TY - JOUR A1 - Chowdhary, S. A1 - Moschner, J. A1 - Mikolajczak, D. J. A1 - Becker, M. A1 - Thünemann, Andreas A1 - Kästner, Claudia A1 - Klemczak, D. A1 - Stegemann, A.-K. A1 - Böttcher, C. A1 - Metrangolo, P. A1 - Netz, R. R. A1 - Koksch, B. T1 - The Impact of Halogenated Phenylalanine Derivatives on NFGAIL Amyloid Formation JF - ChemBioChem N2 - The hexapeptide hIAPP22–27 (NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild‐type hIAPP′s toxicity to β‐cell death. In amyloid research, the role of hydrophobic and aromatic‐aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic‐aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS) to study the impact of side‐chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self‐assembly process. KW - Small-angle X-ray scattering KW - SAXS KW - Nanoparticle KW - Nanostructure KW - Peptide KW - Amyloid PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-518632 DO - https://doi.org/10.1002/cbic.202000373 VL - 21 IS - 24 SP - 3544 EP - 3554 PB - Wiley CY - Weinheim AN - OPUS4-51863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, B. A1 - Meyer, T. A1 - Sieg, H. A1 - Kästner, Claudia A1 - Reichardt, P. A1 - Tentschert, J. A1 - Jungnickel, H. A1 - Estrela-Lopis, I. A1 - Burel, A. A1 - Chevance, S. A1 - Gauffre, F. A1 - Jalili, P. A1 - Meijer, J. A1 - Böhmert, L. A1 - Braeuning, A. A1 - Thünemann, Andreas A1 - Emmerling, Franziska A1 - Fessard, V. A1 - Laux, P. A1 - Lampen, A. A1 - Luch, A. T1 - Characterization of aluminum, aluminum oxide and titanium dioxide nanomaterials using a combination of methods for particle surface and size analysis JF - RSC Advances N2 - The application of appropriate analytical techniques is essential for nanomaterial (NM) characterization. In this study, we compared different analytical techniques for NM analysis. Regarding possible adverse health effects, ionic and particulate NM effects have to be taken into account. As NMs behave quite differently in physiological media, special attention was paid to techniques which are able to determine the biosolubility and complexation behavior of NMs. Representative NMs of similar size were selected: aluminum (Al0) and aluminum oxide (Al2O3), to compare the behavior of metal and metal oxides. In addition, titanium dioxide (TiO2) was investigated. Characterization techniques such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) were evaluated with respect to their suitability for fast characterization of nanoparticle dispersions regarding a particle's hydrodynamic diameter and size distribution. By application of inductively coupled plasma mass spectrometry in the single particle mode (SP-ICP-MS), individual nanoparticles were quantified and characterized regarding their size. SP-ICP-MS measurements were correlated with the information gained using other characterization techniques, i.e. transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The particle surface as an important descriptor of NMs was analyzed by X-ray diffraction (XRD). NM impurities and their co-localization with biomolecules were determined by ion beam microscopy (IBM) and confocal Raman microscopy (CRM). We conclude advantages and disadvantages of the different techniques applied and suggest options for their complementation. Thus, this paper may serve as a practical guide to particle characterization techniques. KW - Small-angle X-ray scattering KW - SAXS PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-447057 DO - https://doi.org/10.1039/C8RA00205C SN - 2046-2069 VL - 8 IS - 26 SP - 14377 EP - 14388 PB - The Royal Society of Chemistry AN - OPUS4-44705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia T1 - Food-dependent aggregation of silver nanoparticles during an artificial digestion N2 - In the last decade the utilization of silver nanoparticles in consumer related products is strongly enhanced. Therefore, many studies focus on investigations regarding their toxicological potential. This includes investigations concerning uptake, distribution and excretion of the particles. However, little attention was paid to changes of physical and chemical properties of the particles in the human body. A major question is if the particles are size and shape persistent and can survive the digestion process. In this study we analytically monitored the changes in the size distribution of colloidal silver during an artificial digestion process with the help of small angle X-ray scattering. We synthesized poly(acrylic acid) stabilized ultra-small silver nanoparticles with a radius of 3.1 nm and a size distribution width of 20%. The artificial digestion process mimics the gastro-intestinal passage and simulates the oral, gastric and small intestinal conditions. Additionally, we used as food components oil, starch, skimmed milk powder and mixture thereof to provide a preferably realistic environment. Large aggregates of up to 56 nm were determined in the absence of food additives. In contrast, the presence of oil and starch limit the radii of aggregates to about 10 nm. Only small aggregates of 6 nm radii were found in the presence of milk powder. It prevents primary particles from etching in the intestinal