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21.
EFFECT OF GELATINE SCAFFOLDS FABRICATION AS POLYPROPYLENE MESH COAT ON IMPLANT BIOCOMPATIBILITY
Selestina Gorgieva, 2014, doktorska disertacija

Opis: This work presents the methodological study, processing and optimization of novel, technologically acceptable procedure for in situ coating of polypropylene (PP) mesh (used for hernia treatment) with physico-chemically, mechanically and micro-structurally different gelatin (GEL) scaffolds to assess implant composite biocompatibility impact. In order to systematically follow the experimental work progress and respective achievements, whole research path is subdivided into three main sections. In the first section, the procedure for fabrication of gradiently micro-porous GELscaffolds on the cryo-unit’s cooling plate surface, using spatiotemporal and temperature- controlled gelation and freezing, followed by lyophylizaton was studied. Subsequently, cross-linking procedure using different molarities of reagents (EDC and NHS) and reaction media (100% PBS or 20/80% PBS/EtOH mixture) was performed for variable time extensions (1-24 h), rendering scaffolds physico-chemical properties. In this way, scaffolds with micro-structures having porosity gradient from 100 µm to 1000 µm and pores with rounded to ellipsoid morphology were formed, which, in combination with ethanol (EtOH) addition in cross-linking media modulates the swelling capacity towards twice lower percentages (~600%) comparing with scaffolds cross-linked in 100% PBS. Whilst the presence of EtOH reduce the cross-linking kinetic by retaining the scaffolds’ micro-structure formed during freezing, the 100% PBS and higher EDC molarity resulted in 40% cross-linking degree, being expressed as a thermal resistance up to 73 °C. The presented integral fabrication procedure was shown to allow tuning of both, the physical and micro-structural properties of scaffold, utilized in preparation of materials for specific biomedical applications. In the second part, the complex relation between surface and interface-related physico-chemical properties and gradient micro-structuring of 3D GELscaffolds, being fabricated by simultaneous temperature- controlled freeze-thawing cycles and in situ cross-linking using variable conditions (pH and molarity of carbodiimide reagent) and fibroblast cells viability (by tracking of their spreading and morphology) was established. Rarely- populated cells with rounded morphology and small elongations were observed on scaffolds with apparently negatively- charged surface with a lower cross-linking degree (CD) and consequently higher molecular mobility and availability of cell-recognition sequences, in comparison with the prominently- elongated and densely- populated cells on a scaffold’s with positively- charged surface, higher CD and lower mobility. Surface micro-structure effect was demonstrated by cell’s vacuolization and their pure inter-communication being present on scaffold’s bottom side with smaller pores (25±19 µm) and thinner pore walls (9±5 µm), over the air- exposed side with twice bigger pores (56±38 µm) and slightly thicker pore walls (12±6 µm). Strong correlation of preparation conditions (pH and reagents molarity) with CD (r2=0.96) and moderate correlation with local molecular mobility (r2 =-0.44), as well as micro-structure features being related to temperature gradient, imply on possibility to modulate scaffold’s properties in a direction to guide cell’s viability and most likely its genotype development. The third part presents an innovative strategy for the fabrication of bio-active PPmesh-GELscaffold composites with a potential for abdominal hernia treatment, where mesothelial cells in-growth have to be stimulated together with fibroblasts on-site proliferation, while formation of fibrin-developing, viscera-to-abdominal wall adhesions should be reduced, together with bacteria- related infections. In this respect, the plasma pre-activated PPmesh was coated with micro-structured GELscaffold, with pore size in 50 µm to 100 µm range at the upper-side and loosely- porous network at the composite bottom side, being modulated by sample thickness and freezing end- temperature applied. Simultaneously, the
Ključne besede: gelatin, targeted cross-linking, controlled freezing, gradiental micro-porosity, scaffold, surface and interface chemistry, physico-mechanical properties, polypropylene mesh, composite, biocompatibility.
Objavljeno: 07.05.2014; Ogledov: 1418; Prenosov: 106
.pdf Celotno besedilo (4,98 MB)

