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1,065 results on '"Stark, Wendelin"'

7. SAXS imaging reveals optimized osseointegration properties of bioengineered oriented 3D-PLGA/aCaP scaffolds in a critical size bone defect model

Author

Casanova, Elisa A., Rodriguez-Palomo, Adrian, Stähli, Lisa, Arnke, Kevin, Gröninger, Olivier, Generali, Melanie, Neldner, Yvonne, Tiziani, Simon, Dominguez, Ana Perez, Guizar-Sicairos, Manuel, Gao, Zirui, Appel, Christian, Nielsen, Leonard C., Georgiadis, Marios, Weber, Franz E., Stark, Wendelin, Pape, Hans-Christoph, Cinelli, Paolo, and Liebi, Marianne

Published
2023
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8. Nondestructive in-line sub-picomolar detection of magnetic nanoparticles in flowing complex fluids

Author

Bougas, Lykourgos, Langenegger, Lukas D., Mora, Carlos A., Zeltner, Martin, Stark, Wendelin J., Wickenbrock, Arne, Blanchard, John W., and Budker, Dmitry

Subjects
Physics - Applied Physics
Abstract

Over the last decades, the use of magnetic nanoparticles in research and commercial applications has increased dramatically. However, direct detection of trace quantities remains a challenge in terms of equipment cost, operating conditions and data acquisition times, especially in flowing conditions within complex media. Here we present the in-line, non-destructive detection of magnetic nanoparticles using high performance atomic magnetometers at ambient conditions in flowing media. We achieve sub-picomolar sensitivities measuring $\sim$30 nm ferromagnetic iron and cobalt nanoparticles that are suitable for biomedical and industrial applications, under flowing conditions in water and whole blood. Additionally, we demonstrate real-time surveillance of the magnetic separation of nanoparticles from water and whole blood. Overall our system has the merit of inline direct measurement of trace quantities of ferromagnetic nanoparticles with so far unreached sensitivities and could be applied in the biomedical field (diagnostics and therapeutics) but also in the industrial sector.

Published
2018

11. DNA-Based Chemical Unclonable Functions for Cryptographic Anticounterfeit Tagging of Pharmaceuticals

Author

Luescher, Anne M., Stark, Wendelin J., and Grass, Robert N.

Abstract

Counterfeit products are a problem known across many industries. Chemical products such as pharmaceuticals belong to the most targeted markets, with harmful consequences for consumer health and safety. However, many of the currently used anticounterfeit measures are associated with the packaging, with the readout method and level of security varying between different solutions. Identifiers that can be directly and safely mixed into the product to securely authenticate a batch would be desirable. For this purpose, we propose the use of chemical unclonable functions based on pools of short random DNA oligos, which allow the integration of a cryptographic authentication system into chemical products. We demonstrate and characterize a simplified workflow for readout, showing that results are robust and clearly differentiate between the correct tag and a counterfeit. As a proof of concept, we demonstrate the labeling of an acetaminophen formulation with a chemical unclonable function. The acetaminophen was successfully authenticated from a subsample of the product at a DNA admixing concentration of below 50 ng/g. Stability tests revealed that the readout is stable at room temperature for several years, exceeding the shelf life of most drug products. Our work thus shows that chemical unclonable functions are a valid alternative to state-of-the-art anticounterfeit methods, enabling a secure authentication scheme that is physically linked to the product and safe for consumption. The method is widely applicable beyond pharmaceuticals, allowing for more secure product tracing across industries.

Published
2024
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12. Safe One-Pot Synthesis of Fluorescent Carbon Quantum Dots from Lemon Juice for a Hands-On Experience of Nanotechnology

Author

Schneider, Elia M., Bärtsch, Amadeus, Stark, Wendelin J., and Grass, Robert N.

Abstract

A simple synthesis of fluorescent carbon quantum dots from lemon juice is described to introduce advanced high-school students and undergraduate college students to nanoparticle synthesis and quantum dots. The synthesis is based on the carbonization of lemon juice using only a hot plate stirrer. Column chromatography is used to separate different carbon quantum dots according to their size. This laboratory experiment can be carried out within a 2 h laboratory course and introduces the students to (1) nanotechnology and nanoparticle synthesis, using safe and commonly available chemicals. Furthermore, (2) the concept of fluorescence can be visualized in an intriguing manner using a pocket UV lamp. (3) This experiment serves as an introduction into size-exclusion chromatography. (4) An insight into possible sensing applications is given by the specific fluorescence quenching with an iron(III) solution. The experiment has been tested with 80 students in 4 Swiss high schools, and the knowledge of the students was tested before and after the experiment with a questionnaire. The performance increased by 0.42 [plus or minus] 0.39 on a grading scale of 1 to 6. The calculated average effect size was 0.76, which is in the range of a medium- to large-effect size, indicating a favorable effect of the experiment on the nanoparticle knowledge of the students.

