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Functional 3D printed polysaccharide derivative scaffolds for vascular graft application : doctoral disertation
Fazilet Gürer, 2023, doktorska disertacija

Opis: Tissue engineering (TE) is an interdisciplinary field that aims towards replacement, healing or reconstruction of damaged tissue and organs. Incurable diseases are currently treated with organ transplantation, that have the disadvantages of insufficient donors, immune response, and organ rejection after transplantation. TE imitate the functions of extracellular matrix (ECM) to develop biocompatible/biodegradable scaffolds with appropriate features which are utilized to provide mechanical support, cellular infiltration, migration, and tissue formation, and to mimic the biochemical and biophysical cues of cells. Several fabrication methods have been introduced to mimic the 3D structure of ECM and 3D printing is one of the additive manufacturing techniques, widely used in TE because of its feasibility to build complex tissue constructs and control over fabrication and cell distribution. The polysaccharide-peptide conjugate has gained enormous interest in recent years owing to its biocompatibility, degradability, flexibility, and structural matching to natural proteoglycans. In this context, we reported here on investigation of biocompatibility with HUVECs, surface modification of 3D printed PCL scaffolds with an amine group and chemically crosslinked oxidized HA-amino acid/peptide conjugates (OHACs) was used to develop a novel biomaterial for use as a tissue engineered vascular graft. Modified polysaccharides were characterized with respect to their chemical structure, charge, UV and fluorescence properties and cytotoxicity. The successful conjugation was demonstrated by XPS, and a decrease in the free amine peaks on the surface was observed after conjugation. In addition, the water contact angle measurements showed improved wetting, an indication that the conjugation to the PCL-A surface was successful. Finally, the biocompatibility of the novel scaffolds was characterized by the MTS and the live- dead assay. In both assays, proliferation of cells was observed after 7 days and cell spreading on the surface was detected by phalloidin staining of actin filaments. In conclusion, it was possible to prepare surface-active scaffolds by combining the advantages of biocompatibility and mechanical strength of polysaccharides and polyesters, respectively.
Ključne besede: 3D tiskanje, karboksimetilceluloza, hialuronska kislina, polikaprolakton, kemija karbodiimida, kemija Shiffove baze, endotelizacija 3D printing, carboxymethyl cellulose, hyaluronic acid, polycaprolactone, carbodiimide chemistry, shiff-base chemistry, endothelialization
Objavljeno v DKUM: 06.10.2023; Ogledov: 367; Prenosov: 42
.pdf Celotno besedilo (7,97 MB)

Preparation of Three Dimensional Structures of Polysaccharide Derivatives for Application in Regenerative Medicine : doctoral disertation
Andreja Dobaj-Štiglic, 2022, doktorska disertacija

Opis: Biocompatible polysaccharide scaffolds with controllable pore size, good mechanical properties, and no hazardous chemical crosslinkers are desirable for long-term tissue engineering applications. Despite decades of development of novel scaffolds, there are still many challenges to be solved regarding their production and optimization for specifically engineered tissues. Herein, we have fabricated several three-dimensional (3D) scaffolds using polysaccharide or polysaccharide-protein composite hydrogels or inks for 3D printing, featuring strong shear thinning behavior and adequate printability. The inks, composed of various combinations of chitosan, nanofibrillated cellulose, carboxymethyl cellulose, collagen, and citric acid, were 3D printed, freeze-dried, and dehydrothermally heat-treated to obtain dimensionally and mechanically stable scaffolds. The heat-assisted step induced the formation of covalent amide and ester bonds between the functional groups of chosen polysaccharides and protein collagen. Citric acid was chosen as a non-hazardous and „green” crosslinker to further tailor the mechanical properties and long-term stability of the scaffolds. We have investigated how the complexation conditions, charge ratio, dehydrothermal treatment, and degree of crosslinking influence the scaffolds' chemical, surface, swelling, and degradation properties in the dry and hydrated states. The compressive strength, elastic modulus, dimensional stability and shape recovery of the (crosslinked) scaffolds increased significantly with balanced charge ratio, dehydrothermal treatment, and increased concentrations of citric acid crosslinker and collagen concentrations. The prepared crosslinked scaffolds promoted (clustered) cell adhesion and showed no cytotoxic effects, as determined by cell viability assays and live/dead staining with human bone tissue-derived osteoblasts and human adipose tissue-derived mesenchymal stem cells. The water-based and non-hazardous crosslinking methods presented here can be extended to all polysaccharide- or polysaccharide-protein-based materials to develop cell-friendly scaffolds with tailored properties suitable for various tissue engineering applications.
Ključne besede: chitosan, carboxymethyl cellulose, nanofibrillated cellulose, citric acid, collagen, freeze drying, 3D printing, dehydrothermal treatment
Objavljeno v DKUM: 11.10.2022; Ogledov: 576; Prenosov: 150
.pdf Celotno besedilo (33,63 MB)

Design, Characterisation and Applications of Cellulose-Based Thin Films, Nanofibers and 3D Printed Structures : A Laboratory Manual
Tanja Pivec, Tamilselvan Mohan, Rupert Kargl, Manja Kurečič, Karin Stana-Kleinschek, 2021, drugo učno gradivo

Opis: 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.
Ključne besede: multifunctional polymers, polysaccharides, cellulose, electrospun, spin coating, 3D printing, nanofibers, thin films, multifunctional materials, laboratory manuals
Objavljeno v DKUM: 09.03.2021; Ogledov: 863; Prenosov: 23
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Development of polymeric materials with rutin and polyrutin for healing of chronic leg ulcers
Tanja Pivec, 2018, doktorska disertacija