22.
VPLIV MAGNETNEGA POLJA NA BAKTERIJE V BIOLOŠKIH ČISTILNIH NAPRAVAH IN NA PRETVORBO DUŠIKA
Jasmina Filipič, 2013, doktorska disertacija

Opis: V doktorski disertaciji predstavljamo študijo čiščenja odpadne vode z vidika odstranjevanja dušikovih spojin s pomočjo srednje močnega statičnega magnetnega polja (SMP). Veljavna zakonodaja in visoki stroški okoljskih dajatev za onesnaževanje voda, namreč težijo k iskanju novih naprednih tehnologij čiščenja odpadne vode. V dosedanjih raziskavah je bilo ugotovljeno, da se pod vplivom SMP, poveča odstranjevanje organskih substratov iz odpadne vode. Naše raziskave kažejo, da SMP gostote, B = (30, 50) mT (toda ne B = 10 mT) pozitivno vpliva na odstranjevanje dušikovih spojin v SBR reaktorjih. Amonij-oksidacijska hitrost se pri SMP gostote, B = 50 mT drastično poveča, in sicer za w = 85 ± 5 %. Glede na pozitiven učinek SMP na čiščenje odpadne vode, smo v nadaljevanju raziskave preučili vpliv SMP na tri bakterije odpadne vode ˗ Nitrosomonas europaea, Escherichia coli in Pseudomonas putida. Rezultati raziskave kažejo, da SMP (B = 17 mT) negativno vpliva na rast bakterij E.coli in P.putida, toda pozitivno na dehidrogenazno aktivnost in koncentracijo znotrajceličnega ATP. Inhibitorni vpliv na omenjeni bakteriji je bil največji pri njunih optimalnih temperaturah rasti. V okviru doktorske naloge smo kot prvi dokazali, da SMP (B = 17 mT) pozitivno vpliva na oksidacijo amonijevega dušika pri bakteriji N.europaea. SMP prav tako pozitivno vpliva na mešano združbo amonij-oksidirajočih bakterij v odpadni vodi, s povečanjem za w = 40 % pod vplivom SMP in na čisto kulturo N.europaea s povečanjem števila bakterij po sedmih dneh izpostavitve SMP za w = 60 %, v primerjavi s kontrolnimi vzorci. Iz rezultatov je razvidno, da lahko z ustrezno gostoto SMP, časom izpostavitve in temperaturo znatno povečamo odstranjevanje dušikovih spojin iz odpadne vode ter pospešimo rast enega izmed najpomembnejših nitrifikatorjev odpadne vode – Nitrosomonas europaea.
Ključne besede: odpadna voda, bakterije, statično magnetno polje, dušikove spojine, nitrifikacija, denitrifikacija
Objavljeno: 04.06.2013; Ogledov: 1796; Prenosov: 242
.pdf Celotno besedilo (2,99 MB)

23.
DOLOČEVANJE MONOSAHARIDOV S KAPILARNO ELEKTROFOREZO
Natalija Virant, 2012, diplomsko delo

Opis: Namen diplomskega dela je bil s pomočjo kapilarne elektroforeze kvalitativno in kvantitativno ovrednotiti sestavo monosaharidov v vzorcih kefirana. Optimirali smo celoten postopek z uporabo različnih dolžin kapilare ter različnih dodatkov acetonitrila k boratnemu pufru. Vzorce kefirana smo hidrolizirali s H2SO4, derivatizacijo pa smo izvedli z reduktivno aminacijo, ob uporabi natrijevega cianoborohidrida. Rezultati so pokazali, da kefiran vsebuje glukozo in galaktozo. Določili smo, da je skupna vrednost monosaharidov v območju od 29,2 % do 55,8 %. Koncentracija glukoze je bila v območju od 62,8 mg/L do 113,7 mg/L, medtem ko se je koncentracije galaktoze gibala med 55,2 mg/L in 110,1 mg/L. Ugotovili smo, da je najboljša ločljivost komponent potekla ob uporabi kapilare dolžine 37 cm in 30 % dodatkom acetonitrila k boratnemu pufru.
Ključne besede: kapilarna elektroforeza, elektroosmotski tok, monosaharidi, kefiran
Objavljeno: 04.10.2012; Ogledov: 1595; Prenosov: 227
.pdf Celotno besedilo (2,87 MB)

