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Heparin adsorption onto model poly(ethylene terephtalate) (PET) surfaces monitored by QCM-D
Aleš Doliška, Simona Strnad, Karin Stana-Kleinschek, 2012, izvirni znanstveni članek

Opis: The adsorption of anticoagulant heparin onto model poly(ethylene terephtalate) (PET) film was monitored using a quartz crystal microbalance with a dissipation unit (QCM-D). Synthetic vascular grafts are usually made from PET, a material with appropriate mechanical properties but moderate haemocompatibility. Therefore anticoagulant heparin is usually used to improve haemocompatibility of PET surfaces. Heparin possesses a high negative charge and as such does not adsorb directly onto hydrophobic PET, which is also negatively charged. To increase heparin adsorption different cationic polymers were investigated as spacers and the highest adsorption was achieved using polyethyleneimine (PEI) as an anchoring agent. The heparin was adsorbed from water solution as well as from phosphate buffer saline (PBS). Heparin dissolved in PBS adsorb better onto PET than heparin from water solution. The results were characterized using Sauerbrey equation and Voigt based viscoelastic model. We found out that heparin adsorbed onto PET formed a thin and rigid film and that Sauerbrey equation is appropriate for characterization of heparin adsorption onto PET.
Ključne besede: poly(ethyleneterephtalate), PET, heparin, QCM-D, haemocompatibility
Objavljeno: 01.06.2012; Ogledov: 1110; Prenosov: 38
.pdf Celotno besedilo (416,79 KB)
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Substrate-induced coagulation (SIC) of nano-disperse titania in non-aqueous media : the dispersibility and stability of titania in N-methyl-2-pyrrolidinone
Angelika Basch, Simona Strnad, Volker Ribitsch, 2009, izvirni znanstveni članek

Opis: Dispersions of 1 wt% titandioxide (titania or TiO2) were investigated with respect to their stability in non-aqueous media. The objective of this work was to find conditions for the substrate-induced coagulation (SIC) process in N-methyl-2-pyrrolidinone (NMP). The SIC process is a dip-coating process that enhances adsorption of fine dispersed particles on a pre-conditioned surface. The wetting behavior of titania and NMP was investigated by the powder contact angle method. The absorption process of the polar solvent NMP on the acid oxide TiO2and Aerosol OT (AOT) (bis-2-ethylhexyl sodium sulfosuccinate) was also investigated and a polar or hydrophilic interaction was found. The stability of titania in NMP dispersions and the influence of the solvent AOT and the electrolyte LiCl was investigated. By studying the electrophoretic mobilities of titania particles in NMP and the influence on solutes by the electrophoretic method phase analysis light scattering (PALS) and the electroacoustic method this paper explores suitable conditions for non-aqueous substrate-induced coagulation of titania.
Ključne besede: contact angle, non-aqueous dispersions, electrophoretic mobilities, substrate-induced coagulation, titandioxide, zeta potential
Objavljeno: 01.06.2012; Ogledov: 1197; Prenosov: 51
URL Povezava na celotno besedilo

Characterization of amino groups for cotton fibers coated with chitosan
Lidija Fras Zemljič, Simona Strnad, Olivera Šauperl, Karin Stana-Kleinschek, 2009, izvirni znanstveni članek

Opis: The adsorption of chitosan onto cellulose cotton fibers introduces antimicrobial properties, mainly created by the amount and location of amino groups. Therefore, it is important to be able to analyze both parameters, especially in a heterogeneous system, namely cotton fibers coated with chitosan. In this research, three different analytical techniques were applied to determine amino groups of cotton fibers coated with chitosan. The number of positively charged groups was determined indirectly by the spectrophotometric method using Acid Orange 7 dye, and the use of polyelectrolyte titration. In addition, the chemical surface composition regarding non-modified, as well as modified cotton fibers (coated with chitosan), was investigated using X-ray Photoelectron Spectroscopy (XPS). The results from a combination of these methods show that chitosan treatment introduces more than 14 mmol/kg of accessible amino groups onto the cotton fibers. The results were in good agreement with the results of XPS. The use of spectrophotometric and titration methods in combination with XPS appears to be a very useful tool for identifying the formation of amino groups in modified cotton fibers and their surfaces.
Ključne besede: cotton, cellulose, oxidation, chitosan, amino-groups, titration, XPS
Objavljeno: 01.06.2012; Ogledov: 1023; Prenosov: 99
URL Povezava na celotno besedilo

Adsorption of fucoidan and chitosan sulfate on chitosan modified PET films monitored by QCM-D
Tea Indest, Janne Laine, Leena Sisko Johansson, Karin Stana-Kleinschek, Simona Strnad, Renate Dworczak, Volker Ribitsch, 2009, izvirni znanstveni članek

