Prof. Dr. Axel Rosenhahn

Analytical Chemistry
Ruhr-Universität Bochum


  • Micro x-ray fluorescence analysis of trace element distribution in frozen hydrated HeLa cells at the P06 beamline at Petra III
    Rumancev, C. and Vöpel, T. and Stuhr, S. and Von Gundlach, A. and Senkbeil, T. and Ebbinghaus, S. and Garrevoet, J. and Falkenberg, G. and De Samber, B. and Vincze, L. and Rosenhahn, A. and Schroeder, W.
    Biointerphases 16 (2021)
    X-ray fluorescence analysis enables the study of trace element distributions in biological specimens. When this analysis is done under cryogenic conditions, cells are cryofixed as closely as possible to their natural physiological state, and the corresponding intracellular elemental densities can be analyzed. Details about the experimental setup used for analysis at the P06 beamline at Petra III, DESY and the used cryo-transfer system are described in this work. The system was applied to analyze the elemental distribution in single HeLa cells, a cell line frequently used in a wide range of biological applications. Cells adhered to silicon nitride substrates were cryoprotected within an amorphous ice matrix. Using a continuous scanning scheme and a KB x-ray focus, the distribution of elements in the cells was studied. We were able to image the intracellular potassium and zinc levels in HeLa cells as two key elements relevant for the physiology of cells. © 2021 Author(s).
    view abstract10.1116/6.0000593
  • Synthesis and Characterization of Dendritic and Linear Glycol Methacrylates and Their Performance as Marine Antifouling Coatings
    Wanka, R. and Koschitzki, F. and Puzovic, V. and Pahl, T. and Manderfeld, E. and Hunsucker, K.Z. and Swain, G.W. and Rosenhahn, A.
    ACS Applied Materials and Interfaces (2021)
    Dendritic polyglycerol (PG) was covalently coupled to 2-hydroxyethyl methacrylate (HEMA) by an anionically catalyzed ring-opening polymerization generating a dendritic PG-HEMA with four PG repetition units (PG4MA). Coatings of the methacrylate monomer were prepared by grafting-through and compared against commercially available hydrophilic monomers of HEMA, poly(ethylene) glycol methacrylate (PEGMA), and poly(propylene) glycol methacrylate (PPGMA). The obtained coatings were characterized by modern surface analytical techniques, including water contact angle goniometry (sessile and captive bubble), attenuated total internal reflection Fourier transform infrared spectroscopy, and atomic force microscopy. The antifouling (AF) and fouling-release (FR) properties of the coatings were tested against the model organisms Cobetia marina and Navicula perminuta in laboratory-scale dynamic accumulation assays as well as in a dynamic short-term field exposure (DSFE) in the marine environment. In addition, the hydration of the coatings and their susceptibility toward silt uptake were evaluated, revealing a strong correlation between water uptake, silt incorporation, and field assay performance. While all glycol derivatives showed good resistance in laboratory settlement experiments, PPGMA turned out to be less susceptible to silt incorporation and outperformed PEGMA and PG4MA in the DSFE assay. © 2021 American Chemical Society.
    view abstract10.1021/acsami.0c21212
  • Visible light-induced controlled surface grafting polymerization of hydroxyethyl methacrylate from isopropylthioxanthone semipinacol-terminated organic monolayers
    Balasubramaniam, A. and Manderfeld, E. and Krause, L.M.K. and Wanka, R. and Schwarze, J. and Beyer, C.D. and Rosenhahn, A.
    Polymer Chemistry 12 (2021)
    A visible light-induced living polymerization of a hydrophilic model monomer was initiated on organic silane monolayers using isopropylthioxanthone (ITX). The type II photoinitiator ITX was covalently introduced to the octadecyltrichlorosilane monolayers by UV-induced (254 nm) hydrogen abstraction and a subsequent coupling step through recombination. The resulting dormant isopropylthioxanthone semi-pinacol (ITXSP) groups can be reactivated by irradiation with visible light to initiate a controlled surface grafting polymerization. Using this surface-initiated polymerization approach, hydroxyethyl methacrylate (HEMA) was polymerized under visible light irradiation (385 nm) at room temperature. The polymer layer thickness depends linearly on the irradiation time, which is in good agreement with previous reports on the living characteristics of the polymerization reactions. It is possible to accurately control the thickness of the grafted layer by simply altering the irradiation time. © The Royal Society of Chemistry 2021.
    view abstract10.1039/d0py01410a
  • Amphiphilic Dicyclopentenyl/Carboxybetaine-Containing Copolymers for Marine Fouling-Release Applications
    Koschitzki, F. and Wanka, R. and Sobota, L. and Koc, J. and Gardner, H. and Hunsucker, K.Z. and Swain, G.W. and Rosenhahn, A.
    ACS Applied Materials and Interfaces 12 (2020)
    Zwitterionic materials received great attention in recent studies due to their high antifouling potential, though their application in practical coatings is still challenging. Amphiphilic polymers have been proven to be an effective method to combat fouling in the marine environment. This study reports the incorporation of small amounts of zwitterionic carboxybetaine methacrylate (CBMA) into hydrophobic ethylene glycol dicyclopentenyl ether acrylate (DCPEA). A new set of copolymers with varying amphiphilicities was synthesized and coated on chemically modified glass substrates. The antifouling capabilities were assessed against the diatom Navicula perminuta and multiple species in the field. Unsurprisingly, high diatom densities were observed on the hydrophobic control coatings. The integration of small zwitterionic contents of only ∼5 wt % was already sufficient to rapidly form a hydrophilic interface that led to a strong reduction of fouling. Ultralow fouling was also observed for the pure zwitterionic coatings in laboratory experiments, but it failed when tested in the real ocean environment. We noticed that the ability to absorb large amounts of water and the diffuse nature of the interphase correlate with the adsorption of silt, which can mask the hydrophilic chemistries and facilitate the settlement of organisms. The amphiphilic coatings showed low fouling in dynamic short-term field exposures, which could be explained by the reduced tendency of the coatings for sediment adsorption. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acsami.0c07599
  • Degradable hyaluronic acid/chitosan polyelectrolyte multilayers with marine fouling-release properties
    Yu, W. and Wanka, R. and Finlay, J.A. and Clarke, J.L. and Clare, A.S. and Rosenhahn, A.
    Biofouling 36 (2020)
    Polysaccharide multilayers consisting of hyaluronic acid and chitosan were prepared by layer-by-layer assembly. To be used in seawater, the multilayers were crosslinked to a different degree using thermal or chemical methods. ATR-FTIR revealed different amide densities as a result of the crosslinking conditions. AFM showed that the crosslinking affected the roughness and swelling behavior of the coatings. The stability and degradability of the multilayers in aqueous environments were monitored with spectroscopic ellipsometry. The resistance of the coatings against non-specific protein adsorption was characterized by SPR spectroscopy. Settlement assays using Ulva linza zoospores and removal assays using the diatom Navicula incerta showed that the slowly degradable coatings were less prone to fouling than the strongly crosslinked ones. Thus, the coatings were a suitable model system to show that crosslinking the multilayers under mild conditions and equipping the coatings with controlled degradation rates enhances their antifouling and fouling-release properties against marine fouling organisms. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/08927014.2020.1846725
  • Effect of Dipole Orientation in Mixed, Charge-Equilibrated Self-assembled Monolayers on Protein Adsorption and Marine Biofouling
    Koc, J. and Schardt, L. and Nolte, K. and Beyer, C. and Eckhard, T. and Schwiderowski, P. and Clarke, J.L. and Finlay, J.A. and Clare, A.S. and Muhler, M. and Laschewsky, A. and Rosenhahn, A.
    ACS Applied Materials and Interfaces 12 (2020)
    While zwitterionic interfaces are known for their excellent low-fouling properties, the underlying molecular principles are still under debate. In particular, the role of the zwitterion orientation at the interface has been discussed recently. For elucidation of the effect of this parameter, self-assembled monolayers (SAMs) on gold were prepared from stoichiometric mixtures of oppositely charged alkyl thiols bearing either a quaternary ammonium or a carboxylate moiety. The alkyl chain length of the cationic component (11-mercaptoundecyl)-N,N,N-trimethylammonium, which controls the distance of the positively charged end group from the substrate's surface, was kept constant. In contrast, the anionic component and, correspondingly, the distance of the negatively charged carboxylate groups from the surface was varied by changing the alkyl chain length in the thiol molecules from 7 (8-mercaptooctanoic acid) to 11 (12-mercaptododecanoic acid) to 15 (16-mercaptohexadecanoic acid). In this way, the charge neutrality of the coating was maintained, but the charged groups exposed at the interface to water were varied, and thus, the orientation of the dipoles in the SAMs was altered. In model biofouling studies, protein adsorption, diatom accumulation, and the settlement of zoospores were all affected by the altered charge distribution. This demonstrates the importance of the dipole orientation in mixed-charged SAMs for their inertness to nonspecific protein adsorption and the accumulation of marine organisms. Overall, biofouling was lowest when both the anionic and the cationic groups were placed at the same distance from the substrate's surface. © 2020 American Chemical Society. All rights reserved.
    view abstract10.1021/acsami.0c11580
  • Effect of ozone stress on the intracellular metabolites from Cobetia marina
    Li, J. and Rumancev, C. and Lutze, H.V. and Schmidt, T.C. and Rosenhahn, A. and Schmitz, O.J.
    Analytical and Bioanalytical Chemistry 412 (2020)
    A GCxGC-MS system was employed with a non-polar × mid-polar column set for the metabolic non-target analysis of Cobetia marina, the model bacteria for marine biofouling. C. marina was treated with ozone to investigate the intracellular metabolic state change under oxidative stress. A minimal inhibitory concentration test was involved to guarantee that the applied ozone dosages were not lethal for the cells. In this study, non-target analyses were performed to identify the metabolites according to the NIST database. As a result, over 170 signals were detected under normal living conditions including 35 potential metabolites. By the comparison of ozone-treated and non-treated samples, five compounds were selected to describe observed trends of signals in the contour plots. Oleic acid exhibited a slight growth by increasing ozone dosage. In contrast, other metabolites such as the amino acid l-proline showed less abundance after ozone treatment, which was more evident once ozone dosage was raised. Thus, this work could provide a hint for searching for up/downregulating factors in such environmental stress conditions for C. marina. [Figure not available: see fulltext.]. © 2020, The Author(s).
    view abstract10.1007/s00216-020-02810-6
  • Effects of crosslink density in zwitterionic hydrogel coatings on their antifouling performance and susceptibility to silt uptake
    Koc, J. and Schönemann, E. and Wanka, R. and Aldred, N. and Clare, A.S. and Gardner, H. and Swain, G.W. and Hunsucker, K. and Laschewsky, A. and Rosenhahn, A.
    Biofouling 36 (2020)
    Hydrogel coatings effectively reduce the attachment of proteins and organisms in laboratory assays, in particular when made from zwitterionic monomers. In field experiments with multiple species and non-living material, such coatings suffer from adsorption of particulate matter. In this study, the zwitterionic monomer 3-[N-(2-methacryloyloxyethyl)-N,N-dimethylammonio] propanesulfonate (SPE) was copolymerized with increasing amounts of the photo-crosslinker benzophenon-4-yloxyethyl methacrylate (BPEMA) to systematically alter the density of crosslinks between the polymer chains. The effect of increasing crosslink density on the antifouling (AF) performance of the coatings was investigated in laboratory assays and fields tests. In both cases, the AF performance was improved by increasing the crosslinker content. The coatings reduced protein, diatom, and barnacle accumulation, and showed better resistance to biomass accumulation. The findings underline that the marine AF performance of hydrogel coatings does not only depend on the specific chemical structure of the polymers, but also on their physico-chemical properties such as rigidity and swelling. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/08927014.2020.1796983
  • Fully convolutional neural network for detection and counting of diatoms on coatings after short-term field exposure
    Krause, L.M.K. and Koc, J. and Rosenhahn, B. and Rosenhahn, A.
    Environmental Science and Technology 54 (2020)
    While the use of deep learning is a valuable technology for automatic detection systems for medical data and images, the biofouling community is still lacking an analytical tool for the detection and counting of diatoms on samples after short-term field exposure. In this work, a fully convolutional neural network was implemented as a fast and simple approach to detect diatoms on two-channel (fluorescence and phase-contrast) microscopy images by predicting bounding boxes. The developed approach performs well with only a small number of trainable parameters and a F1 score of 0.82. Counting diatoms was evaluated on a data set of 600 microscopy images of three different surface chemistries (hydrophilic and hydrophobic) and is very similar to counting by humans while demanding only a fraction of the analysis time. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.est.0c01982
  • Low Fouling Peptides with an All (d) Amino Acid Sequence Provide Enhanced Stability against Proteolytic Degradation while Maintaining Low Antifouling Properties
    Beyer, C.D. and Reback, M.L. and Heinen, N. and Thavalingam, S. and Rosenhahn, A. and Metzler-Nolte, N.
