1. Sustainable cyclodextrin modification and alginate incorporation: viscoelastic properties, release behavior, and morphology in bulk and microbead hydrogel systemsMaja Čič, Nejc Petek, Iztok Dogša, Andrijana Damjanović, Boštjan Genorio, Nataša Poklar Ulrih, Ilja Gasan Osojnik Črnivec, 2025, original scientific article Abstract: Incorporating cyclodextrins (CDs) into ionically crosslinked polysaccharide matrices offers a promising strategy for developing well-defined, safe-by-design and biocompatible carrier systems with tunable rheological properties. In this study, β-cyclodextrin (β-CD) was functionalized with citric acid (CDC) and maleic anhydride (CDM) using solvent-free synthesis to improve compatibility with alginate hydrogels. The modified CDs were characterized by FTIR, 1H NMR, DLS, zeta potential, and MS, confirming successful esterification (4.0 and 3.4 –OH substitution for CDC and CDM, respectively) and stable aqueous dispersion. Rheological measurements showed that native CD accelerated gelation (within approximately 30 s), while CDC and CDM delayed crosslinking (by 2 to 13 min) and reduced gel strength, narrowing the linear viscoelastic range to 0.015–0.089% strain due to competition between polycarboxylated CDs and alginate chains for Ca2+ ions. Vibrational prilling produced alginate microbeads with diameters of 800–1000 µm and a simultaneous increase in size and CD concentration. Hydrogels demonstrated high CD retention (>80% after 28 h) and slightly greater release of CDC and CDM than native CD. Overall, solvent-free modification of CDs with citric and maleic acids provides a sustainable approach to tailoring the gelation kinetics, viscoelasticity, and release behavior of alginate-based hydrogels, offering a versatile, food- and health-compliant platform for controlled delivery of bioactive compounds.
Keywords: cyclodextrin, alginate, dry modification, solvent-free, hydrogels, viscoelasticity, rheometry, microcarrier design
Published in DiRROS: 25.11.2025; Views: 861; Downloads: 152
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2. Nano spray-dried particles of in-situ crosslinked alginate and their toxicological characterisationJaka Levanič, Ilja Gasan Osojnik Črnivec, Iza Rozman, Mihaela Skrt, Alja Štern, Bojana Žegura, Nataša Poklar Ulrih, 2024, original scientific article Abstract: The feasibility and technical capacity for producing crosslinked sub-micron gels with a nano spray-dryer were studied with variable pH systems incorporating alginate, pectin, and pullulan. The obtained powders were characterized for their morphology, particle size distribution, and their toxicological safety profile using genotoxicity and cytotoxicity assays. Additionally, quercetin was added to the encapsulation system to study the potential of the system to encapsulate this material. The produced powders exhibited morphologies and particle size distributions characteristic for nano spray-drying. The addition of pullulan and pectin to the feed solutions resulted in a particle size increase, with crosslinked alginate particles having a mean value of 1.43 μm, while particles with added pectin and pullulan had a mean particle size of 1.70 and 1.75 μm, respectively. The inclusion of quercetin proved to be problematic with this encapsulation system. Extremely high degradation rates and extremely low encapsulation efficiencies were observed due to the alkaline pH (~10) of the system that is needed to keep the feed dispersion in a liquid state and prevent premature crosslinking of the alginate. Although pectin and pullulan provided some protection for quercetin in the alkaline dispersion, the absolute quercetin content in the final product remained very low, with a maximum achieved encapsulation efficiency of 2.06 %. The safety profile of most produced powders was favourable, as they did not exhibit any significant cytotoxic and genotoxic activity in the HepG2 cell line, except in the case of Alginate/Pullulan which showed a 43 % decrease in cell viability at 500 μg/mL. Samples where quercetin was added did not show any increased toxicological effect.
Keywords: alginate, polysaccharides, crosslinking, nano spray drying, toxicological evaluation
Published in DiRROS: 08.05.2025; Views: 853; Downloads: 526
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3. Biocompatible polyelectrolyte multilayers with copper oxide and zinc oxide nanoparticles for inhibiting bacterial growthNives Matijaković Mlinarić, Stefanie Altenried, Atiđa Selmani, Juraj Nikolić, Aleksander Učakar, Anamarija Zore, Anže Abram, Sandro Lehner, Andrijana Sever Škapin, Monika Kušter, Eva Roblegg, Davor Kovačević, Qun Ren, Klemen Bohinc, 2024, original scientific article Abstract: The prevalence of bacterial infections presents a significant challenge in the medical field, demanding effective strategies to impede bacterial adhesion and growth on various surfaces. The conducted study investigates the efficacy of polyelectrolyte multilayers─comprising poly(allylamine hydrochloride) (PAH) and alginate (ALG)─embedded with zinc oxide (ZnO) and copper oxide (CuO) nanoparticles (NPs) to inhibit bacterial adhesion on stainless-steel surfaces. Surface characterization involved zeta potential, contact angle, and roughness assessments. The effect of NP composition, size, and morphology in conjunction with polycation or polyanion terminating multilayers was evaluated against planktonic and surface-adhered Escherichia coli (E. coli) cells. Surfaces with the positively charged PAH-terminating multilayer displayed higher water contact angles (≈ 63°) than the negatively charged ALG-terminating multilayers (≈ 45°). Multilayers containing ZnO NPs showed a significant inhibition of planktonic E. coli growth, >99%. Moreover, complete growth inhibition of surface-adhered E. coli was achieved for multilayers containing both ZnO and CuO. Due to their larger specific surface area, rod-like ZnO NPs displayed higher antibacterial activity. The samples with ALG as the terminating layer showed more substantial antibacterial properties than samples with PAH as the terminating layer. Biocompatibility tests on immortalized human keratinocyte cells revealed good compatibility with multilayers incorporating NPs. In summary, this study underscores the potential of ZnO and CuO NPs within PAH/ALG multilayers for antibacterial applications without compromising their cytocompatibility.
Keywords: polyelectrolyte multilayers, alginate, poly(allylamine hydrochloride), CuO, ZnO, nanoparticles, Escherichia coli
Published in DiRROS: 06.06.2024; Views: 1246; Downloads: 1109
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