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1.
Probiotic Lactobacillus paragasseri K7 nanofiber encapsulation using nozzle‑free electrospinning
Marjana Simonič, Špela Slapničar, Janja Trček, Bojana Bogovič Matijašić, Petra Mohar Lorbeg, Alenka Vesel, Lidija Fras Zemljič, Zdenka Peršin Fratnik, 2023, original scientific article

Abstract: Probiotics are live microorganisms that can have beneficial effects on humans. Encapsu lation offers them a better chance of survival. Therefore, nozzle-free electrospinning was introduced for their embedding in nanofibrous material. Probiotic Lactobacillus paragas seri K7 in lyophilized and fresh form, with and without inulin as prebiotic, was added to a polymer solution of sodium alginate (NaAlg) and polyethylene oxide (PEO). Conductiv ity, viscosity, pH, and surface tension were determined to define the optimal concentration and volume ratio for smooth electrospinning. The success of the formed nanoscale materials was examined by scanning electron microscope (SEM), while the entrapment of probiot ics in the nanofibrous mats was detected by attenuated total reflection—Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Sponta neous diffusion of bacteria from electrospun samples in PBS buffer pH 7.4 was studied by plate counting on MRS agar. By exposing polymer solutions containing L. paragasseri K7 and inulin to a high electric field, the nanofilm was formed on a polypropylene substrate, used as collecting material. When polymer solutions without inulin were used, the bead-like nanofibers may have become visible. The SEM results suggest that inulin, in addition to K7 strain, additionally lowers the conductivity of spinning macromolecular solution and hinders the nanofiber formation. The results of ATR-FTIR confirmed the presence of L. paragasseri K7 embedded in nanocomposites by the appearance of characteristic peaks. The samples containing the probiotic regardless of its form with inulin had similar surface composition, except that the sodium content was higher in the samples with fresh probiotic, probably due to greater and thus less easy embedding of the bacteria in NaAlg. Within 2 h, the largest amount of probiotic strain K7 was spontaneously released from the electrospun sample con taining the inulin and probiotic in freeze-dried form (44%), while the amount released from the nanofibrous sample, which also contained the inulin and probiotic in fresh form, was significantly lower (21%). These preliminary results demonstrate the potential of nozzle-free electrospinning technology for the development of probiotic delivery systems for short-term use, such as feminine hygiene materials (tampons, pads, napkins).
Keywords: probiotics, electrospinning, Lactobacillus paragasseri K7, encapsulation, release
Published in DKUM: 17.07.2024; Views: 59; Downloads: 6
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Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification
Saša Kaloper, Olivija Plohl, Sonja Smole Možina, Alenka Vesel, Vida Šimat, Lidija Fras Zemljič, 2024, original scientific article

Abstract: UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.
Keywords: chitosan, plant extracts, polypropylene, active packaging, surface characterization, bioactivity
Published in DKUM: 27.05.2024; Views: 178; Downloads: 3
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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, original scientific article

Abstract: 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).
Keywords: silicone implants, protein-repellent, antimicrobial, chitosan, lysine, bioactive coatings, adsorption, QCM-D
Published in DKUM: 15.04.2024; Views: 208; Downloads: 9
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Advance analysis of the obtained recycled materials from used disposable surgical masks
Alen Erjavec, Julija Volmajer Valh, Silvo Hribernik, Tjaša Kraševac Glaser, Lidija Fras Zemljič, Tomaž Vuherer, Branko Neral, Mihael Brunčko, 2024, original scientific article

