1. Explicit microrelief-controlled decoupling of initial aerobic decay and leaching (in hummocks) and anaerobic decay (in hollows) in surface layers of a Sphagnum-dominated peatlandMarta Pérez-Rodríguez, A. Alten, Miloš Miler, J. Kaal, 2025, original scientific article Abstract: Understanding decay processes in peat deposits is fundamental for predicting their role as sources or sinks of atmospheric carbon in a changing environment. It is known that the distribution of microhabitats –hummock, lawn and hollow– within peatlands affects organic matter quality and degradation, but microtopography-dependent carbon dynamics are poorly understood on the molecular level. We studied early decomposition across microtopography levels through analyses of superficial moss cores from a Sphagnum-dominated ombrotrophic peatland in Central Germany, and a 400-day incubation experiment, using analytical pyrolysis. Interpretations were aided by analysis of living vegetation and a deep peat core as reference. Stable and labile pools of polysaccharides dominated the pyrolyzates and played a crucial role in decay dynamics. Two distinct degradation processes emerged: 1) anaerobic decay, characterized by loss of polysaccharides and selective preservation of lignin and aliphatic OM; and 2) leaching of labile phenolic compounds (including sphagnum acid) and free carbohydrates with concomitant initial aerobic degradation and selective preservation of structural polysaccharides. The relative importance of these initial decay processes is spatially dependent; anaerobic decay was detectable in only some of the more evolved hollow layers, while aerobic degradation and leaching dominated in hummocks. Sphagnum acid’s molecular markers appeared useful tracers of early decay as it probably has a leaching-sensitive component in hyaline cells (corroborated by SEM micrographs) that is lost rapidly from hummocks, but not from hollows. Hence, the occurrence of sphagnum acid in peat cores is influenced by microrelief position during peat accretion. This study highlights how microhabitat variations within peatlands influence decay mechanisms on the molecular level.
Keywords: Py-GC-MS, THM-GC-MS, peat, organic matter, polysaccharides, Sphagnum acid
Published in DiRROS: 25.07.2025; Views: 563; Downloads: 232
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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. 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, original scientific article Abstract: 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.
Keywords: polysaccharides, chitosan, hyaluronic acid, anti-biofilm, silicone
Published in DiRROS: 19.07.2024; Views: 1278; Downloads: 731
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