juice. Our results indicate that the silver nanoparticles can pass the digestion process in a nanoscale form but undergo a strong and food-dependent transformation in their state of aggregation. T2 - Australian Colloid and Interface Symposium 2017 CY - Coffs Harbour, New South Wales, Australia DA - 29.01.2017 KW - SAXS KW - Food additives KW - Aggregation PY - 2017 AN - OPUS4-39204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia T1 - Creating the Silver Standard: Development of a Silver Nanoparticle Reference Material using SAXS N2 - The utilization of silver nanoparticles in consumer related products has significantly increased over the last decade, especially due to their antimicrobial properties. Today they are used in a high variety of products, which ranges from food containers over children toys and textiles. Therefore, research on the toxicological potential of silver in a nanoscale form becomes increasingly important for a high amount of studies. Unfortunately the results of these studies are extremely diverse and do not lead to a consistent evaluation of the toxicity of silver nanoparticles. The central problem lies in the use of a wide range of silver nanoparticles, which show a broad size distribution. To overcome this problem we report on the synthesis of ultra-small silver nanoparticles and their quantitative characterization by small-angle X-ray scattering. The particles are highly stable and show no aggregation for more than six months. SAXS analysis via a Monte Carlo data evaluation procedure reveal a narrow size distribution of the silver cores with a mean volume weighted radius of 3.0 nm and a distribution width of 0.6 nm. Dynamic light scattering provides a hydrodynamic radius of 10.0 nm and a PDI of 0.09. The particles are stabilized with poly(acrylic acid) (PAA) forming a shell with a thickness of 7.0 nm. It is foreseen to use these thoroughly characterized particles as reference material to compare the catalytic and biological properties of functionalized silver nanoparticles. As a first step the particles are used in the first world-wide inter-laboratory comparison of SAXS. This study reveals that SAXS shows highly reproducible results for particles in the sub-20 nm region independently on the type of instrument used. Furthermore, the stabilizing ligand PAA can be easily exchanged by biomolecules to modify the surface functionality. Replacements of PAA with glutathione (GSH) and bovine serum albumin (BSA) have been performed as examples. With this flexible system first applications regarding biological application in an artificial digestion procedure have been performed. Thereby the changes in size distribution and aggregation state were monitored by SAXS. T2 - SAXS Excites - International SAXS Symposium CY - Graz, Austria DA - 26.09.2017 KW - Silver nanoparticles KW - Artificial digestion KW - Aggregation KW - Reference material PY - 2017 AN - OPUS4-42289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Thünemann, Andreas T1 - Aggregation and deaggregation of silver nanoparticles - what does your gut say? N2 - Due to the increasing utilization of silver nanoparticles in consumer related products, many studies focus on investigations regarding their toxicological potential. This includes investigations concerning uptake, distribution and excretion of the particles. So far, little attention was paid to changes of physical and chemical properties in the human body. During processes like digestion, the question arises whether they can pass this barrier in a nanoscale form. In this study we analytically monitored the changes in the size distribution of silver nanoparticles during an artificial digestion process with the help of small angle x-ray scattering (SAXS). Therefore, we synthesized polyacrylic acid stabilized ultra-small silver nanoparticles with a radius of 3 nm and a size distribution width of 18%. The artificial digestion process mimics the gastro-intestinal passage and simulates the oral, gastric and small intestinal conditions. Additionally, food components like oil, starch, glucose and skimmed milk powder are used to provide a preferably realistic environment. In absence of any food components the low pH initiates aggregation of the particles in the stomach. However, the particles unexpectedly stabilize in a defined cluster form with a mean radius of 12 nm. By the use of the food components oil and starch we observed that the particles are dispersed again. Now we found a bimodal size distribution of primary particles and aggregates. In contrast to that, with skimmed milk powder only a slight aggregation occurs in the stomach. In the gastric tract the particle distribution is stabilized at a mean volume weighted radius of 5 nm. Hence, skimmed milk powder acts as a colloidal stabilizer. For comparison we also used silver nitrate as a control substance. Surprisingly, we observed a formation of nanoparticles already in the saliva. During the digestion process the distribution narrows and finally in the intestine it shows a stable distribution with a mean volume weighted radius of 3 nm and a small fraction of aggregates. These results indicate that the silver