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Protein adsorption on various plasma-treated polyethylene-terephthalate substrates
Nina Recek, Morana Jaganjac, Metod Kolar, Lidija Milković, Miran Mozetič, Karin Stana-Kleinschek, Alenka Vesel, 2013, original scientific article

Abstract: Protein adhesion and cell response to plasma-treated polymer surfaces were studied. The polymer polyethylene terephthalate (PET) was treated in either an oxygen plasma to make the surface hydrophilic, or a tetrafluoromethane CF4 plasma to make the surface hydrophobic. The plasma source was radiofrequency (RF) discharge. The adsorption of albumin and other proteins from a cell-culture medium onto these surfaces was studied using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The cellular response to plasma-treated surfaces was studied as well using an MTT assay and scanning electron microscopy (SEM). The fastest adsorption rate was found on the hydrophilic oxygen plasma-treated sample, and the lowest was found on the pristine untreated sample. Additionally, the amount of adsorbed proteins was higher for the oxygen-plasma-treated surface, and the adsorbed layer was more viscoelastic. In addition, cell adhesion studies support this finding because the best cell adhesion was observed on oxygen-plasma-treated substrates.
Keywords: oxygen and fluorine plasma treatment, polymer surface modification, protein adsorption, cell adhesion, quartz crystal microbalance, QCM
Published: 22.06.2017; Views: 512; Downloads: 285
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Covalent binding of heparin to functionalized PET materials for improved haemocompatibility
Metod Kolar, Miran Mozetič, Karin Stana-Kleinschek, Mirjam Fröhlich, Boris Turk, Alenka Vesel, 2015, original scientific article

Abstract: The hemocompatibility of vascular grafts made from poly(ethylene terephthalate) (PET) is insufficient due to the rapid adhesion and activation of blood platelets that occur upon incubation with whole blood. PET polymer was treated with NHx radicals created by passing ammonia through gaseous plasma formed by a microwave discharge, which allowed for functionalization with amino groups. X-ray photoelectron spectroscopy characterization using derivatization with 4-chlorobenzaldehyde indicated that approximately 4% of the –NH2 groups were associated with the PET surface after treatment with the gaseous radicals. The functionalized polymers were coated with an ultra-thin layer of heparin and incubated with fresh blood. The free-hemoglobin technique, which is based on the haemolysis of erythrocytes, indicated improved hemocompatibility, which was confirmed by imaging the samples using confocal optical microscopy. A significant decrease in number of adhered platelets was observed on such samples. Proliferation of both human umbilical vein endothelial cells and human microvascular endothelial cells was enhanced on treated polymers, especially after a few hours of cell seeding. Thus, the technique represents a promising substitute for wet-chemical modification of PET materials prior to coating with heparin.
Keywords: poly(ethylene terephthalate), vascular graft, biocompatibility, heparin, plasma, functionalization, haemolysis, platelet adhesion, endothelization
Published: 21.06.2017; Views: 563; Downloads: 265
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Modification of PET-polymer surface by nitrogen plasma
Rok Zaplotnik, Metod Kolar, Aleš Doliška, Karin Stana-Kleinschek, 2011, original scientific article

Abstract: Low pressure weakly nitrogen plasma was applied for incorporation of nitrogen-containing functional groups onto poly(ethylene terephthalate) - PET polymer. Nitrogen plasma was created in an electrode-less radiofrequency discharge at the nominal power of 200 W and the frequency of 27.12 MHz. Nitrogen molecules entered the discharge region were highly excited, partially dissociated and weakly ionized. Transformation into the state of plasma allowed for creation of chemically reactive particles with a high potential energy while the kinetic energy remained close to the value typical for room temperature. The chemical reactivity allowed for rapid functionalization with nitrogen-rich functional groups. The appearance of these groups was monitored by X-ray photoelectron spectroscopy - XPS. The polymer surface was quickly saturated with nitrogen indicating that the modification was limited to an extremely thin surface film.
Keywords: poly(ethylene terephthalate), nitrogen plasma, surface modification, functional groups, X-ray photoelectron spectroscopy
Published: 17.03.2017; Views: 517; Downloads: 79
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Tuning of poly(ethylene terephtalate)(PET)surface properties by oxygen plasma treatment
Aleš Doliška, Metod Kolar, 2011, original scientific article

Abstract: Modification of surface properties of poly(ethyleneterephtalate) (PET) thin films by treatment with weakly ionized oxygen plasma was studied by contact angles of water and diiodomethane (DIM) drops. Samples were exposed to oxygen plasma with the ion density of 5 x 1015/m[sup]3 and the neutral oxygen atom density of 3 x 1021/m[sup]3. Just after the treatment they were characterized by contact angle measurements. Results showed a quick decrease of the water contact angle in the first few seconds of plasma treatment, while prolonged treatment did not cause any substantiated modification. The contact angles of DIM, on the other hand, remained rather constant for the first several secondsof plasma treatment, and increased after prolonged treatment. It was found that the dispersion component of the surface free energy decreased with increasing treatment time, while the polar component increased with treatment time. The results were explained by surface functionalization as well as by roughness effects.
Keywords: poly(ethylene terephtalante), PET, oxygen plasma, contact angle, hydrophilic, functionalization
Published: 01.06.2012; Views: 1409; Downloads: 42
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Metod Kolar, 2010, undergraduate thesis

Abstract: Namen diplomskega dela je bil izdelati in okarakterizirati nanodelce, ki nastanejo s tehniko ionotropnega geliranja iz hitozana in natrijevega tripolifosfata (TPP). Nanodelcem smo določili naboj s polielektrolitsko titracijo, velikosti z metodo dinamičnega sipanja laserske svetlobe (DLS) in zeta potencial z elektroforetičnim sipanjem svetlobe ter protimikrobni učinek po standardu ASTM E 2149-01. Preverili smo vpliv različnih masnih razmerij reaktantov in vpliv dodatka stabilizatorja polietilen glikola (PEG) na lastnosti disperzije nanodelcev. Ugotovili smo, da se s povečanjem masnega razmerja hitozan/TPP povečujejo: množina prostih amino skupin in s tem naboj, hidrodinamski radij ter zeta potencial, kakor tudi protimikrobni učinek na nekatere testirane mikroorganizme. Ugotovili smo, da dodatek stabilizatorja polietilen glikola (PEG) k disperziji nanodelcev ne vpliva izrazito na spremembe hidrodinamskega premera nanodelcev, medtem ko znižuje heterodisperznost velikosti nanodelcev in zeta potencial, in tako naredi disperzije manj stabilne. Iz tega sklepamo, da PEG proučevanih molekulskih mas ni najustreznejši stabilizator za disperzije hitozanskih nanodelcev. Ugotovili smo, da so nanodelci protimikrobno učinkoviti; presenetljivo celo bolje inhibirajo rast mikroorganizmov kot sama raztopina hitozana. Nano-formulacija hitozana omogoča njegovo optimalno in nadzorovano difuzijo v celice patogenih mikroorganizomov in je tako njihova degradacije še učinkovitejša.
Keywords: hitozan, nanodelci, TPP, ionotropno geliranje, ionsko geliranje, protimikrobna učinkovitost
Published: 30.09.2010; Views: 2949; Downloads: 384
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