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Bioactive functional nanolayers of chitosan-lysine surfactant with single- and mixed-protein-repellent and antibiofilm properties for medical implants
Urban Ajdnik, Lidija Fras Zemljič, Olivija Plohl, Lourdes Pérez, Janja Trček, Matej Bračič, Tamilselvan Mohan, 2021, izvirni znanstveni članek

Opis: Medical implant-associated infections resulting from biofilm formation triggered by unspecific protein adsorption arethe prevailing cause of implant failure. However, implant surfaces rendered with multifunctional bioactive nanocoatings offer apromising alternative to prevent the initial attachment of bacteria and effectively interrupt biofilm formation. The need to researchand develop novel and stable bioactive nanocoatings for medical implants and a comprehensive understanding of their properties incontact with the complex biological environment are crucial. In this study, we developed an aqueous stable and crosslinker-freepolyelectrolyte−surfactant complex (PESC) composed of a renewable cationic polysaccharide, chitosan, a lysine-based anionicsurfactant (77KS), and an amphoteric antibiotic, amoxicillin, which is widely used to treat a number of infections caused by bacteria.We successfully introduced the PESC as bioactive functional nanolayers on the“model”and“real”polydimethylsiloxane (PDMS)surfaces under dynamic and ambient conditions. Besides their high stability and improved wettability, these uniformly depositednanolayers (thickness: 44−61 nm) with mixed charges exhibited strong repulsion toward three model blood proteins (serumalbumin,fibrinogen, andγ-globulin) and their competitive interactions in the mixture in real-time, as demonstrated using a quartzcrystal microbalance with dissipation (QCM-D). The functional nanolayers with a maximum negative zeta potential (ζ:−19 to−30mV at pH 7.4), water content (1628−1810 ng cm−2), and hydration (low viscosity and elastic shear modulus) correlated with themass, conformation, and interaction nature of proteins. In vitro antimicrobial activity testing under dynamic conditions showed thatthe charged nanolayers actively inhibited the growth of both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcusaureus) bacteria compared to unmodified PDMS. Given the ease of fabrication of multifunctional and charged biobased coatingswith simultaneous protein-repellent and antimicrobial activities, the limitations of individual approaches could be overcome leadingto a better and advanced design of various medical devices (e.g., catheters, prosthetics, and stents).
Ključne besede: silicone implants, protein-repellent, antimicrobial, chitosan, lysine, bioactive coatings, adsorption, QCM-D
Objavljeno v DKUM: 15.04.2024; Ogledov: 3; Prenosov: 0
.pdf Celotno besedilo (4,24 MB)
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Cellulose nanofibrils-reinforced pectin membranes for the adsorption of cationic dyes from a model solution
Alenka Ojstršek, Selestina Gorgieva, 2024, izvirni znanstveni članek

Opis: In the presented research, a facile, one-step method for the fabrication of cellulose nanofibrils/pectin (CNFs/PC) membranes is described, which were tested further for their ability to remove cationic dyes from the prepared model solutions. For this purpose, ten membranes were prepared with different quantities of CNFs and PC with/without citric acid (CA) or CaCl2 as mediated crosslinking agents, and they were characterised comprehensively in terms of their physical, chemical, and hydrophilic properties. All the prepared CNFs/PC membranes were hydrophilic with a Water Contact Angle (WCA) from 51.23◦ (without crosslinker) up to 78.30◦ (CaCl2 ) and swelling of up to 485% (without crosslinker), up to 437% (CaCl2 ) and up to 270% (CA). The stability of membranes was decreased with the increase in PC; thus, only four membranes (M1, M2, M3 and M5) were stable enough in water after 24 h, and these were additionally applied in the adsorption trials, using two structurally different cationic dyes, i.e., C.I. Basic Yellow 28 (BY28) and C.I. Basic Blue 22 (BB22), in four concentrations. The highest total surface charge of M3 (2.83 mmol/g) as compared to the other membranes influenced the maximal removal efficiency of both dyes, up to 37% (BY28) and up to 71% (BB22), depending on the initial dye concentration. The final characteristics of the membranes and, consequently, the dye’s absorption ability could be tuned easily by changing the ratio between the CNFs and PC, as well as the type and amount of crosslinker.
Ključne besede: cellulose nanofibrils, pectin, cationic dyes, adsorption, dye removal
Objavljeno v DKUM: 12.03.2024; Ogledov: 106; Prenosov: 4
.pdf Celotno besedilo (5,33 MB)
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Polyvinylpyrrolidone-stabilised gold nanoparticle coatings inhibit blood protein adsorption
Hanuma Reddy Tiyyagura, Matej Bračič, Rebeka Rudolf, 2024, izvirni znanstveni članek