Opis: 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.
Ključne besede: Chronic wounds, Wound dressings, Cellulose, Polymerization of flavonoids, Rutin, Polyrutin
Objavljeno v DKUM: 11.06.2018; Ogledov: 1665; Prenosov: 238
.pdf Celotno besedilo (7,34 MB)

Vpliv sinteze na velikost nanodelcev
Doris Tkaučič, 2018, magistrsko delo

Opis: V magistrski nalogi je predstavljena primerjava dveh metod priprave nanodelcev, znotraj dveh metod smo spreminjali parametre in spremljali vpliv sprememb na velikost nanodelcev. Nanodelci so se pripravljali iz etil celuloze po emulzijske postopku, kjer smo kot polimerne stabilizatorje uporabljali različne polisaharide, ter spreminjali njihove koncentracije. Druga uporabljena metoda je bila dializna metoda, pri kateri smo uporabili različna topila in različne koncentracije etil celuloze. Velikost delcev smo analizirali z DLS metodo in z elektronskim mikroskopom, stabilnost disperzij smo določili z določanjem zeta potenciala.
Ključne besede: polisaharidi, etil celuloza, nanodelci, emulzijska metoda, dializna metoda
Objavljeno v DKUM: 06.06.2018; Ogledov: 1507; Prenosov: 112
.pdf Celotno besedilo (3,27 MB)

Development and characterization of novel electrospun matrices with embedded CNC for air filtration
Manja Kurečič, Tanja Pivec, Mojca Božič, Silvo Hribernik, Karin Stana-Kleinschek, 2018, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: nanotechnology, cellulose nanocrystals
Objavljeno v DKUM: 31.05.2018; Ogledov: 1658; Prenosov: 81
.pdf Celotno besedilo (2,43 MB)

Polyurethanes for medical use
Tanja Pivec, Majda Sfiligoj-Smole, Petra Gašparič, Karin Stana-Kleinschek, 2017, pregledni znanstveni članek

Opis: Polyurethanes are synthetic copolymers containing urethane linkages in their complex chemical structure. They consist of three monomers: a diisocyanate, a polyol and a chain extender, which enables the synthesis of an endless number of polyurethanes with different physicochemical and mechanical properties. The physicochemical properties of various polyurethanes are largely dependent on the conformation of polyols, which may contain two or more different polyols, stabilisers, catalysts, liquids or solid additives and, in the case of foams, foaming agents. Depending on the structure of the polyols, i.e. the length of the chain, structure of the units (aliphatic or aromatic), ester or ether groups, or functionalisation by hydroxyl groups, polyurethanes may be flexible or rigid, and therefore suitable for various applications. In addition to the physical and chemical structure of polyurethanes, this review paper specifically addresses their use in medicine, particularly in wound dressings, tissue engineering scaffolds and drug delivery with nanoparticles and nanocapsules, and provides guidelines for the development of new biodegradable polyurethane materials.
Ključne besede: segmented polyurethanes, chemical structure, reactants, medical applications
Objavljeno v DKUM: 03.10.2017; Ogledov: 1659; Prenosov: 478
.pdf Celotno besedilo (383,90 KB)
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Zeta potencial PA 6
Robert Šoster, Nika Veronovski, Lidija Tušek, Karin Stana-Kleinschek, Simona Strnad, Volker Ribitsch, 2003, izvirni znanstveni članek

Opis: V raziskavi smo preučevali elektrokinetične lastnosti poliamida 6 v obliki (a) folije in (b) tekstilnega filamenta ob uporabi dveh merilnih celic. Merili smo potencial zaradi pretoka in iz tega določili zeta potencial (▫$\zeta$▫ v odvisnosti od pH vrednosti medija. Meritve na posameznem materialu smo preučevali s stališča ponovljivosti. S tem namenom smo opravili meritve na 10 preskušancih istega vzorca. Določili smo osnovne statistične pokazatelje ponovljivosti za ▫$\zeta$▫ pri pH 3 in 9 ter izoelektrično tocko. Metodo smo optimirali glede na čas nabrekanja v raztopini elektrolita pred meritvijo in maso materiala v cilindrični celici. Meritve v 0,001 M KCl na obeh vrstah materiala kljub različni nadmolekulski in površinski strukturi dobro sovpadajo. Krivulje ▫$\zeta$▫=▫$\zeta$▫(pH) imajo pričakovan potek. PA 6 kaže amfoterno naravo zaradi vsebnosti amino in karboksilnih skupin. V alkalnem mediju disociirajo karboksilne skupine, kar povzroči negativen ▫$\zeta$▫ (folija: (-32,9▫$\pm$▫ 1,6) mV, filament: (-35,2▫$\pm$▫2,0) mV pri pH 9). V kislem mediju kaže PA kationski značaj zaradi disociacije amino skupin (folija: (24,5▫$\pm$▫1,7) mV, filament: (15,1▫$\pm$▫1,1) mV pri pH 3). Izoelektrična točka, kjer je ▫$\zeta$▫ enak 0, se nahaja za folijo pri pH vrednosti 4,7▫$\pm$▫0,1, za filament pa pri 4,9▫$\pm$▫ 0,1.
Ključne besede: polimeri, poliamid 6, elektrokinetične lastnosti, potencial zaradi pretoka, zeta potencial, filament, folija
Objavljeno v DKUM: 01.09.2017; Ogledov: 1604; Prenosov: 147
.pdf Celotno besedilo (420,18 KB)
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