1. Heterogeneous surface recombination of oxygen atoms on vertically oriented multilayer graphene sheets deposited on a metal substrateDomen Paul, Miran Mozetič, Gregor Primc, Alenka Vesel, Sandra Drev, Rok Zaplotnik, 2025, izvirni znanstveni članek Povzetek: The kinetics of surface recombination of neutral oxygen atoms on nanocarbon deposited on oxidized cobalt catalyst in inductively coupled radiofrequency plasma sustained in propane in the H-mode is presented. The coefficient was measured in the range of temperatures between 300 and 800 K and pressures between 40 and 200 Pa. A deep minimum in the coefficient at 0.03–0.06 was observed and explained by a deposition of a rather smooth carbon film on the cobalt catalyst. Prolonged deposition caused the growth of perpendicularly oriented multilayer graphene sheets with the distance between the neighboring sheets around 100 nm. The large aspect ratio of the gaps, whose depth reached several micrometers after deposition time over 100 s, caused the trapping of oxygen atoms and, thus, numerous collisions with the graphene-like surface, so the coefficient increased for over an order of magnitude. The maximum coefficient over 0.5 was observed at low pressures and elevated temperatures. The evolution of the recombination coefficient was explained by the peculiarities of the binding sites for oxygen atoms on graphene surfaces.
Ključne besede: carbon nanowalls, plasma, oxygen, chemical vapor deposition
Objavljeno v DiRROS: 17.06.2025; Ogledov: 39; Prenosov: 15
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2. Improved adhesion and biocompatibility of chitosan-coated super-hydrophilic PVC polymer substrates for urothelial cathetersAlenka Vesel, Helena Motaln, Miran Mozetič, Dane Lojen, Nina Recek, 2025, izvirni znanstveni članek Povzetek: Chitosan is a water-soluble polysaccharide with good adherence to negatively charged surfaces and reported antimicrobial and anti-inflammatory properties. Coating the surfaces of medical devices with chitosan is a promising strategy for harnessing these benefits. However, the surface properties of commercial polymers need to be altered to enable the bonding of thin chitosan films. In this study, the adhesion of chitosan onto plasma-treated polyvinyl chloride (PVC) and the metabolic activity of urothelial cells on chitosan-coated medical-grade PVC used for the synthesis of urinary catheters were evaluated. To improve the adhesion of chitosan onto the PVC catheters, PVC samples were made “super-hydrophilic”. PVC substrates were briefly treated with a powerful hydrogen plasma and weakly ionised oxygen plasma afterglow to obtain a chlorine-free surface film, which was rich in oxygen functional groups, followed by incubation of the plasma-treated substrates in an aqueous solution of chitosan. Then, urothelial RT4 cells were seeded on the treated and untreated PVC substrates, and their metabolic activity, confluency, and cell morphology were examined. X-ray photoelectron spectroscopy was used to measure the nitrogen concentration, which corresponded to the chitosan concentration on the substrate. The results showed that the substrates were uniformly covered by a thin layer of chitosan only on plasma-treated surfaces and not on untreated surfaces. Moreover, the chitosan coating provided a stimulated environment for cell adhesion and growth. In conclusion, the chitosan-coated super-hydrophilic PVC substrate shows potential to improve the overall performance and safety of medical devices such as urinary catheters.