Abstract: The production of personal protective equipment (PPE) has increased dramatically in recent years, not only because of the pandemic, but also because of stricter legislation in the field of Employee Protection. The increasing use of PPE, including disposable surgical masks (DSMs), is putting additional pressure on waste collectors. For this reason, it is necessary to find high-quality solutions for this type of waste. Mechanical recycling is still the most common type of recycling, but the recyclates are often classified as low-grade materials. For this reason, a detailed analysis of the recyclates is necessary. These data will help us to improve the properties and find the right end application that will increase the value of the materials. This work represents an extended analysis of the recyclates obtained from DSMs, manufactured from different polymers. Using surface and morphology tests, we have gained insights into the distribution of different polymers in polymer blends and their effects on mechanical and surface properties. It was found that the addition of ear loop material to the PP melt makes the material tougher. In the polymer blends obtained, PP and PA 6 form the surface (affects surface properties), while PU and PET are distributed mainly inside the injection-molded samples.
Keywords: mechanical recycling, disposable surgical mask, morphology, surface properties, mechanical properties, nonwoven materials, PPE
Published in DKUM: 09.04.2024; Views: 176; Downloads: 9
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Fabrication of poly(ethylene furanoate)/silver and titanium dioxide nanocomposites with improved thermal and antimicrobial properties
Johan Stanley, Eleftheria Xanthopoulou, Lidija Fras Zemljič, Panagiotis A. Klonos, Apostolos Kyritsis, Dimitra A. Lambropoulou, Dimitrios Bikiaris, 2024, original scientific article

Abstract: Poly(ethylene furanoate) (PEF)-based nanocomposites were fabricated with silver (Ag) and titanium dioxide (TiO2) nanoparticles by the in-situ polymerization method. The importance of this research work is to extend the usage of PEF-based nanocomposites with improved material properties. The PEF-Ag and PEF-TiO2 nanocomposites showed a significant improvement in color concentration, as determined by the color colorimeter. Scanning electron microscopy (SEM) photographs revealed the appearance of small aggregates on the surface of nanocomposites. According to crystallinity investigations, neat PEF and nanocomposites exhibit crystalline fraction between 0–6%, whereas annealed samples showed a degree of crystallinity value above 25%. Combining the structural and molecular dynamics observations from broadband dielectric spectroscopy (BDS) measurements found strong interactions between polymer chains and nanoparticles. Contact angle results exhibited a decrease in the wetting angle of nanocomposites compared to neat PEF. Finally, antimicrobial studies have been conducted, reporting a significant rise in inhibition of over 15% for both nanocomposite films against gram-positive and gram-negative bacteria. From the overall results, the synthesized PEF-based nanocomposites with enhanced thermal and antimicrobial properties may be optimized and utilized for the secondary packaging (unintended food-contact) materials.
Keywords: active agents, antimicrobial studies, biobased polymers, crystallinity, poly(ethylene 2, 5-furandicarboxylate)
Published in DKUM: 03.04.2024; Views: 172; Downloads: 7
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10.
Eco-finishing of cotton with chitosan and giant goldenrod (Solidago gigantea Aiton) aqueous extract for development of antioxidant and UV protective textiles
Sebastijan Šmid, Anja Verbič, Lidija Fras Zemljič, Marija Gorjanc, 2023, original scientific article

Abstract: Giant goldenrod (S. gigantea Aiton) is considered an invasive weed in Europe, Asia, Australia, and New Zealand. In this research, the untreated and chitosan-treated cotton fabrics were functionalized with goldenrod inflorescences aqueous extract, at room temperature and 95°C. Zeta potential of fabrics was determined as a function of pH and the results showed an increased isoelectric point from 2.50 to 5.25 and amphoteric character of the chitosan-treated sample. The antioxidant activity (AA) of extract and functionalized fabrics was determined using DPPH analysis, while color and ultraviolet protection factor (UPF) were determined spectroscopically before and after wash and lightfastness testing. The chitosan pretreatment and dyeing of cotton at higher temperature increased AA (from 41.19 ± 0.28 to 56.08 ± 0.25), UPF (from 33.05 to 51.59) and color strength (K/S) (from 1.74 to 2.21), providing dyed cotton with excellent UV protection and a free radical inhibition activity. The samples had good wash fastness in terms of color (ΔEab* < 1), but not in terms of UV protection (UPF value decreased after washing to 23.47). The overall lightfastness was good to excellent (the UPF values of chitosan and dyed samples did not change much after lightfastness test (UPF = 51.75).
Keywords: Goldenrod, invasive plant, eco-functionalisation, cotton, antioxidant activity, UV protection
Published in DKUM: 25.03.2024; Views: 213; Downloads: 9
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