Published
2019
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14. Low-nuclearity CuZn ensembles on ZnZrOx catalyze methanol synthesis from CO2

Author

Universidad de Alicante. Departamento de Química Inorgánica, Universidad de Alicante. Instituto Universitario de Materiales, Pinheiro Araújo, Thaylan, Giannakakis, Georgios, Morales-Vidal, Jordi, Agrachev, Mikhail, Ruiz-Bernal, Zaira, Preikschas, Phil, Zou, Tangsheng, Krumeich, Frank, Willi, Patrik O., Stark, Wendelin J., Grass, Robert N., Jeschke, Gunnar, Mitchell, Sharon, López, Núria, Pérez-Ramírez, Javier, Universidad de Alicante. Departamento de Química Inorgánica, Universidad de Alicante. Instituto Universitario de Materiales, Pinheiro Araújo, Thaylan, Giannakakis, Georgios, Morales-Vidal, Jordi, Agrachev, Mikhail, Ruiz-Bernal, Zaira, Preikschas, Phil, Zou, Tangsheng, Krumeich, Frank, Willi, Patrik O., Stark, Wendelin J., Grass, Robert N., Jeschke, Gunnar, Mitchell, Sharon, López, Núria, and Pérez-Ramírez, Javier

Abstract

Metal promotion could unlock high performance in zinc-zirconium catalysts, ZnZrOx, for CO2 hydrogenation to methanol. Still, with most efforts devoted to costly palladium, the optimal metal choice and necessary atomic-level architecture remain unclear. Herein, we investigate the promotion of ZnZrOx catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) prepared via a standardized flame spray pyrolysis approach. Cu emerges as the most effective promoter, doubling methanol productivity. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses and density functional theory simulations reveal that Cu0 species form Zn-rich low-nuclearity CuZn clusters on the ZrO2 surface during reaction, which correlates with the generation of oxygen vacancies in their vicinity. Mechanistic studies demonstrate that this catalytic ensemble promotes the rapid hydrogenation of intermediate formate into methanol while effectively suppressing CO production, showcasing the potential of low-nuclearity metal ensembles in CO2-based methanol synthesis.

Published
2024

15. Murine iPSC-Loaded Scaffold Grafts Improve Bone Regeneration in Critical-Size Bone Defects

Author

Kessler, Franziska, Arnke, Kevin; https://orcid.org/0009-0002-8199-7465, Eggerschwiler, Benjamin, Neldner, Yvonne, Märsmann, Sonja, Gröninger, Olivier, Casanova, Elisa A, Weber, Fabienne A, König, Matthias A; https://orcid.org/0000-0001-6376-3492, Stark, Wendelin J, Pape, Hans-Christoph; https://orcid.org/0000-0002-2059-4980, Cinelli, Paolo; https://orcid.org/0000-0002-0163-9055, Tiziani, Simon, Kessler, Franziska, Arnke, Kevin; https://orcid.org/0009-0002-8199-7465, Eggerschwiler, Benjamin, Neldner, Yvonne, Märsmann, Sonja, Gröninger, Olivier, Casanova, Elisa A, Weber, Fabienne A, König, Matthias A; https://orcid.org/0000-0001-6376-3492, Stark, Wendelin J, Pape, Hans-Christoph; https://orcid.org/0000-0002-2059-4980, Cinelli, Paolo; https://orcid.org/0000-0002-0163-9055, and Tiziani, Simon