    Langmuir 36 (2020)
    Peptide-functionalized surfaces, composed of optimized l-peptides, show a high resistance toward nonspecific adsorption of proteins. As l-peptides are known to be prone to proteolytic degradation, the aim of this work is to enhance the stability against enzymatic degradation by using the all d-peptide mirror image of the optimized l-peptides and to determine if the all d-enantiomer retains the protein-resistant and antifouling properties. Two l-peptides and their d-peptide mirror images, some of them containing the nonproteinogenic amino acid α-aminoisobutyric acid (Aib), were synthesized and tested against non-specific adsorption of the proteins lysozyme and fibrinogen and the settlement of marine diatom Navicula perminuta and marine bacteria Cobetia marina. Both the d-enantiomer and the insertion of Aib protected the peptides from proteolytic degradation. Protein resistance was enhanced with the d-enantiomers while maintaining the resistance toward diatoms. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.langmuir.0c01790
  • Microfluidic accumulation assay to quantify the attachment of the marine bacterium Cobetia marina on fouling-release coatings
    Schwarze, J. and Wanka, R. and Rosenhahn, A.
    Biointerphases 15 (2020)
    Testing the adhesion of marine biofilm formers on bioresistant coatings is important to determine their fouling-release and antifouling properties. A dynamic attachment assay for the marine bacterium Cobetia marina (C. marina) was developed to test the adhesion on coatings and bioresistant surfaces. With well-defined culture conditions, the reproducibility of the microfluidic accumulation experiments with C. marina was verified using self-assembling monolayers as model surfaces. The assay discriminated the attachment of C. marina on four different surfaces with different wettability and protein resistances. In addition to these benchmark experiments on self-assembled monolayers, the adhesion of C. marina on polyglycerol coatings with different thicknesses was investigated. © 2020 Author(s).
    view abstract10.1116/6.0000240
  • Soft X-ray diffraction patterns measured by a LiF detector with sub-micrometre resolution and an ultimate dynamic range
    Makarov, S. and Pikuz, S. and Ryazantsev, S. and Pikuz, T. and Buzmakov, A. and Rose, M. and Lazarev, S. and Senkbeil, T. and Von Gundlach, A. and Stuhr, S. and Rumancev, C. and Dzhigaev, D. and Skopintsev, P. and Zaluzhnyy, I. and Viefhaus, J. and Rosenhahn, A. and Kodama, R. and Vartanyants, I.A.
    Journal of Synchrotron Radiation 27 (2020)
    The unique diagnostic possibilities of X-ray diffraction, small X-ray scattering and phase-contrast imaging techniques applied with high-intensity coherent X-ray synchrotron and X-ray free-electron laser radiation can only be fully realized if a sufficient dynamic range and/or spatial resolution of the detector is available. In this work, it is demonstrated that the use of lithium fluoride (LiF) as a photoluminescence (PL) imaging detector allows measuring of an X-ray diffraction image with a dynamic range of ∼107 within the sub-micrometre spatial resolution. At the PETRA III facility, the diffraction pattern created behind a circular aperture with a diameter of 5μm irradiated by a beam with a photon energy of 500eV was recorded on a LiF crystal. In the diffraction pattern, the accumulated dose was varied from 1.7 × 105Jcm-3 in the central maximum to 2 × 10-2Jcm-3 in the 16th maximum of diffraction fringes. The period of the last fringe was measured with 0.8μm width. The PL response of the LiF crystal being used as a detector on the irradiation dose of 500eV photons was evaluated. For the particular model of laser-scanning confocal microscope Carl Zeiss LSM700, used for the readout of the PL signal, the calibration dependencies on the intensity of photopumping (excitation) radiation (λ = 488nm) and the gain have been obtained. © 2020. J. Synchrotron Rad.
    view abstract10.1107/S1600577520002192
  • Sol-Gel-Based Hybrid Materials as Antifouling and Fouling-Release Coatings for Marine Applications
    Wanka, R. and Koc, J. and Clarke, J. and Hunsucker, K.Z. and Swain, G.W. and Aldred, N. and Finlay, J.A. and Clare, A.S. and Rosenhahn, A.
    ACS Applied Materials and Interfaces 12 (2020)
    Hybrid materials (HMs) offer unique properties as they combine inorganic and organic components into a single material. Here, we developed HM coatings for marine antifouling applications using sol-gel chemistry and naturally occurring polysaccharides. The coatings were characterized by spectroscopic ellipsometry, contact angle goniometry, AFM, and ATR-FTIR, and their stability was tested in saline media. Marine antifouling and fouling-release properties were tested in laboratory assays against the settlement of larvae of the barnacle Balanus improvisus and against the settlement and removal of the diatom Navicula incerta. Furthermore, laboratory data were confirmed in short-term dynamic field assays in Florida, USA. All hybrid coatings revealed a superior performance in the assays compared to a hydrophobic reference. Within the hybrids, those with the highest degree of hydrophilicity and negative net charge across the surface performed best. Alginate and heparin showed good performance, making these hybrid materials promising building blocks for fouling-resistant coatings. © 2020 American Chemical Society.
    view abstract10.1021/acsami.0c15288
  • Synthesis of Novel Sulfobetaine Polymers with Differing Dipole Orientations in Their Side Chains, and Their Effects on the Antifouling Properties
    Schönemann, E. and Koc, J. and Aldred, N. and Clare, A.S. and Laschewsky, A. and Rosenhahn, A. and Wischerhoff, E.
    Macromolecular Rapid Communications 41 (2020)
    The impact of the orientation of zwitterionic groups, with respect to the polymer backbone, on the antifouling performance of thin hydrogel films made of polyzwitterions is explored. In an extension of the recent discussion about differences in the behavior of polymeric phosphatidylcholines and choline phosphates, a quasi-isomeric set of three poly(sulfobetaine methacrylate)s is designed for this purpose. The design is based on the established monomer 3-[N-2-(methacryloyloxy)ethyl-N,N-dimethyl]ammonio-propane-1-sulfonate and two novel sulfobetaine methacrylates, in which the positions of the cationic and the ionic groups relative to the polymerizable group, and thus also to the polymer backbone, are altered. The effect of the varied segmental dipole orientation on their water solubility, wetting behavior by water, and fouling resistance is compared. As model systems, the adsorption of the model proteins bovine serum albumin (BSA), fibrinogen, and lysozyme onto films of the various polyzwitterion surfaces is studied, as well as the settlement of a diatom (Navicula perminuta) and barnacle cyprids (Balanus improvisus) as representatives of typical marine fouling communities. The results demonstrate the important role of the zwitterionic group's orientation on the polymer behavior and fouling resistance. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/marc.201900447
  • Thermoregeneration of Plastrons on Superhydrophobic Coatings for Sustained Antifouling Properties
    Simovich, T. and Rosenhahn, A. and Lamb, R.N.
    Advanced Engineering Materials 22 (2020)
    A popular and desirable function of superhydrophobic coatings is their remarkable ability to retain an entrapped layer of air, called a plastron, when submerged underwater. The drawback is that the air layer is short-lived due to solvation into the surrounding liquid. While manipulating the solubility of gases using temperature is a possible approach, it generally requires inefficiently heating large volumes of water. Following the demonstrated ability to maintain air bubbles on superhydrophobic surfaces for drag reduction, this article introduces a novel method of extracting gas from water to replenish and stabilize the plastron on superhydrophobic surfaces for sustained antifouling abilities. This method involves locally heating the liquid surrounding a superhydrophobic coating, reducing gas solubility, and causing the gas to nucleate at the liquid–air interface. The approach requires a relatively low energy input, due to the small volume of locally heated water. With a constant supply of equilibrated water and minimal energy input, the plastron can survive indefinitely without the need for a mechanical delivery of air. The thermoregenerating superhydrophobic samples were shown to exhibit excellent antifouling behavior and inhibited diatom attachment over a period of 5 days. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/adem.201900806
  • α-Aminoisobutyric acid-stabilized peptide sams with low nonspecific protein adsorption and resistance against marine biofouling
    Beyer, C.D. and Reback, M.L. and Gopal, S.M. and Nolte, K.A. and Finlay, J.A. and Clare, A.S. and Schäfer, L.V. and Metzler-Nolte, N. and Rosenhahn, A.
    ACS Sustainable Chemistry and Engineering 8 (2020)
    A series of low fouling peptide self-assembled monolayers (SAMs) was developed to understand how the effects of subtle sequence alterations determine the properties of peptide-terminated SAMs and settlement and adhesion of two model fouling organisms, the green alga Ulva linza and the diatom Navicula perminuta, and adsorption of two different proteins, fibrinogen and lysozyme. Insertion of the bulky, nonproteinogenic amino acid α-aminoisobutyric acid (Aib) was examined for how it affects the peptide surfaces and performance in the assays. By exchanging the serine (S) of the sequence (SGKGSSGSS) with alanine (A), we slightly altered the hydrophilicity and found reduced fouling by N. perminuta. The inclusion of Aib residues resulted in surface structural changes of the peptides from a mixture of β-sheet/random coil to strictly random coil and a decrease in the overall packing density by about 17-37%. Notably, these changes had little effect on the ability of the surface to resist nonspecific adsorption of fibrinogen and lysozyme and attachment of N. perminuta. The sequences containing Aib were 50-84% better than without Aib against the settlement of the zoospore of U. linza. Furthermore, the inclusion of Aib helped to create peptides that were 100% resistant against enzymatic degradation by trypsin, whereas the peptides without Aib were 95% degraded after 4 h. © 2020 American Chemical Society.
    view abstract10.1021/acssuschemeng.9b05889
  • Antifouling Properties of Dendritic Polyglycerols against Marine Macrofouling Organisms
    Wanka, R. and Aldred, N. and Finlay, J.A. and Amuthalingam, A. and Clarke, J.L. and Clare, A.S. and Rosenhahn, A.
    Langmuir 35 (2019)
    Dendritic polyglycerols (PGs) were synthesized and postmodified by grafting of poly(ethylene glycol) (PEG) and polypropylene glycol (PPG) diglycidyl ether groups, and their antifouling and fouling-release properties were tested. Coating characterization by spectroscopic ellipsometry, contact angle goniometry, attenuated total internal reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and atomic force microscopy showed brushlike morphologies with a high degree of microscale roughness and the ability to absorb large amounts of water within seconds. PGs with three different thicknesses were tested in laboratory assays against settlement of larvae of the barnacle Balanus improvisus and against the settlement and removal of zoospores of the alga Ulva linza. Very low coating thicknesses, e.g., 11 nm, reduced the settlement of barnacles, under static conditions, to 2% compared with 55% for an octadecyltrichlorosilane reference surface. In contrast, zoospores of U. linza settled readily but the vast majority were removed by exposure to a shear force of 52 Pa. Both PEG and PPG modification increased the antifouling properties of the PG films, providing a direct comparison of the ultralow fouling properties of all three polymers. Both, the modified and the nonmodified PGs are promising components for incorporation into amphiphilic fouling-resistant coatings. © 2019 American Chemical Society.
    view abstract10.1021/acs.langmuir.9b02720
  • BioSAxS measurements reveal that two antimicrobial peptides induce similar molecular changes in Gram-negative and Gram-positive bacteria
    Von Gundlach, A. and Ashby, M.P. and Gani, J. and Lopez-Perez, P.M. and Cookson, A.R. and Huws, S.A. and Rumancev, C. and Garamus, V.M. and Mikut, R. and Rosenhahn, A. and Hilpert, K.
    Frontiers in Pharmacology 10 (2019)
    Two highly active short broad-spectrum AMPs (14D and 69D) with unknown mode of action have been investigated in regards to their effect against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria methicillin-resistant Staphylococcus aureus (MRSA). Minimal inhibitory concentration (MIC) measurements using a cell density of 108 cfu/ml resulted in values between 16 and 32 µg/ml. Time-kill experiments using 108 cfu/ml revealed complete killing, except for 69D in combination with MRSA, where bacterial load was reduced a million times. Small-angle X-ray scattering of biological samples (BioSAXS) at 108 cfu/ml was applied to investigate the ultrastructural changes in E. coli and MRSA in response to these two broad-spectrum AMPs. In addition, electron microscopy (EM) was performed to visualize the treated and non-treated bacteria. As expected, the scattering curves generated using BioSAXS show the ultrastructure of the Gram-positive and Gram-negative bacteria to be very different (BioSAXS is not susceptible to the outer shape). After treatment with either peptide, the scattering curves of E. coli and MRSA cells are much more alike. Whereas in EM, it is notoriously difficult to observe changes for spherical Gram-positives; the BioSAXS results are superior and reveal strongly similar effects for both peptides induced in Gram-positive as well as Gram-negative bacteria. Given the high-throughput possibility and robust statistics, BioSAXS can support and speed up mode of action research in AMPs and other antimicrobial compounds, making a contribution toward the development of urgently needed drugs against resistant bacteria. Copyright © 2019 von Gundlach, Ashby, Gani, Lopez-Perez, Cookson, Ann Huws, Rumancev, Garamus, Mikut, Rosenhahn and Hilpert. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
    view abstract10.3389/fphar.2019.01127
  • Layer-by-layer constructed hyaluronic acid/chitosan multilayers as antifouling and fouling-release coatings
    Yu, W. and Koc, J. and Finlay, J.A. and Clarke, J.L. and Clare, A.S. and Rosenhahn, A.