24.
Decolorization of textile dyes by whole cultures of Ischnoderma Resinosum and by purified laccase and Mn-peroxidase
Vanja Kokol, Aleš Doliška, Ivana Eichlerová, Petr Baldrian, František Nerud, 2007, izvirni znanstveni članek

Opis: Ischnoderma resinosum produced extracellular ligninolytic enzymes laccase and MnP. The activity of laccase achieved the maximum on day 10 (29.4 U L-1), the MnP on day 14 (34.5 U L-1). Laccase and Mn-peroxidase were purified from the culture liquid using gel permeation and ion-exchange chromatographies. Purified Mn-peroxidase performed decolorization of all textile dyes tested (Reactive Black 5, Reactive Blue 19, Reactive Red 22 and Reactive Yellow 15). Laccase was inactive with Reactive Black 5 and Reactive Red 22, while all dyes were decolorized after addition of the redox mediators violuric acid (VA) and hydroxybenzotriazole (HBT). The culture liquid from I. resinosum cultures was also able to decolorize all dyes as well as the synthetic dyebaths in the presence of VA and HBT. The highest decolorization rates were detected in acidic pH (3-4).
Ključne besede: Ischnoderma resinosum, Basidiomycetes, Laccase, Mn-peroxidase, Textile dyes, ligninolytic enzymes
Objavljeno: 01.06.2012; Ogledov: 1180; Prenosov: 68
URL Povezava na celotno besedilo

25.
The influence of enzymatic treatment on wool fibre properties using PEG-modified proteases
Suzana Jus, Marc Schroeder, Georg M. Gübitz, Elisabeth Heine, Vanja Kokol, 2007, izvirni znanstveni članek

Opis: The main contribution of the presented work was to introduce the use of proteases modified with the soluble polymer polyethylene glycol (PEG) in the bio-finishing process of wool fibres, to target enzyme action to the outerparts of wool fibres, i.e. to avoid the diffusion and consequent destroying of the inner parts of the wool fibre structure, in the case of native proteases using. Different proteolytic enzymes from Bacillus lentus and Bacillus subtilis in native and PEG-modified forms were investigated and their influence on the modification of wool fibres morphology surface, chemical structure, as well as the hydrolysis of wool proteins, the physico-mechanical properties, and the sorption properties of 1:2 metal complex dye during dyeing were studied. SEM images of wool fibres confirmed smoother and cleaner fibre surfaces without fibre damages using PEG-modified proteases. Modified enzyme products have a benefit effect on the wool fibres felting behaviours (14%) in the case when PEG-modified B. lentus is used, without markedly fibre damage expressed by tensile strength and weight loss ofthe fibre. Meanwhile the dye exhaustion showed slower but comparable level of dye uptake at the end of the dyeing.
Ključne besede: volnena vlakna, proteolitski encimi, encimske modifikacije, sorpcija barve, morfologija vlaken, wool fibres, proteolytic enzymes, enzyme modification, felting, dye sorption, protein hydrolysis, XPS-analysis, fibre morphology
Objavljeno: 01.06.2012; Ogledov: 1990; Prenosov: 90
URL Povezava na celotno besedilo

26.
A novel metalloprotease from Bacillus cereus for protein fibre processing
Fernanda de Sousa, Suzana Jus, Anita Erbel, Vanja Kokol, Artur Cavaco-Paulo, Georg M. Gübitz, 2007, izvirni znanstveni članek

