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Antimicrobial medical textiles based on chitosan nanoparticles for gynaecological treatment
Tijana Ristić, 2014, doktorska disertacija

Opis: The aim of this dissertation was to develop a novel medical tampon for alternative gynaecological treatment using chitosan nanoparticles as an antimicrobial agent or as a drug delivery system. For this purpose viscose tampon band was used and functionalized with chitosan and trimethyl chitosan nanoparticles. A comprehensive of interactions between chitosan and cellulose as well as characterization of prepared materials were done. At the beginning, chitosan (CS) and trimethyl chitosan (TMC) solutions, as well as nanoparticles synthesised by ionic gelation were studied. Their characterization was focused on determining the charge and antimicrobial properties against common pathogenic microorganism. The influence of cationic charge on the inhibition of microbial growth was confirmed. Since CS and TMC solutions and nanoparticles dispersions exhibited antibacterial activity against Lactobacillus, a detailed investigation in chitosan’s antimicrobial mode of action was performed using a novel diffusion nuclear magnetic resonance (D-NMR). D-NMR allowed the monitoring of intra- and extracellular water exchange from the cells indicating the membrane alteration and leakage of intracellular constituencies. Further, in order to study the adsorption phenomena and molecular interactions between CS/TMC (solution or nanoparticles) and cellulose material, model cellulose surfaces were used, and adsorption was studied by quartz crystal microbalance with dissipation. CS and TMC were favourably deposited onto cellulose model surface at higher ionic strength, higher pH values, i.e. factors causing lower solubility, where the presence of electrostatic interactions was negligible and non-electrostatic interactions were dominant. The knowledge gained from the model surfaces was extremely helpful in characterization of real systems, i.e. functionalized cellulose fibres and for understanding the obtained results. Immobilization of CS and TMC (in the form of solution and/or nanoparticles) onto cellulose viscose fibres was confirmed with several analytical methods. The attachment of chitosan onto fibres was reversible, as endorsed with desorption studies mimicking the conditions of vaginal usage. Evaluation of antimicrobial properties was performed using two different techniques, both revealing a high inhibition of the tested microorganism. In addition, Lactobacillus susceptibility testing has shown that chitosan-coated fibres do not have any negative influence on the resident microbiota. Assessment of in-vitro cytotoxicity demonstrated that samples do not cause a cytotoxic effect in direct contact. Additionally, model drug was incorporated into chitosan nanoparticles and subsequently attached onto fibres in order to create modern, vaginal drug delivery systems. Antimicrobial medical textiles investigated in the scope of this dissertation show the potential for their exploitation in gynaecological field as preventive or curative treatment without triggering any adverse effects for the user.
Ključne besede: chitosan, N, N, N-trimethyl chitosan, nanoparticles, antimicrobial activity, cellulose model films, regenerated cellulose fibres, diffusion nuclear magnetic resonance, quartz crystal microbalance, vaginal infections, drug delivery systems, cytotoxicity
Objavljeno: 13.02.2014; Ogledov: 2028; Prenosov: 85
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Country's development as a determinant of early-stage entrepreneurial activity
Miha Marič, Jasmina Žnidaršič, Miha Uhan, Vlado Dimovski, Marko Ferjan, Maja Djurica, Mitja Jeraj, Matej Janežič, 2013, izvirni znanstveni članek

Opis: Our study is built on the dependence of early-stage entrepreneurial activity on GDP per capita, GDP real growth rate, unemployment rate, inflation rate, investments and public debt of different countries. We divide the early-stage entrepreneurial activity into necessity-driven and improvement-driven opportunistic entrepreneurial activity. To establish the dependencies we have conducted the regression analyses. Our three main findings are: (a) early-stage entrepreneurial activity does depend on our predictors; (b) necessity-driven entrepreneurial activity is negatively correlated to country’s development; and (c) improvement-driven opportunistic entrepreneurial activity is positively correlated to country’s development.
Ključne besede: entrepreneurship, early-stage entrepreneurial activity, economic developmnet indicators
Objavljeno: 10.07.2015; Ogledov: 750; Prenosov: 199
.pdf Celotno besedilo (206,00 KB)
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Antioxidant and antimicrobial activity of PGSStm micronized curcuma powder
Željko Knez, Tina Perko, Mojca Škerget, 2012, objavljeni znanstveni prispevek na konferenci

