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1.
Study of ▫$Ni/Y_2O_3/polylactic$▫ acid composite
Tilen Švarc, Matej Zadravec, Žiga Jelen, Peter Majerič, Blaž Kamenik, Rebeka Rudolf, 2023, izvirni znanstveni članek

Opis: This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.
Ključne besede: ultrasound spray pyrolysis, Ni/Y2O3, lyophilization, PLA, extrusion, injection moulding
Objavljeno v DKUM: 05.04.2024; Ogledov: 54; Prenosov: 2
.pdf Celotno besedilo (3,29 MB)
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2.
Razvoj au nanodelcev z metodo ultrazvočne razpršilne pirolize za detekcijo protiteles proti SARS-CoV-2 : doktorska disertacija
Žiga Jelen, 2023, doktorska disertacija

Opis: V doktorskem delu so predstavljene študije, eksperimentalno delo, tehnike karakterizacije, rezultati in analize, s pomočjo katerih smo potrdili hipotezo, da je možno Au nanodelce (AuND) pripravljene z metodo ultrazvočne razpršilne pirolize (USP), konjugirati s ciljnimi antigeni SARS-CoV-2 in rekombinantnim IgG, da bodo delovali v imunoserološkem hitrem testu na lateralni tok (LFIA), za potrditev potencialne prisotnosti protiteles proti virusu SARS-CoV-2. S ciljno izbranimi parametri (0,5 g/l Au, 5 l/min N2, 2,5 l/min H2) smo z USP sintetizirali AuND iz prekurzorja na osnovi zlatovega (III) klorida. AuND smo zbirali v steklenicah z demineralizirano vodo. Določili smo optimalne stabilizatorje in njihove koncentracije: 2,5 g/L PVP 40K ((C6H9NO)n) ter naknadno dodani 1 g/L trinatrijevega citrata (Na3C6H5O7) in saharoze (C12H22O11), da bi preprečili AuND aglomeracijo. Presevna elektronska mikroskopija AuND je pokazala, da so okrogli, s povprečno velikostjo okoli 50 nm in ozko velikostno porazdelitvijo, brez defektov in nizkim ZETA potencialom, 2,4 mV, pri pH 7,5. Za odstranitev vode iz suspenzije z AuND in stabilizatorji je bila uporabljena liofiliazcija, ki je bila izvedena pri naslednjih pogojih: zamrzovanje pri –40 °C, 4 h, atmosferski tlak; primarno sušenje pri +20 °C, 12 h, 1–4 Pa; sekundarno sušenje pri +30 °C, 33 h, 1–4 Pa. Nastali posušeni AuND so ohranili vse lastnosti, ki so potrebne za funkcijo oznak v hitrih LFIA testih: visoka površinska energija, površinska plazmonska resonanca in proste karboksilne skupine za konjugacijo. V nadaljevanju izvajanja eksperimentov smo, da bi potrdili doktorske hipoteze, izvedli raziskavo in optimizacijo konjugacije AuND z antigenom SARS-CoV-2, ki je bodičasti protein S1 (ak 1-681), in s protitelesi na zajčji IgG (RMG03). Za določitev poteka konjugacije AuND smo uporabili posredne (gelske elektroforeze, UV-Vis, preizkus delovanja) in direktne (XPS, SIMS) metode. Rezultati so pokazali, da se med našim postopkom konjugacije, v fazah čiščenja odstranimo večinski delež PVP in saharoze, ter s tem sprostimo proste karboksilne funkcionalne skupine citratnih ionov, ki so vezani na povšini AuND. Na teh prostih mestih lahko poteče konjugacija prek prostih -NH2 skupin na proteinih. Njihovo funkcionalnost smo ovrednotili z eksperimentalnimi testiranji lastno razvitega LFIA testa. Na osnovi tega smo postavili model in mehanizem konjugacije AuND, ki predpostavlja, da poteka konjugacija z antigeni oziroma protitelesi prek tvorbe peptidnih vezi med N-koncem proteina in prostimi karboksilnimi skupinami citratnega iona, ki je vezan na površino AuND prek svojih karboksilnih skupin. Za dodatno potrditev funkcionalizacije AuND z izbranimi biomolekulami smo v sklepnem delu doktorskega dela izvedli klinično študijo na pacientih UKC MB, ki je bila odobrena s sklepom KME RS št. 0120-148/2021/3. Rezultati študije so pokazali, da testi dosegajo visoko občutljivost (83 %) tako na vzorcih nosnega sluza kot na vzorcih seruma, slabšo specifičnost (66 % sluz, 74 % serum), visoko negativno napovedno vrednost (94 %) in slabšo pozitivno napovedno vrednost (38 % sluz, 45 % serum). S študijo smo potrdili delovanje AuND v funkciji oznak, saj so se testne in kontrolne linije v lastno razvitem LFIA hitrem testu obarvale.
Ključne besede: Nanodelci zlata, SARS-CoV-2 virus, stabilizacija, konjugacija, LFIA testi, karakterizacija
Objavljeno v DKUM: 28.03.2024; Ogledov: 72; Prenosov: 10
.pdf Celotno besedilo (5,61 MB)

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Recovery study of gold nanoparticle markers from lateral flow immunoassays
Tilen Švarc, Peter Majerič, Darja Feizpour, Žiga Jelen, Matej Zadravec, Timi Gomboc, Rebeka Rudolf, 2023, izvirni znanstveni članek