nanoparticles can pass the biological barriers of the digestion process in a nanoscale form but undergo a transformation in the size distribution. However, even from pure silver nitrate nanoparticle formation can be observed. This sketches a complex mechanism in which not only food components but also silver ions cause changes in nanoparticle size and aggregation. T2 - 11th International Conference on Biological Barriers CY - Saarbrücken, Germany DA - 07.03.2016 KW - digestion KW - small-angle X-ray scattering KW - silver nanoparticles PY - 2016 AN - OPUS4-35539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Thünemann, Andreas T1 - Artificial Digestion of Colloidal Silver Monitored by Small-Angle X-Ray Scattering N2 - In the last decade the utilization of silver nanoparticles in consumer related products is enhanced. Therefore, many studies focus on investigations regarding their toxicological potential. This includes investigations concerning uptake, distribution and excretion of the particles. So far, little attention was paid to changes of physical and chemical properties in the human body. During processes like digestion, the question arises whether they can pass this barrier in a nanoscale form. In this study we analytically monitored the changes in the size distribution of colloidal silver during an artificial digestion process with the help of small angle x-ray scattering (SAXS). Therefore, we synthesized polyacrylic acid stabilized ultra-small silver nanoparticles with a radius of 3 nm and a size distribution width of 18%. The artificial digestion process mimics the gastro-intestinal passage and simulates the oral, gastric and small intestinal conditions. Additionally, food components like oil, starch, glucose and skimmed milk powder are used to provide a preferably realistic environment. In absence of any food components the low pH initiates aggregation of the particles in the stomach. However, the particles unexpectedly stabilize in a defined cluster form with a mean radius of 12 nm. By the use of the food components oil and starch we observed that the particles are dispersed again. Now we found a bimodal size distribution of primary particles and aggregates. In contrast to that, with skimmed milk powder only a slight aggregation occurs in the stomach. In the gastric tract the particle distribution is stabilized at a mean volume weighted radius of 5 nm. Hence, skimmed milk powder acts as a colloidal stabilizer. For comparison we also used silver nitrate as a control substance. Surprisingly, we observed a formation of nanoparticles already in the saliva. During the digestion process the distribution narrows and finally in the intestine it shows a stable distribution with a mean volume weighted radius of 3 nm and a small fraction of aggregates. These results indicate that the silver nanoparticles can pass the digestion process in a nanoscale form but undergo a transformation in the size distribution. However, even from pure silver nitrate nanoparticle formation can be observed. This sketches a complex mechanism in which not only food components but also silver ions cause changes in nanoparticle size and aggregation. T2 - 6th International Colloids Conference CY - Berlin, Germany DA - 19.06.2016 KW - SAXS KW - Artificial digestion KW - Silver nanoparticles PY - 2016 AN - OPUS4-36888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Thünemann, Andreas T1 - The Solution Structure of Essential Proteins in the Presence of Ultra-Small Silver Nanoparticles: Fluorescent Nanosilver T2 - SAS 2015 - 16th International Conference on Small Angle Scattering T2 - SAS 2015 - 16th International Conference on Small Angle Scattering CY - Berlin, Germany DA - 2015-09-13 PY - 2015 AN - OPUS4-34382 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Sieg, H. A1 - Böhmert, L. A1 - Braeuning, A. A1 - Lampen, A. A1 - Thünemann, Andreas T1 - Creating the silver standard: Development and applications of a silver nanoparticle reference material N2 - The utilization of silver nanoparticles in consumer related products has significantly increased over the last decade, especially due to their antimicrobial properties. Today they are used in a high variety of products ranging from food containers over children toys and textiles. Therefore, research on the toxicological potential of silver nanoparticles becomes increasingly important for a high amount of studies. Unfortunately, the results of these studies are extremely diverse and do not lead to a consistent evaluation. The central problem lies in the use of a wide range of silver nanoparticles, which show a broad size distribution. To overcome this problem we report on the synthesis and application of small silver nanoparticles with a narrow size distribution (R = 3.1 nm, σ = 0.6 nm). The poly(acrylic acid) stabilized particles are thoroughly characterized by small-angle X-ray scattering, dynamic light scattering and UV/Vis spectroscopy. The particles are highly stable and show no aggregation for more than six months. It is foreseen to use these thoroughly characterized nanoparticles as reference material to compare the catalytic and biological properties of