Opis: The adsorption behavior of fucoidan as well as chitosan derivatives (chitosan sulfate) on poly(ethylene terephthalate) (PET) model film surface was studied using the quartz crystal microbalance technique. These systems were chosen for this study due to their promising biocompatible properties. Moreover, fucoidan and chitosan sulfate have promising anticoagulant properties and represent an alternative to heparin treatment of vascular grafts. As a first step, PET foils were activated by alkaline hydrolysis to increase their hydrophilicity. From these foils, model PET films were prepared by the spin coating technique on a silica quartz crystal. The selected polysaccharides (chitosan, fucoidan, and chitosan sulfate) were adsorbed from aqueous solutions on the PET surfaces. The adsorption was monitored using a quartz crystal microbalance with a dissipation unit. The surface chemistry and morphology of the chitosan/fucoidan or chitosan/chitosan sulfate coated PET-H films was analyzed using XPS and AFM. It was found that chitosan/fucoidan films were thinner and more compressed, while in the case of chitosan/chitosansulfate, large amounts of chitosan sulfate were adsorbed, indicating a loose and thick adsorbed film.
Ključne besede: PET films, fucoidan, chitosan sulfate, adsorption, anticoagulant properties
Objavljeno: 01.06.2012; Ogledov: 1102; Prenosov: 50
URL Povezava na celotno besedilo

Attenuation of cerebral vasospasm in rabbits using clonidine hydrochloride, a central adrenergic agonist
Gorazd Bunc, Srečko Kovačič, Simona Strnad, 2003, kratki znanstveni prispevek

Opis: The aim of this study was to assess, firstly, if exclusion of central noradrenergic areas in the hypothalamus and brain stem with the central sympathetic blocker clonidine hydrochloride could prevent the development of chronic vasospasm following experimental subarachnoid haemorrhage in rabbits and, secondly, if, parallel with the effect on cerebral arteries, changes in dopamine -hydroxylase concentration in the hypothalamus and brain stem could also be detected. Experimental subarachnoid haemorrhage, in concentrations of 1 ml of autologous arterial bloodž1 kg of body weight was carried out on 18 New Zealand rabbits. Histological specimens were obtained by the method of perfusion fixation after the rabbits were sacrificed on day 8 after subarachnoid haemorrhage. The spastic effect of experimentally induced subarachnoid haemorrhage was determined by assessing the intensity of corrugation of the intima of the rabbit basilar artery by the previously developed method of corrugation coefficient and computer image analysis. The concentration and localization of dopamine -hydroxylase in noradrenaline-containing neurons was immunohistochemically assessed (semiquantitatively as 0, 1 and 2) with anti-dopamine -hydroxylase, at precisely defined sites of the hypothalamus and brain stem of the same rabbit. The results revealed less corrugated and smoother intima in the basilar artery and significantly lower dopamine -hydroxylase concentration in the control group of rabbits with sham subarachnoid haemorrhage and without any additional interventions (mean corrugation COEFFICIENT=1.123 0.024, P=0.3510-3č mean dopamine -hydroxylase=0.350 0.071, P=0.22 10-3), and smootherintima in the basilar artery with significantly lower concentration ofdopamine -hydroxylase in the clonidine group (rabbits with subarachnoid haemorrhage and central 2-blocker clonidine hydrochloride at a daily dose of 0.03 mgžkg of body weight for 8 daysč mean corrugation COEFFICIENT=1.177 0.058, P=1.7 10-3č mean dopamine -hydroxylase=0.583 0.175, P=1.1 10-3). In comparison, the haemorrhage only group (rabbits with subarachnoid haemorrhage and without medicationč mean corrugation COEFFICIENT=1.370 0.101č mean dopamine -hydroxylase=1.214 0.313) displayed intensive corrugation of the intima of the basilar artery and a significantly more intensive accumulation of dopamine -hydroxylase than did the control group and the clonidine group. The results of this study demonstrated that the central 2-blocker clonidine hydrochloride effectively prevents vasospasm, and diminishes the concentration of cerebral dopamine -hydroxylase in the hypothalamus and brain stem after experimental subarachnoid haemorrhage in rabbits.
Ključne besede: medicine, neurology, subarachnoid haemorrage, cerevral vasospasm, clonidine hydrochloride, central adrenergic blockade, rabbits
Objavljeno: 01.06.2012; Ogledov: 1089; Prenosov: 53
URL Povezava na celotno besedilo

The influence of structural properties on the dye diffusion and dyeability of PA 6 fibres
Simona Strnad, Slava Jeler, Karin Stana-Kleinschek, Tatjana Kreže, 2003, izvirni znanstveni članek