Ključne besede: medical-grade PVC, chitosan coating, urinary catheter, urothelial cells, cytotoxicity, adhesion, biocompatibility
Objavljeno v DiRROS: 28.02.2025; Ogledov: 243; Prenosov: 139
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3. Vacuum ultraviolet radiation from gaseous plasma for destruction of water contaminantsMark Zver, Rok Zaplotnik, Miran Mozetič, Alenka Vesel, Arijana Filipić, David Dobnik, Belisa Alcantara Marinho, Gregor Primc, 2025, izvirni znanstveni članek Povzetek: Innovative technological solutions are needed for water decontamination to combat the diverse pollutants present in water systems, as no single optimal decontamination technique is appropriate for all circumstances. Vacuum-ultraviolet (V-UV) radiation is a source of energetic photons that break molecular bonds, producing a plethora of chemically reactive agents, most notably OH● radicals, which can cause the degradation of harmful pollutants. Low-pressure gaseous plasma is a good source of V-UV radiation; however, its application to liquid water poses challenges. We constructed an inductively coupled radiofrequency plasma to produce high-intensity V-UV radiation, which was applied to contaminated water via a V-UV-transparent window. Plasma was sustained in hydrogen, as it produces the highest V-UV intensity among all gases at selected discharge parameters. Bacteriophage MS2 was used as an indicator of microbial decontamination efficiency. Reactive oxygen and nitrogen species were measured at various treatment setups to quantify their effect on MS2 inactivation and elucidate the primary inactivation factors. At optimal conditions, the concentration of active virus dropped by 9 log10 PFU/mL in 60 s. The optimal experimental setup was then used to treat bacteria E. coli, S. aureus, antibiotic tetracycline, and synthetic dye methylene blue as representatives of other types of pollutants, all of which were effectively removed/degraded within 10 min of treatment. A comparison of energy efficiency (EEO) to other disinfection setups was made for bacteriophage inactivation. With a low EEO value, we showcase the potential of this technique for further work in this field.
Ključne besede: water treatment, radical
Objavljeno v DiRROS: 07.02.2025; Ogledov: 287; Prenosov: 149
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4. Improved adhesion of bacterial cellulose on plasma-treated cotton fabric for development of all-cellulose biocompositesLinda Ogrizek, Janja Lamovšek, Gregor Primc, Mirjam Leskovšek, Alenka Vesel, Miran Mozetič, Marija Gorjanc, 2024, izvirni znanstveni članek Ključne besede: all-cellulose biocomposite, bacterial cellulose, cotton, oxygen plasma, surface changes, adhesion
Objavljeno v DiRROS: 31.12.2024; Ogledov: 325; Prenosov: 198
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5. Antiviral respiratory masks with plasma-functionalized polypropylene textiles for optimal adsorption of antiviral substanceMark Zver, David Dobnik, Rok Zaplotnik, Miran Mozetič, Alenka Vesel, Arijana Filipić, Polona Kogovšek, Katja Fric, Alja Štern, Gregor Primc, 2024, izvirni znanstveni članek Povzetek: During the COVID-19 pandemic, face masks were the first line of defense against the spread of infection. However, infectious viruses may remain on medical textiles, potentially serving as an additional source of infection. Due to their chemical inertness, many textiles cannot be enhanced with antiviral functionalities. Through treatment with low-pressure gaseous plasma, we have activated the surface of a medical-grade melt-blown, non-woven polypropylene textile so that it can absorb sodium dodecyl sulfate, an antimicrobial surfactant. Within two hours of contact time, the functionalized textile has been able to inactivate over 7 log10 PFU mL−1 of bacteriophage phi6, a surrogate of enveloped viruses such as SARS-CoV-2, and it has retained its antiviral properties for over 100 days. The functionalized material has not disrupted facial mask filtration efficiency or breathability. In addition, the in vitro biocompatibility testing in accordance with ISO 10993-5 for testing of medical devices has demonstrated that the selected formulation causes no adverse effects on the mouse fibroblast cell line L-929. With the treatment processes that have been completed within seconds, the method seems to have great potential to produce antiviral textiles against future outbreaks.
