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247 results on '"Rehbock, Christoph"'

2. Particle-Based Simulations of Electrophoretic Deposition with Adaptive Physics Models

Author

Karnes, John J., Pascall, Andrew J., Rehbock, Christoph, Ramesh, Vaijayanthi, Worsley, Marcus A., Barcikowski, Stephan, Lee, Elaine, and Giera, Brian

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Computational Physics
Abstract

This work represents an extension of mesoscale particle-based modeling of electrophoretic deposition (EPD), which has relied exclusively on pairwise interparticle interactions described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. With this standard treatment, particles continuously move and interact via excluded volume and electrostatic pair potentials under the influence of external fields throughout the EPD process. The physics imposed by DLVO theory may not be appropriate to describe all systems, considering the vast material, operational, and application space available to EPD. As such, we present three modifications to standard particle-based models, each rooted in the ability to dynamically change interparticle interactions as simulated deposition progresses. This approach allows simulations to capture charge transfer and/or irreversible adsorption based on tunable parameters. We evaluate and compare simulated deposits formed under new physical assumptions, demonstrating the range of systems that these adaptive physics models may capture., Comment: 34 pages, 10 figures

Published
2023

3. Multidimensional thermally-induced transformation of nest-structured complex Au-Fe nanoalloys towards equilibrium

Author

Johny, Jacob, Prymak, Oleg, Kamp, Marius, Calvo, Florent, Kim, Se-Ho, Tymoczko, Anna, El-Zoka, Ayman, Rehbock, Christoph, Schürmann, Ulrich, Gault, Baptiste, Kienle, Lorenz, and Barcikowski, Stephan

Subjects
Condensed Matter - Materials Science
Abstract

Bimetallic nanoparticles are often superior candidates for a wide range of technological and biomedical applications, thanks to their enhanced catalytic, optical, and magnetic properties, which are often better than their monometallic counterparts. Most of their properties strongly depend on their chemical composition, crystallographic structure, and phase distribution. However, little is known of how their crystal structure, on the nanoscale, transforms over time at elevated temperatures, even though this knowledge is highly relevant in case nanoparticles are used in, e.g., high-temperature catalysis. Au-Fe is a promising bimetallic system where the low-cost and magnetic Fe is combined with catalytically active and plasmonic Au. Here, we report on the in situ temporal evolution of the crystalline ordering in Au-Fe nanoparticles, obtained from a modern laser ablation in liquids synthesis. Our in-depth analysis, complemented by dedicated atomistic simulations, includes a detailed structural characterization by X-ray diffraction and transmission electron microscopy as well as atom probe tomography to reveal elemental distributions down to a single atom resolution. We show that the Au-Fe nanoparticles initially exhibit highly complex internal nested nanostructures with a wide range of compositions, phase distributions, and size-depended microstrains. The elevated temperature induces a diffusion-controlled recrystallization and phase merging, resulting in the formation of a single face-centered-cubic ultrastructure in contact with a body-centered cubic phase, which demonstrates the metastability of these structures. Uncovering these unique nanostructures with nested features could be highly attractive from a fundamental viewpoint as they could give further insights into the nanoparticle formation mechanism under non-equilibrium conditions.

Published
2021

7. Synergetic Enhancing Effects between Platinum Nanosensitizers and Clinically Approved Stabilizing Ligands in Proton Therapy, Causing High‐Yield Double‐Strand Breaks of Plasmid DNA at Relevant Dose.

Author

Zwiehoff, Sandra, Hensel, Astrid, Rishmawi, Ramin, Shakibaei, Parisa, Behrends, Carina, Hommel, Katrin, Bäumer, Christian, Knauer, Shirley Karin, Timmermann, Beate, Rehbock, Christoph, and Barcikowski, Stephan

Subjects
POLYETHYLENE glycol, REACTIVE oxygen species, LIGANDS (Biochemistry), PROTON therapy, SERUM albumin
Abstract