Opis: In this work, the ability of polyvinylpyrrolidone (PVP)-stabilised gold nanoparticle (AuNP) coatings to inhibit blood protein adsorption was evaluated by studying timeresolved solid–liquid interactions of the coatings with the model blood protein bovine serum albumin (BSA). Inhibiting unspecific blood protein adsorption is of crucial importance for blood-contacting implant devices, e.g. vascular grafts, stents, artificial joints, and others, as a preventive strategy for bacterial biofilm formation. A quartz crystal microbalance was used in this work to coat the AuNPs on piezoelectric sensors and to follow time-resolved solid–liquid interactions with the proteins. The AuNP coatings were evaluated for their wettability by contact angle measurements, their surface morphology by lightand atomic force microscopy, and their chemical composition by energy-dispersive X-ray spectroscopy. Results revealed a homogeneous distribution of AuNPs on the sensor surface with a dry mass coverage of 3.37 ± 1.46 µg/cm2 and a contact angle of 25.2 ± 1.1°. Solid–liquid interaction studies by quartz crystal microbalance showed a high repellence of BSA from the PVP-stabilised AuNP coatings and the importance of the PVP in the mechanism of repellence. Furthermore, the conformation of the polymer on the coatings as well as its viscoelastic properties were revealed. Finally, the activated partial thrombin time test and fibrinogen adsorption studies revealed that the AuNPs do not accelerate blood coagulation and can partially inhibit the adhesion of fibrinogen, which is a crucial factor in the common blood coagulation cascade. Such AuNPs have the potential to be used in blood-contact medical applications.
Ključne besede: gold nanoparticles, ultrasonic spray pyrolysis, haemocompatibility, protein adsorption, quartz crystal microbalance
Objavljeno v DKUM: 30.01.2024; Ogledov: 179; Prenosov: 11
.pdf Celotno besedilo (4,61 MB)
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RFCS project methenergy+ methane recovery and harnessing for energy and chemical uses at coal mine sites
Matjaž Kamenik, Janez Rošer, Salvador Ordonez, 2022, izvirni znanstveni članek

Opis: Ventilation Air Methane emissions (VAM) from coal mines lead to environmental concern because of their high global warming potential and the loss of methane (CH4) resources. How to tackle methane harnessing and its use was studied and analysed in the scope of the RCFS project, which was performed from 2017 till 2020, and coordinated by the University of Oviedo in Spain within the scope of an international consortium of eleven entities from Poland, Spain, the United Kingdom, Czechia, Greece, Slovenia and Sweden, combining universities, research institutions and industry (mostly Polish mines and the Slovenian Velenje mine). The main challenge tackled in the project was the use of methane released from both operating and abandoned mines, which is an environmental and safety hazard and also a useful source of energy. Therefore, the effective extraction of methane, its enrichment, purification, separation, thermal or chemical upgrading, and its use, considering coal mine site specifics, was assessed. Despite good operational results, after in-depth economic analysis of the integration, CAPEX and OPEX calculation, there turned out to be a high economic dependence on the cost of adsorbent, since adsorption was the most promising technology for concentrating the methane in these emissions. Therefore, the economic viability depends on the development of materials that meet a minimum cost and performance. Within the scope of the project, a lot of activities were carried out in order to widen and exploit the results.
Ključne besede: ventilation air methane, abandoned mine methane, coalmining, methane recovery, harnessing, thermal upgrading, chemical upgrading, adsorption-based technologies, materials development, thermal regenerative oxidizers, catalytic regenerative oxidizers, methanol, greenhouse gases
Objavljeno v DKUM: 30.10.2023; Ogledov: 361; Prenosov: 5
.pdf Celotno besedilo (1,30 MB)
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Izraba obnovljivih virov energije za proizvodnjo sintetičnega metana : magistrsko delo
Klemen Rola, 2023, magistrsko delo

