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247 results on '"Rehbock, Christoph"'

51. Impact of Ligands on Structural and Optical Properties of Ag29 Nanoclusters

Author

Zeng, Yuan, primary, Havenridge, Shana, additional, Gharib, Mustafa, additional, Baksi, Ananya, additional, Weerawardene, K. L. Dimuthu M., additional, Ziefuß, Anna Rosa, additional, Strelow, Christian, additional, Rehbock, Christoph, additional, Mews, Alf, additional, Barcikowski, Stephan, additional, Kappes, Manfred M., additional, Parak, Wolfgang J., additional, Aikens, Christine M., additional, and Chakraborty, Indranath, additional

Published
2021
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53. Triple Modification of Alginate Hydrogels by Fibrin Blending, Iron Nanoparticle Embedding, and Serum Protein-Coating Synergistically Promotes Strong Endothelialization

Author

Richter, Alena, Li, Yaya, Rehbock, Christoph, Barcikowski, Stephan, Haverich, Axel, Wilhelmi, Mathias, Böer, Ulrike, Richter, Alena, Li, Yaya, Rehbock, Christoph, Barcikowski, Stephan, Haverich, Axel, Wilhelmi, Mathias, and Böer, Ulrike

Abstract

Stent therapy can reduce both morbidity and mortality of chronic coronary stenosis and acute myocardial infarction. However, delayed re-endothelialization, endothelial dysfunction, and chronic inflammation are still unsolved problems. Alginate hydrogels can be used as a coating for stent surfaces; however, complete and fast endothelialization cannot be achieved. In this study, alginate hydrogels are modified by fibrin blending, iron nanoparticle (Fe-NP) embedding, and serum protein coating (SPC) while surface properties and endothelialization capacity are monitored. Only a triple, synergetic modification of the alginate coating by simultaneous I) fibrin blending, II) Fe-NP addition complemented by III) SPC is found to significantly improve endothelial cell viability (live–dead-staining) and proliferation (WST-8 assay). These conditions yield formation of closed endothelial cell monolayers and an up to threefold increase (p < 0.01) in viability, while, interestingly, no effect is found when the modifications (I)–(III) are conducted individually. This synergetic effect is attributed to an accumulation of agglomerated Fe-NP and serum proteins along fibrin fibers, observed via laser scanning microscopy tracking nanoparticle scattering and tetramethylrhodamine (TRITC)-albumin fluorescence. These synergetic effects can pave the way toward a novel strategy for the modification of various hydrogel-based biomaterials and biomaterial coatings.

Published
2021

54. Laser-generated high entropy metallic glass nanoparticles as bifunctional electrocatalysts

Author

Johny, Jacob, Li, Yao, Kamp, Marius, Prymak, Oleg, Liang, Shun-Xing, Krekeler, Tobias, Ritter, Martin, Kienle, Lorenz, Rehbock, Christoph, Barcikowski, Stephan, Reichenberger, Sven, Johny, Jacob, Li, Yao, Kamp, Marius, Prymak, Oleg, Liang, Shun-Xing, Krekeler, Tobias, Ritter, Martin, Kienle, Lorenz, Rehbock, Christoph, Barcikowski, Stephan, and Reichenberger, Sven

Abstract

High entropy metallic glass nanoparticles (HEMG NPs) are very promising materials for energy conversion due to the wide tuning possibilities of electrochemical potentials offered by their multimetallic character combined with an amorphous structure. Up until now, the generation of these HEMG NPs involved tedious synthesis procedures where the generated particles were only available on highly specialized supports, which limited their widespread use. Hence, more flexible synthetic approaches to obtain colloidal HEMG NPs for applications in energy conversion and storage are highly desirable. We utilized pulsed laser ablation of bulk high entropy alloy targets in acetonitrile to generate colloidal carbon-coated CrCoFeNiMn and CrCoFeNiMnMo HEMG NPs. An in-depth analysis of the structure and elemental distribution of the obtained nanoparticles down to single-particle levels using advanced transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) methods revealed amorphous quinary and senary alloy phases with slight manganese oxide/hydroxide surface segregation, which were stabilized within graphitic shells. Studies on the catalytic activity of the corresponding carbon-HEMG NPs during oxygen evolution and oxygen reduction reactions revealed an elevated activity upon the incorporation of moderate amounts of Mo into the amorphous alloy, probably due to the defect generation by atomic size mismatch. Furthermore, we demonstrate the superiority of these carbon-HEMG NPs over their crystalline analogies and highlight the suitability of these amorphous multi-elemental NPs in electrocatalytic energy conversion. [Figure not available: see fulltext.]

