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Your search keyword '"Nachev, Milen"' showing total 238 results
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238 results on '"Nachev, Milen"'

19. Matrix-specific mechanism of Fe ion release from laser-generated 3D-printable nanoparticle-polymer composites and their protein adsorption properties

Author

Li, Yaya, Rehbock, Christoph, Nachev, Milen, Stamm, Jacqueline, Sures, Bernd, Blaeser, Andreas, Barcikowski, Stephan, Li, Yaya, Rehbock, Christoph, Nachev, Milen, Stamm, Jacqueline, Sures, Bernd, Blaeser, Andreas, and Barcikowski, Stephan

Abstract

Nanocomposites have been widely applied in medical device fabrication and tissue-engineering applications. In this context, the release of metal ions as well as protein adsorption capacity are hypothesized to be two key processes directing nanocomposite-cell interactions. The objective of this study is to understand the polymer-matrix effects on ion release kinetics and their relations with protein adsorption. Laser ablation in macromolecule solutions was employed for synthesizing Au and Fe nanoparticle-loaded nanocomposites based on thermoplastic polyurethane (TPU) and alginate. Confocal microscopy revealed a three-dimensional homogeneous dispersion of laser-generated nanoparticles in the polymer. The physicochemical properties revealed a pronounced dependence upon embedding of Fe and Au nanoparticles in both polymer matrices. Interestingly, the total Fe ion concentration released from alginate gels under static conditions decreased with increasing mass loadings, a phenomenon only found in the Fe-alginate system and not in the Cu/Zn-alginate and Fe-TPU control system (where the effects were proportioonal to the nanoparticle load). A detailed mechanistic examination of iron the ion release process revealed that it is probably not the redox potential of metals and diffusion of metal ions alone, but also the solubility of nano-metal oxides and affinity of metal ions for alginate that lead to the special release behaviors of iron ions from alginate gels. The amount of adsorbed bovine serum albumin (BSA) and collagen I on the surface of both the alginate and TPU composites was significantly increased in contrast to the unloaded control polymers and could be correlated with the concentration of released Fe ions and the porosity of composites, but was independent of the global surface charge. Interestingly, these effects were already highly pronounced at minute loadings with Fe nanoparticles down to 200 ppm. Moreover, the laser-generated Fe or Au nanoparticle-loaded algin

Published
2024

23. Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala

Author

Perrot-Minnot Marie-Jeanne, Cozzarolo Camille-Sophie, Amin Omar, Barčák Daniel, Bauer Alexandre, Filipović Marijić Vlatka, García-Varela Martín, Servando Hernández-Orts Jesús, Yen Le T.T., Nachev Milen, Orosová Martina, Rigaud Thierry, Šariri Sara, Wattier Rémi, Reyda Florian, and Sures Bernd

Subjects
acanthocephala, environmental parasitology, host ranges, integrative taxonomy, transmission strategies, Infectious and parasitic diseases, RC109-216
Abstract

Although interest in Acanthocephala seems to have reached only a small community of researchers worldwide, we show in this opinion article that this group of parasites is composed of excellent model organisms for studying key questions in parasite molecular biology and cytogenetics, evolutionary ecology, and ecotoxicology. Their shared ancestry with free-living rotifers makes them an ideal group to explore the origins of the parasitic lifestyle and evolutionary drivers of host shifts and environmental transitions. They also provide useful features in the quest to decipher the proximate mechanisms of parasite-induced phenotypic alterations and better understand the evolution of behavioral manipulation. From an applied perspective, acanthocephalans’ ability to accumulate contaminants offers useful opportunities to monitor the impacts – and evaluate the possible mitigation – of anthropogenic pollutants on aquatic fauna and develop the environmental parasitology framework. However, exploring these exciting research avenues will require connecting fragmentary knowledge by enlarging the taxonomic coverage of molecular and phenotypic data. In this opinion paper, we highlight the needs and opportunities of research on Acanthocephala in three main directions: (i) integrative taxonomy (including non-molecular tools) and phylogeny-based comparative analysis; (ii) ecology and evolution of life cycles, transmission strategies and host ranges; and (iii) environmental issues related to global changes, including ecotoxicology. In each section, the most promising ideas and developments are presented based on selected case studies, with the goal that the present and future generations of parasitologists further explore and increase knowledge of Acanthocephala.

Published
2023
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28. Stable isotopes (15N) facilitate non‐invasive labelling of large quantities of macroinvertebrates across different species and feeding types.

Author

Enss, Julian, Nachev, Milen, Jochmann, Maik A., Schmidt, Torsten C., and Feld, Christian K.

Subjects
*AQUATIC invertebrates, *STABLE isotopes, *INVERTEBRATES, *FOOD chains, *SPECIES, *INSECTS
Abstract

While macroinvertebrate dispersal operates at the individual level, predictions of their dispersal capabilities often rely on indirect proxies rather than direct measurements. To gain insight into the dispersal of individual specimens, it is crucial to mark (label) and capture individuals. Isotopic enrichment with 15N is a non‐invasive method with the potential of labelling large quantities of macroinvertebrates. While the analysis of 15N is widely utilised in food web studies, knowledge on the specific utility of isotopic enrichment with 15N for mass labelling of macroinvertebrate individuals across different taxa and feeding types is limited. Previous studies have focused on single species and feeding types, leaving gaps in our understanding of the broader applicability of this method. Therefore, this study aimed to test and compare isotopic mass enrichment across several macroinvertebrate taxa and feeding types. We released 15NH4Cl at five stream reaches in North‐Rhine Westphalia, Germany, and successfully enriched 12 distinct macroinvertebrate taxa (Crustacea and Insecta). Significant enrichment was achieved in active and passive filter feeders, grazers, shredders and predators, and predominantly showed positive correlations with the enrichment of the taxa's main food sources phytobenthos and particulate organic matter. Enrichment levels rose rapidly and peaked at distances between 50 m and 300 m downstream of the isotopic inlet; significant enrichment occurred up to 2000 m downstream of the isotopic inlet in all feeding types. Macroinvertebrate density estimates on the stream bottom averaged to a total of approximately 3.4 million labelled individuals of the 12 investigated taxa, thus showing the high potential of isotopic (15N) enrichment as a non‐invasive method applicable for mass labelling across different macroinvertebrate feeding types. Hence, isotopic enrichment can greatly assist the analysis of macroinvertebrate dispersal through mark‐and‐recapture experiments, as it allows to measure the movement at the level of individual specimens. [ABSTRACT FROM AUTHOR]

Published
2024
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43. Delineation of the exposure-response causality chain of chronic copper toxicity to the zebra mussel, Dreissena polymorpha, with a TK-TD model based on concepts of biotic ligand model and subcellular metal partitioning model

Author

Nachev Milen, Daniel Grabner, T.T. Yen Le, A. Jan Hendriks, Willie J.G.M. Peijnenburg, and Bernd Sures

Subjects
Bivalves, Environmental Engineering, Health, Toxicology and Mutagenesis, Ligands, Dreissena, Lipid peroxidation, chemistry.chemical_compound, Chronic toxicity, Subcellular partitioning, medicine, Environmental Chemistry, Animals, biology, Chemistry, Ligand, Copper toxicity, Public Health, Environmental and Occupational Health, Biotic Ligand Model, Biotic ligand model, General Medicine, General Chemistry, Metabolism, medicine.disease, biology.organism_classification, Pollution, Metals, Environmental chemistry, Zebra mussel, Toxicokinetic-toxicodynamic model, Biologie, Environmental Sciences, Biomarkers, Copper, Water Pollutants, Chemical
Abstract

A toxicokinetic-toxicodynamic model was constructed to delineate the exposure-response causality. The model could be used: to predict metal accumulation considering the influence of water chemistry and biotic ligand characteristics; to simulate the dynamics of subcellular partitioning considering metabolism, detoxification, and elimination; and to predict chronic toxicity as represented by biomarker responses from the concentration of metals in the fraction of potentially toxic metal. The model was calibrated with data generated from an experiment in which the Zebra mussel Dreissena polymorpha was exposed to Cu at nominal concentrations of 25 and 50 mu g/L and with varied Na+ concentrations in water up to 4.0 mmol/L for 24 days. Data used in the calibration included physicochemical conditions of the exposure environment, Cu concentrations in subcellular fractions, and oxidative stress-induced responses, i.e. glutathione-S-transferase activity and lipid peroxidation. The model explained the dynamics of subcellular Cu partitioning and the effect mechanism reasonably well. With a low affinity constant for Na+ binding to Cu2+ uptake sites, Na+ had limited influence on Cu2+ uptake at low Na+ concentrations in water. Copper was taken up into the metabolically available pool (MAP) at a largely higher rate than into the cellular debris. Similar Cu concentrations were found in these two fractions at low exposure levels, which could be attributed to sequestration pathways (metabolism, detoxification, and elimination) in the MAP. However, such sequestration was inefficient as shown by similar Cu concentrations in detoxified fractions with increasing exposure level accompanied by the increasing Cu concentration in the MAP.

Published
2022

44. Effects of multiple stressors in fish : How parasites and contaminants interact

Author

Sures, Bernd and Nachev, Milen

Subjects
Biologie
Abstract

in press Interest in local environmental conditions and the occurrence and behaviour of parasites has increased over the last three decades, leading to the discipline of Environmental Parasitology. The aim of this discipline is to investigate how anthropogenically altered environmental factors influence the occurrence of parasites and how the combined effects of pollutants and parasites affect the health of their hosts. Accordingly, in this paper we provide an overview of the direct and indirect effects of pollutants on the occurrence and distribution of fish parasites. However, based on current knowledge, it is difficult to draw general conclusions about these interdependencies, as the effects of pollutants on free-living (larval) parasite stages, as well as their effects on ectoparasites, depend on the pollutant-host-parasite combination as well as on other environmental factors that can modulate the harmful effects of pollutants. Furthermore, the question of the combined effects of the simultaneous occurrence of parasites and pollutants on the physiology and health of the fish hosts is of interest. For this purpose, we differentiate between dominance effects of individual stressors over other, additive or synergistically reinforcing effects as well as combined antagonistic effects. For the latter, there are only very few studies, most of which were also carried out on invertebrates, so that this field of research presents itself as very promising for future investigations.

Published
2022

48. Photoluminescence of Fully Inorganic Colloidal Gold Nanocluster and Their Manipulation Using Surface Charge Effects

Author

Ziefuss, Anna R., primary, Steenbock, Torben, additional, Benner, Dominik, additional, Plech, Anton, additional, Göttlicher, Jörg, additional, Teubner, Melissa, additional, Grimm‐Lebsanft, Benjamin, additional, Rehbock, Christoph, additional, Comby‐Zerbino, Clothilde, additional, Antoine, Rodolphe, additional, Amans, David, additional, Chakraborty, Indranath, additional, Bester, Gabriel, additional, Nachev, Milen, additional, Sures, Bernd, additional, Rübhausen, Michael, additional, Parak, Wolfgang J., additional, and Barcikowski, Stephan, additional

Published
2021
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