Opis: Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed that the recovery of gold nanoparticles from lateral flow immunoassays is possible, and the newly synthesised gold nanoparticles represent the possibility for incorporation into new products.
Ključne besede: gold nanoparticles, recovery, LFIA, ultrasonic spray pyrolysis, characterisation
Objavljeno v DKUM: 09.02.2024; Ogledov: 152; Prenosov: 14
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6.
Melting point of dried gold nanoparticles prepared with ultrasonic spray pyrolysis and lyophilisation
Žiga Jelen, Marcin Krajewski, Franc Zupanič, Peter Majerič, Tilen Švarc, Ivan Anžel, Jernej Ekar, Sz-Chian Liou, Jerzy Kubacki, Mateusz Tokarczyk, Rebeka Rudolf, 2023, izvirni znanstveni članek

Opis: A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C.
Ključne besede: gold nanoparticles, melting point, ultrasonic spray pyrolysis, characterisation
Objavljeno v DKUM: 08.12.2023; Ogledov: 242; Prenosov: 20
.pdf Celotno besedilo (2,83 MB)
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7.
Study of gold nanoparticles conjugated with SARS-CoV-2 S1 spike protein fragments
Žiga Jelen, Janez Kovač, Rebeka Rudolf, 2023, izvirni znanstveni članek

Opis: This study reports on the successful conjugation of SARS-CoV-2 S1 spike protein fragments with gold nanoparticles (AuNPs) that were synthesised with Ultrasonic Spray Pyrolysis (USP). This method enables the continuous synthesis of AuNPs with a high degree of purity, round shapes, and the formation of a surface that allows various modifications. The conjugation mechanism of USP synthesized AuNPs with SARS-CoV-2 S1 spike protein fragments was investigated. A gel electrophoresis experiment confirmed the successful conjugation of AuNPs with SARS-CoV-2 S1 fragments indirectly. X-ray Photoelectron Spectroscopy (XPS) analysis confirmed the presence of characteristic O1s and N1s peaks, which indicated that specific binding between AuNPs and SARS-CoV-2 S1 spike protein fragments takes place via a peptide bond formed with the citrate stabiliser. This bond is coordinated to the AuNP’s surface and the N-terminals of the protein, with the conjugate displaying the expected response within a prototype LFIA test. This study will help in better understanding the behaviour of AuNPs synthesised with USP and their potential use as sensors in colorimetric or electrochemical sensors and LFIA tests.
Ključne besede: gold nanoparticles, ultrasonic spray pyrolysis, conjugation, SARS-CoV-2 S1, characterisation
Objavljeno v DKUM: 07.12.2023; Ogledov: 231; Prenosov: 17
.pdf Celotno besedilo (3,41 MB)
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8.
Physicochemical properties of gold nanoparticles for skin care creams
Peter Majerič, Zorana Jović, Tilen Švarc, Žiga Jelen, Andrej Horvat, Djuro Koruga, Rebeka Rudolf, 2023, izvirni znanstveni članek

Opis: Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream’s complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV–vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs’ properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.
Ključne besede: gold nanoparticles, ultrasonic spray pyrolysis, freeze drying, characterization, creams
Objavljeno v DKUM: 19.04.2023; Ogledov: 560; Prenosov: 53
.pdf Celotno besedilo (5,34 MB)
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9.
Metoda dropshipping v spletni trgovini
Žiga Jelen, 2022, diplomsko delo

Opis: V diplomskem delu Metoda dropshipping v spletni trgovini, smo najprej opisali teorijo spletne trgovine in to podkrepili s primeri različnih vrst le teh. V nadaljevanju smo opisali postopek izdelave spletne trgovine in s pomočjo teorije ter vodiča, v katerem smo to po korakih prikazali na spletni platformi Shopify. Na koncu smo razložili, kako poiskati donosno nišo za vaše lastno podjetje in predstavili postopek izbire pravega dobavitelja, kateri vam bo pomagal pri uresničevanju vaših načrtov.
Ključne besede: metoda dropshipping, spletna trgovina, spletna prodaja
Objavljeno v DKUM: 11.11.2022; Ogledov: 503; Prenosov: 91
.pdf Celotno besedilo (1,93 MB)

10.
Oblikovanje pohodne plošče iz polimera
Primož Paulin, 2019, magistrsko delo

Opis: V magistrskem delu smo oblikovali pohodno ploščo iz polimera. Oblika je posledica robnih pogojev, materiala in optimiranja več podpornih vzorcev glede na količino potrebnega volumna in trdnostne lastnosti. Pri optimiranju smo upoštevali tudi tehnološka priporočila za oblikovanje brizganih izdelkov. Izvedli smo več geometrijskih rešitev ter jih numerično analizirali na tlačne in upogibne karakteristike. S končno rešitvijo, ki zadovoljuje vse konstrukcijske in tehnološke zahteve, smo dosegli sedemnajstodstotno zmanjšanje volumna kvadratnega metra plošč glede na konkurenco.
Ključne besede: SolidWorks, numerične simulacije, pohodne plošče, polimeri
Objavljeno v DKUM: 21.10.2019; Ogledov: 1580; Prenosov: 24  (1 glas)
.pdf Celotno besedilo (6,51 MB)

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