Proton therapy is used to eradicate tumors in sensitive areas by targeted delivery of energy. Its effectiveness can be amplified using nanoparticles (NPs) as sensitizers, due to the production of reactive oxygen species at the NP's catalytically active surface, causing the cleavage of DNA. However, the impact of stabilizing macromolecular ligands capping the particles, needed for nanosensitizer dispersion in physiological fluids, is underexplored. Herein, ligand‐free colloidal platinum NPs (PtNPs) fabricated by scalable laser synthesis in liquids are used, which allows studying particle and ligand effects separately. PtNPs are incubated with stabilizing concentrations of the clinically approved ligands albumin, Tween, and polyethylene glycol, and irradiated with proton beams at clinically relevant doses (2 and 5 Gy). At these doses, plasmid DNA cleavage larger than 55% of clustered DNA damage is achieved. Bovine serum albumin, Tween, and polyethylene glycol on the NP surface work as double‐strand breaks (DSB) enhancers and synergetic effects occur even at low and clinically relevant particle concentrations and irradiation doses. Here, DSB enhancement by ligand‐capped PtNP even exceeds the sum of the individual ligand and particle effects. The presented fundamental correlations provide selection rules for nanosensitizer design in proton therapy. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Laser Synthesis of Colloids: Applications

Author

Gökce, Bilal, Rehbock, Christoph, Ramesh, Vaijayanthi, Kohsakowski, Sebastian, Hupfeld, Tim, Reichenberger, Sven, Barcikowski, Stephan, Ostendorf, Andreas, Section editor, Kanitz, Alexander, Section editor, and Sugioka, Koji, editor

Published
2021
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12. Synthesis of Fluorescent Silver Nanoclusters: Introducing Bottom-Up and Top-Down Approaches to Nanochemistry in a Single Laboratory Class

Author

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

Abstract

A laboratory class was developed and evaluated to illustrate the synthesis of metal nanoclusters (NCs) and to explain their photoluminescence properties for the case of silver. The described experiment employs a synthetic protocol that consists of two sequential phases in a single reaction pot: the reduction of silver ions into plasmonic silver nanoparticles (NPs) (bottom-up), followed by etching the formed silver NPs into ultrasmall atomically precise fluorescent silver NCs (top-down), Ag[subscript 29] (DHLA)[subscript 12] (DHLA: dihydrolipoic acid). UV-vis absorption and fluorescence spectroscopy were employed as a function of reaction time to confirm the development of the plasmonic character of silver NPs (reaction intermediate) and, later on, the onset of fluorescence emission of the silver NCs (final product). Collectively, this experiment was found to be simple to carry out, safe, reproducible, and cost-effective, and it achieved the intended learning outcomes. Participating students found this laboratory class suitable to be implemented into an upper-division undergraduate or graduate curriculum.

Published
2020
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14. Synergetic enhancing effects between platinum nano-sensitizers and clinically approved stabilizing ligands in proton therapy, causing high-yield double-strand breaks of plasmid DNA at relevant dose

Author

Zwiehoff, Sandra, primary, Hensel, Astrid, additional, Rishmawi, Ramin, additional, Shakibaei, Parisa, additional, Behrends, Carina, additional, Hommel, Katrin, additional, Bäumer, Christian, additional, Knauer, Shirley K., additional, Timmermann, Beate, additional, Rehbock, Christoph, additional, and Barcikowski, Stephan, additional

Published
2024
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15. 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

16. Golden Plasmophores with Tunable Photoluminescence and Outstanding Thermal and Photothermal Stability.

Author

Gharib, Mustafa, Yates, A. J., Sanders, Stephen, Gebauer, Johannes, Graf, Sebastian, Ziefuß, Anna Rosa, Nonappa, Kassier, Günther, Rehbock, Christoph, Barcikowski, Stephan, Weller, Horst, Alabastri, Alessandro, Nordlander, Peter, Parak, Wolfgang J., and Chakraborty, Indranath

Subjects
THERMAL stability, GOLD clusters, HYBRID systems, PHOTOLUMINESCENCE, ACOUSTIC imaging, FLUOROPHORES
Abstract