Opis: The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.
Ključne besede: textiles, PA 6 fibres, dyeing, dyeability, fibre structure, crystallinity, chemical modification
Objavljeno: 01.06.2012; Ogledov: 1417; Prenosov: 12
URL Povezava na celotno besedilo

Ajra Hadela, 2014, diplomsko delo

Opis: Zanimanje za raziskovanje biopolimerov iz obnovljivih virov se v zadnjem desetletju močno povečuje zaradi pomanjkanja naravnih virov energentov. Zanimiva skupina biopolimerov so hemiceluloze, ki imajo zaradi svoje strukturne raznolikosti možnost uporabe na različnih področjih. Pri proizvodnji termomehanske pulpe v papirni industriji so galaktoglukomanani prevladujoče hemiceluloze, ki se sproščajo v procesne vode. Raztopljene manane je mogoče iz vodne faze odstraniti z adsorpcijo na vlakna pulpe, s čimer se poveča trdnost proizvedenega papirja. Zato sem pri svojem delu postavila hipotezo, da se bo galaktoglukomanan vezal tudi na ostala vlakna in jim spremenil lastnosti. Namen diplomske naloge je bil adsorbirati galaktoglukomanan iz vodnih raztopin na poletilentereftalatna vlakna in jim s tem izboljšati hidrofilnost. Preizkušanja adsorpcije sem najprej opravila na polietilentereftalatnih modelnih filmih s pomočjo kremenove mikrotehtnice. Po ugotovljenem optimalnem postopku sem nato obdelala polietilentereftalatno tkanino in uspešnost adsorpcije ugotavljala z metodami določanja celotnega organskega ogljika in z infrardečo spektroskopijo. Nazadnje sem ugotavljala uspešnost povečanja hidrofilnosti obdelane tkanine z določanjem vsebnosti vlage, s tenziometrijo in s fotogoniometrijo. Rezultati so pokazali, da je bil uporabljen postopek adsorpcije galaktoglukomanana na polietilentereftalatno tkanino uspešen. S pomočjo določanja kontaktnih kotov z vodo, pa sem dokazala tudi povečanje hidrofilnosti polietilentereftalatne tkanine obdelane z galaktoglukomnanom.
Ključne besede: hemiceluloze, galaktoglukomanan, poliester, polietilentereftalat, hidrofilnost/hidrofobnost, kremenova mikrotehtnica, stični kot
Objavljeno: 16.01.2014; Ogledov: 1048; Prenosov: 144
.pdf Celotno besedilo (1,84 MB)

Vpliv fizikalno-kemijskih parametrov vlaken na rezultate protimikrobnih testiranj
Nives Vodišek, 2014, magistrsko delo

Opis: Potreba in zahteva po protimikrobni obdelavi tekstilij je zelo velika. Raziskanih je že precej različnih spojin, ki imajo te lastnosti, vendar jih je veliko škodljivih za ljudi in okolje. Zato je trend v iskanju naravnih in neškodljivih protimikrobnih sredstev. Žal pa je njihova vezava na tekstilno matrico in tudi stopnja učinkovitosti po navadi slabša. Problem s katerim smo se soočili že v diplomskem delu je, da smo dobili redukcijo mikroorganizmov na vzorcih, ki sploh niso bili obdelani s protimikrobnim sredstvom. Učinkovitost obdelanih tekstilij s protimikrobnimi sredstvi se določa z različnimi metodami, standardiziranimi in nestandardiziranimi. Vsaka od teh metod ima različen pristop k vrednotenju. Najbolj pogosto uporabljene so AATCC 100, AATCC 147, ASTM E 2149 in JIS L 1902. Problem pri nekaterih metodah je, da so rezultati pokazali nerazumljivo inhibicijo patogenih organizmov, kjer naj ne bi bila prisotna kot na primer pri neobdelanem vzorcu. Velikokrat prihaja tudi do napačne interpretacije rezultatov. Zato smo se v tem magistrskem delu osredotočili na testiranje neobdelanih tekstilnih vzorcev po različnih metodah. Izbrali smo najbolj pogoste in nam dostopne metode ASTM E 2149, ASTM E 2315 in JIS L 1902. Vzorce smo dali testirati v različne laboratorije. Kot vidimo v poglavju, Rezultati in meritve v preglednici 4.10 smo kljub temu dobili redukcijo mikroorganizmov. Zato smo preučili vpliv fizikalno-kemijskih parametrov vlaken, na mikrobiološke lastnosti vlaken.
Ključne besede: celuloza, bombaž, viskoza, PES vlakna, mikrobiološko testiranje, time-kill metoda ASTM E 2315, stresalna metoda ASTM E 2149, JIS L 1902, tenziometer, stični kot, površinska napetost, površinska energija
Objavljeno: 04.04.2014; Ogledov: 919; Prenosov: 106
.pdf Celotno besedilo (2,43 MB)

