Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-24538 Zeitschriftenartikel Weidner, Steffen; Knappe, Patrick; Panne, Ulrich MALDI-TOF imaging mass spectrometry of artifacts in 'dried droplet' polymer samples Matrix-assisted laser desorption/ionization-timeof-flight (MALDI-TOF) imaging of polystyrenes with various molecular masses was applied to study spatial molecular mass distribution of polymers in sample spots prepared by the 'dried droplet' method. When different solvents and target surfaces were examined, a segregation of single homologous polymers was observed depending upon the evaporation rate of the solvent. For the observed Patterns left by the evaporating droplet, a hypothesis is offered taking into account different hydrodynamic interactions and diffusion. The results illustrate that spot preparation using the conventionally 'dried droplet' method is prone to artifacts and should be avoided for reliable and reproducible MALDI mass spectrometry experiments with regards to the Determination of molecular masses and mass distributions. Berlin Springer 2011 Analytical and bioanalytical chemistry 401 1 127 134 10.1007/s00216-011-4773-1 2016-02-19 OPUS4-18658 Zeitschriftenartikel Thünemann, Andreas; Rolf, Simone; Knappe, Patrick; Weidner, Steffen In Situ Analysis of a Bimodal Size Distribution of Superparamagnetic Nanoparticles The dispersed iron oxide nanoparticles of ferrofluids in aqueous solution are difficult to characterize due to their protective polymer coatings. We report on the bimodal size distribution of superparamagnetic iron oxide nanoparticles found in the MRI contrast agent Resovist, which is a representative example of commercial nanoparticle-based pharmaceutical formulations. The radii of the majority of the nanoparticles (>99%) range from 4 to 13 nm (less than 1% of the particles display radii up to 21 nm). The maxima of the size distributions are at 5.0 and 9.9 nm. The analysis was performed with in situ characterization of Resovist via online coupling of asymmetrical flow field-flow fractionation (A4F) with small-angle X-ray scattering (SAXS) using a standard copper X-ray tube as a radiation source. The outlet of the A4F was directly coupled to a flow capillary on the SAXS instrument. SAXS curves of nanoparticle fractions were recorded at 1-min time intervals. We recommend using the A4F-SAXS coupling as a routine method for analysis of dispersed nanoparticles with sizes in the range of 1-100 nm. It allows a fast and quantitative comparison of different batches without the need for sample preparation. Washington, DC American Chemical Society 2009 Analytical chemistry 81 1 296 301 10.1021/ac802009q 2016-02-19 OPUS4-20567 Zeitschriftenartikel Thünemann, Andreas; Knappe, Patrick; Bienert, Ralf; Weidner, Steffen Online coupling of field-flow fractionation with SAXS and DLS for polymer analysis We report on a hyphenated polymer analysis method consisting of asymmetrical flow field-flow fractionation (A4F) coupled online with small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). A mixture of six poly(styrene sulfonate)s with molar masses in the range of 6.5 × 103 to 1.0 × 106 g mol-1 was used as a model system for polyelectrolytes in aqueous solutions with a broad molar mass distribution. A complete polymer separation and analysis was performed in 60 min. Detailed information for all polymer fractions are available on i) the radii of gyration, which were determined from the SAXS data interpretation in terms of the Debye model (Gaussian chains), and ii) the diffusion coefficients (from DLS). We recommend using the A4F-SAXS-DLS coupling as a possible new reference method for the detailed analysis of complex polymer mixtures. Advantages of the use of SAXS are seen in comparison to static light scattering for polymers with radii of gyration smaller then 15 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution. Cambridge RSC Publ. Royal Society of Chemistry 2009 Analytical methods 1 177 182 10.1039/b9ay00107g 2016-02-19 OPUS4-21222 Zeitschriftenartikel Knappe, Patrick; Bienert, Ralf; Weidner, Steffen; Thünemann, Andreas Characterization of poly/N-vinyl-2-pyrrolidone)s with broad size distributions We report on the characterization of the solution structure of poly(N-vinyl-2-pyrrolidone)s (PVP) by small-angle X-ray scattering (SAXS) and by online coupling of asymmetrical flow field-flow fractionation (A4F), SAXS and dynamic light scattering (DLS). The commercial products PVP K30 and PVP K90 with nominal molar masses of 40 × 103 and 360 × 103 g mol-1, respectively, were investigated separately and as binary mixture. Detailed information for all polymer fractions is available on the polymer contour lengths and the diffusion coefficients. Key areas of applications for the A4F-SAXS-DLS coupling are seen in comparison to static light scattering for polymers with radii of gyration smaller than 10 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution. Berlin Springer 2010 Polymer 51 8 1723 1727 10.1016/j.polymer.2010.02.039 2016-02-19 OPUS4-22005 Zeitschriftenartikel Knappe, Patrick; Bienert, Ralf; Weidner, Steffen; Thünemann, Andreas Poly(acrylic acid): A combined analysis with field-flow fractionation and SAXS Polyelectrolytes such as PAA and its salts are widely used, but are notoriously difficult to characterize due to their polyelectrolyte properties and broad molecular mass distributions. In this paper, we report on a new PAA analysis by combining asymmetrical flow field-flow fractionation and an advanced SAXS technique using an acoustic levitator to minimize background scattering. The proof-of-principle is demonstrated with a mixture of three standard PAAs with different molecular masses. Detailed information on the PAA fractions is available on radii of gyration, polymer contour lengths, and coil conformation. Our method is expected to be applicable for a wide range of water-soluble synthetic and natural polymers and ideal for molecular masses of 5 × 103-2 × 105 g · mol-1. Weinheim Wiley-VCH Verl. 2010 Macromolecular chemistry and physics 211 19 2148 2153 10.1002/macp.201000163 2016-02-19 OPUS4-29926 Zeitschriftenartikel Böhmert, L.; Girod, Matthias; Hansen, Ulf; Maul, Ronald; Knappe, Patrick; Niemann, B.; Weidner, Steffen; Thünemann, Andreas; Lampen, A. Analytically monitored digestion of silver nanoparticles and their toxicity on human intestinal cells Orally ingested nanoparticles may overcome the gastrointestinal barrier, reach the circulatory system, be distributed in the organism and cause adverse health effects. However, ingested nanoparticles have to pass through different physicochemical environments, which may alter their properties before they reach the intestinal cells. In this study, silver nanoparticles are characterised physicochemically during the course of artificial digestion to simulate the biochemical processes occurring during digestion. Their cytotoxicity on intestinal cells was investigated using the Caco-2 cell model. Using field-flow fractionation combined with dynamic light scattering and small-angle X-ray scattering, the authors found that particles only partially aggregate as a result of the digestive process. Cell viabilities were determined by means of CellTiter-Blue® assay, 4',6-diamidino-2-phenylindole-staining and real-time impedance. These measurements reveal small differences between digested and undigested particles (1-100 µg/ml or 1-69 particles/cell). The findings suggest that silver nanoparticles may indeed overcome the gastrointestinal juices in their particulate form without forming large quantities of aggregates. Consequently, the authors presume that the particles can reach the intestinal epithelial cells after ingestion with only a slight reduction in their cytotoxic potential. The study indicates that it is important to determine the impact of body fluids on the nanoparticles of interest to provide a reliable interpretation of their nano-specific cytotoxicity testing in vivo and in vitro. London Informa Healthcare 2014 Nanotoxicology 8 6 631 642 10.3109/17435390.2013.815284 2016-02-20