Ključne besede: surgical face masks, plasma functionalization, antiviral materials, virus filtration, breathability
Objavljeno v DiRROS: 07.10.2024; Ogledov: 545; Prenosov: 527
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6. Cell proliferation on polyethylene terephthalate treated in plasma created in ▫$SO_2/O_2$▫ mixturesNina Recek, Matic Resnik, Rok Zaplotnik, Miran Mozetič, Helena Motaln, Tamara Lah Turnšek, Alenka Vesel, 2017, izvirni znanstveni članek Povzetek: Samples of polymer polyethylene terephthalate were exposed to a weakly ionized gaseous plasma to modify the polymer surface properties for better cell cultivation. The gases used for treatment were sulfur dioxide and oxygen of various partial pressures. Plasma was created by an electrodeless radio frequency discharge at a total pressure of 60 Pa. X-ray photoelectron spectroscopy showed weak functionalization of the samples’ surfaces with the sulfur, with a concentration around 2.5 at %, whereas the oxygen concentration remained at the level of untreated samples, except when the gas mixture with oxygen concentration above 90% was used. Atomic force microscopy revealed highly altered morphology of plasma-treated samples; however, at high oxygen partial pressures this morphology vanished. The samples were then incubated with human umbilical vein endothelial cells. Biological tests to determine endothelialization and possible toxicity of the plasma-treated polyethylene terephthalate samples were performed. Cell metabolic activity (MTT) and in vitro toxic effects of unknown compounds (TOX) were assayed to determine the biocompatibility of the treated substrates. The biocompatibility demonstrated a well-pronounced maximum versus gas composition which correlated well with development of the surface morphology.
Objavljeno v DiRROS: 25.07.2024; Ogledov: 553; Prenosov: 455
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7. Crystalloids vs. colloids for fluid optimization in patients undergoing brain tumour surgeryJasmina Markovič Božič, Božidar Visočnik, Polona Mušič, Iztok Potočnik, Alenka Spindler-Vesel, 2022, izvirni znanstveni članek Povzetek: Background. This randomised, double-blinded, single-centre study prospectively investigated the impact of goal directed therapy and fluid optimization with crystalloids or colloids on perioperative complications in patients un-dergoing brain tumour surgery. Main aim of the study was to investigate the impact of fluid type on postoperative complications.Patients and methods. 80 patients were allocated into two equal groups to be optimised with either crystalloids (n = 40) or colloids (n = 40). Invasive hemodynamic monitoring was used to adjust and maintain mean arterial pressure and cerebral oxygenation within the baseline values (± 20%) and stroke volume variation (SVV) ≤ 10%. Postoperative complications from different organ systems were monitored during the first 15 days after surgery. Hospital stay was also recorded.Results. Crystalloid group received significantly more fluids (p = 0.003) and phenylephrine (p = 0.02) compared to colloid group. This did not have any significant impact on perioperative complications and hospital stay, since no dif-ferences between groups were observed. Conclusions. Either crystalloids or colloids could be used for fluid optimization in brain tumour surgery. If protocol-ised perioperative haemodynamic management is used, the type of fluid does not have significant impact on the outcome.
Objavljeno v DiRROS: 25.07.2024; Ogledov: 582; Prenosov: 155
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8. Polysaccharide-based bilayer coatings for biofilm-inhibiting surfaces of medical devicesUrban Ajdnik, Thomas Luxbacher, Alenka Vesel, Alja Štern, Bojana Žegura, Janja Trček, Lidija Fras Zemljič, 2021, izvirni znanstveni članek Povzetek: Chitosan (Chi) and 77KS, a lysine-derived surfactant, form polyelectrolyte complexes that reverse their charge from positive to negative at higher 77KS concentrations, forming aggregates that have been embedded with amoxicillin (AMOX). Dispersion of this complex was used to coat polydimethylsiloxane (PDMS) films, with an additional layer of anionic and hydrophilic hyaluronic acid (HA) as an outer adsorbate layer to enhance protein repulsion in addition to antimicrobial activity by forming a highly hydrated layer in combination with steric hindrance. The formed polysaccharide-based bilayer on PDMS was analyzed by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and surface zeta (ζ)-potential. All measurements show the existence and adhesion of the two layers on the PDMS surface. Part of this study was devoted to understanding the underlying protein adsorption phenomena and identifying the mechanisms associated with biofouling. Thus, the adsorption of a mixed-protein solution (bovine serum albumin, fibrinogen, γ-globulin) on PDMS surfaces was studied to test the antifouling properties. The adsorption experiments were performed using a quartz crystal microbalance with dissipation monitoring (QCM-D) and showed improved antifouling properties by these polysaccharide-based bilayer coatings compared to a reference or for only one layer, i.e., the complex. This proves the benefit of a second hyaluronic acid layer. Microbiological and biocompatibility tests were also performed on real samples, i.e., silicone discs, showing the perspective of the prepared bilayer coating for medical devices such as prostheses, catheters (balloon angioplasty, intravascular), delivery systems (sheaths, implants), and stents.