Priprava in analiza filmov iz mešanice glukomanana in keratina iz piščančjega perja
Zala Urisk, 2014, magistrsko delo

Opis: Perutninsko perje predstavlja pomemben industrijski odpadek, ki vsakodnevno nastaja pri proizvodnji in predelavi perutninskega mesa. Zaradi tega potekajo številne raziskave možnosti njegove ponovne uporabe oziroma razvoja novih materialov in produktov iz perutninskega perja. Uporaba keratina iz perja za izdelavo funkcionalnih filmov je ena od pomembnejših smeri razvoja na tem področju, saj je zamenjava izdelkov, temelječih na petrokemičnih polimerih, z organskimi eden od osnovnih ciljev razvoja materialov v prihodnje. V magistrskem delu z naslovom »Priprava in analiza filmov iz mešanic glukomanana in keratina iz piščančjega perja« je bil namen preučiti možnosti uporabe keratina, pridobljenega iz piščančjega perja, v mešanicah z glukomananom za pripravo filmov, ki bi lahko predstavljali nosilce za različne protimikrobne aktivne substance, antibiotike, antioksidante, ipd. Pri pripravi filmov smo keratinu, ekstrahiranemu iz piščančjega perja, za izboljšanje fizikalnih lastnosti dodajali drug biopolimer z visokim povprečjem molskih mas, konjak glukomanan. S pomočjo analiznih metod, kot so optična mikroskopija, FTIR spektroskopija, določanje mehanskih lastnosti, analiza nabrekanja filmov v vodi in navzemanje vlage, določanje termičnih lastnosti ter določanje kontaktnega kota z vodo, smo ugotavljali, kakšne fizikalne in kemične lastnosti imajo pripravljeni filmi in kakšne so njihove možnosti za nadaljnjo uporabo. Ugotovili smo, da dodatek konjak glukomanana keratinu močno vpliva na mehanske lastnosti filmov, zaradi uvedbe velikega števila hidroksilnih skupin pa zviša adsorpcijo vlage.
Ključne besede: piščančje perje, keratin, glukomanan, funkcionalni filmi, kontaktni kot, FTIR spektroskopija, termogravimetrija
Objavljeno: 29.10.2014; Ogledov: 1130; Prenosov: 95
.pdf Celotno besedilo (3,00 MB)

Priprava in analiza filmov iz mešanic hitozana in keratina iz piščančjega perja
Andreja Križanec, 2014, magistrsko delo

Opis: Perutninsko perje predstavlja pomemben industrijski odpadek, ki vsakodnevno nastaja pri proizvodnji in predelavi perutninskega mesa. Zato potekajo številne raziskave možnosti njegove ponovne uporabe oz. razvoja novih materialov in produktov iz perutninskega perja. Uporaba keratina iz perja za izdelavo funkcionalnih filmov je ena od pomembnejših smeri razvoja na tem področju, saj je zamenjava izdelkov temelječih na petrokemičnih polimerih z organskimi eden od osnovnih ciljev razvoja materialov v prihodnje. Zaradi relativno nizkega povprečja molskih mas, imajo filmi iz čistega keratina slabše fizikalne lastnosti. Hitozan je polisaharid z dobro izraženimi protimikrobnimi lastnostmi. V zadnjih letih potekajo številne raziskave možnosti njegove uporabe pri razvoju funkcionalne embalaže. Cilj magistrske naloge je bil pripraviti filme iz mešanice hitozana in keratina iz perutninskega perja in jih analizirati ter ugotoviti področja potencialne uporabe (za različne materiale in izdelke). Rezultati analiz so pokazali, da imajo filmi iz mešanice hitozana in keratina ob dodatku glicerola antibakterijski učinek, so transparentni, trdnejši, fleksibilnejši in biorazgradljivi v primerjavi s filmi izdelanimi iz čistega keratina. Izboljšane lastnosti filmov izdelanih iz mešanic hitozana in keratina, odpirajo nove možnosti uporabe odpadnega perutninskega perja kot izhodnega vira keratina.
Ključne besede: Keratin iz piščančjega perja, hitozan, biopolimerni filmi, analizne metode, hidrofilnost/hidrofobnost.
Objavljeno: 29.10.2014; Ogledov: 946; Prenosov: 103
.pdf Celotno besedilo (3,21 MB)

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