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1.
Design, Characterisation and Applications of Cellulose-Based Thin Films, Nanofibers and 3D Printed Structures
Tanja Pivec, Tamilselvan Mohan, Rupert Kargl, Manja Kurečič, Karin Stana-Kleinschek, 2021, other educational material

Abstract: The introduction of the Laboratory Manual gives the theoretical bases on cellulose and its derivatives, which are used as starting polymers for the preparation of multifunctional polymers with three different advanced techniques - spin coating, electrospinning and 3D printing. In the following, each technique is presented in a separate Lab Exercise. Each exercise covers the theoretical basics on techniques for polymer processing and methods for their characterisation, with an emphasis on the application of prepared materials. The experimental sections contain all the necessary information needed to implement the exercises, while the added results provide students with the help to implement correct and successful exercises and interpret the results.
Keywords: multifunctional polymers, polysaccharides, cellulose, electrospun, spin coating, 3D printing, nanofibers, thin films, multifunctional materials, laboratory manuals
Published: 09.03.2021; Views: 124; Downloads: 9
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Development of polymeric materials with rutin and polyrutin for healing of chronic leg ulcers
Tanja Pivec, 2018, doctoral dissertation

Abstract: In this work, the development of cellulose wound dressing materials with rutin (RU) and polyrutin (PR) for the healing of chronic leg ulcers is presented as a new approach of local treatment of this wound type. The flavonoid rutin is a known antioxidant substance of plant origin with wound healing promoting properties. Despite the proven beneficial properties of rutin, its potential application in wound healing is limited due to its low water solubility. This limitation can be overcome by polymerization of rutin into polyrutin. In this work an enzymatic polymerization of rutin in water without addition of organic solvents was performed to obtain a water-soluble polymer polyrutin. The chemical structure of rutin and polyrutin were investigated using UV-Vis spectroscopy, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, size-exclusion chromatography and potentiometric titrations. Biological activity related to a desired positive influence on chronic leg ulcers was investigated through the determination of the antioxidant activity, iron-chelation ability, cell viability, determination of cell proliferation and through use of the so called “scratch assay” to measure in vitro wound healing performance. Results indicate that rutin and polyrutin have a positive influence on the healing of chronic wounds. Rutin and polyrutin water dispersions at different pH and ionic strength were further characterised by means of dynamic light scattering in order to determine the size of particles and their pH dependent ζ-potential. The knowledge gained from these measurements aided the systematic interaction studies of rutin and polyrutin dispersions with cellulose-based surfaces via model and real wound healing systems. The model cellulose surfaces were thin films prepared by dissolution of trimethylsilyl cellulose in tetrahydrofuran, spin-coating of this solution on sensors of a quartz crystal microbalance (QCM-D) and subsequent regeneration of trimethylsilyl cellulose to cellulose with acid vapors. The influence of pH, salt concentration, and rutin/polyrutin concentration on the interaction with cellulose thin films was evaluated by means of a quartz crystal microbalance with dissipation. This knowledge was transferred to the application of the coatings on real wound healing systems i.e. cellulose non-wovens. The surface morphology was further characterised on model and real wound healing systems. The antioxidant activity and release kinetics were investigated for a real wound healing system, similar to the clinically used, cellulose based wound dressing materials. The main results showed that a higher solubility of polyrutin at low ionic strength contributes to the formation of continuous layers of polyrutin on cellulose surface, while the low solubility of rutin and reduced solubility of polyrutin at higher ionic strengths contribute to deposition of particles of rutin and polyrutin on the cellulose surface. The presence of particles on the surface of non-woven cellulose fibres led to a faster initial release of rutin and polyrutin. On the contrary, a continuous layer of the well soluble polyrutin contributes to a prolonged release. Namely, adsorption of the water soluble polyrutin at pH 2 without the addition of salt results in higher masses of attached polyrutin that release slower and over longer time periods. Since wound dressing materials for chronic leg ulcers often require a lower frequency of dressing change, the latter could provide an efficient therapeutic approach to their treatment.
Keywords: Chronic wounds, Wound dressings, Cellulose, Polymerization of flavonoids, Rutin, Polyrutin
Published: 11.06.2018; Views: 825; Downloads: 135
.pdf Full text (7,34 MB)

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Sol-gel/Ag coating and oxygen plasma treatment effect on synthetic wound fluid sorption by non-woven cellulose material
Zdenka Peršin, Tanja Pivec, Miran Mozetič, Karin Stana-Kleinschek, 2017, short scientific article

Abstract: Non-woven cellulose material was functionalized using two techniques, i.e. the coating with AgCl via sol-gel and oxygen plasma. The treatment effects were studied regarding the wound fluid adsorption potential using physiological saline, synthetic exudate and synthetic blood. Plasma treatment was most efficient since a significant improvement by absorbency rate and capacity was evident, less pronounced in case of synthetic blood. The combination of both treatments showed a similar trend, while the effects were less prominent, but still sufficient by managing fluid-associated as well as infected wounds.
Keywords: non-woven cellulose fabric, sol-gel, oxygen plasma, absorption, synthetic wound fluids
Published: 31.08.2017; Views: 681; Downloads: 303
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Effects of ultrasound irradiation on the preparation of ethyl cellulose nanocapsules containing spirooxazine dye
Julija Volmajer Valh, Simona Vajnhandl, Lidija Škodič, Aleksandra Lobnik, Matejka Turel, Bojana Vončina, 2017, original scientific article