Ključne besede: polysaccharides, chitosan, hyaluronic acid, anti-biofilm, silicone
Objavljeno v DiRROS: 19.07.2024; Ogledov: 778; Prenosov: 369
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9. Kinetics of surface wettability of aromatic polymers (PET, PS, PEEK, and PPS) upon treatment with neutral oxygen atoms from non-equilibrium oxygen plasmaAlenka Vesel, Rok Zaplotnik, Gregor Primc, Miran Mozetič, 2024, izvirni znanstveni članek Povzetek: The wettability of polymers is usually inadequate to ensure the appropriate spreading of polar liquids and thus enable the required adhesion of coatings. A standard ecologically benign method for increasing the polymer wettability is a brief treatment with a non-equilibrium plasma rich in reactive oxygen species and predominantly neutral oxygen atoms in the ground electronic state. The evolution of the surface wettability of selected aromatic polymers was investigated by water droplet contact angles deposited immediately after exposing polymer samples to fluxes of oxygen atoms between 3 × 1020 and 1 × 1023 m−2 s −1 . The treatment time varied between 0.01 and 1000 s. The wettability evolution versus the O-atom fluence for all aromatic polymers followed similar behavior regardless of the flux of O atoms or the type of polymer. In the range of fluences between approximately 5 × 1020 and 5 × 1023 m−2 , the water contact angle decreased exponentially with increasing fluence and dropped to 1/e of the initial value after receiving the fluence close to 5 × 1022 m−2
Objavljeno v DiRROS: 19.06.2024; Ogledov: 630; Prenosov: 246
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10. Evolution of surface functional groups and aromatic ring degradation upon treatment of polystyrene with hydroxyl radicalsAlenka Vesel, Rok Zaplotnik, Gregor Primc, Miran Mozetič, 2023, izvirni znanstveni članek Povzetek: The surface properties of hydrocarbon polymers are inadequate for numerous applications. Hence, they require alteration via functionalisation with desired functional groups. Hydroxyl groups are often preferred, since they enable appropriate polarity for the irreversible grafting of desired molecules. In this study, the surface kinetics resulting from the treatment of polystyrene with hydroxyl (OH) radicals from the gas phase was fundamentally investigated through a precisely-designed experiment. Polystyrene samples were exposed to various known fluences of OH radicals, and the evolution of surface functional groups versus the OH fluence was monitored using high-resolution X-ray photoelectron spectroscopy (XPS). The fluences of OH radicals varied between 1 × 1018 and 4 × 1023 m−2 in the process of finding a threshold fluence for the formation of specific groups. The surface concentration of carbonyl (C=O) groups could be measured using XPS at a fluence of approximately 5 × 1020 m−2. The C=O groups became measurable at a fluence of approximately 1.5 × 1021 m−2, and carboxyl (COOH)/ester groups at approximately 4 × 1021 m−2. As deduced from the XPS, a concentration of C=O groups at approximately 5 % occurred before the degradation of the aromatic ring. The formation of other oxygen-functional groups required opening of the aromatic ring. The results have been explained using a two-step process, considering available theories vis-a-vis initial stages in the functionalisation of PS with polar functional groups.
Ključne besede: polistiren, kinetika površinske funkcionalizacije, OH radikali, vpliv doze radikalov, časovni razvoj, polystyrene, surface functionalisation kinetics, OH radicals
Objavljeno v DiRROS: 09.11.2023; Ogledov: 1017; Prenosov: 352
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