurements model films were prepared from PET by spin coating technique. Adsorption studies were performed at different conditions, such as pH, concentration and ionic strength of xylan solutions. For all the chemically modified xylans the adsorption was improved at pH 5 and with increased ionic strength with divalent ions. The adsorption increased as well with increasing of xylan solution concentration. In order to improve binding of adsorbed xylans so-called anchoring polymers were applied. When anchoring polymers were applied, better adsorption and fixation of adsorbed layer was confirmed, thus the adsorbed masses of xylans after rinsing with water were significantly higher in comparison to the adsorption without immediate anchoring layer. On the basis of these results, real PET fabric surfaces were treated using chemically modified xylans. The xylan solutions were applied onto PET fabric samples using spray coating technique, which is the best approximate to the large-scale procedures. In the first step, PET fabric was activated by alkaline hydrolysis and after that, anchoring agents and carboxymethylated and/or cationized xylans were adsorbed. The success of these treatments was evaluated by the determination of negative and positive charge of the treated PET fabric samples by titration techniques, methylene blue and acid orange 7 adsorption methods, water contact angles and wettability determination. From the potentiometric titrations results it was clearly seen that each new adsorbed layer onto PET fabric totally screened the charge of the former one. FESEM images showed rather thick layers covering the
Ključne besede: hemicellulose, polyethylene terephthalate, glucuronoxylan, arabinoxylan, carboxymethylation, cationization, PET model films, quartz crystal microbalance, PET fabric, surface free energy, wettability, antimicrobial properties
Objavljeno: 11.03.2016; Ogledov: 1294; Prenosov: 84
.pdf Celotno besedilo (4,53 MB)

Tyrosinase-catalysed coating of wool fibres with different protein-based biomaterials
Suzana Jus, Vanja Kokol, Georg M. Gübitz, 2009, izvirni znanstveni članek

Opis: The potential of tyrosinases to activate tyrosine residues of wool protein fibres for cross-linking with different materials like collagen, elastin and gelatine was assessed. Natural fibres like wool offer an excellent environment for the growth of micro-organisms when the conditions like moisture, oxygen and temperature are appropriate. Coating with collagen, a very useful biomaterial with bactericidal and fungicidal properties, could be used to improve the properties of wool-based materials, especially when applied in hygienically sensitive applications like in hospitals. Tyrosinases were shown to catalyse the oxidation of tyrosine residues in wool and wool hydrolysates as model substrates, as determined by UV-Vis spectroscopy. Structural differences of the surface were evident from the increase of the intensity in the NH bending and stretching regions in the spectra of NIR FT Raman analysis of the enzyme treated and grafted wool fibres. The durability of the coating was also shown by using FITC-labelled collagen that was bound to the wool fibres, even after severe washing. Additionally, antimicrobial properties were successfully imparted due to the collagen grafted on the wool fibres. The functional and mechanical properties of the treated wool fibres showed no significant changes.
Ključne besede: textile fibres, wool, protein substrates, tyrosinase, enzymatic coupling, antimicrobial properties, coating
Objavljeno: 01.06.2012; Ogledov: 1254; Prenosov: 73
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Binding silver nano-particles onto viscose non-woven using different commercial sol-gel procedures
Tanja Pivec, Zdenka Peršin, Silvo Hribernik, Tina Maver, Mitja Kolar, Karin Stana-Kleinschek, 2012, izvirni znanstveni članek

Opis: The paper presents possible solution of Ag binding using commercial sol-gel systems which enable its low release into a wound, providing a good antimicrobial effect on those bacterial cultures that are most likely present in the wound. The influence of different sol-gel systems on the hydrophilic properties of carrier materials and the level of released silver has been studied. The results showed that sol-gel as binding-systems could provide proper hydrophilic properties of material, whilst binding silver strongly enough providing at the same time excellent antimicrobial activity of the treated viscose meterials.
Ključne besede: silver nano-particles, sol-gel, viscose non-woven, silver release, hydrophilicity, antimicrobial properties
Objavljeno: 01.06.2012; Ogledov: 2350; Prenosov: 63
.pdf Celotno besedilo (235,88 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: 1397; Prenosov: 86
.pdf Celotno besedilo (75,93 KB)
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Antioxidant and antimicrobial activity of guarana seed extracts
Lucija Majhenič, Mojca Škerget, Željko Knez, 2007, izvirni znanstveni članek

Opis: The antioxidant and antibacterial activities of guarana (Paullinia cupana) seed extracts were determined. The seeds were extracted with water, methanol, 35% acetone and 60% ethanol at room (TR) and at boiling (TB) temperature of solvent.Extracts were analyzed for the contents of caffeine and catechins, epicatechin (EC), catechin (C) and epicatechin gallate (ECG), by high performance liquid chromatography (HPLC). The contents of total phenols (according to the Folin-Ciocalteu procedure) and proanthocyanidins were analysed by UV spectrophotometry. The guarana seed water extract obtained at room temperature contained higher amounts of caffeine and catechins than did alcoholic guarana seed extracts. The antioxidant and radical-scavenging activities of guarana seed extracts were evaluated using the ß-carotene-linoleic acid emulsion system and the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH ). All tested guarana seed extracts displayed strong antioxidant and radical-scavenging properties. The guarana seed extracts were tested against three food-borne fungi: Aspergillus niger, Trichoderma viride and Penicillium cyclopium, and three health-damaging bacteria: Escherichia coli, Pseudomonas fluorescens and Bacillus cereus by theagar well diffusion and broth dilution assay. The alcoholic guarana seed extracts displayed stronger antimicrobial activity against all tested microorganisms than did water extracts. Results presented here may suggest that seed extracts of guarana possess strong antimicrobial and antioxidant properties, and they can therefore be used as a natural additive in food, cosmetic and pharmaceutical industries.
Ključne besede: chemical processing, guarana extract, Paullinia cupana, seed extracts, antimicrobial properties, antioxidative properties
Objavljeno: 31.05.2012; Ogledov: 1487; Prenosov: 100
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