Abstract: This article presents the influence of low frequency, high intensity ultrasonic irradiation on the characteristics (average size, polydispersity index) of ethyl cellulose nanocapsules encapsulating a photochromic dye. Photochromic nanocapsules were prepared by the emulsion-solvent evaporation method. The acoustic densities entering the system were systematically studied with respect to their abilities to modify and reduce the average sizes and polydispersity indexes of the nanocapsules. Scanning electron microscope, confocal laser microscope, and dynamic light scattering were utilised to characterise the structure, shape, size, and polydispersity of ethyl cellulose photochromic nanocapsules. We were able to tailor the size of the photochromic nanocapsules simply by varying the acoustic densities entering the system. At an acoustic density of 1.5 W/mL and 60 s of continuous irradiation, we were able to prepare an almost monodispersed population of the nanocapsules with an average size of 193 nm.
Keywords: encapsulation, ethyl cellulose microcapsules, nanocapsules
Published: 09.08.2017; Views: 871; Downloads: 276
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Chemical binding of chitosan and chitosan nanoparticles onto oxidized cellulose
Olivera Šauperl, Mirjana Kostić, Jovana Milanovic, Lidija Fras Zemljič, 2015, original scientific article

Abstract: The aim of this study was to analyze binding of chitosan and chitosan nanoparticles onto cellulose via oxidized cellulose. The ability of chitosan and chitosan nanoparticles to be adsorbed onto surfaces was determined by the use of the XPS spectroscopy which provided information about chemical composition of the fiber surface. On the other hand, the gravimetric method was also used by which the amount of chitosan and chitosan nanoparticles bounded onto surface was calculated based on the difference in masses before and after functionalization. The most important was to study the influence of aldehyde groups on the stability of chitosan binding onto cellulose. Thus, desorption of chitosan/chitosan nanoparticles from the fiber surfaces was evaluated by the presence of total nitrogen (TN) in desorption bath as well as by polyelectrolyte titrations. Together with these two methods, desorption was evaluated also by gravimetric method, where the extent of desorption was evaluated on the basis of the differences in the masses of fibers before and after desorption. It is concluded that the chitosan and chitosan nanoparticles are more efficiently bounded onto oxidized cellulose in comparison with the non-oxidized (reference) ones. Despite the binding of the positively-charged amino groups with the negative groups of cellulose and consequently smaller amount of available/residual protonated amino groups that are responsible for bioactivity, such functionalized fibers are still specifically antimicrobial.
Keywords: cellulose, oxidized cellulose, oxidation, chitosan, chitosan nanoparticles, FTIR, XPS, antimicrobial functionalization
Published: 02.08.2017; Views: 704; Downloads: 381
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Hydrophilic/hydrophobic characteristics of different cellulose fibres monitored by tensiometry
Zdenka Peršin, Karin Stana-Kleinschek, Tatjana Kreže, 2002, original scientific article

Abstract: Wettability and sorptivity improvements for different textile materials are the major tasks during textile finishing. In order to improve the sorption characteristics of a cellulose fabric, different pre-treatment processes are applied, usually washing, bleaching and mecerisation. Differences in the sorption properties of untreated and pretreated (washed and bleached) regenerated cellulose fibres were obtained using tensiometry and compared with the classical method for determining moisture adsorption. Results show that compared to raw fibres, viscose fibres have the highest moisture and the smallest contact angle whilst modal fibres have the biggest contact angle. Pretreatment increases the sorption abilities and makes the material more accessible to chemicals used in the finishing process. Using the conventional method, it can be confirmed that fibres with the highest moisture have the smallest contact angle (tensiometry).
Keywords: textile materials, regenerated cellulose fibres, sorption, pretreatment, tensiometry
Published: 05.07.2017; Views: 556; Downloads: 79
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Photoregeneration of trimethylsilyl cellulose as a tool for microstructuring ultrathin cellulose supports
Archim Wolfberger, Rupert Kargl, Thomas Grießer, Stefan Spirk, 2014, original scientific article

Abstract: Microstructured thin films based on cellulose, the most abundant biopolymer on Earth, have been obtained by UV-irradiation of acid-labile trimethylsilyl cellulose thin films in the presence of N-hydroxynaphtalimide triflate as photoacid generator. We demonstrate that this photoregeneration process can be exploited for the manufacture of cellulose patterns having feature sizes down to 1 μm, with potential applications in life sciences.
Keywords: cellulose thin films, cellulose regeneration, patterning of cellulose, photoregeneration
Published: 22.06.2017; Views: 725; Downloads: 350
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