Among various hybrid nanomaterials, the combination of plasmonic nanoparticles and fluorophores in a single multifunctional nanoplatform, so‐called plasmophores, has attracted significant attention in different fields such as dark field, fluorescence, and photoacoustic imaging, biosensing, photothermal, and photodynamic therapy. Herein, author report a facile and controlled synthesis route of hybrid nanoplatforms composed of fluorescent gold nanoclusters (GNCs) coupled to plasmonic gold nanorods (GNRs) using controlled silica (SiO2) dielectric spacers of different thicknesses from now on referred to as GNR@SiO2@GNC plasmophores. The results show different degrees of plasmon‐enhanced fluorescence of the GNCs in their plasmophore hybrid system when placed at different distances from the plasmonic cores of the GNRs. On the other hand, these plasmophores show enhanced thermal stability compared to GNRs@CTAB (CTAB, cetyl trimethyl ammonium bromide). This results also demonstrated that upon annealing at elevated temperatures (800–1000 °C), the GNRs in the plasmophores are more thermally stable and robust than the GNRs@CTAB. More surprisingly, despite the commonly reported very low melting temperature of smaller‐size nanocrystals, the GNCs in the plasmophores showed high thermal stability and do not exhibit significant structural changes at elevated temperatures (800–1000 °C). [ABSTRACT FROM AUTHOR]

Published
2024
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21. The Origin of the Intracellular Silver in Bacteria: A Comprehensive Study using Targeting Gold–Silver Alloy Nanoparticles

Author

Streich, Carmen, primary, Stein, Frederic, additional, Jakobi, Jurij, additional, Ingendoh‐Tsakmakidis, Alexandra, additional, Heine, Nils, additional, Rehbock, Christoph, additional, Winkel, Andreas, additional, Grade, Sebastian, additional, Kühnel, Mark, additional, Migunov, Vadim, additional, Kovács, András, additional, Knura, Thomas, additional, Stiesch, Meike, additional, Sures, Bernd, additional, and Barcikowski, Stephan, additional

Published
2023
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23. Surface Chemistry and Specific Surface Area Rule the Efficiency of Gold Nanoparticle Sensitizers in Proton Therapy

Author

Johny, Jacob, primary, van Halteren, Charlotte E. R., additional, Cakir, Fatih‐Can, additional, Zwiehoff, Sandra, additional, Behrends, Carina, additional, Bäumer, Christian, additional, Timmermann, Beate, additional, Rauschenbach, Laurèl, additional, Tippelt, Stephan, additional, Scheffler, Björn, additional, Schramm, Alexander, additional, Rehbock, Christoph, additional, and Barcikowski, Stephan, additional

Published
2023
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24. Laser Synthesis of Colloids: Applications

Author

Gökce, Bilal, primary, Rehbock, Christoph, additional, Ramesh, Vaijayanthi, additional, Kohsakowski, Sebastian, additional, Hupfeld, Tim, additional, Reichenberger, Sven, additional, and Barcikowski, Stephan, additional

Published
2020
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26. List of Contributors

Author

Aguado, Andrés, primary, Baletto, Francesca, additional, Barcaro, Giovanni, additional, Barcikowski, Stephan, additional, Bauer, Joanna, additional, Bhattarai, Nabraj, additional, Brune, Harald, additional, Carlos, Netzahualcoyotl, additional, Cottancin, Emmanuel, additional, Courty, Alexa, additional, Dorantes-Dávila, Jesús, additional, Fechete, Ioana, additional, Ferrando, Riccardo, additional, Ferrari, Piero, additional, Fortunelli, Alessandro, additional, Hernandez-Robles, Andrei, additional, Janssens, Ewald, additional, Kaszkur, Zbigniew, additional, Londoño-Calderon, Alejandra, additional, McNamara, Karrina, additional, Miranda, Caetano R., additional, Moreno, Mario, additional, Mulvihill, John J.E., additional, Negreiros, Fabio, additional, Parajuli, Prakash, additional, Pastor, Gustavo M., additional, Pellarin, Michel, additional, Petit, Christophe, additional, Piccolo, Laurent, additional, Ponce, Arturo, additional, Rabilloud, Franck, additional, Rehbock, Christoph, additional, Repain, Vincent, additional, Rigo, Vagner A., additional, Rossi, Kevin, additional, Sanzone, Giuseppe, additional, Sementa, Luca, additional, Thorat, Nanasaheb D., additional, Tofail, Syed A.M., additional, Yacamán, Miguel José, additional, and Yin, Jinlong, additional

Published
2020
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27. Bacteria‐Epithelial Cell Interaction Influences Cytotoxicity and Antibacterial Effect of Silver‐Gold Alloy Nanoparticles on a Species‐Specific Level.