Opis: Magistrsko delo predstavlja proizvodnjo sintetičnega metana, ki bi lahko nadomestil zemeljski plin. Za reakcijo metanacije je potreben vodik. Ta se v delu proizvede z elektrolizo, ki jo poganja elektrika obnovljivih virov. Proces je namenjen sezonskemu shranjevanju energije, kjer se viški elektrike poletnega časa shranijo v obliki metana za obdobja primanjkljajev energije. V ta namen, smo s programom Aspen Plus najprej izvedli poenostavljeno enostopenjsko simulacijo metanacije CO2. Pretok CO2 je baziral na ocenjeni sestavi in pretoku bioplina iz realne bioplinarne. Upoštevali smo, da se tudi celoten bioplin lahko uporabi kot reaktant. Enostopenjska metanacija je služila predvsem za razumevanje obnašanja reakcije. Ker z eno reakcijsko stopnjo v produktu nismo dosegali dovolj visokega deleža metana, smo izvedli še poenostavljeno dvostopenjsko metanacijo. Določili smo pogoje, pri katerih bi dosegali dovolj visoko vsebnost metana, da bi produkt bil primeren za injiciranje v plinovode. Za primer, ko se bioplin ne uporabi v metanaciji, smo v programu Aspen Adsorption izvedli dinamični simulaciji nadgradnje bioplina z adsorpcijskimi tehnikami. Mešanico bioplina smo z nizkimi izgubami metana uspešno nadgradili do biometana, s sestavo, ki je primerna za injiciranje v plinovode. S pomočjo rezultatov začetne dvostopenjske simulacije smo razvili delno integrirano shemo s sočasno proizvodnjo elektrike, ki je sposobna proizvesti od 1 t/h do 1,3 t/h sintetičnega metana. Pri tem je v procesu možna uporaba čistega CO2, ali pa celo mešanice bioplina in CO2. Proizveden sintetični metan je vseboval več kot 97 mol.% CH4, po dehidraciji s silikagelom, pa smo zagotovili sestavo, ki je primerna za injiciranje v plinovode mnogih Evropskih držav.
Ključne besede: Sintetični metan, bioplin, metanacija CO2, adsorpcija, Aspen Plus, Aspen Adsorption
Objavljeno v DKUM: 14.09.2023; Ogledov: 391; Prenosov: 0
.pdf Celotno besedilo (13,41 MB)

Assessment of the Capability of Magnetic Nanoparticles to Recover Neodymium Ions from Aqueous Solution
Ana Ambrož, Irena Ban, Thomas Luxbacher, 2022, izvirni znanstveni članek

Opis: Magnetic nanoparticles (MNPs) have received increasing attention for various applications due to their fast synthesis, versatile functionalization, and recyclability by the application of a magnetic field. The high surface-to-volume ratio of MNP dispersions has suggested their use as an adsorbent for the removal of heavy metal ions. We investigated the applicability of MNPs composed of a maghemite core surrounded by a silica shell functionalized with aminopropylsilane, γ-Fe2O3-NH4OH@SiO2(APTMS), for the removal of neodymium ions (Nd3+) from aqueous solution. The MNPs were characterized for their size, composition, surface functionality and charge. Despite of the promising properties of MNPs, their removal from the aqueous dispersion with an external magnet was not sufficient to reliably quantify the adsorption of Nd3+ by UV-Vis spectroscopy.
Ključne besede: rare earth elements, maghemite, nanoparticles, UV-Vis spectroscopy, adsorption
Objavljeno v DKUM: 08.08.2023; Ogledov: 302; Prenosov: 20
.pdf Celotno besedilo (829,86 KB)
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Protein-repellent surface coatings made of polycaprolactone-polysaccharide blends : master's thesis
Jan Marko, 2022, magistrsko delo

Opis: This work is focused on surface characterization and fibrinogen adsorption studies of polycaprolactone/chondroitin sulfate (tetrabutylammonium hydroxide) blends. Mixed polymer solutions were spin-coated to form two-phase thin films, which exhibit various patterns depending on the mass ratio of the spin-coating solution. Stability in the aqueous media, however, presents an uncertainty, due to the solubility of chondroitin sulfate (tetrabutylammonium hydroxide) in water. In spite of this, it is observed that the introduction of chondroitin sulfate (tetrabutylammonium hydroxide) in the film increases the repulsion of fibrinogen. Two methods frequently used for polymer characterization, mass determination using Quartz Crystal Microbalance with Dissipation monitoring and the zeta potential measurement, were found to be comparable techniques when studying protein adsorption and complementary techniques when analysing the stability of thin films.
Ključne besede: polycaprolactone, chondroitin sulfate, zeta potential, QCM-D, fibrinogen, adsorption
Objavljeno v DKUM: 15.07.2022; Ogledov: 518; Prenosov: 38
.pdf Celotno besedilo (5,10 MB)

Removal of neodymium ions from aqueous solution by magnetic nanoparticles : magistrsko delo
Ana Ambrož, 2021, magistrsko delo