    Biointerphases 14 (2019)
    Polyelectrolyte multilayers (PEMs) consisting of hyaluronic acid (HA) and chitosan (Ch) are extensively studied for biomedical applications and suppress bacterial and protein attachment. Here, we prepared and tested HA/Ch PEMs as marine fouling-release coatings. PEMs were constructed by layer-by-layer assembly using spin coating. The multilayers were crosslinked for enhanced stability in the sea water environment by chemical and thermal treatment. Protein-repelling properties of the crosslinked multilayers were investigated by surface plasmon resonance spectroscopy. The marine antifouling and fouling-release properties were tested against the settlement of zoospores of the green alga Ulva linza and the subsequent development and removal of sporelings. With spin coating and thermal crosslinking, a thick yet homogeneous coating was obtained with antifouling properties against marine algal zoospores indicating the potential of these compounds for application in protective coatings. © 2019 Author(s).
    view abstract10.1116/1.5110887
  • Low-Fouling Thin Hydrogel Coatings Made of Photo-Cross-Linked Polyzwitterions
    Koc, J. and Schönemann, E. and Amuthalingam, A. and Clarke, J. and Finlay, J.A. and Clare, A.S. and Laschewsky, A. and Rosenhahn, A.
    Langmuir 35 (2019)
    Although zwitterionic chemistries are among the most promising materials for producing nonfouling surfaces, their structural diversity has been low until now. Here, we compare the in vitro fouling behavior of a set of four systematically varied sulfa-/sulfobetaine-containing zwitterionic hydrogel coatings against a series of proteins and nonmotile as well as motile marine organisms as model foulers. The coatings are prepared by simultaneous photoinduced cross-linking and surface anchoring to elucidate the effect of the molecular structure of the zwitterionic moieties on their antifouling activity. Analogously prepared coatings of poly(butyl methacrylate) and poly(oligoethylene glycol methacrylate) serve as references. Photoreactive polymers are synthesized by the statistical copolymerization of sulfobetaine or sulfabetaine methacrylates and methacrylamides with a benzophenone derivative of 2-hydroxyethyl methacrylate and are applied as a thin film coating. While keeping the density of the zwitterionic and cross-linker groups constant, the molecular structure of the zwitterionic side chains is varied systematically, as is the arrangement of the ion pairs in the side chain by changing the classical linear geometry to a novel Y-shaped geometry. All of the polyzwitterions strongly reduce fouling compared to poly(butyl methacrylate). Overall, the sulfabetaine polyzwitterion coatings studied matches the high antifouling effectiveness of oligo(ethylene glycol)-based ones used as a control. Nevertheless, performances varied individually for a given pair of polymer and fouler. The case of the polysulfobetaines exemplifies that minor chemical changes in the polymer structure affect the antifouling performance markedly. Accordingly, the antifouling performance of such polymers cannot be correlated simply to the type of zwitterion used (which could be generally ranked as better performing or poorer performing) but is a result of the polymer's precise chemical structure. Our findings underline the need to enlarge the existing structural diversity of polyzwitterions for antifouling purposes to optimize the potential of their chemical structure. © 2018 American Chemical Society.
    view abstract10.1021/acs.langmuir.8b02799
  • Microfluidic Shear Force Assay to Determine Cell Adhesion Forces
    Hümmer, J. and Koc, J. and Rosenhahn, A. and Lee-Thedieck, C.
    Methods in Molecular Biology 2017 (2019)
    Cell adhesion is implicated in many physiological settings such as the retention of hematopoietic stem cells (HSCs) in their bone marrow niches or their migration into the bloodstream. During HSC mobilization these adhesion sites are cleaved and have to be newly formed during HSC homing and engraftment. To determine the adhesive properties of HSCs on different extracellular matrix (ECM) molecules, we present a microfluidic shear force assay, where a laminar flow is used to detach a semi-adherent cell population, the HSC model cell line KG-1a, from an ECM protein-coated substrate. This technique combines the high throughput of population-based assays with the ability to observe cell detachment in real time. Additionally, it is suitable for weakly adherent cells, as the setup allows cell incubation on various substrates and application of shear stress ranging several orders of magnitude in one setup without additional washing or transfer steps. As a measure for the adhesion strength of the studied cell population on the substrate, the critical shear force τ50 is determined which is required to remove 50% of the initially adherent cell fraction. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
    view abstract10.1007/978-1-4939-9574-5_6
  • Molecular Design of Zwitterionic Polymer Interfaces: Searching for the Difference
    Laschewsky, A. and Rosenhahn, A.
    Langmuir 35 (2019)
    The widespread occurrence of zwitterionic compounds in nature has incited their frequent use in designing biomimetic materials. Therefore, zwitterionic polymers are a thriving field. A particular interest for this particular polymer class has currently focused on their use in establishing neutral, low-fouling surfaces. After highlighting strategies to prepare model zwitterionic surfaces as well as those that are more suitable for practical purposes relying strongly on radical polymerization methods, we present recent efforts to diversify the structure of the hitherto quite limited variety of zwitterionic monomers and of the derived polymers. We identify key structural variables, consider their influence on essential properties such as overall hydrophilicity and long-term stability, and discuss promising targets for the synthesis of new variants. © 2018 American Chemical Society.
    view abstract10.1021/acs.langmuir.8b01789
  • Sediment challenge to promising ultra-low fouling hydrophilic surfaces in the marine environment
    Koc, J. and Simovich, T. and Schönemann, E. and Chilkoti, A. and Gardner, H. and Swain, G.W. and Hunsucker, K. and Laschewsky, A. and Rosenhahn, A.
    Biofouling 35 (2019)
    Hydrophilic coatings exhibit ultra-low fouling properties in numerous laboratory experiments. In stark contrast, the antifouling effect of such coatings in vitro failed when performing field tests in the marine environment. The fouling release performance of nonionic and zwitterionic hydrophilic polymers was substantially reduced compared to the controlled laboratory environment. Microscopy and spectroscopy revealed that a large proportion of the accumulated material in field tests contains inorganic compounds and diatomaceous soil. Diatoms adhered to the accumulated material on the coating, but not to the pristine polymer. Simulating field tests in the laboratory using sediment samples collected from the test sites showed that incorporated sand and diatomaceous earth impairs the fouling release characteristics of the coatings. When exposed to marine sediment from multiple locations, particulate matter accumulated on these coatings and served as attachment points for diatom adhesion and enhanced fouling. Future developments of hydrophilic coatings should consider accumulated sediment and its potential impact on the antifouling performance. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/08927014.2019.1611790
  • Surface modification by polyzwitterions of the sulfabetaine-type, and their resistance to biofouling
    Schönemann, E. and Laschewsky, A. and Wischerhoff, E. and Koc, J. and Rosenhahn, A.
    Polymers 11 (2019)
    Films of zwitterionic polymers are increasingly explored for conferring fouling resistance to materials. Yet, the structural diversity of polyzwitterions is rather limited so far, and clear structure-property relationships are missing. Therefore, we synthesized a series of new polyzwitterions combining ammonium and sulfate groups in their betaine moieties, so-called poly(sulfabetaine)s. Their chemical structures were varied systematically, the monomers carrying methacrylate, methacrylamide, or styrene moieties as polymerizable groups. High molar mass homopolymers were obtained by free radical polymerization. Although their solubilities in most solvents were very low, brine and lower fluorinated alcohols were effective solvents in most cases. A set of sulfabetaine copolymers containing about 1 mol % (based on the repeat units) of reactive benzophenone methacrylate was prepared, spin-coated onto solid substrates, and photo-cured. The resistance of these films against the nonspecific adsorption by two model proteins (bovine serum albumin-BSA, fibrinogen) was explored, and directly compared with a set of references. The various polyzwitterions reduced protein adsorption strongly compared to films of poly(n-butyl methacrylate) that were used as a negative control. The poly(sulfabetaine)s showed generally even somewhat higher anti-fouling activity than their poly(sulfobetaine) analogues, though detailed efficacies depended on the individual polymer-protein pairs. Best samples approach the excellent performance of a poly(oligo(ethylene oxide) methacrylate) reference. © 2019 by the authors.
    view abstract10.3390/polym11061014
  • A Multiperspective Approach to Solvent Regulation of Enzymatic Activity: HMG-CoA Reductase
    Dirkmann, M. and Iglesias-Fernández, J. and Muñoz, V. and Sokkar, P. and Rumancev, C. and von Gundlach, A. and Krenczyk, O. and Vöpel, T. and Nowack, J. and Schroer, M.A. and Ebbinghaus, S. and Herrmann, C. and Rosenhahn, A. and Sanchez-Garcia, E. and Schulz, F.
    ChemBioChem 19 (2018)
    3-Hydroxy-3-methylglutaryl–coenzyme A (HMG-CoA) reductase was investigated in different organic cosolvents by means of kinetic and calorimetric measurements, molecular dynamics simulations, and small-angle X-ray scattering. The combined experimental and theoretical techniques were essential to complement each other's limitations in the investigation of the complex interaction pattern between the enzyme, different solvent types, and concentrations. In this way, the underlying mechanisms for the loss of enzyme activity in different water-miscible solvents could be elucidated. These include direct inhibitory effects onto the active center and structural distortions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/cbic.201700596
  • Amphiphilic Alginates for Marine Antifouling Applications
    Jakobi, V. and Schwarze, J. and Finlay, J.A. and Nolte, K.A. and Spöllmann, S. and Becker, H.-W. and Clare, A.S. and Rosenhahn, A.
    Biomacromolecules 19 (2018)
    Amphiphilic polymers are promising candidates for novel fouling-release coatings for marine applications. We grafted amphiphilic alginates with fluorinated side chains to glass and silicon substrates and characterized the obtained films by contact angle goniometry, spectroscopic ellipsometry, XPS, and ATR-FTIR. The potential to inhibit protein attachment was tested against four different proteins, and intermediate fluorine loadings showed the strongest reduction with respect to hydrophobic, aliphatic controls. A similar trend was observed in dynamic attachment experiments using Navicula perminuta diatoms and settlement experiments with zoospores of the green algae Ulva linza. The results indicate that amphiphilic alginates are promising natural and renewable biomacromolecules that could be included in future protective coating technologies. © 2017 American Chemical Society.
    view abstract10.1021/acs.biomac.7b01498
  • Dynamic field testing of coating chemistry candidates by a rotating disk system
    Nolte, K.A. and Koc, J. and Barros, J.M. and Hunsucker, K. and Schultz, M.P. and Swain, G.W. and Rosenhahn, A.
    Biofouling 34 (2018)
    Quick and reliable testing is crucial for the development of new fouling release (FR) coatings. Exposure of these coatings to natural multispecies communities is essential in evaluating their efficacy. To this end, we present a rotating disk setup for dynamic field exposure. To achieve a well-defined flow on the surface of the disk, an easy to use sample mounting system was developed that provides a smooth and even surface. We related the angular velocity of the disk to the wall shear stress on the surface with a hydrodynamic model. The wall shear stress was adjusted to values previously found to be suitable to discriminate dynamic diatom attachment on different coating chemistries in the lab. The effect of the dynamic conditions was shown by comparing polystyrene slides under static and dynamic exposure. Using a set of self-assembled monolayers, the discrimination potential of the assay in a multispecies environment was demonstrated. © 2018 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/08927014.2018.1459578
  • Encapsulation Efficiency and Release Behavior of Fat Microcapsules with Lipophilic Emulsifiers [Verkapselungseffizienz und Freisetzungsverhalten fettbasierter Mikrokapseln mit lipophilen Emulgatoren]
    Scholz, R. and Davico, L. and Jakobi, V. and Kareth, S. and Rosenhahn, A. and Weidner, E.
    Chemie-Ingenieur-Technik 90 (2018)
    Encapsulated systems are particularly important for food industry and pharmacy. The challenge in producing microcapsules is to achieve the highest possible amount of entrapped material and to control the release of this material. In this study, two lipophilic emulsifiers and their influence on the encapsulation efficiency and the release behavior of the obtained microcapsules, consisting of a hard fat and a salt solution, concerning the release in aqueous environment are compared. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/cite.201700118
  • Exploring the long-term hydrolytic behavior of zwitterionic polymethacrylates and polymethacrylamides
    Schönemann, E. and Laschewsky, A. and Rosenhahn, A.
    Polymers 10 (2018)
    The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl- N, N-dimethyl) ammoniopropanesulfonate) ("sulfobetaine methacrylate"), and poly(3-(N-3-methacryamidopropyl- N, N-dimethyl)ammoniopropanesulfonate) ("sulfobetaine methacrylamide") as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by 1H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile. © 2018 by the authors.
    view abstract10.3390/polym10060639
  • Fouling-Release Properties of Dendritic Polyglycerols against Marine Diatoms
    Wanka, R. and Finlay, J.A. and Nolte, K.A. and Koc, J. and Jakobi, V. and Anderson, C. and Clare, A.S. and Gardner, H. and Hunsucker, K.Z. and Swain, G.W. and Rosenhahn, A.
    ACS Applied Materials and Interfaces 10 (2018)
    Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reaction, and the fouling-release properties against marine organisms were determined. The coatings were characterized by spectroscopic ellipsometry, contact angle goniometry, ATR-FTIR, and stability tests in different aqueous media. A high resistance toward the attachment of different proteins was found. The PG coatings with three different thicknesses were tested in a laboratory assay against the diatom Navicula incerta and in a field assay using a rotating disk. Under static conditions, the PG coatings did not inhibit the initial attachment of diatoms, but up to 94% of attached diatoms could be removed from the coatings after exposure to a shear stress of 19 Pa. Fouling release was found to be enhanced if the coatings were sufficiently thick. The excellent fouling-release properties were supported in dynamic field-immersion experiments in which the samples were continually exposed to a shear stress of 0.18 Pa. © 2018 American Chemical Society.
    view abstract10.1021/acsami.8b12017
  • Parallelized microfluidic diatom accumulation assay to test fouling-release coatings
    Nolte, K.A. and Schwarze, J. and Beyer, C.D. and Özcan, O. and Rosenhahn, A.
    Biointerphases 13 (2018)
    Assessing the efficiency of the next generation of protective marine coatings is highly relevant for their optimization. In this paper, a parallelized microfluidic testing device is presented to quantify the accumulation of a model organism (Navicula perminuta) under constant laminar flow. Using automated microscopy in conjunction with image analysis, the adhesion densities on the tested surfaces could be determined after exposure to a flow of suspended algae for 90 min. The optimized protocol for the assay is presented, and the reproducibility of the densities of attached diatoms was verified on four identical surfaces (self-assembled dodecanethiol monolayers). A set of well-characterized self-assembled monolayers with different chemical terminations was used to validate the performance of the assay and its capability to discriminate diatom accumulation on different surface chemistries under dynamic conditions. The observed trends are in good agreement with previously published results obtained in single channel accumulation and detachment assays. To demonstrate the practical relevance of the dynamic experiment, diatom attachment on four technically relevant silicone coatings with different fouling-release properties could clearly be distinguished. © 2018 Author(s).
    view abstract10.1116/1.5034090
  • Quantitative ptychographic bio-imaging in the water window
    Rose, M. and Senkbeil, T. and Von Gundlach, A.R. and Stuhr, S. and Rumancev, C. and Dzhigaev, D. and Besedin, I. and Skopintsev, P. and Loetgering, L. and Viefhaus, J. and Rosenhahn, A. and Vartanyants, I.A.
    Optics Express 26 (2018)
    Coherent X-ray ptychography is a tool for highly dose e cient lensless nano-imaging of biological samples. We have used partially coherent soft X-ray synchrotron radiation to obtain a quantitative image of a laterally extended, dried, and unstained fibroblast cell by ptychography. We used data with and without a beam stop that allowed us to measure coherent di raction with a high-dynamic range of 1.7·106. As a quantitative result, we obtained the refractive index values for two regions of the cell with respect to a reference area. Due to the photon energy in the water window we obtained an extremely high contrast of 53% at 71 nm half-period resolution. The dose applied in our experiment was 9.5·104 Gy and is well below the radiation damage threshold. The concept for dynamic range improvement for low dynamic range detectors with a beam stop opens the path for high resolution nano-imaging of a variety of samples including cryo-preserved, hydrated and unstained biological cells. © 2018 Optical Society of America.
    view abstract10.1364/OE.26.001237
  • Structure and Chemical Organization in Damselfly Calopteryx haemorrhoidalis Wings: A Spatially Resolved FTIR and XRF Analysis with Synchrotron Radiation
    Stuhr, S. and Truong, V.K. and Vongsvivut, J. and Senkbeil, T. and Yang, Y. and Al Kobaisi, M. and Baulin, V.A. and Werner, M. and Rubanov, S. and Tobin, M.J. and Cloetens, P. and Rosenhahn, A. and Lamb, R.N. and Luque, P. and Marchant, R. and Ivanova, E.P.
    Scientific Reports 8 (2018)
    Insects represent the majority of known animal species and exploit a variety of fascinating nanotechnological concepts. We investigated the wings of the damselfly Calopteryx haemorrhoidalis, whose males have dark pigmented wings and females have slightly pigmented wings. We used scanning electron microscopy (SEM) and nanoscale synchrotron X-ray fluorescence (XRF) microscopy analysis for characterizing the nanostructure and the elemental distribution of the wings, respectively. The spatially resolved distribution of the organic constituents was examined by synchrotron Fourier transform infrared (s-FTIR) microspectroscopy and subsequently analyzed using hierarchical cluster analysis. The chemical distribution across the wing was rather uniform with no evidence of melanin in female wings, but with a high content of melanin in male wings. Our data revealed a fiber-like structure of the hairs and confirmed the presence of voids close to its base connecting the hairs to the damselfly wings. Within these voids, all detected elements were found to be locally depleted. Structure and elemental contents varied between wing membranes, hairs and veins. The elemental distribution across the membrane was rather uniform, with higher Ca, Cu and Zn levels in the male damselfly wing membranes. © 2018 The Author(s).
    view abstract10.1038/s41598-018-26563-6
  • CD44 mediates the catch-bond activated rolling of HEPG2Iso epithelial cancer cells on hyaluronan
    Hanke-Roos, M. and Fuchs, K. and Maleschlijski, S. and Sleeman, J. and Orian-Rousseau, V. and Rosenhahn, A.
    Cell Adhesion and Migration (2017)
    The attachment of cancer cells to the endothelium is an essential step during metastatic dissemination. The cell surface receptor CD44 is capable of binding to hyaluronan (HA) produced by tumor cells and by cells of the tumor microenvironment, including blood endothelial cells. Here, we investigated the role of CD44 in the interaction between the liver cancer cell line HepG2Iso and HA surfaces. The rolling interaction was quantitatively analyzed using a microfluidic shear force setup. It was found that rolling of the liver cancer cells on HA depends on CD44, which mediates a catch-bond interaction and thus a flow-induced rolling of the cells. Reduction of CD44 expression by means of siRNA, inhibition of the interaction of CD44 with HA by antibody blocking, and treatment with low molecular weight HA inhibited liver cancer cell rolling on HA-coated surfaces. The results not only clearly show the dependency of the shear-induced catch-bond interaction of HepG2Iso cells on CD44 and HA, but also for the first time demonstrate CD44-mediated rolling for epithelium-derived cells that are typically adherent. © 2016 Taylor & Francis
    view abstract10.1080/19336918.2016.1260809
  • Compositional fingerprint of soy sauces via hydrophobic surface interaction
    Jakobi, V. and Salmen, P. and Paulus, M. and Tolan, M. and Rosenhahn, A.
    Food Chemistry 218 (2017)
    In this work, the interaction of soy sauces with hydrophobic surfaces has been analyzed. Hydrophobic self-assembled monolayers on gold or silicon dioxide were used to harvest conditioning layers from soy sauce products with varying amounts of additives. The data was compared to adsorption of soy protein and glutamic acid as common ingredients. Spectral ellipsometry revealed that all tested sauces led to the formation of thin overlayers on hydrophobic surfaces. Products with less additives yielded adlayers in the same thickness range as pure soy protein. In contrast, sauces with more ingredients create distinctly thicker films. Using water contact angle goniometry, it is shown that all adlayers render the substrate more hydrophilic. Infrared spectroscopy provided a deeper insight into the adlayer chemistry and revealed that the adlayer composition is dominated by protein rich components. X-ray reflectivity on selected films provided further insight into the density profiles within the adlayers on the molecular scale. © 2016 Elsevier Ltd
    view abstract10.1016/j.foodchem.2016.09.045
  • Data compression strategies for ptychographic diffraction imaging
    Loetgering, L. and Rose, M. and Treffer, D. and Vartanyants, I.A. and Rosenhahn, A. and Wilhein, T.
    Advanced Optical Technologies 6 (2017)
    Ptychography is a computational imaging method for solving inverse scattering problems. To date, the high amount of redundancy present in ptychographic data sets requires computer memory that is orders of magnitude larger than the retrieved information. Here, we propose and compare data compression strategies that significantly reduce the amount of data required for wavefield inversion. Information metrics are used to measure the amount of data redundancy present in ptychographic data. Experimental results demonstrate the technique to be memory efficient and stable in the presence of systematic errors such as partial coherence and noise. © 2017 THOSS Media & De Gruyter, Berlin/Boston.
    view abstract10.1515/aot-2017-0053
  • High-dynamic-range water window ptychography
    Rose, M. and Dzhigaev, D. and Senkbeil, T. and Von Gundlach, A.R. and Stuhr, S. and Rumancev, C. and Besedin, I. and Skopintsev, P. and Viefhaus, J. and Rosenhahn, A. and Vartanyants, I.A.
    Journal of Physics: Conference Series 849 (2017)
    Ptychographic imaging with soft X-rays, especially in the water window energy range, suffers from limited detector dynamic range that directly influences the maximum spatial resolution achievable. High-dynamic-range data can be obtained by multiple exposures. By this approach we have increased the dynamic range of a ptychographic data set by a factor of 76 and obtained diffraction signal till the corners of the detector. The real space half period resolution was improved from 50 nm for the single exposure data to 18 nm for the high-dynamic-range data. © Published under licence by IOP Publishing Ltd.
    view abstract10.1088/1742-6596/849/1/012027
  • Microfluidic accumulation assay probes attachment of biofilm forming diatom cells
    Nolte, K.A. and Schwarze, J. and Rosenhahn, A.
    Biofouling 33 (2017)
    Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organism Navicula perminuta is introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences of N. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/08927014.2017.1328058
  • Morphological analysis of cerium oxide stabilized nanoporous gold catalysts by soft X-ray ASAXS
    Rumancev, C. and Von Gundlach, A.R. and Baier, S. and Wittstock, A. and Shi, J. and Benzi, F. and Senkbeil, T. and Stuhr, S. and Garamusx, V.M. and Grunwaldt, J.-D. and Rosenhahn, A.
    RSC Advances 7 (2017)
    Nanoporous (np) gold is a promising catalyst material for selective oxidation reactions. Especially the addition of oxide deposits like ceria (CeO2) promises enhanced morphological stability for high temperature applications. Describing such temperature induced morphological changes in porous materials is challenging. Here, X-ray nanoanalysis is particularly promising due to the high penetration depth that allows studying of the bulk properties with high spatial sensitivity. We applied soft X-ray small angle scattering (SAXS) to determine temperature induced structural changes in nanoporous gold catalysts. The results show that CeO2 deposits enhance the temperature stability of the nanoporous gold catalyst. Moreover, we demonstrate the ability of soft X-rays to selectively provide structural information on the stabilizing cerium oxide deposits via resonant, anomalous SAXS (ASAXS) measurements at the cerium M-edge, revealing no growth of the ceria particles. © 2017 The Royal Society of Chemistry.
    view abstract10.1039/c7ra05396g
  • Topographic cues guide the attachment of diatom cells and algal zoospores
    Xiao, L. and Finlay, J.A. and Röhrig, M. and Mieszkin, S. and Worgull, M. and Hölscher, H. and Callow, J.A. and Callow, M.E. and Grunze, M. and Rosenhahn, A.
    Biofouling (2017)
    Surface topography plays a key role in the colonization of substrata by the colonizing stages of marine fouling organisms. For the innovation of marine antifouling coatings, it is essential to understand how topographic cues affect the settlement of these organisms. In this study, tapered, spiked microstructures and discrete honeycombs of varying feature dimensions were designed and fabricated in order to examine the influence of topography on the attachment of zoospores of the green macroalga Ulva linza and cells of the diatom (microalga) Navicula incerta. Contrasting results were obtained with these two species of algae. Indeed, the preferred location of cells of N. incerta was dominated by attachment point theory, which suggested a positive correlation between the density of cells adhering and the amount of available attachment points, while the settlement of spores of U. linza was mainly regulated by both Wenzel roughness and local binding geometry. © 2017 Informa UK Limited, trading as Taylor & Francis Group
    view abstract10.1080/08927014.2017.1408801
  • Attachment of Algal Cells to Zwitterionic Self-Assembled Monolayers Comprised of Different Anionic Compounds
    Bauer, S. and Finlay, J.A. and Thomé, I. and Nolte, K. and Franco, S.C. and Ralston, E. and Swain, G.E. and Clare, A.S. and Rosenhahn, A.
    Langmuir 32 (2016)
    The influence of zwitterionic self-assembled monolayers on settlement and removal of algae was studied. The monolayers were constructed either from zwitterionic thiols or from solutions of positively and negatively charged thiols. The cationic component was composed of quaternary ammonium terminated thiols and the anionic component contained sulfate or carboxylate termination. During assembly, all surfaces showed a strong tendency for equilibration of the surface charge. Settlement and adhesion assays with zoospores of Ulva linza and the diatom Navicula incerta, and field tests of the initial surface colonization revealed the relevance of charge equilibration for the biological inertness of the prepared surfaces. © 2016 American Chemical Society.
    view abstract10.1021/acs.langmuir.6b00839
  • Catch bond interaction allows cells to attach to strongly hydrated interfaces
    Hanke-Roos, M. and Meseck, G.R. and Rosenhahn, A.
    Biointerphases 11 (2016)
    Hyaluronans are a class of glycosaminoglycans that are widespread in the mammalian body and serve a variety of functions. Their most striking characteristic is their pronounced hydrophilicity and their capability to inhibit unspecific adhesion when present at interfaces. Catch-bond interactions are used by the CD44 receptor to interact with this inert material and to roll on the surfaces coated with hyaluronans. In this minireview, the authors discuss the general properties of hyaluronans and the occurrence and relevance of the CD44 catch-bond interaction in the context of hematopoiesis, cancer development, and leukemia. © 2016 American Vacuum Society.
    view abstract10.1116/1.4939040
  • Imaging SPR combined with stereoscopic 3D tracking to study barnacle cyprid-surface interactions
    Maleshlijski, S. and Sendra, G.H. and Aldred, N. and Clare, A.S. and Liedberg, B. and Grunze, M. and Ederth, T. and Rosenhahn, A.
    Surface Science 643 (2016)
    Barnacle larvae (cyprids) explore surfaces to identify suitable settlement sites. This process is selective, and cyprids respond to numerous surface cues. To better understand the settlement process, it is desirable to simultaneously monitor both the surface exploration behavior and any close interactions with the surface. Stereoscopic 3D tracking of the cyprids provides quantitative access to surface exploration and pre-settlement rituals. Imaging surface plasmon resonance (SPR) reveals any interactions with the surfaces, such as surface inspection during bipedal walking and deposition of temporary adhesives. We report on a combination of both techniques to bring together information on swimming behavior in the vicinity of the interface and physical interactions of the cyprid with the surface. The technical requirements are described, and we applied the setup to cyprids of Balanus amphitrite. Initial data shows the applicability of the combined instrument to correlate exploration and touchdown events on surfaces with different chemical termination. © 2015 Published by Elsevier B.V.
    view abstract10.1016/j.susc.2015.08.027
  • In vivo and in situ synchrotron radiation-based μ-XRF reveals elemental distributions during the early attachment phase of barnacle larvae and juvenile barnacles
    Senkbeil, T. and Mohamed, T. and Simon, R. and Batchelor, D. and Di Fino, A. and Aldred, N. and Clare, A.S. and Rosenhahn, A.
    Analytical and Bioanalytical Chemistry 408 (2016)
    Barnacles are able to establish stable surface contacts and adhere underwater. While the composition of adult barnacle cement has been intensively studied, far less is known about the composition of the cement of the settlement-stage cypris larva. The main challenge in studying the adhesives used by these larvae is the small quantity of material available for analysis, being on the order of nanograms. In this work, we applied, for the first time, synchrotron radiation-based μ-X-ray fluorescence analysis (SR-μ-XRF) for in vivo and in situ analysis of young barnacles and barnacle cyprids. To obtain biologically relevant information relating to the body tissues, adhesives, and shell of the organisms, an in situ sample environment was developed to allow direct microprobe investigation of hydrated specimens without pretreatment of the samples. In 8-day-old juvenile barnacles (Balanus improvisus), the junctions between the six plates forming the shell wall showed elevated concentrations of calcium, potassium, bromine, strontium, and manganese. Confocal measurements allowed elemental characterization of the adhesive interface of recently attached cyprids (Balanus amphitrite), and substantiated the accumulation of bromine both at the point of initial attachment as well as within the cyprid carapace. In situ measurements of the cyprid cement established the presence of bromine, chlorine, iodine, sulfur, copper, iron, zinc, selenium, and nickel for both species. The previously unrecognized presence of bromine, iron, and selenium in the cyprid permanent adhesive will hopefully inspire further biochemical investigations of the function of these substances. © 2015 Springer-Verlag Berlin Heidelberg.
    view abstract10.1007/s00216-015-9253-6
  • Ions and solvation at biointerfaces
    Valtiner, M. and Erbe, A. and Rosenhahn, A.
    Biointerphases 11 (2016)
    view abstract10.1116/1.4942207
  • Resistance of Amphiphilic Polysaccharides against Marine Fouling Organisms
    Bauer, S. and Alles, M. and Arpa-Sancet, M.P. and Ralston, E. and Swain, G.W. and Aldred, N. and Clare, A.S. and Finlay, J.A. and Callow, M.E. and Callow, J.A. and Rosenhahn, A.
    Biomacromolecules 17 (2016)
    Amphiphilic coatings are promising candidates for fouling-release applications. As hydrophilic components, polysaccharides are interesting and environmentally benign building blocks. We used covalently coupled alginic acid (AA) and hyaluronic acid (HA) and postmodified them with a hydrophobic fluorinated amine. The surfaces showed good stability under marine conditions and fluorination led to a decreased uptake of Ca2+ ions after modification. In single species settlement assays (bacteria, diatoms, barnacle cypris larvae), the modification decreased the settlement density and/or the adhesion strength of many of the tested species. Field studies supported findings of the laboratory experiments, as hydrophobic modification of AA and HA decreased diatom colonization. © 2016 American Chemical Society.
    view abstract10.1021/acs.biomac.5b01590
  • Small angle X-ray scattering as a high-throughput method to classify antimicrobial modes of action
    Von Gundlach, A.R. and Garamus, V.M. and Gorniak, T. and Davies, H.A. and Reischl, M. and Mikut, R. and Hilpert, K. and Rosenhahn, A.
    Biochimica et Biophysica Acta - Biomembranes 1858 (2016)
    Multi-drug resistant bacteria are currently undermining our health care system worldwide. While novel antimicrobial drugs, such as antimicrobial peptides, are urgently needed, identification of new modes of action is money and time consuming, and in addition current approaches are not available in a high throughput manner. Here we explore how small angle X-ray scattering (SAXS) as high throughput method can contribute to classify the mode of action for novel antimicrobials and therefore supports fast decision making in drug development. Using data bases for natural occurring antimicrobial peptides or predicting novel artificial peptides, many candidates can be discovered that will kill a selected target bacterium. However, in order to narrow down the selection it is important to know if these peptides follow all the same mode of action. In addition, the mode of action should be different from conventional antibiotics, in consequence peptide candidates can be developed further into drugs against multi-drug resistant bacteria. Here we used one short antimicrobial peptide with unknown mode of action and compared the ultrastructural changes of Escherichia coli cells after treatment with the peptide to cells treated with classic antibiotics. The key finding is that SAXS as a structure sensitive tool provides a rapid feedback on drug induced ultrastructural alterations in whole E. coli cells. We could demonstrate that ultrastructural changes depend on the used antibiotics and their specific mode of action. This is demonstrated using several well characterized antimicrobial compounds and the analysis of resulting SAXS curves by principal component analysis. To understand the result of the PCA analysis, the data is correlated with TEM images. In contrast to real space imaging techniques, SAXS allows to obtain nanoscale information averaged over approximately one million cells. The measurement takes only seconds, while conventional tests to identify a mode of action require days or weeks per single substance. The antimicrobial peptide showed a different mode of action as all tested antibiotics including polymyxin B and is therefore a good candidate for further drug development. We envision SAXS to become a useful tool within the high-throughput screening pipeline of modern drug discovery. This article is part of a Special Issue entitled: Antimicrobial peptides edited by Karl Lohner and Kai Hilpert. © 2015 Elsevier B.V.
    view abstract10.1016/j.bbamem.2015.12.022
  • Tuning the Cell Adhesion on Biofunctionalized Nanoporous Organic Frameworks
    Schmitt, S. and Hümmer, J. and Kraus, S. and Welle, A. and Grosjean, S. and Hanke-Roos, M. and Rosenhahn, A. and Bräse, S. and Wöll, C. and Lee-Thedieck, C. and Tsotsalas, M.
    Advanced Functional Materials 26 (2016)
    The ability to control the structure and surface chemistry of biomaterials on a molecular level is crucial for optimizing their performance. Here, a novel type of nanoporous organic framework that is suited for the fabrication of thin films is described. These surface-grafted gels (SURGELs) are prepared and functionalized using two orthogonal, metal-free click chemistries. The SURGELs are shown to be cytocompatible and to efficiently mediate adhesion of osteoblast-like cells. This process can be further enhanced by surface modification. In addition, the use of light-triggered reactions in combination with photomasks allows a patterned functionalization of the substrates. The potential to vary and exactly adjust the parameters within the SURGEL polymer network (including porosity and exact network topology on the nanometer scale as well as addressable functional groups) combined with the ability to functionalize their surfaces with any clickable biomolecule of choice in any desired pattern allow the targeted design of novel SURGEL-based biomaterials for applications in nanomedicine, tissue engineering scaffolds, wound dressing,and medical implants. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/adfm.201603054
  • Use of small-angle X-ray scattering to resolve intracellular structure changes of Escherichia coli cells induced by antibiotic treatment
    Von Gundlach, A.R. and Garamus, V.M. and Willey, T.M. and Ilavsky, J. and Hilpert, K. and Rosenhahn, A.
    Journal of Applied Crystallography 49 (2016)
    The application of small-angle X-ray scattering (SAXS) to whole Escherichia coli cells is challenging owing to the variety of internal constituents. To resolve their contributions, the outer shape was captured by ultra-small-angle X-ray scattering and combined with the internal structure resolved by SAXS. Building on these data, a model for the major structural components of E. coli was developed. It was possible to deduce information on the occupied volume, occurrence and average size of the most important intracellular constituents: ribosomes, DNA and proteins. E. coli was studied after treatment with three different antibiotic agents (chloramphenicol, tetracycline and rifampicin) and the impact on the intracellular constituents was monitored. A combination of small- and ultra-small-angle X-ray scattering enabled the resolution of important intracellular constituents in Escherichia coli (ribosomes, DNA and proteins). The impact of treatment with three antibiotic agents was monitored. © A. R. von Gundlach et al. 2016.
    view abstract10.1107/S1600576716018562
  • Classification of the pre-settlement behaviour of barnacle cyprids
    Maleschlijski, S. and Bauer, S. and Aldred, N. and Clare, A.S. and Rosenhahn, A.
    Journal of the Royal Society Interface 12 (2015)
    Barnacle cyprids exhibit a complex swimming and exploratory behaviour on surfaces and settlement is a consequence of extensive surface probing and selection of suitable settlement sites. In this work, the behaviour of cyprids in their pre-settlement phase was studied by three-dimensional video stereoscopy. With this technique, three-dimensional trajectories were obtained that were quantitatively analysed. The velocity during vertical sinking of cyprids of Balanus amphitritewas used with a modified form of Stokes' law to calculate their mean body density. Furthermore, a classification of the swimming patterns allowed the extension of existing models describing cyprid locomotion and swimming behaviour. The patterns were characterized with respect to their occurrence, transition between patterns and their velocity distribution, and motions were identified that led to surface contacts. This analysis provides a classification framework, which can assist future attempts to identify behavioural responses of cyprids to specific settlement cues. © 2014 The Author(s) Published by the Royal Society.
    view abstract10.1098/rsif.2014.1104
  • Holographic microscopy provides new insights into the settlement of zoospores of the green alga Ulva linza on cationic oligopeptide surfaces
    Vater, S.M. and Finlay, J. and Callow, M.E. and Callow, J.A. and Ederth, T. and Liedberg, B. and Grunze, M. and Rosenhahn, A.
    Biofouling 31 (2015)
    Interaction of zoospores of Ulva linza with cationic, arginine-rich oligopeptide self-assembled monolayers (SAMs) is characterized by rapid settlement. Some spores settle (ie permanently attach) in a ‘normal’ manner involving the secretion of a permanent adhesive, retraction of the flagella and cell wall formation, whilst others undergo ‘pseudosettlement’ whereby motile spores are trapped (attached) on the SAM surface without undergoing the normal metamorphosis into a settled spore. Holographic microscopy was used to record videos of swimming zoospores in the vicinity of surfaces with different cationic oligopeptide concentrations to provide time-resolved insights into processes associated with attachment of spores. The data reveal that spore attachment rate increases with increasing cationic peptide content. Accordingly, the decrease in swimming activity in the volume of seawater above the surface accelerated with increasing surface charge. Three-dimensional trajectories of individual swimming spores showed a ‘hit and stick’ motion pattern, exclusively observed for the arginine-rich peptide SAMs, whereby spores were immediately trapped upon contact with the surface. © 2015 Taylor & Francis.
    view abstract10.1080/08927014.2015.1022534
  • Microfluidic detachment assay to probe the adhesion strength of diatoms
    Alles, M. and Rosenhahn, A.
    Biofouling 31 (2015)
    Fouling release (FR) coatings are increasingly applied as an environmentally benign alternative for controlling marine biofouling. As the technology relies on removing fouling by water currents created by the motion of ships, weakening of adhesion of adherent organisms is the key design goal for improved coatings. In this paper, a microfluidic shear force assay is used to quantify how easily diatoms can be removed from surfaces. The experimental setup and the optimization of the experimental parameters to study the adhesion of the diatom Navicula perminuta are described. As examples of how varying the physico-chemical surface properties affects the ability of diatoms to bind to surfaces, a range of hydrophilic and hydrophobic self-assembled monolayers was compared. While the number of cells that attached (adhered) was barely affected by the coatings, the critical shear stress required for their removal from the surface varied significantly. © 2015 Taylor & Francis.
    view abstract10.1080/08927014.2015.1061655
  • Shear-Induced Detachment of Polystyrene Beads from SAM-Coated Surfaces
    Cho, K.L. and Rosenhahn, A. and Thelen, R. and Grunze, M. and Lobban, M. and Karahka, M.L. and Kreuzer, H.J.
    Langmuir 31 (2015)
    In this work we experimentally and theoretically analyze the detachment of microscopic polystyrene beads from different self-assembled monolayer (SAM) surfaces in a shear flow in order to develop a mechanistic model for the removal of cells from surfaces. The detachment of the beads from the surface is treated as a thermally activated process applying an Arrhenius Ansatz to determine the activation barrier and attempt frequency of the rate determing step in bead removal. The statistical analysis of the experimental shear detachment data obtained in phosphate-buffered saline buffer results in an activation energy around 20 kJ/mol, which is orders of magnitude lower than the adhesion energy measured by atomic force microscopy (AFM). The same order of magnitude for the adhesion energy measured by AFM is derived from ab initio calculations of the van der Waals interaction energy between the polystyrene beads and the SAM-covered gold surface. We conclude that the rate determing step for detachment of the beads is the initiation of rolling on the surface (overcoming static friction) and not physical detachment, i.e., lifting the particle off the surface. © 2015 American Chemical Society.
    view abstract10.1021/acs.langmuir.5b02321
  • Water window ptychographic imaging with characterized coherent X-rays
    Rose, M. and Skopintsev, P. and Dzhigaev, D. and Gorobtsov, O. and Senkbeil, T. and Von Gundlach, A. and Gorniak, T. and Shabalin, A. and Viefhaus, J. and Rosenhahn, A. and Vartanyants, I.
    Journal of Synchrotron Radiation 22 (2015)
    A ptychographical coherent diffractive imaging experiment in the water window with focused soft X-rays at 500eV is reported. An X-ray beam with high degree of coherence was selected for ptychography at the P04 beamline of PETRA III synchrotron radiation source. The beam coherence was measured with the newly developed non-redundant array method, and a coherence length of 4.1μm and global degree of coherence of 35% at 100μm exit slit opening in the vertical direction were determined. A pinhole, 2.6μm in size, selected the coherent part of the beam that was used to obtain ptychographic reconstruction results of a lithographically manufactured test sample and a fossil diatom. The achieved resolution was 53nm for the test sample and was only limited by the size of the detector. The diatom was imaged at a resolution better than 90nm.
    view abstract10.1107/S1600577515005524
  • Barnacle cyprid motility and distribution in the water column as an indicator of the settlement-inhibiting potential of nontoxic antifouling chemistries
    Maleschlijski, S. and Bauer, S. and Di Fino, A. and Sendra, G.H. and Clare, A.S. and Rosenhahn, A.
    Biofouling 30 (2014)
    Testing of new coatings to control fouling frequently involves single-species laboratory bioassays. Barnacle cyprids are among the most widely used model organisms in marine biofouling research, and surfaces that inhibit their settlement are considered to be promising candidates for new coating concepts. An analysis of motility parameters (mean velocity and swimming area coefficient) and distribution of cyprids of Balanus amphitrite in different swimming regions in the vicinity of model surfaces (self-assembled monolayers) is presented. The data are correlated with the settlement preferences of cyprids on these surfaces. Cyprids were predominantly found in interfacial regions and the transition frequencies between swimming regions of different depths were determined. © 2014, © 2014 Taylor & Francis.
    view abstract10.1080/08927014.2014.966097
  • Conditioning of self-assembled monolayers at two static immersion test sites along the east coast of Florida and its effect on early fouling development
    Thome, I. and Bauer, S. and Vater, S. and Zargiel, K. and Finlay, J.A. and Arpa-Sancet, M.P. and Alles, M. and Callow, J.A. and Callow, M.E. and Swain, G.W. and Grunze, M. and Rosenhahn, A.
    Biofouling 30 (2014)
    Among the first events after immersion of surfaces in the ocean is surface ‘conditioning’. Here, the accumulation and composition of the conditioning films formed after immersion in the ocean are analyzed. In order to account for different surface chemistries, five self-assembled monolayers that differ in resistance to microfouling and wettability were used. Water samples from two static immersion test sites along the east coast of Florida were collected at two different times of the year and used for experiments. Spectral ellipsometry revealed that conditioning films were formed within the first 24 h and contact angle goniometry showed that these films changed the wettability and rendered hydrophobic surfaces more hydrophilic and vice versa. Infrared reflection adsorption spectroscopy showed that the composition of the conditioning film depended on both the wettability and immersion site. Laboratory and field assays showed that the presence of a conditioning film did not markedly influence settlement of microorganisms. © 2014, © 2014 Taylor & Francis.
    view abstract10.1080/08927014.2014.957195
  • Differences between healthy hematopoietic progenitors and leukemia cells with respect to CD44 mediated rolling versus adherence behavior on hyaluronic acid coated surfaces
    Hanke, M. and Hoffmann, I. and Christophis, C. and Schubert, M. and Hoang, V.T. and Zepeda-Moreno, A. and Baran, N. and Eckstein, V. and Wuchter, P. and Rosenhahn, A. and Ho, A.D.
    Biomaterials 35 (2014)
    We previously demonstrated that leukemia cell lines expressing CD44 and hematopoietic progenitor cells (HPC) from umbilical cord blood (CB) showed rolling on hyaluronic acid (HA)-coated surfaces under physiological shear stress. In the present study, we quantitatively assessed the interaction of HPC derived from CB, mobilized peripheral blood (mPB) and bone marrow (BM) from healthy donors, as well as primary leukemia blasts from PB and BM of patients with acute myeloid leukemia (AML) with HA. We have demonstrated that HPC derived from healthy donors showed relative homogeneous rolling and adhesion to HA. In contrast, highly diverse behavioral patterns were found for leukemia blasts under identical conditions. The monoclonal CD44 antibody (clone BU52) abrogated the shear stress-induced rolling of HPC and leukemia blasts, confirming the significance of CD44 in this context. On the other hand, the immobile adhesion of leukemia blasts to the HA-coated surface was, in some cases, not or incompletely inhibited by BU52. The latter property was associated with non-responsiveness to induction chemotherapy and subsequently poor clinical outcome. © 2013 Elsevier Ltd.
    view abstract10.1016/j.biomaterials.2013.11.011
  • Influence of zwitterionic SAMs on protein adsorption and the attachment of algal cells
    Bauer, S. and Alles, M. and Finlay, J.A. and Callow, J.A. and Callow, M.E. and Rosenhahn, A.
    Journal of Biomaterials Science, Polymer Edition 25 (2014)
    Zwitterionic polymers are non-fouling materials with immense potential for a range of biological applications. Here, we describe the resistance of zwitterionic self-assembled monolayers prepared from different solution ratios of positively and negatively charged thiols towards the adhesion of proteins, zoospores of the green alga Ulva linza, and cells of the unicellular alga Navicula perminuta. While mixed zwitterionic surfaces with a high hydrophilic nature significantly reduced the adhesion strength of the two algae, the positively and negatively charged components were far less effective. © 2014 Taylor and Francis.
    view abstract10.1080/09205063.2014.929429
  • Nano-scale morphology of melanosomes revealed by small-angle X-ray scattering
    Gorniak, T. and Haraszti, T. and Garamus, V.M. and Buck, A.R. and Senkbeil, T. and Priebe, M. and Hedberg-Buenz, A. and Koehn, D. and Salditt, T. and Grunze, M. and Anderson, M.G. and Rosenhahn, A.
    PLoS ONE 9 (2014)
    Melanosomes are highly specialized organelles that produce and store the pigment melanin, thereby fulfilling essential functions within their host organism. Besides having obvious cosmetic consequences - determining the color of skin, hair and the iris - they contribute to photochemical protection from ultraviolet radiation, as well as to vision (by defining how much light enters the eye). Though melanosomes can be beneficial for health, abnormalities in their structure can lead to adverse effects. Knowledge of their ultrastructure will be crucial to gaining insight into the mechanisms that ultimately lead to melanosome-related diseases. However, due to their small size and electron-dense content, physiologically intact melanosomes are recalcitrant to study by common imaging techniques such as light and transmission electron microscopy. In contrast, X-ray-based methodologies offer both high spatial resolution and powerful penetrating capabilities, and thus are well suited to study the ultrastructure of electron-dense organelles in their natural, hydrated form. Here, we report on the application of small-angle X-ray scattering - a method effective in determining the three-dimensional structures of biomolecules - to whole, hydrated murine melanosomes. The use of complementary information from the scattering signal of a large ensemble of suspended organelles and from single, vitrified specimens revealed a melanosomal sub-structure whose surface and bulk properties differ in two commonly used inbred strains of laboratory mice. Whereas melanosomes in C57BL/6J mice have a well-defined surface and are densely packed with 40-nm units, their counterparts in DBA/2J mice feature a rough surface, are more granular and consist of 60-nm building blocks. The fact that these strains have different coat colors and distinct susceptibilities to pigment-related eye disease suggest that these differences in size and packing are of biological significance.
    view abstract10.1371/journal.pone.0090884
  • Plerixafor induces the rapid and transient release of stromal cell-derived factor-1 alpha from human mesenchymal stromal cells and influences the migration behavior of human hematopoietic progenitor cells
    Wuchter, P. and Leinweber, C. and Saffrich, R. and Hanke, M. and Eckstein, V. and Ho, A.D. and Grunze, M. and Rosenhahn, A.
    Cell and Tissue Research 355 (2014)
    The interaction between the stromal cell-derived factor-1 alpha (SDF-1α, CXCL12) and its chemokine receptor CXCR4 has been reported to regulate stem cell migration, mobilization and homing. The CXCR4 antagonist plerixafor is highly efficient in mobilizing hematopoietic progenitor cells (HPCs). However, the precise regulatory mechanisms governing the CXCR4/SDF-1α axis between the bone marrow niche and HPCs remain unclear. In this study, we quantify the impact of plerixafor on the interaction between human bone marrow derived mesenchymal stromal cells (MSCs) and human CD34+ HPCs. An assessment of SDF-1α levels in the supernatant of MSC cultures revealed that exposure to plerixafor led to a transient increase but had no long-term effect. In Transwell experiments, we observed that the addition of SDF-1α significantly stimulated HPC migration; this stimulation was almost completely antagonized by the addition of plerixafor, confirming the direct impact of the CXCR4/SDF-1α interaction on the migration capacity of HPCs. We also developed a new microstructural niche model to determine the chemotactic sensitivity of HPCs. Time-lapse microscopy demonstrated that HPCs migrated actively along an SDF-1α gradient within the microchannels and the quantitative assessment of the required minimum gradient initiating this chemotaxis revealed a surprisingly high sensitivity of HPCs. These data demonstrate the fine-tuned balance of the CXCR4/SDF-1α axis and the synergistic effects of plerixafor on HPCs and MSCs, which most likely represent the key mechanisms for the consecutive mobilization of HPCs from the bone marrow niche into the circulating blood. © 2013 Springer-Verlag Berlin Heidelberg.
    view abstract10.1007/s00441-013-1759-7
  • Ptychographic X-ray Microscopy with the vacuum imaging apparatus HORST
    Gorniak, T. and Rosenhahn, A.
    Zeitschrift fur Physikalische Chemie 228 (2014)
    Imaging is one of the key drivers for new scientific insights - from the observation of distant stars in astronomy to microscopic studies of sub-cellular structures in biology. In the latter case, X-rays are a versatile probe due to their small wavelength and thus high spatial sensitivity. We give an overview of applicable lensless, coherent imaging approaches relying on scattering with a focus on ptychographic microscopy and discuss the experimental requirements for the soft X-ray scattering experiment HORST. Besides the experiment itself, we highlight the importance of sample environments, especially when biological specimens are investigated. Here, the water window is of central importance. In addition to exploitation of the contrast and resolution, resonant ptychography allows to distinguish chemical species at high spatial resolution with both phase and amplitude contrast. © 2014 Walter de Gruyter Berlin/Boston.
    view abstract10.1515/zpch-2014-0554
  • Support and challenges to the melanosomal casing model based on nanoscale distribution of metals within iris melanosomes detected by X-ray fluorescence analysis
    Gorniak, T. and Haraszti, T. and Suhonen, H. and Yang, Y. and Hedberg-Buenz, A. and Koehn, D. and Heine, R. and Grunze, M. and Rosenhahn, A. and Anderson, M.G.
    Pigment Cell and Melanoma Research 27 (2014)
    Melanin within melanosomes exists as eumelanin or pheomelanin. Distributions of these melanins have been studied extensively within tissues, but less often within individual melanosomes. Here, we apply X-ray fluorescence analysis with synchrotron radiation to survey the nanoscale distribution of metals within purified melanosomes of mice. The study allows a discovery-based characterization of melanosomal metals, and, because Cu is specifically associated with eumelanin, a hypothesis-based test of the 'casing model' predicting that melanosomes contain a pheomelanin core surrounded by a eumelanin shell. Analysis of Cu, Ca, and Zn shows variable concentrations and distributions, with Ca/Zn highly correlated, and at least three discrete patterns for the distribution of Cu vs. Ca/Zn in different melanosomes - including one with a Cu-rich shell surrounding a Ca/Zn-rich core. Thus, the results support predictions of the casing model, but also suggest that in at least some tissues and genetic contexts, other arrangements of melanin may co-exist. © 2014 John Wiley & Sons A/S.
    view abstract10.1111/pcmr.12278
  • Swimming behavior of Pseudomonas aeruginosa studied by holographic 3D tracking
    Vater, S.M. and Weiße, S. and Maleschlijski, S. and Lotz, C. and Koschitzki, F. and Schwartz, T. and Obst, U. and Rosenhahn, A.
    PLoS ONE 9 (2014)
    Holographic 3D tracking was applied to record and analyze the swimming behavior of Pseudomonas aeruginosa. The obtained trajectories allow to qualitatively and quantitatively analyze the free swimming behavior of the bacterium. This can be classified into five distinct swimming patterns. In addition to the previously reported smooth and oscillatory swimming motions, three additional patterns are distinguished. We show that Pseudomonas aeruginosa performs helical movements which were so far only described for larger microorganisms. Occurrence of the swimming patterns was determined and transitions between the patterns were analyzed. © 2014 Vater et al.
    view abstract10.1371/journal.pone.0087765
  • Adherent cells avoid polarization gradients on periodically poled LiTaO3 ferroelectrics
    Christophis, C. and Cavalcanti-Adam, E.A. and Hanke, M. and Kitamura, K. and Gruverman, A. and Grunze, M. and Dowben, P.A. and Rosenhahn, A.
    Biointerphases 8 (2013)
    The response of fibroblast cells to periodically poled LiTaO3 ferroelectric crystals has been studied. While fibroblast cells do not show morphological differences on the two polarization directions, they show a tendency to avoid the field gradients that occur between polarization domains of the ferroelectric. The response to the field gradients is fully established after one hour, a time at which fibroblasts form their first focal contacts. If suspension cells, with a lower tendency to establish strong surface contacts are used, no influence of the field gradients is observed.
    view abstract10.1186/1559-4106-8-27
  • Adhesion of marine fouling organisms on hydrophilic and amphiphilic polysaccharides
    Bauer, S. and Arpa-Sancet, M.P. and Finlay, J.A. and Callow, M.E. and Callow, J.A. and Rosenhahn, A.
    Langmuir 29 (2013)
    Polysaccharides are a promising material for nonfouling surfaces because their chemical composition makes them highly hydrophilic and able to form water-storing hydrogels. Here we investigated the nonfouling properties of hyaluronic acid (HA) and chondroitin sulfate (CS) against marine fouling organisms. Additionally, the free carboxyl groups of HA and CS were postmodified with the hydrophobic trifluoroethylamine (TFEA) to block free carboxyl groups and render the surfaces amphiphilic. All coatings were tested with respect to their protein resistance and against settlement and adhesion of different marine fouling species. Both the settlement and adhesion strength of a marine bacterium (Cobetia marina), zoospores of the seaweed Ulva linza, and cells of a diatom (Navicula incerta) were reduced compared to glass control surfaces. In most cases, TFEA capping increased or maintained the performance of the HA coatings, whereas for the very well performing CS coatings the antifouling performance was reduced after capping. © 2013 American Chemical Society.
    view abstract10.1021/la3038022
  • Controlled growth of protein resistant PHEMA brushes via S-RAFT polymerization
    Zamfir, M. and Rodriguez-Emmenegger, C. and Bauer, S. and Barner, L. and Rosenhahn, A. and Barner-Kowollik, C.
    Journal of Materials Chemistry B 1 (2013)
    The reversible addition-fragmentation chain transfer polymerization of 2-hydroxyethyl methacrylate (HEMA) from surfaces (S-RAFT) using an R-group-attached chain transfer agent (CTA) is presented. The approach was exploited for the efficient preparation of well-defined PHEMA brushes of up to 50 nm thickness in a controlled fashion without using any cytotoxic catalyst. The chemical composition, morphology and wettability of the samples were assessed by X-ray photoelectron spectroscopy, atomic force microscopy and water contact angle measurements, while the growth kinetics were studied by monitoring the dry thickness via spectroscopic ellipsometry. The mechanism and kinetics of the RAFT polymerization on the surface-in the presence of a sacrificial CTA and of solvent mixtures with different polarities-were investigated. A marked effect of the concentration of the sacrificial CTA on the kinetics was observed. Importantly-and for the first time-the living PHEMA brushes were exploited as macroRAFT agents for chain extension, and thicknesses up to 70 nm were achieved. The prepared PHEMA brushes were challenged with protein solutions demonstrating their resistance to fouling. © 2013 The Royal Society of Chemistry.
    view abstract10.1039/c3tb20880j
  • Correlative imaging of structural and elemental composition of bacterial Biofilms
    Yang, Y. and Heine, R. and Xu, F. and Suhonen, H. and Helfen, L. and Rosenhahn, A. and Gorniak, T. and Kirchen, S. and Schwartz, T. and Baumbach, T.
    Journal of Physics: Conference Series 463 (2013)
    Synchrotron-based phase contrast tomography (holotomography) and scanning hard X-ray fluorescence microscopy (SXFM) are combined to characterize the three-dimensional (3D) structural and corresponding elemental distribution of bacterial biofilms of Pseudomonas aeruginosa. Samples were fixed without contrast agents or microtomal sectioning. Within an intact microbial community single bacteria are clearly resolved, and their morphology can be directly visualized together with the elemental content. Such 3D set of complementary information at cellular level is essential for gaining a deeper understanding of biofilm evolution aiming to develop potential strategies on biofilm growth control and prevention. © Published under licence by IOP Publishing Ltd.
    view abstract10.1088/1742-6596/463/1/012053
  • Drift correction in ptychographic diffractive imaging
    Beckers, M. and Senkbeil, T. and Gorniak, T. and Giewekemeyer, K. and Salditt, T. and Rosenhahn, A.
    Ultramicroscopy 126 (2013)
    X-ray ptychography is a rapidly developing phase retrieval technique that combines the experimental advantages of coherent diffractive imaging with the possibility to image extended specimens. Data collection requires imaging at several scan points with high positional accuracy, which implies susceptibility to mechanical drift. This is a well-known problem in ptychographic scans, which can reduce reconstruction quality and limit the achievable resolution. Using a simple model for positional drift, we show that a set of corrected positions can be found systematically, leading to strong improvements in the reconstruction of a Siemens star dataset severely affected by drift. © 2012 Elsevier B.V.
    view abstract10.1016/j.ultramic.2012.11.006
  • Hot embossed microtopographic gradients reveal morphological cues that guide the settlement of zoospores
    Xiao, L. and Thompson, S.E.M. and Röhrig, M. and Callow, M.E. and Callow, J.A. and Grunze, M. and Rosenhahn, A.
    Langmuir 29 (2013)
    Among different surface cues, the settlement of cells and larvae of marine macrofouling organisms has been found to be strongly influenced by surface microtopographies. In this article, the settlement of zoospores of the green alga Ulva linza on a surface topographic gradient has been investigated. "Honeycomb" gradient structures with feature sizes ranging from 1 to 10 μm were prepared by hot embossing, and the effect on the density of spores that attached in settlement assays was quantified. The highest density of spores was found when the size of the microstructures was similar to or larger than the size of the spores. With decreasing size of the structures, spore settlement density decreased. Interestingly, spore settlement density correlated with the Wenzel roughness of the surfaces. "Kink sites" on the surface played an important role and resembled preferred attachment positions. Furthermore, the gradients allowed the minimum pit size that the spores were able to squeeze into to be determined. © 2012 American Chemical Society.
    view abstract10.1021/la303832u
  • Single pulse coherence measurements in the water window at the free-electron laser FLASH
    Mai, D.D. and Hallmann, J. and Reusch, T. and Osterhoff, M. and Dusterer, S. and Treusch, R. and Singer, A. and Beckers, M. and Gorniak, T. and Senkbeil, T. and Dronyak, R. and Gulden, J. and Yefanov, O.M. and Al-Shemmary, A. and Rosenhahn, A. and Mancuso, A.P. and Vartanyants, I.A. and Salditt, T.
    Optics Express 21 (2013)
    The spatial coherence of free-electron laser radiation in the water window spectral range was studied, using the third harmonic (3rd = 2.66 nm) of DESY's Free-electron LASer in Hamburg (FLASH). Coherent single pulse diffraction patterns of 1,2-Dioleoyl-sn-glycero-3- phosphocholine (DOPC) multilamellar lipid stacks have been recorded. The intensity histogram of the speckle pattern around the first lamellar Bragg peak, corresponding to the d = 5 nm periodicity of the stack, reveals an average number of transverse modes of M = 3.0 of the 3rd harmonic. Using the lipid stack as a 'monochromator', pulse-to-pulse fluctuations in the third harmonic l3rd have been determined to be 0.033 nm. © 2013 Optical Society of America.
    view abstract10.1364/OE.21.013005
  • Slippery liquid-infused porous surfaces showing marine antibiofouling properties
    Xiao, L. and Li, J. and Mieszkin, S. and Di Fino, A. and Clare, A.S. and Callow, M.E. and Callow, J.A. and Grunze, M. and Rosenhahn, A. and Levkin, P.A.
    ACS Applied Materials and Interfaces 5 (2013)
    Marine biofouling is a longstanding problem because of the constant challenges placed by various fouling species and increasingly restricted environmental regulations for antifouling coatings. Novel nonbiocidal strategies to control biofouling will necessitate a multifunctional approach to coating design. Here we show that slippery liquid-infused porous surfaces (SLIPSs) provide another possible strategy to obtaining promising antifouling coatings. Microporous butyl methacrylate-ethylene dimethacrylate (BMA-EDMA) surfaces are prepared via UV-initiated free-radical polymerization. Subsequent infusion of fluorocarbon lubricants (Krytox103, Krytox100, and Fluorinert FC-70) into the porous microtexture results in liquid-repellent slippery surfaces. To study the interaction with marine fouling organisms, settlement of zoospores of the alga Ulva linza and cypris larvae of the barnacle Balanus amphitrite is tested in laboratory assays. BMA-EDMA surfaces infused with Krytox103 and Krytox100 exhibit remarkable inhibition of settlement (attachment) of both spores and cyprids to a level comparable to that of a poly(ethylene glycol) (PEG)-terminated self-assembled monolayer. In addition, the adhesion strength of sporelings (young plants) of U. linza is reduced for BMA-EDMA surfaces infused with Krytox103 and Krytox100 compared to pristine (noninfused) BMA-EDMA and BMA-EDMA infused with Fluorinert FC-70. Immersion tests suggest a correlation between the stability of slippery coatings in artificial seawater and fouling resistance efficacy. The results indicate great potential for the application of this concept in fouling-resistant marine coatings. © 2013 American Chemical Society.
    view abstract10.1021/am402635p
  • Surface anchored metal-organic frameworks as stimulus responsive antifouling coatings
    Sancet, M.P.A. and Hanke, M. and Wang, Z. and Bauer, S. and Azucena, C. and Arslan, H.K. and Heinle, M. and Gliemann, H. and Wöll, C. and Rosenhahn, A.