functionalized silver nanoparticles. As a first step the particles are used in the first world-wide inter-laboratory comparison of SAXS. Furthermore, the stabilizing ligand PAA can be easily exchanged by biomolecules to modify the surface functionality. Replacements of PAA with glutathione (GSH) and bovine serum albumin (BSA) have been performed as examples. With this flexible system first applications regarding biological application in an artificial digestion procedure have been performed. Thereby the changes in size distribution and aggregation state were monitored by SAXS. Additionally these particles show a high catalytic activity of (436 ± 24) L g-1 s-1 in the reduction of 4- nitrophenol to 4-aminophenol. This activity is two orders of magnitude higher than for other silver particles in the literature. T2 - NanoWorkshop 2018 CY - Berlin, Germany DA - 14.05.2018 KW - Silver nanoparticles KW - SAXS KW - Artificial digestion KW - Catalysis PY - 2018 AN - OPUS4-44911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Böhmert, L. A1 - Lampen, A. A1 - Thünemann, Andreas T1 - What does your gut see? – Silver nanoparticles in an artificial digestion N2 - Over the last decade nanoparticles are progressively included in products of our daily life. Due to their antimicrobial properties, silver nanoparticles are used in a high variety of consumer products ranging from food containers over medicine and textiles. Therefore, research on the toxicological potential of nanosilver becomes increasingly important. This includes investigations concerning uptake, distribution and excretion of the particles. However, little attention was paid to changes of physical and chemical properties of the particles in the human body. One of the most important questions is if the particles can pass the digestion process without altering their shape and size. In this study we report on a versatile system of ultra-small silver nanoparticles with a mean volume weighted radius of 3.1 nm and a narrow size distribution width of 20%. The nanoparticles’ coating of poly (acrylic acid) can easily be exchanged by biocompatible ligands like albumin or glutathione. The particles are thoroughly characterized by small angle X-ray scattering (SAXS), DLS, IR and UV/Vis spectroscopy. We used the particles in an artificial digestion procedure which mimics the gastro-intestinal passage (Figure 1). Thereby the changes in the size distribution during the digestion process were analytically monitored by SAXS. Additionally, we used as food components oil, starch, skimmed milk powder and mixture thereof to provide a preferably realistic environment. Large aggregates of up to 56 nm were formed in the absence of food additives. In contrast, the presence of oil and starch limit the radii of aggregates to about 10 nm. Milk powder shows strong protective properties resulting in only small aggregates of 6 nm radii. Our results indicate that silver can indeed pass the digestion process in a nanoscale form depending on the nanoparticle coating and additional ingredients. These results have an impact on future toxicological considerations regarding silver nanoparticle-containing consumer products. T2 - 5th Nano Today Conference CY - Waikoloa Village, HI, USA DA - 06.12.2017 KW - SAXS KW - Artificial digestion KW - Silver nanoparticles KW - Food additives PY - 2017 AN - OPUS4-43499 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kästner, Claudia A1 - Thünemann, Andreas T1 - Highly enhanced catalytic activity of silver N2 - Silver nanoparticles are one of the most widespread consumer related nanoparticles worldwide. Since the particles show special optical and antibacterial properties they are used for a wide range of applications from biological investigations over medical applications and catalysis. Especially the outstanding question of applicable alternatives for catalysts in diverse reactions can be addressed with the design of versatile system of small silver nanoparticles. In this study we present the synthesis and application of ultra-small silver nanoparticles with a narrow size distribution (R = 3.1 nm, σ = 0.6 nm). The particles are thoroughly characterized by small angle X-ray scattering, dynamic light scattering and UV/Vis spectroscopy. As a representative test reaction the reduction of 4-nitrophenol to 4-aminophenol was chosen. The particles show a catalytic activity of (436 ± 24) L g-1 s-1, which is two orders of magnitude higher than for other silver particles in the literature. The particles surrounding shell, composed of poly(acrylic acid), provides the particles with a good accessibility for the reactants. Since the catalytic activity strongly depends on the surrounding ligand, the particles shell can also be exchanged by other ligands enabling a tuning of the catalytic activity to a desired value. This shows the high flexibility of this system which can also be applied for other catalytic reactions. T2 - 5th Nano Today Conference CY - Waikoloa Village, HI, USA DA - 06.12.2017 KW - SAXS KW - Catalysis KW - Silver nanoparticles KW - Reduction 4-nitrophenol PY - 2017 AN - OPUS4-43496 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -