R. Zellner

University of Duisburg-Essen, Essen, North Rhine-Westphalia, Germany

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Publications (155)231.62 Total impact

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    ABSTRACT: Whilst the physical and chemical properties of nanoparticles in the gas or idealized solvent phase can nowadays be characterized with sufficient accuracy, this is no longer the case for particles in the presence of a complex biological environment. Interactions between nanoparticles and biomolecules are highly complex on a molecular scale. The detailed characterization of nanoparticles under these conditions and the mechanistic knowledge of their molecular interactions with the biological world is, however, needed for any solid conclusions with regards to the relationship between the biological behavior of such particles and their physicochemical properties. In the present article we discuss some of the challenges with characterization and behavior of nanoparticles that are associated with their presence in chemically complex biological environments. Our focus is on the stability of colloids as well as on the formation and characteristics of protein coronae that have recently been shown to significantly modify the properties of pristine particles. Finally, we discuss the perspectives that may be expected from an improved understanding of nanoparticles in biological media.
    Physical Chemistry Chemical Physics 06/2014; 16(29). DOI:10.1039/c4cp00058g · 4.20 Impact Factor
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    ABSTRACT: PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm, a hydrodynamic diameter of 120 nm and a zeta potential of -20 mV were prepared and investigated with regard to their biological activity. This review summarizes the physicochemical properties (dissolution, protein adsorption, dispersability) of these nanoparticles and the cellular consequences of the exposure of a broad range of biological test systems to this defined type of silver nanoparticles. Silver nanoparticles dissolve in water in the presence of oxygen. In addition, in biological media (i.e., in the presence of proteins) the surface of silver nanoparticles is rapidly coated by a protein corona that influences their physicochemical and biological properties including cellular uptake. Silver nanoparticles are taken up by cell-type specific endocytosis pathways as demonstrated for hMSC, primary T-cells, primary monocytes, and astrocytes. A visualization of particles inside cells is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM analysis. By staining organelles, their localization inside the cell can be additionally determined. While primary brain astrocytes are shown to be fairly tolerant toward silver nanoparticles, silver nanoparticles induce the formation of DNA double-strand-breaks (DSB) and lead to chromosomal aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo induced a moderate pulmonary toxicity, however, only at rather high concentrations. The same was found in precision-cut lung slices of rats in which silver nanoparticles remained mainly at the tissue surface. In a human 3D triple-cell culture model consisting of three cell types (alveolar epithelial cells, macrophages, and dendritic cells), adverse effects were also only found at high silver concentrations. The silver ions that are released from silver nanoparticles may be harmful to skin with disrupted barrier (e.g., wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the data obtained on the effects of this well-defined type of silver nanoparticles on various biological systems clearly demonstrate that cell-type specific properties as well as experimental conditions determine the biocompatibility of and the cellular responses to an exposure with silver nanoparticles.
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    ABSTRACT: The interfacing of colloidal nanoparticles with mammalian cells is now well into its second decade. In this review our goal is to highlight the more generally accepted concepts that we have gleaned from nearly twenty years of research. While details of these complex interactions strongly depend, amongst others, upon the specific properties of the nanoparticles used, the cell type, and their environmental conditions, a number of fundamental principles exist, which are outlined in this review.
    Beilstein Journal of Nanotechnology 01/2014; 5:1477-90. DOI:10.3762/bjnano.5.161 · 2.33 Impact Factor
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    ABSTRACT: The deliquescence behavior of ternary inorganic (ammonium sulfate and ammonium nitrate)/organic (glutaric acid and malonic acid)/water aerosol particles has been investigated at 293 K using a novel surface aerosol microscopy (SAM) technique. The results obtained for the deliquescence relative humidities (DRH) for particles of variable inorganic/organic contents show a eutectic behavior with the mixed particles showing deliquescence at lower DRH compared to the pure inorganic and organic components, respectively. This behavior has been quantitatively modeled using the extended aerosol inorganics (E-AIM) thermodynamic model of Clegg et al. in combination with the UNIFAC group activity approach to account for organic molecular solutes. In addition, we have investigated the crystallization behavior of supersatured and formerly deliquesced ternary solution droplets using space resolved Raman spectroscopy. It is found that such droplets produce solid particles in which the inorganic and organic phases show some spatial separation with the organic component being predominantly found at the outer part of the particle. Independent measurements of the contact angles of such ternary droplets reveal that their angles are within experimental error identical to those of the purely organic/water solutions.
    The Journal of Physical Chemistry A 04/2012; 116(24):6199-210. DOI:10.1021/jp211522t · 2.77 Impact Factor
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    ABSTRACT: In biological fluids, proteins associate with nanoparticles, leading to a protein "corona" defining the biological identity of the particle. However, a comprehensive knowledge of particle-guided protein fingerprints and their dependence on nanomaterial properties is incomplete. We studied the long-lived ("hard") blood plasma derived corona on monodispersed amorphous silica nanoparticles differing in size (20, 30, and 100 nm). Employing label-free liquid chromatography mass spectrometry, one- and two-dimensional gel electrophoresis, and immunoblotting the composition of the protein corona was analyzed not only qualitatively but also quantitatively. Detected proteins were bioinformatically classified according to their physicochemical and biological properties. Binding of the 125 identified proteins did not simply reflect their relative abundance in the plasma but revealed an enrichment of specific lipoproteins as well as proteins involved in coagulation and the complement pathway. In contrast, immunoglobulins and acute phase response proteins displayed a lower affinity for the particles. Protein decoration of the negatively charged particles did not correlate with protein size or charge, demonstrating that electrostatic effects alone are not the major driving force regulating the nanoparticle-protein interaction. Remarkably, even differences in particle size of only 10 nm significantly determined the nanoparticle corona, although no clear correlation with particle surface volume, protein size, or charge was evident. Particle size quantitatively influenced the particle's decoration with 37% of all identified proteins, including (patho)biologically relevant candidates. We demonstrate the complexity of the plasma corona and its still unresolved physicochemical regulation, which need to be considered in nanobioscience in the future.
    ACS Nano 08/2011; 5(9):7155-67. DOI:10.1021/nn201950e · 12.03 Impact Factor
  • Lennart Treuel, Alice Sandmann, Reinhard Zellner
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    ABSTRACT: This work examines the crystals resulting from the efflorescence of internally mixed aqueous aerosols comprising ammonium sulphate and different dicarboxylic acids. Most studies on the deliquescence of aerosols use previously effloresced aerosols in their experiments. However, during efflorescence a highly supersaturated solution crystallises in a kinetically controlled way unlike the case of thermodynamically controlled crystallisation. Herein the distribution of individual substances within the effloresced crystals is investigated using Raman scanning experiments. The data presented show an intriguingly complex behaviour of these ternary and quarternary aerosols. A spatial separation of substances in the crystals resulting from the efflorescence of previously internally mixed ternary salt/dicarboxylic acid/water aerosol droplets is demonstrated and mechanistic aspects are discussed.
    ChemPhysChem 04/2011; 12(6):1109-17. DOI:10.1002/cphc.201000738 · 3.36 Impact Factor
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    ABSTRACT: Interactions between differently functionalised silver and gold nanoparticles (NPs) as well as polystyrene nanoparticles with bovine serum albumin (BSA) are studied using circular dichroism (CD) spectroscopy. It is found that the addition of NPs to the protein solution destroys part of the helical secondary structure of the protein as a result of surface adsorption. From the loss of free protein and hence the extent of their structural change adsorption equilibrium constants are derived. The results reveal that citrate-coated gold and silver NPs exhibit much stronger interactions with BSA than polymeric or polymer-coated metallic NPs. It is therefore concluded that for the particles considered, the influence of surface composition on the interaction behaviour dominates that of the core.
    ChemPhysChem 10/2010; 11(14):3093-9. DOI:10.1002/cphc.201000174 · 3.36 Impact Factor
  • D. Hoelscher, R. Zellner
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 08/2010; 33(32). DOI:10.1002/chin.200232017
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 07/2010; 27(30). DOI:10.1002/chin.199630027
  • Reinhard Zellner
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    ABSTRACT: Das Verständnis und die Bedeutung des Verhaltens von Spurenstoffen in der Atmosphäre sind innerhalb der letzten 20 Jahre stark gewachsen. Dies ist darauf zurückzuführen, daß die Grundlagenforschung an Breite und Tiefe zugenommen hat. Allerdings zeigt die wissenschaftliche Deutung drohender regionaler und globaler Umweltveränderungen, daß Politik und Gesellschaft handeln müssen.
    Nachrichten aus der Chemie 07/2010; 47(7):790-792. DOI:10.1002/nadc.19990470718 · 0.20 Impact Factor
  • Reinhard Zellner
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    ABSTRACT: Für die Enquête-Kommission „Schutz der Erdatmosphäre” hat Prof. Dr. Reinhard Zellner, Universität Essen, im Auftrag des Deutsche/! Bundestages den hier vorgelegten Statusbericht 1991/92 zum Ozonabbau in der Stratosphäre erarbeitet.
    Nachrichten aus der Chemie 07/2010; 40(7‐8):801 - 810. DOI:10.1002/nadc.19920400705 · 0.20 Impact Factor
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    ABSTRACT: Since chemical and radiative effects of atmospheric aerosols are size and phase related, they are strongly influenced by the ambient relative humidity (RH) due to water absorbing hygroscopic components, changing both particle diameter and wavelength dependent refractive indices. Therefore, the assessment of the net effect on chemistry and/or climate for a given atmospheric particle load will critically depend on the level of scientific understanding regarding the phase behaviour of complex organic/ inorganic aerosols. The influence of organic substances such as dicarboxylic acids on the deliquescence behaviour has been subject of numerous studies over the past years. In this work a number of different mixtures comprising ammonium sulphate (AS) and different dicarboxylic acids (glutaric acid, maleic acid, malonic acid, succinic acid, and oxalic acid) have been used in Raman scanning experiments to study the spacial distribution of substances in the crystalline aerosol formed from the efflorescence process of internally mixed ternary ammonium sulphate / dicarboxylic acid / water aerosols. The results give intriguing insights into the complexity of the behaviour of highly supersaturated ternary organic/inorganic solutions and reveal substantial differences in the spacial distributions of organic and inorganic crystalline substances resulting from the efflorescence of these originally internally mixed systems. The relevance of these findings for the interpretations of the complex, concentration dependent phase behaviour of organic/ inorganic aerosols will be discussed. Modelling the behaviour of these complex solution aerosols frequently involves calculations of interactions between individual ionic components. In order to quantify these impacts the ammonium salts for a number of dicarboxylic acids have been synthesised and their thermodynamic behaviour has been elucidated with the surface aerosol microscope (SAM) setup. The results have been used to test and validate critical parameters of the aerosol inorganics model (AIM). In this work we present activity measurements for aqueous aerosols containing these organic ammonium salts as well as a comparison of AIM model data and experimental results.
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    ABSTRACT: Spherical silver nanoparticles with a diameter of 50 ± 20 nm and stabilized with either poly(N-vinylpyrrolidone) (PVP) or citrate were dispersed in different cell culture media: (i) pure RPMI, (ii) RPMI containing up to 10% of bovine serum albumin (BSA), and (iii) RPMI containing up to 10% of fetal calf serum (FCS). The agglomeration behavior of the nanoparticles was studied with dynamic light scattering and optical microscopy of individually tracked single particles. Whereas strong agglomeration was observed in pure RPMI and in the RPMI–BSA mixture within a few hours, the particles remained well dispersed in RPMI–FCS. In addition, the biological effect of PVP-stabilized silver nanoparticles and of silver ions on human mesenchymal stem cells (hMSCs) was studied in pure RPMI and also in RPMI–BSA and RPMI–FCS mixtures, respectively. Both proteins considerably increased the cell viability in the presence of silver ions and as well as silver nanoparticles, indicating a binding of silver by these proteins.
    Journal of Materials Chemistry 01/2010; 20(3). DOI:10.1039/b914875b · 6.63 Impact Factor
  • Sabine Seisel, Thorsten Keil, Reinhard Zellner
    Zeitschrift für Physikalische Chemie 12/2009; 223(12):1477-1495. DOI:10.1524/zpch.2009.5499 · 1.18 Impact Factor
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    ABSTRACT: A molecular beam technique has been used to study the dynamics and mass accommodation of HCl molecules in collision with sulfuric acid-water surfaces. The experiments were performed by directing a nearly mono-energetic beam of HCl molecules onto a continuously renewed liquid film of 54-76 wt% sulfuric acid at temperatures between 213 K and 243 K. Deuterated sulfuric acid was used to separate sticking but non-reactive collisions from those that involved penetration through the phase boundary followed by dissociation and recombination with D+. The results indicate that the mass accommodation of HCl on sulfuric acid-water surfaces decreases sharply with increasing acidity over the concentration range 54-76 wt%. Using the capillary wave theory of mass accommodation this effect is explained by a change of the surface dynamics. Regarding the temperature dependence it is found that the mass accommodation of HCl increases with increasing temperature and is limited by the bulk phase viscosity and driven by the restoring forces of the surface tension. These findings imply that under atmospheric conditions the uptake of HCl from the gas phase depends crucially on the bulk phase parameters of the sulfuric acid aerosol.
    Physical Chemistry Chemical Physics 10/2009; 11(36):8048-55. DOI:10.1039/b904629a · 4.20 Impact Factor
  • L Treuel, S Pederzani, R Zellner
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    ABSTRACT: The deliquescence behaviour of ternary aerosols composed of ammonium sulfate (AS) and water, internally mixed with malonic acid (MOA), maleic acid (MEA) and glutaric acid (GAA), has been studied using a new surface aerosol microscope setup (SAM) as well as an electrodynamic balance (EDB). In each of the systems studied the addition of the organic acids to ammonium sulfate leads to a decrease of the deliquescence relative humidities (DRH). However, the observed behaviour of the DRH values over a large range of acid concentrations is complex and indicates a eutectic behaviour. Moreover, the ternary AS/MOA/water aerosols show a two step deliquescence process whose magnitude and concentration dependence have been quantitatively investigated for the first time. The results suggest that previous DRH interpretations underestimate the strength and the atmospheric implications of the MOA influence. In addition to the deliquescence behaviour, effloresced ternary aerosols were studied with respect to their morphology and crystal behaviour using environmental scanning electron microscopy (ESEM) and Raman microscopy (RM), respectively. It is found that in each case crystalline mixtures consisting of the pure AS and pure organic acid are formed. However, the crystalline appearances of the solids formed are different from those of the effloresced pure acids. Moreover, a maximum size of the single crystallites formed during the efflorescence of these complex ternary aerosols has been assigned.
    Physical Chemistry Chemical Physics 10/2009; 11(36):7976-84. DOI:10.1039/b905007h · 4.20 Impact Factor
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    Peter Behr, Ulrich Scharfenort, Reinhard Zellner
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    ABSTRACT: The collisions of hyperthermal noble gases (He, Ne, Ar, Kr, Xe) with supercooled binary sulfuric acid-water mixtures (57-77 wt%) were explored in the temperature range between 210 and 240 K. The experiments were performed by directing a molecular beam of the respective gases onto a continuously renewed liquid surface and monitoring the velocity of the scattered molecules by mass spectrometry. Depending on the initial translational energies and molecular masses, we observe both inelastic scattering from the surface as well as thermalization followed by subsequent desorption. The experiments indicate that the repulsive momentum transfer in the inelastic scattering channel increases with increasing mass of the impinging gas, while it is only weakly affected by the initial velocities. The final energy of the thermally desorbing atoms can always be approximated by a Maxwell-Boltzmann distribution equal to the liquid bulk phase temperature. The influence of the binary composition of the liquid phase is only noticeable in the case of Ne, whilst this dependence diminishes for gases with molecular masses >or=40 amu. The probability of thermalisation relative to inelastic scattering increases with the bulk phase temperature, independent of the molecular masses of the colliding gas. In contrast, the fractional energy transfer during collision does not increase with temperature, except for Neon. These results can be interpreted in the model framework of hard-sphere collisions of noble gases with the surface, during which water and sulfuric acid molecules interact independently with the impinging gas.