Abstract

In certain situations, bones do not heal completely after fracturing. One of these situations is a critical-size bone defect where the bone cannot heal spontaneously. In such a case, complex fracture treatment over a long period of time is required, which carries a relevant risk of complications. The common methods used, such as autologous and allogeneic grafts, do not always lead to successful treatment results. Current approaches to increasing bone formation to bridge the gap include the application of stem cells on the fracture side. While most studies investigated the use of mesenchymal stromal cells, less evidence exists about induced pluripotent stem cells (iPSC). In this study, we investigated the potential of mouse iPSC-loaded scaffolds and decellularized scaffolds containing extracellular matrix from iPSCs for treating critical-size bone defects in a mouse model. In vitro differentiation followed by Alizarin Red staining and quantitative reverse transcription polymerase chain reaction confirmed the osteogenic differentiation potential of the iPSCs lines. Subsequently, an in vivo trial using a mouse model (n = 12) for critical-size bone defect was conducted, in which a PLGA/aCaP osteoconductive scaffold was transplanted into the bone defect for 9 weeks. Three groups (each n = 4) were defined as (1) osteoconductive scaffold only (control), (2) iPSC-derived extracellular matrix seeded on a scaffold and (3) iPSC seeded on a scaffold. Micro-CT and histological analysis show that iPSCs grafted onto an osteoconductive scaffold followed by induction of osteogenic differentiation resulted in significantly higher bone volume 9 weeks after implantation than an osteoconductive scaffold alone. Transplantation of iPSC-seeded PLGA/aCaP scaffolds may improve bone regeneration in critical-size bone defects in mice.

Published
2024

18. Selective Chemical Modification of Graphene surfaces: Distinction between Single and Bilayer Graphene

Author

Koehler, Fabian M., Jacobsen, Arnhild, Ensslin, Klaus, Stampfer, Christoph, and Stark, Wendelin J.

Subjects
Condensed Matter - Materials Science
Abstract

Graphene modifications with oxygen or hydrogen are well known in contrast to carbon attachment to the graphene lattice. The chemical modification of graphene sheets with aromatic diazonium ions (carbon attachment) is analyzed by confocal Raman spectroscopy. The temporal and spatial evolution of surface adsorbed species allowed accurate tracking of the chemical reaction and identification of intermediates. The controlled transformation of sp2 to sp3 carbon proceeds in two separate steps. The presented derivatization is selective for single layer graphene and allows controlled transformation of adsorbed diazonium reagents into covalently bound surface derivatives with enhanced reactivity at the edge of single layer graphene. On bi-layer graphene the derivatization proceeds to an adsorbed intermediate without further reaction to form a covalent attachment on the carbon surface.

Published
2010
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20. Rapid Production of a Porous Cellulose Acetate Membrane for Water Filtration Using Readily Available Chemicals

Author

Kaiser, Adrian, Stark, Wendelin J., and Grass, Robert N.

Abstract

A chemistry laboratory experiment using everyday items and readily available chemicals is described to introduce advanced high school students and undergraduate college students to porous polymer membranes. In a three-step manufacturing process, a membrane is produced at room temperature. The filtration principle of the membrane is then illustrated by filtering solutions containing pigmentary watercolor or food coloring. A comparison of the filtration results shows that insoluble watercolor pigments are too large to pass the pores of the membrane and are successfully rejected by the membrane, whereas the food coloring is completely soluble in water and easily passes the membrane. The laboratory experiment can be performed in a 2 h activity and serves the purpose of (1) exposing students to a new and interesting field of material science. It (2) makes them familiar with porous membranes for the production of safe drinking water and (3) introduces them to a template-removal technique utilizing acid/base theory. There were 52 advanced high school students and 55 high school teachers in Switzerland who already successfully performed the laboratory experiment and found the activity engaging and motivating.

Published
2017
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24. Development and evaluation of PlasmoPod: A cartridge-based nucleic acid amplification test for rapid malaria diagnosis and surveillance

Author

Bechtold, Philippe, primary, Wagner, Philipp, additional, Hosch, Salome, additional, Gregorini, Michele, additional, Stark, Wendelin J., additional, Gody, Jean Chrysostome, additional, Kodia-Lenguetama, Edwige Régina, additional, Pagonendji, Marilou Sonia, additional, Donfack, Olivier Tresor, additional, Phiri, Wonder P., additional, García, Guillermo A., additional, Nsanzanbana, Christian, additional, Daubenberger, Claudia A., additional, Schindler, Tobias, additional, and Vickos, Ulrich, additional

Published
2023
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28. Low-nuclearity CuZn ensembles on ZnZrOx catalyze methanol synthesis from CO2.

Author

Pinheiro Araújo, Thaylan, Giannakakis, Georgios, Morales-Vidal, Jordi, Agrachev, Mikhail, Ruiz-Bernal, Zaira, Preikschas, Phil, Zou, Tangsheng, Krumeich, Frank, Willi, Patrik O., Stark, Wendelin J., Grass, Robert N., Jeschke, Gunnar, Mitchell, Sharon, López, Núria, and Pérez-Ramírez, Javier

Abstract

Metal promotion could unlock high performance in zinc-zirconium catalysts, ZnZrOx, for CO2 hydrogenation to methanol. Still, with most efforts devoted to costly palladium, the optimal metal choice and necessary atomic-level architecture remain unclear. Herein, we investigate the promotion of ZnZrOx catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) prepared via a standardized flame spray pyrolysis approach. Cu emerges as the most effective promoter, doubling methanol productivity. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses and density functional theory simulations reveal that Cu0 species form Zn-rich low-nuclearity CuZn clusters on the ZrO2 surface during reaction, which correlates with the generation of oxygen vacancies in their vicinity. Mechanistic studies demonstrate that this catalytic ensemble promotes the rapid hydrogenation of intermediate formate into methanol while effectively suppressing CO production, showcasing the potential of low-nuclearity metal ensembles in CO2-based methanol synthesis.The ideal metal selection and atomic-level arrangement for catalysts in CO2 hydrogenation are still uncertain. Here, copper is identified as the most effective promoter for enhancing ZnZrOx catalysts when precisely structured into CuZn ensembles, offering new insights for designing superior catalysts for CO2-based methanol synthesis. [ABSTRACT FROM AUTHOR]

Published
2024
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33. SAXS imaging reveals optimized osseointegration properties of bioengineered oriented 3D-PLGA/aCaP scaffolds in a critical size bone defect model

Author

Casanova, Elisa A, Rodriguez-Palomo, Adrian, Stähli, Lisa, Arnke, Kevin, Gröninger, Olivier, Generali, Melanie, Neldner, Yvonne, Tiziani, Simon, Dominguez, Ana Perez, Guizar-Sicairos, Manuel, Gao, Zirui, Appel, Christian, Nielsen, Leonard C, Georgiadis, Marios, Weber, Franz E, Stark, Wendelin, Pape, Hans-Christoph, Cinelli, Paolo, Liebi, Marianne, Casanova, Elisa A, Rodriguez-Palomo, Adrian, Stähli, Lisa, Arnke, Kevin, Gröninger, Olivier, Generali, Melanie, Neldner, Yvonne, Tiziani, Simon, Dominguez, Ana Perez, Guizar-Sicairos, Manuel, Gao, Zirui, Appel, Christian, Nielsen, Leonard C, Georgiadis, Marios, Weber, Franz E, Stark, Wendelin, Pape, Hans-Christoph, Cinelli, Paolo, and Liebi, Marianne

Abstract

Healing large bone defects remains challenging in orthopedic surgery and is often associated with poor outcomes and complications. A major issue with bioengineered constructs is achieving a continuous interface between host bone and graft to enhance biological processes and mechanical stability. In this study, we have developed a new bioengineering strategy to produce oriented biocompatible 3D PLGA/aCaP nanocomposites with enhanced osseointegration. Decellularized scaffolds -containing only extracellular matrix- or scaffolds seeded with adipose-derived mesenchymal stromal cells were tested in a mouse model for critical size bone defects. In parallel to micro-CT analysis, SAXS tensor tomography and 2D scanning SAXS were employed to determine the 3D arrangement and nanostructure within the critical-sized bone. Both newly developed scaffold types, seeded with cells or decellularized, showed high osseointegration, higher bone quality, increased alignment of collagen fibers and optimal alignment and size of hydroxyapatite minerals.

Published
2023

41. Role and Dynamics of Transition Metal Carbides in Methane Coupling

Author

Zhang, Seraphine B.X.Y., primary, Pessemesse, Quentin, additional, Lätsch, LUKAS, additional, Engel, Konstantin M., additional, Stark, Wendelin Jan, additional, van Bavel, Alexander P., additional, Horton, Andrew, additional, Payard, Pierre-Adrien, additional, and Coperet, Christophe, additional

Published
2023
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46. Role and Dynamics of Transition Metal Carbides in Methane Coupling

Author

Zhang, Seraphine B.X.Y., primary, Pessemesse, Quentin, additional, Lätsch, Lukas, additional, Engel, Konstantin M., additional, Stark, Wendelin J., additional, van Bavel, Alexander P., additional, Horton, Andrew D., additional, Payard, Pierre-Adrien, additional, and Copéret, Christophe, additional

Published
2022
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