Opis: This work is focused on the synthesis and characterization of surface-functionalized γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles, their applications, and performance for Nd3+ removal from aqueous solutions, with an emphasis on the characterization of MNPs and Nd(NO3)3•6H2O. The γ-Fe2O3 nanoparticles were obtained by the co-precipitation method, stabilized with ammonia solution, and functionalized by SiO2 and APTMS. Neodymium nitrate hexahydrate (Nd(NO3)3•6H2O) used in aqueous solution was synthesised from neodymium oxide (Nd2O3) powder. The thermal behaviour and stability of the magnetic nanoparticles and Nd(NO3)3•6H2O was studied with thermogravimetric analysis (TGA) in O2, N2, and air atmosphere. Transmission electron microscopy (TEM) images were obtained in order to analyse the particle morphology and measure the size distribution of the nanoparticles. The hydrodynamic diameter of particles and the zeta potential were measured to determine the stability of particles in the solution. ATR-FTIR spectroscopy was used to confirm the functionalization of the magnetic nanoparticles and the adsorption of Nd3+ ions. The effect of the REE adsorption on the MNPs was studied by comparing the sample’s UV-Vis absorption spectra. The laboratory testing and analysis of the results indicate promising applications for the removal of the REE from aqueous solutions with magnetic nanoparticles. However, the coating of the MNP core by SiO2(APTMS) is inefficient for the removal of Nd3+ ions.
Ključne besede: Magnetic nanoparticles, Rare earth elements, Neodymium, Adsorption, Zeta potential, UV-Vis spectroscopy
Objavljeno v DKUM: 03.05.2021; Ogledov: 1300; Prenosov: 152
.pdf Celotno besedilo (2,51 MB)

Modificiranje zeolitov za izboljšanje selektivnosti pri separaciji plinov : diplomsko delo univerzitetnega študijskega programa I. stopnje
Mitja Čuš, 2019, diplomsko delo

Opis: Diplomsko delo je potekalo v sodelovanju s podjetjem Silkem d.o.o v njihovem raziskovalnem laboratoriju. Delo zajema modificiranje zeolitov z namenom, da izboljšamo separacijo plinov, natančneje kisika in dušika iz atmosferskega zraka. Namen diplomskega dela je ugotoviti in laboratorijsko preveriti kateri zeoliti so primerni za molekularna sita za namene adsorpcije pod povišanim tlakom in pod podtlakom. Zeolit Na13X smo modificirali z ionsko izmenjavo s CaCl2 in s tem dobili zeolit Ca13X. Molekularna sita so temeljnega pomena pri separaciji zraka s procesom adsorpcije pod povišanim tlakom (PSA-pressure swing adsorption) in adsropcije pod podtlakom (VPSA-vacuum pressure swing adsorption). PSA in VPSA sta procesa pridobivanja oziroma bogatenja kisika, ki sta energetsko manj potratna kot pridobivanje kisika z uveljavljenimi metodami kot je to utekočinjanje zraka (ohlajevanje zraka), med seboj pa se razlikujeta po obratovalnem tlaku. Zeolitna molekularna sita se uporabljajo za proizvodnjo medicinskega kisika v kisikovih generatorjih. Raziskovali smo kako vplivajo struktura zeolita, obratovalni tlak, višina kolone in zadrževalni čas na učinkovitost adsorpcije. Velja, da je separacija zraka učinkovitejša z večjo aktivno površino zeolita, separacijski učinek pa višji z višjim obratovalnim tlakom. Višja kot je kolona, daljši je zadrževalni čas, z večanje višine pa je tudi večja količina polnila, kar pomeni večjo aktivno površino in s tem boljšo adsorpcijo. Modifikacija zeolita Na13X je potekala tako, da smo omenjen zeolit dodali v raztopino CaCl2 in šaržo intenzivno mešali 48 ur. Šaržo smo nato prefiltrirali in posušili. Ca13X smo granulirali v laboratoriju z Eirichovim granulatorju. Zeolitu Ca13X smo dodali deionizirano vodo in vezivo atapulgit ter granulirali do velikosti, primerne za nasutje. Pred uporabo zeolita smo granule kalcinirali pri 500 °C, saj s kalcininacijo dosežemo aktivacijo zeolita in izparevanje vlage ter drugih adsorbiranih snovi. Z aktiviranimi zeoliti smo napolnili kolono in merili koncentracijo kisika na izhodu s kisikovim merilcem. Ugotovili smo, da je ionsko izmenjan kalcijev zeolit Ca13X bolj primeren za molekularno sito pri separaciji plinov iz zraka. Visoke koncentracije kisika doseže tudi zeolit 5A, vendar je za procesa PSA in VPSA bolj primeren kalcijev zeolit Ca13X.
Ključne besede: ionska izmenjava, zeolit 13X, kalcijev zeolit 13X, adsorpcija, Pressure swing adsorption, Vacuum pressure swing adsorption, separacija zraka.
Objavljeno v DKUM: 10.10.2019; Ogledov: 1461; Prenosov: 171
.pdf Celotno besedilo (1,24 MB)

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