Ključne besede: antioxidant, antimicrobial activity, curcumin extract
Objavljeno: 10.07.2015; Ogledov: 498; Prenosov: 13
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Viscose functionalisation with a combination of chitosan/BTCA using microwaves
Olivera Šauperl, Julija Volmajer Valh, 2013, izvirni znanstveni članek

Opis: Improved hygiene and health care standards have a great impact on the development of hygiene and health care products. For this purpose, viscose is a very popular substrate. One of the most promising anti-microbial compounds of modern times is chitosan. The anti-microbial action of this polysaccharide depends on the amino group amount, which is crucial for ensuring the effectiveness of anti-microbial treated material. In textile finishing, 1,2,3,4-buthanetetracarboxylic acid (BTCA) is usually used as a non-formaldehyde crease-resistant reagent. But, on the other hand, the negatively charged carboxyl groups of BTCA can be explored as additional binding sites for positively-charged protonated amino groups of chitosan. When using microwaves, polar materials (e.g. chitosan) orient and reorient themselves according to the direction of the electro-magnetic field, which means that chitosan chain-bending may have taken place during the drying with microwaves. This could result in a higher specific surface of the chitosan and, consequently, in a higher proportion of available amino groups. It is concluded that the combination chitosan/BTCA supported by microwaves drying represents an ideal combination to increase the proportion of available amino groups.
Ključne besede: viskoza, protimikrobna zaščita, viscose, chitosan/BTCA, microwawes, Acid Orange VII, methylene blue, antimicrobial activity
Objavljeno: 10.07.2015; Ogledov: 679; Prenosov: 16
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Potential of phenolic antioxidants
Iva Ružić, Mojca Škerget, Željko Knez, 2010, pregledni znanstveni članek

Opis: In vitro studies have shown a link between the consumption of food rich in (poly)phenols, especially flavonoids, and reduced risk of coronary heart diseases. Several flavonoids have been reported to prevent low density lipoprotein cholesterol oxidation in vitro. The aim of our work was to determine antioxidant and radical scavenging activity of flavonoids myricetin,quercetin, rutin, luteolin, apigenin, kaempferol, catechin, epicatechin and epigallocatechin gallate and to study the influence of chemical structure and flavonoid interactions on the ability to inhibit oxidation and scavenge free radicals. Two in vitro methods, i.e. oxidation of â-carotene in an emulsion system and DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging assay, were applied. In addition, a review of in vivo studies that investigate the effectiveness of food flavonoids in reducing oxidative damage in human body was done and their results were analyzed and compared to in vitro results obtained in our laboratory. Although all tested flavonoids except apigenin showed strong antioxidant and antiradical properties in vitro, these findings can not be completely confirmed from the reviewed in vivo human studies since those results are sometimes contradictoryand inconsistent.
Ključne besede: phenolics, flavonoids, antioxidant activity, antiradical activity
Objavljeno: 10.07.2015; Ogledov: 538; Prenosov: 32
.pdf Celotno besedilo (250,25 KB)
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Strawberries from integrated and organic production
Janja Kristl, Andreja Urbanek Krajnc, Branko Kramberger, Silva Grobelnik Mlakar, 2013, izvirni znanstveni članek

Opis: As the nutritional quality of food is becoming increasingly more important forconsumers, significant attention needs to be devoted to agricultural practices and their influences on the nutrient contents in food. The presentedinvestigation studied the mineral contents and antioxidant activitiesin the fruits of four organically-grown strawberry cultivars 'St. Pierre', 'Elsanta', 'Sugar Lia' and 'Thuchampion' when compared to those of integrated-grown plants. The strawberries were digested and analyzed for K, Mg, Fe, Zn, Cu, and Mn using an atomic absorption spectrometer, whilst P was analyzed using a vanadate-molybdate method. In addition, antioxidant activity was estimated by using the ABTS assay. The results showed that the mineral contents and antioxidant activities in strawberries depends on the cultivar, and its production system. Organically-grown fruits showed higher antioxidant activities and Cu content than the integrated fruits, whilst the integrated fruits were superior in their contents of P, K, Mg, Fe and Mn. All the cultivars showed similar Zn content, probably reflecting the fact that the Zn content in strawberries does not depend on the cultivar.
Ključne besede: strawberries, minerals, antioxidant activity, production system
Objavljeno: 30.12.2015; Ogledov: 566; Prenosov: 75
.pdf Celotno besedilo (117,29 KB)
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