Opis: A novel protease produced by Bacillus cereus grown on wool as carbon and nitrogen source was purified. B. cereus protease is a neutral metalloprotease with a molecular mass of 45.6 kDa. The optimum activity was at 45 °C and pH 7.0. The substrate specificity was assessed using oxidized insulin B-chain and synthetic peptide substrates. The cleavage of the insulin B-chain was determined to be Asn3, Leu6, His10-Leu11, Ala14, Glu21, after 12 h incubation. Among the peptide substrates, the enzyme did not exhibit activity towards ester substrates; with p-nitroanilide, the kinetic data indicate that aliphatic and aromatic amino acids were the preferred residues at the P1 position. For furylacryloyl peptides substrates, which are typical substrates for thermolysin, the enzyme exhibited high hydrolytic activity with a Km values of 0.858 and 2.363 mM for N-(3-[2-Furyl]acryloyl)-Ala-Phe amide and N-(3-[2-Furyl]acryloyl)-Gly-Leu amide, respectively. The purified protease hydrolysed proteins substrates such as azocasein, azocoll, keratin azure and wool.
Ključne besede: textile finishing, enzymatic modification, wool fibre, enzymes, Bacilus cereus, specificity, kinetics, metalloprotease
Objavljeno: 01.06.2012; Ogledov: 1357; Prenosov: 82
URL Povezava na celotno besedilo

27.
Ecological alternatives to the reduction and oxidation processes in dyeing with vat and sulphur dyes
Mojca Božič, Vanja Kokol, 2008, pregledni znanstveni članek

Opis: This article gives a summary of the most commonly used ecologically unfriendly processes for the reduction and oxidation of vat and sulphur dyes. It also describes the new alternatives that are in the development stage and could be important in the near future. Sodium dithionite as the dominant reducing agent produces large amounts of sodium sulphate, and also toxic sulphite and thiosulphate as by-products. Consequently, high amounts of hydrogen peroxide and alkali are required for the treatment of effluents, which add to the cost of the process. Attempts have been made to use organic biodegradable reducing agents, enzymes, catalytic hydrogenation, and also indirect or direct, electrochemical reductive methods that employ a redox mediator (electron-carrier). The reduction has also been carried out via the dye radical molecule or, in the case of indigo, by direct electrochemical reduction using graphite as the electrode material. Physical techniques, for example using ultrasound, magnetic fields or UV have been shown to be effective only when used to accelerate methods using classical reduction and oxidation processes. However, although these methods offer some environmental benefits, there is still no satisfactory alternative reducing and/or oxidising agent available today.
Ključne besede: textile dyeing, vat dyes, sulphur dyes, reduction, oxidation, catalysis, ecology, organic agents, electrochemistry, ultrasound, magnetic field, UV application, biotechnology
Objavljeno: 01.06.2012; Ogledov: 2121; Prenosov: 97
URL Povezava na celotno besedilo

28.
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: 1186; Prenosov: 72
URL Povezava na celotno besedilo

29.
Collagen- vs. gelatine-based biomaterials and their biocompatibility : review and perspectives
Selestina Gorgieva, Vanja Kokol, 2011, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Ključne besede: material biomimetism, collagen, gelatine, immunogenicity, antigenicity, pepsin, cross-linking
Objavljeno: 01.06.2012; Ogledov: 1217; Prenosov: 66
URL Povezava na celotno besedilo

30.
The influence of increased cross-linker chain length in thermosensitive microspheres on potential sun-protection activity
Witold Musiał, Vanja Kokol, Bojana Vončina, 2010, izvirni znanstveni članek

Opis: The sun protection should involve substances with protecting activity against both UVB and UVA radiation. In this research the evaluation of thermosensitive microspheres as potential molecules for sunscreen formulations was approached, using modified Boots star rating system. The microspheres, thermosensitive N-isopropylacrylamide derivatives, have potential protecting activity against UV radiation. The MX and DX microspheres, with ethylene glycol dimethacrylate and diethylene glycol dimethacrylate crosslinker respectively, due to theirs thermosensitivity exhibit increase in protecting activity against UV radiation when heated to 45°C. The MX microspheres have higher increase in terms of UV absorbance, comparing to DX microspheres, when heated in the 25°C to 45°C range. Studied microspheres have high potential forapplication as components of sun-screens used in elevated temperatures.
Ključne besede: thermosensitive microspheres, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ultraviolet radiation, sun-screen
Objavljeno: 31.05.2012; Ogledov: 1134; Prenosov: 21
URL Povezava na celotno besedilo

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