Published
2021

55. Formation of Co–Au Core–Shell Nanoparticles with Thin Gold Shells and Soft Magnetic ε-Cobalt Cores Ruled by Thermodynamics and Kinetics

Author

Johny, Jacob, primary, Kamp, Marius, additional, Prymak, Oleg, additional, Tymoczko, Anna, additional, Wiedwald, Ulf, additional, Rehbock, Christoph, additional, Schürmann, Ulrich, additional, Popescu, Radian, additional, Gerthsen, Dagmar, additional, Kienle, Lorenz, additional, Shaji, Sadasivan, additional, and Barcikowski, Stephan, additional

Published
2021
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60. Limited Elemental Mixing in Nanoparticles Generated by Ultrashort Pulse Laser Ablation of AgCu Bilayer Thin Films in a Liquid Environment: Atomistic Modeling and Experiments

Author

Shih, Cheng-Yu, primary, Chen, Chaobo, additional, Rehbock, Christoph, additional, Tymoczko, Anna, additional, Wiedwald, Ulf, additional, Kamp, Marius, additional, Schuermann, Ulrich, additional, Kienle, Lorenz, additional, Barcikowski, Stephan, additional, and Zhigilei, Leonid V., additional

Published
2021
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61. Origin of Laser-Induced Colloidal Gold Surface Oxidation and Charge Density, and Its Role in Oxidation Catalysis

Author

Ziefuß, Anna R., primary, Haxhiaj, Ina, additional, Müller, Stefan, additional, Gharib, Mustafa, additional, Gridina, Olga, additional, Rehbock, Christoph, additional, Chakraborty, Indranath, additional, Peng, Baoxiang, additional, Muhler, Martin, additional, Parak, Wolfgang J., additional, Barcikowski, Stephan, additional, and Reichenberger, Sven, additional

Published
2020
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65. Iron Nanoparticle Composite Hydrogels for Studying Effects of Iron Ion Release on Red Blood Cell In Vitro Production

Author

Brändle, Katharina, Bergmann, Timna C., Raic, Annamarija, Li, Yaya, Million, Nina, Rehbock, Christoph, Barcikowski, Stephan, Lee-Thedieck, Cornelia, Brändle, Katharina, Bergmann, Timna C., Raic, Annamarija, Li, Yaya, Million, Nina, Rehbock, Christoph, Barcikowski, Stephan, and Lee-Thedieck, Cornelia

Abstract

Growing numbers of complex surgical interventions increase the need for blood transfusions, which cannot be fulfilled by the number of donors. Therefore, the interest in producing erythrocytes from their precursors—the hematopoietic stem and progenitor cells (HSPCs)—in laboratories is rising. To enable this, in vitro systems are needed, which allow analysis of the effects of essential factors such as iron on erythroid development. For this purpose, iron ion-releasing systems based on poly(ethylene glycol) (PEG)–iron nanocomposites are developed to assess if gradual iron release improves iron bioavailability during in vitro erythroid differentiation. The nanocomposites are synthesized using surfactant-free pulsed laser ablation of iron directly in the PEG solution. The iron concentrations released from the material are sufficient to influence in vitro erythropoiesis. In this way, the production of erythroid cells cultured on flat PEG–iron nanocomposite hydrogel pads can be enhanced. In contrast, erythroid differentiation is not enhanced in the biomimetic macroporous 3D composite scaffolds, possibly because of local iron overload within the pores of the system. In conclusion, the developed iron nanoparticle-PEG composite hydrogel allows constant iron ion release and thus paves the way (i) to understand the role of iron during erythropoiesis and (ii) toward the development of biomaterials with a controlled iron release for directing erythropoiesis in culture.

Published
2020

67. Synthesis of Fluorescent Silver Nanoclusters: Introducing Bottom-Up and Top-Down Approaches to Nanochemistry in a Single Laboratory Class

Author

Zhu, Lin, primary, Gharib, Mustafa, additional, Becker, Charline, additional, Zeng, Yuan, additional, Ziefuß, Anna R., additional, Chen, Lizhen, additional, Alkilany, Alaaldin M., additional, Rehbock, Christoph, additional, Barcikowski, Stephan, additional, Parak, Wolfgang J., additional, and Chakraborty, Indranath, additional

Published
2019
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79. MOESM1 of Optical and electron microscopy study of laser-based intracellular molecule delivery using peptide-conjugated photodispersible gold nanoparticle agglomerates

Author

Krawinkel, Judith, Richter, Undine, Torres-Mapa, Maria, Westermann, Martin, Gamrad, Lisa, Rehbock, Christoph, Barcikowski, Stephan, and Heisterkamp, Alexander

Abstract

Additional file 1. Detailed information on CPP-AuNPs, TEM, the release criteria and viability. The additional file includes a more detailed description of the particle synthesis, the preparation of the TEM samples and additional characteristics of CPP-AuNP agglomerates. Additionally, a gallery of further TEM-images as well as of primary AuNPs without CPPs and individualized AuNPs after irradiation are presented. Further, the ImageJ analysis including a selection of sample images to obtain the fluorescent area per cell before and after irradiation as well as the results of the cellular viability directly after laser treatment are shown.