    Physical Chemistry Chemical Physics 10/2009; 11(33):7292-302. DOI:10.1039/b821751c · 4.20 Impact Factor
  • H Somnitz, T Ufer, R Zellner
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    ABSTRACT: Pressure dependent CO and CO2 quantum yields in the laser pulse photolysis of acetone at 248 nm and T = 298 K have been measured directly using quantitative infrared diode laser absorption. The experiments cover the pressure range from 50 to 900 mbar. It is found that the quantum yields show a significant dependence on total pressure, with Phi(CO) decreasing from around 0.5 at 20 mbar to approximately 0.3 at 900 mbar. The corresponding CO2 yields as observed when O2 exists in the reaction mixture, exhibit exactly the opposite behaviour. For the sum of both a value of 1.05(-0.05)(+0.02) independent of pressure is obtained, showing that the sum of (Phi(CO) + Phi(CO2)) is a measure for the primary quantum yield in the photolysis of acetone. In addition, CO quantum yields and corresponding pressure dependences were measured in experiments using different bath gases including He, Ar, Kr, SF6, and O2 as third body colliders. The theoretical framework in which we discuss these data is based on our previous findings that the pressure dependence of the CO yield is a consequence of a stepwise fragmentation mechanism during which acetone decomposes initially into methyl and a vibrationally 'hot' acetyl radical, with the latter being able to decompose promptly into methyl plus CO. The pressure dependence of the CO yield then originates from the second step and is modelled quantitatively via statistical dynamical calculations using a combination of RRKM theory with a time-dependent master equation (ME) approach. From a comparison of experiment with theory the amount of excess energy in the vibrationally hot acetyl radicals (E* approximately 65 kJ mol(-1)) as well as the characteristic collision parameters for interaction of acetyl with the different bath gases were derived. Values of 90, 280, 310, 545, 550 and 1800 cm(-1) for the average energy transferred per downward collision for the bath gases He, Ar, Kr, O2, N2, and SF6, respectively, are obtained. The calculations also considered different models for the energy transfer kernel P(E,E') and best fits were obtained with a rho-weighted exponential down model.
    Physical Chemistry Chemical Physics 10/2009; 11(38):8522-31. DOI:10.1039/b906751e · 4.20 Impact Factor
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    R. Zellner
    Chemie Ingenieur Technik 08/2009; 81(8):1125-1126. DOI:10.1002/cite.200950636 · 0.70 Impact Factor

Publication Stats

2k Citations
231.62 Total Impact Points


  • 1992–2014
    • University of Duisburg-Essen
      • Group of Physical Chemistry
      Essen, North Rhine-Westphalia, Germany
  • 1995–2000
    • University Hospital Essen
      Essen, North Rhine-Westphalia, Germany
    • IHU de Strasbourg
      Strasburg, Alsace, France
  • 1999
    • Klinikum Karlsruhe
      Carlsruhe, Baden-Württemberg, Germany
    • Georg-August-Universität Göttingen
      Göttingen, Lower Saxony, Germany
  • 1990–1998
    • Klinikum Garmisch-Partenkirchen
      Markt Garmisch-Partenkirchen, Bavaria, Germany
    • Klinikum Darmstadt
      Darmstadt, Hesse, Germany
  • 1997
    • ETH Zurich
      Zürich, Zurich, Switzerland
  • 1996
    • New York State
      New York City, New York, United States
  • 1994–1996
    • Humboldt-Universität zu Berlin
      Berlín, Berlin, Germany
    • HagaZiekenhuis van Den Haag
      's-Gravenhage, South Holland, Netherlands
    • University of Leipzig
      Leipzig, Saxony, Germany
  • 1993
    • SH-Gen Wiesbaden
      Wiesbaden, Hesse, Germany
  • 1991
    • Hochschule Bochum
      Bochum, North Rhine-Westphalia, Germany
  • 1988
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
    • University of East Anglia
      • School of Environmental Sciences
      Norwich, England, United Kingdom
  • 1987
    • Bergische Universität Wuppertal
      • Physical and Theoretical Chemistry
      Wuppertal, North Rhine-Westphalia, Germany