Author

Doll‐Nikutta, Katharina, Heine, Nils, Kheirmand‐Parizi, Marjan, Stein, Frederic, Ulrich, Jennifer, Rehbock, Christoph, Winkel, Andreas, Barcikowski, Stephan, and Stiesch, Meike

Subjects
SILVER-gold alloys, CYTOTOXINS, GOLD nanoparticles, DRUG resistance in bacteria, LASER ablation, PORPHYROMONAS gingivalis, SILVER nanoparticles, SILVER alloys
Abstract

The rising number of antibiotic‐resistant bacteria requires alternative antibacterial substances as therapeutics. However, besides a strong effect against bacteria, they should not exhibit cytotoxicity towards human cells. Typically, both properties are tested in separate in vitro experiments that do not take into account naturally occurring interactions. To analyze whether the bacteria‐cell interaction influences the results of antibacterial and cytotoxic testing, surfactant‐free antibacterial silver‐gold alloy nanoparticles produced by laser ablation in liquid were examined both separately and in a straightforward coculture setup. Whereas different commensal bacteria and human skin cells exhibited reduced metabolic activity at comparable concentrations when treated separately, their response completely differed when analyzed in a combined coculture. For the combination of oral keratinocytes and Staphylococcus aureus, reduced cytotoxicity with increasing cell numbers, but a similar antibacterial effect quantified by standard plate counting could be observed. In contrast, coculture of keratinocytes and Porphyromonas gingivalis resulted in a complete absence of cytotoxicity and antibacterial effect, probably due to bacterial invasion of cells. These results clearly showed that the bacteria‐cell interaction greatly influences the results of antibacterial and cytotoxic testing and highlight the importance of more complex in vitro experiments to reliably characterize novel antibacterial substances for efficient clinical translation. [ABSTRACT FROM AUTHOR]

Published
2024
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34. Mechanical Stability of Nano‐Coatings on Clinically Applicable Electrodes, Generated by Electrophoretic Deposition

Author

Ramesh, Vaijayanthi, primary, Stratmann, Nadine, additional, Schaufler, Viktor, additional, Angelov, Svilen D., additional, Nordhorn, Ilona D., additional, Heissler, Hans E., additional, Martínez‐Hincapié, Ricardo, additional, Čolić, Viktor, additional, Rehbock, Christoph, additional, Schwabe, Kerstin, additional, Karst, Uwe, additional, Krauss, Joachim K., additional, and Barcikowski, Stephan, additional

Published
2022
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36. Elektrophoretische Beschichtung von Elektroden mit Platin-Neuropartikeln reduzieren und stabilisieren die Impedanz in vitro und in vivo in einem Rattenmodell während der tiefen Hirnstimulation

Author

Angelov, Svilen, Ramesh, Vaijayanthi, Rehbock, Christoph, Heissler, Hans E., Alam, Mesbah, Schwabe, Kerstin, Barcikowski, Stephan, and Krauss, Joachim K.

Subjects
ddc: 610, Medicine and health
Abstract

Objective: Electrodes for neural stimulation and recording are used for the treatment of neurological disorders, including deep brain stimulation (DBS). Their features critically depend on impedance and interaction with brain tissue. Methods: Platin-iridium electrodes were coated using pulsed-DC [for full text, please go to the a.m. URL]

Published
2022

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

Author

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

Subjects
Chemie
Published
2021

49. 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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50. Multidimensional thermally-induced transformation of nest-structured complex Au-Fe nanoalloys towards equilibrium

Author

Johny, Jacob, primary, Prymak, Oleg, additional, Kamp, Marius, additional, Calvo, Florent, additional, Kim, Se-Ho, additional, Tymoczko, Anna, additional, El-Zoka, Ayman, additional, Rehbock, Christoph, additional, Schürmann, Ulrich, additional, Gault, Baptiste, additional, Kienle, Lorenz, additional, and Barcikowski, Stephan, additional

Published
2021
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