Published
2016
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80. Efficient nucleic acid delivery to murine regulatory T cells by gold nanoparticle conjugates

Author

Gamrad, Lisa, Rehbock, Christoph, Westendorf, Astrid M., Buer, Jan J., Barcikowski, Stephan, and Hansen, Wiebke

Subjects
Medizinische Fakultät » Universitätsklinikum Essen » Institut für Medizinische Mikrobiologie, Immunology, Green Fluorescent Proteins, Chemie, Metal Nanoparticles, chemical and pharmacologic phenomena, T-Lymphocytes, Regulatory, Article, Forschungszentren » Center for Nanointegration Duisburg-Essen (CENIDE), Drug Delivery Systems, Microscopy, Electron, Transmission, Nucleic Acids, Animals, ddc:610, RNA, Small Interfering, Mice, Inbred BALB C, Microscopy, Confocal, Gene Transfer Techniques, Reproducibility of Results, hemic and immune systems, Chemical biology, ddc:54, ddc:540, Fakultät für Chemie » Technische Chemie, Gold, Biologie
Abstract

Immune responses have to be tightly controlled to guarantee maintenance of immunological tolerance and efficient clearance of pathogens and tumorigenic cells without induction of unspecific side effects. CD4(+) CD25(+) regulatory T cells (Tregs) play an important role in these processes due to their immunosuppressive function. Genetic modification of Tregs would be helpful to understand which molecules and pathways are involved in their function, but currently available methods are limited by time, costs or efficacy. Here, we made use of biofunctionalized gold nanoparticles as non-viral carriers to transport genetic information into murine Tregs. Confocal microscopy and transmission electron microscopy revealed an efficient uptake of the bioconjugates by Tregs. Most importantly, coupling eGFP-siRNA to those particles resulted in a dose and time dependent reduction of up to 50% of eGFP expression in Tregs isolated from Foxp3eGFP reporter mice. Thus, gold particles represent a suitable carrier for efficient import of nucleic acids into murine CD4(+) CD25(+) Tregs, superior to electroporation.

Published
2016

81. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles

Author

Wagener, Philipp, Jakobi, Jurij, Rehbock, Christoph, Chakravadhanula, Venkata Sai Kiran, Thede, Claas, Wiedwald, Ulf, Bartsch, Mathias, Kienle, Lorenz, and Barcikowski, Stephan

Subjects
Technology, Forschungszentren » Center for Nanointegration Duisburg-Essen (CENIDE), Structural properties, Magnetic properties and materials, ddc:53, ddc:660, Fakultät für Chemie » Technische Chemie, Nanoparticles, ddc:530, Metals and alloys, ddc:600, Article, Transmission electron microscopy
Abstract

This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications.

Published
2016

87. Characterizing the Effect of Multivalent Conjugates Composed of Aβ-Specific Ligands and Metal Nanoparticles on Neurotoxic Fibrillar Aggregation

Author

Streich, Carmen, primary, Akkari, Laura, additional, Decker, Christina, additional, Bormann, Jenny, additional, Rehbock, Christoph, additional, Müller-Schiffmann, Andreas, additional, Niemeyer, Felix Carlsson, additional, Nagel-Steger, Luitgard, additional, Willbold, Dieter, additional, Sacca, Barbara, additional, Korth, Carsten, additional, Schrader, Thomas, additional, and Barcikowski, Stephan, additional

Published
2016
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95. Templated Dealloying: Designing Ultrastructures by Memory Effect

Author

Kamp, Marius, Tymoczko, Anna, Schürmann, Ulrich, Jakobi, Jurij, Rehbock, Christoph, Barcikowski, Stephan, and Kienle, Lorenz

Abstract

Tailoring the morphology of nanoporous structures widens the scope of applications in catalysis and sensing. The synthesis of versatile nanoporous morphologies with the spatial distribution of porosity is permitted by the dealloying of unique, metastable Au–Fe alloy template nanoparticles generated by laser ablation in liquids. This approach opens the door to a novel process, which involves a special transformation mechanism, including oxidation and Kirkendall effect, which is decisive for the stabilization of hollow structures with the spatial distribution of porosity and represents a memory effect of morphology. Within this work, nanoporous Au particles, hollow nanoporous Au shells with the spatial distribution of porosity, and yolk–shell-like Au nanoparticles encapsulated in ultrathin Au shells are synthesized. A distinct variation of crystallinity and an increased lattice strain is observed, which implies an improved catalytic activity for oxidation reactions.

Published
2024
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