Protein adsorption on various plasma-treated polyethylene terephthalate substrates

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

Prilagoditev lastnosti površine polietilen tereftalata (PET) z obdelavo v kisikovi plazmi

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.Površinske lastnosti polimera polietilentereftalata (PET) smo prilagodili specifičnim zahtevam po visoki hidrofilnosti z obdelavo v kisikovi plazmi. Stopnjo hidrofilnosti smo določali iz meritev stičnih kotov dveh kapljevin, in sicer vode in dijodometana. Vzorce smo obdelovali v kisikovi plazmi z gostoto ionov 5 x 1015/m[na]3 in gostoto nevtralnih kisikovih atomov 3 x 1021/m[na]3. Meritve stičnih kotov kapljic smo opravili takoj po plazemski obdelavi. Rezultati so pokazali hiter padec stičnega kota vodnih kapljic že v prvih sekundah plazemske obdelave. Podaljšan čas obdelave ni prinesel bistvenih sprememb. Stični koti dijodometana so ostali praktično nespremenjeni po prvih nekaj sekundah, z nadaljnjo obdelavo pa so začeli padati. Ugotovili smo, da disperzijska komponenta površinske energije počasi pada s plazemsko obdelavo, medtem ko polarna komponenta raste. Rezultate smo pojasnili s površinsko funkcionalizacijo polimera in povečano hrapavostjo površine

Covalent Binding of Heparin to Functionalized PET Materials for Improved Haemocompatibility

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

PRODUCTION AND CHARACTERIZATION OF CHITOSAN NANOPARTICLES FOR MEDICAL USE

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 učinkovitipresenetljivo 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.In this study, we tried to obtain nanoparticles from chitosan and sodium tripolyphosphate (TPP) using ionotropic gelation techniques. The obtained nanoparticles were characterized for positive charge using polyelectrolyte titrations, particle size using dynamic light scattering (DLS), zeta potential of particles using electrophoretic light scattering, as well as antibacterial activities of nanoparticles were examined using standard ASTM E 2149-01. The results show that an increase in the w/w ratio of chitosan/TPP triggers an increase in the amount of free amino groups (positive charge), hydrodynamic diameter, zeta potential and also intensifies the antimicrobial effect of nanoparticles. The results also show that the addition of stabilizer polyethylene glycol (PEG) does not have major effect on the hydrodynamic diameter of nanoparticles, however it decreases heterodispersity of the size as well zeta potential, thus making dispersions less stable. This leads to the conclusion that PEG is not an appropriate stabilizer for studied nanoparticles dispersions. Moreover, the antibacterial activity results suggests that the chitosan in nanoparticulate form display higher antibacterial activity against all tested microorganisms than the chitosan in the free form. Nano-formulation of chitosan enables optimal and controlled diffusion of chitosan into the cells of pathogen microorganisms, thus making their degradation more efficient

Haemostatic Response of Polyethylene Terephthalate Treated by Oxygen and Nitrogen Plasma Afterglows

Samples of polymer polyethylene terephthalate were coated with heparin and the haemostatic response has been determined by optical imaging of samples after incubation with fresh blood from a healthy donor. Prior to coating the samples were treated by neutral reactive particles of the oxygen or nitrogen plasma flowing afterglow. X-ray photoelectron spectroscopy analysis showed intensive functionalization of the polymer foils upon treatment with afterglows; however, the concentration of sulphur from heparin remained below the detection limit. The optical imaging showed densely distributed blood platelets in highly activated forms on untreated samples, whereas treatment with both afterglows revealed improved hemocompatibility. Best results were obtained for oxygen-functionalized polymer, whereas additional coating with heparin caused moderate loss of hemocompatibility, that was explained by deactivation of surface functional groups upon incubation with heparin

Modifikacija površine PET-polimera z dušikovo plazmo

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.Nizkotlačno, šibko ionizirano dušikovo plazmo smo uporabili za površinsko modifikacijo polimera polietilen tereftalat z dušikovimi funkcionalnimi skupinami. Plazmo smo vzbujali v brezelektrodni visokofrekvenčni plinski razelektritvi z generatorjem, ki deluje pri koristni moči okoli 200 W in osnovni frekvenci 27,12 MHz. Dušikove molekule, ki vstopijo v plinsko razelektritev, se vzbudijo v visoka vzbujena stanj, delno disociirajo in šibko ionizirajo. Transformacija plina v stanje plazme omogoča nastanek kemično reaktivnih delcev z veliko potencialno energijo, medtem ko ostane njihova kinetična energija blizu vrednosti, ki je značilna za plinske molekule pri sobni temperaturi. Velika kemijska reaktivnost dušikove plazme omogoča hitro funkcionalizacijo površine PET-polimera z dušikom bogatimi funkcionalnimi skupinami. Ta pojav smo spremljali z rentgensko fotoelektronsko spektroskopijo. Polimerni vzorci so postali hitro nasičeni z dušikom, iz česar je mogoče sklepati, da je funkcionalizacija omejena na zelo tanko plast prav ob površini vzorcev

Covalent binding of heparin to functionalized PET materials for improved haemocompatibility

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

Protein adsorption on various plasma-treated polyethylene-terephthalate substrates

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

Covalent Binding of Heparin to Functionalized PET Materials for Improved Haemocompatibility

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