    Biointerphases 8 (2013)
    Surface-anchored, crystalline and oriented metal organic frameworks (SURMOFs) have huge potential for biological applications due to their well-defined and highly-porous structure. In this work we describe a MOF-based, fully autonomous system, which combines sensing, a specific response, and the release of an antimicrobial agent. The Cu-containing SURMOF, Cu-SURMOF 2, is stable in artificial seawater and shows stimulus-responsive anti-fouling properties against marine bacteria. When Cobetia marina adheres on the SURMOF, the framework's response is lethal to the adhering microorganism. A thorough analysis reveals that this response is induced by agents secreted from the microbes after adhesion to the substrate, and includes a release of Cu ions resulting from a degradation of the SURMOF. The stimulus-responsive antifouling effect of Cu-SURMOF 2 demonstrates the first application of Cu-SURMOF 2 as autonomous system with great potential for further microbiological and cell culture applications. © 2013 Arpa Sancet et al.
    view abstract10.1186/1559-4106-8-29
  • A quantitative 3D motility analysis of Trypanosoma brucei by use of digital in-line holographic microscopy
    Weiße, S. and Heddergott, N. and Heydt, M. and Pflästerer, D. and Maier, T. and Haraszti, T. and Grunze, M. and Engstler, M. and Rosenhahn, A.
    PLoS ONE 7 (2012)
    We present a quantitative 3D analysis of the motility of the blood parasite Trypanosoma brucei. Digital in-line holographic microscopy has been used to track single cells with high temporal and spatial accuracy to obtain quantitative data on their behavior. Comparing bloodstream form and insect form trypanosomes as well as mutant and wildtype cells under varying external conditions we were able to derive a general two-state-run-and-tumble-model for trypanosome motility. Differences in the motility of distinct strains indicate that adaption of the trypanosomes to their natural environments involves a change in their mode of swimming. © 2012 Weiße et al.
    view abstract10.1371/journal.pone.0037296
  • Conditioning of surfaces by macromolecules and its implication for the settlement of zoospores of the green alga Ulva linza
    Thome, I. and Pettitt, M.E. and Callow, M.E. and Callow, J.A. and Grunze, M. and Rosenhahn, A.
    Biofouling 28 (2012)
    Conditioning, ie the adsorption of proteins and other macromolecules, is the first process that occurs in the natural environment once a surface is immersed in seawater, but no information is available either regarding the conditioning of surfaces by artificial seawater or whether conditioning affects data obtained from laboratory assays. A range of self-assembled monolayers (SAMs) with different chemical terminations was used to investigate the time-dependent formation of conditioning layers in commercial and self-prepared artificial seawaters. Subsequently, these results were compared with conditioning by solutions in which zoospores of the green alga Ulva linza had been swimming. Spectral ellipsometry and contact angle measurements as well as infrared reflection absorption spectroscopy (IRRAS) were used to reveal the thickness and chemical composition of the conditioning layers. The extent that surface preconditioning affected the settlement of zoospores of U. linza was also investigated. The results showed that in standard spore settlement bioassays (45-60 min), the influence of a molecular conditioning layer is likely to be small, although more substantial effects are possible at longer settlement times. © 2012 Copyright Taylor and Francis Group, LLC.
    view abstract10.1080/08927014.2012.689288
  • Dynamics of colloidal crystals studied by pump-probe experiments at FLASH
    Dronyak, R. and Gulden, J. and Yefanov, O.M. and Singer, A. and Gorniak, T. and Senkbeil, T. and Meijer, J.-M. and Al-Shemmary, A. and Hallmann, J. and Mai, D.D. and Reusch, T. and Dzhigaev, D. and Kurta, R.P. and Lorenz, U. and Petukhov, A.V. and Düsterer, S. and Treusch, R. and Strikhanov, M.N. and Weckert, E. and Mancuso, A.P. and Salditt, T. and Rosenhahn, A. and Vartanyants, I.A.
    Physical Review B - Condensed Matter and Materials Physics 86 (2012)
    We present a time-resolved infrared (IR) pump and extreme-ultraviolet (XUV) probe diffraction experiment to investigate ultrafast structural dynamics in colloidal crystals with picosecond resolution. The experiment was performed at the FLASH facility at DESY with a fundamental wavelength of 8 nm. In our experiment, the temporal changes of Bragg peaks were analyzed, and their frequency components were calculated using Fourier analysis. Periodic modulations in the colloidal crystal were localized at a frequency of about 4-5 GHz. Based on the Lamb theory, theoretical calculations of vibrations of the isotropic elastic polystyrene spheres of 400 nm in size reveal a 5.07-GHz eigenfrequency of the ground (breathing) mode. © 2012 American Physical Society.
    view abstract10.1103/PhysRevB.86.064303
  • Hologram reconstruction corrected for measurements through layers with different refractive indices in digital in-line holographic microscopy
    Sendra, G.H. and Weisse, S. and Maleschlijski, S. and Rosenhahn, A.
    Applied Optics 51 (2012)
    Digital in-line holographic microscopy (DIHM) using point sources has been shown to be a versatile technique, especially for three-dimensional tracking of particles or microorganisms. However, the spherical source wave is altered when measurements are performed through layers with different refractive indices, such as water cuvettes. The situations where a layer of medium with a refractive index different than that of the predominant surrounding propagation medium (usually air) is situated behind or in front of the plane to be reconstructed are analyzed in detail, and a general approach for reconstruction under such circumstances is developed. The proposed refractive index correction is tested experimentally and compared to conventional reconstruction algorithms. Using 3D traces of swimming algal spores, the influence on the velocity calculation is also shown. © 2012 Optical Society of America.
    view abstract10.1364/AO.51.003416
  • Microfluidic assay to quantify the adhesion of marine bacteria
    Arpa-Sancet, M.P. and Christophis, C. and Rosenhahn, A.
    Biointerphases 7 (2012)
    For both, environmental and medical applications, the quantification of bacterial adhesion is of major importance to understand and support the development of new materials. For marine applications, the demand is driven by the quest for improved fouling-release coatings. To determine the attachment strength of bacteria to coatings, a microfluidic adhesion assay has been developed which allows probing at which critical wall shear stress bacteria are removed from the surface. Besides the experimental setup and the optimization of the assay, we measured adhesion of the marine bacterium Cobetia marina on a series of differently terminated self-assembled monolayers. The results showed that the adhesion strength of C. marina changes with surface chemistry. The difference in critical shear stress needed to remove bacteria can vary by more than one order of magnitude if a hydrophobic material is compared to an inert chemistry such as polyethylene glycol. © The Author(s) 2012.
    view abstract10.1007/s13758-012-0026-x
  • Settlement behavior of zoospores of Ulva linza during surface selection studied by digital holographic microscopy
    Heydt, M. and Pettitt, M.E. and Cao, X. and Callow, M.E. and Callow, J.A. and Grunze, M. and Rosenhahn, A.
    Biointerphases 7 (2012)
    Settlement of the planktonic dispersal stages of marine organisms is the crucial step for the development of marine biofouling. Four-dimensional holographic tracking reveals the mechanism by which algal spores select surfaces suitable for colonization. Quantitative analysis of the three dimensional swimming trajectories of motile spores of a macroalga (Ulva linza) in the vicinity of surfaces functionalized with different chemistries reveals that their search strategy and swimming behavior is correlated to the number of settled spores found in spore settlement bioassays conducted over 45 min. The spore motility and exploration behavior can be classified into different motion patterns, with their relative occurrence changing with the surface chemistry. Based on the detailed motility analysis we derived a model for the surface selection and settlement process of Ulva zoospores. © The Author(s) 2012.
    view abstract10.1007/s13758-012-0033-y
  • Spatial and temporal coherence properties of single free-electron laser pulses
    Singer, A. and Sorgenfrei, F. and Mancuso, A.P. and Gerasimova, N. and Yefanov, O.M. and Gulden, J. and Gorniak, T. and Senkbeil, T. and Sakdinawat, A. and Liu, Y. and Attwood, D. and Dziarzhytski, S. and Mai, D.D. and Treusch, R. and Weckert, E. and Salditt, T. and Rosenhahn, A. and Wurth, W. and Vartanyants, I.A.
    Optics Express 20 (2012)
    The experimental characterization of the spatial and temporal coherence properties of the free-electron laser in Hamburg (FLASH) at a wavelength of 8.0 nm is presented. Double pinhole diffraction patterns of single femtosecond pulses focused to a size of about 10×10 μm2 were measured. A transverse coherence length of 6.2 ± 0.9 μm in the horizontal and 8.7 ±1.0 μm in the vertical direction was determined from the most coherent pulses. Using a split and delay unit the coherence time of the pulses produced in the same operation conditions of FLASH was measured to be 1.75 ±0.01 fs. From our experiment we estimated the degeneracy parameter of the FLASH beam to be on the order of 1010 to 1011, which exceeds the values of this parameter at any other source in the same energy range by many orders of magnitude. © 2012 Optical Society of America.
    view abstract10.1364/OE.20.017480
  • Surface sensing and settlement strategies of marine biofouling organisms
    Rosenhahn, A. and Sendra, G.H.
    Biointerphases 7 (2012)
    This review article summarizes some recent insights into the strategies used by marine organisms to select surfaces for colonization. While larger organisms rely on their sensory machinery to select surfaces, smaller microorganisms developed less complex but still effective ways to probe interfaces. Two examples, zoospores of algae and barnacle larvae, are discussed and both appear to have build-in test mechanisms to distinguish surfaces with different physicochemical properties. Some systematic studies on the influence of surface cues on exploration, settlement and adhesion are summarized. The intriguing notion that surface colonization resembles a parallelized surface sensing event is discussed towards its complementarity with conventional surface analytical tools. The strategy to populate only selected surfaces seems advantageous as waves, currents and storms constantly challenge adherent soft and hard fouling organism. © The Author(s) 2012.
    view abstract10.1007/s13758-012-0063-5
  • The biocompatibility of metal-organic framework coatings: An investigation on the stability of SURMOFs with regard to water and selected cell culture media
    Hanke, M. and Arslan, H.K. and Bauer, S. and Zybaylo, O. and Christophis, C. and Gliemann, H. and Rosenhahn, A. and Wöll, C.
    Langmuir 28 (2012)
    Highly porous thin films based on a [Cu(bdc) 2] n (bdc = benzene-1,4-dicarboxylic acid) metal-organic framework, MOF, grown using liquid-phase epitaxy (LPE) show remarkable stability in pure water as well as in artificial seawater. This opens the possibility to use these highly porous coatings for environmental and life science applications. Here we characterize in detail the stability of these SURMOF 2 thin films under aqueous and cell culture conditions. We find that the material degrades only very slowly in water and artificial seawater (ASW) whereas in typical cell culture media (PBS and DMEM) a rapid dissolution is observed. The release of Cu 2+ ions resulting from the dissolution of the SURMOF 2 in the liquids exhibits no adverse effect on the adhesion of fibroblasts, prototype eukaryotic cells, to the substrate and their subsequent proliferation, thus demonstrating the biocompatibility of SURMOF 2 surface coatings. Thus, the results are an important step toward application of these porous materials as a slow release matrix, for example, for pharmaceuticals and growth factors. © 2012 American Chemical Society.
    view abstract10.1021/la300457z
  • Three dimensional tracking of exploratory behavior of barnacle cyprids using stereoscopy
    Maleschlijski, S. and Sendra, G.H. and Di Fino, A. and Leal-Taixé, L. and Thome, I. and Terfort, A. and Aldred, N. and Grunze, M. and Clare, A.S. and Rosenhahn, B. and Rosenhahn, A.
    Biointerphases 7 (2012)
    Surface exploration is a key step in the colonization of surfaces by sessile marine biofoulers. As many biofouling organisms can delay settlement until a suitable surface is encountered, colonization can comprise surface exploration and intermittent swimming. As such, the process is best followed in three dimensions. Here we present a low-cost transportable stereoscopic system consisting of two consumer camcorders. We apply this novel apparatus to behavioral analysis of barnacle larvae (≈ 800 lm length) during surface exploration and extract and analyze the three-dimensional patterns of movement. The resolution of the system and the accuracy of position determination are characterized. As a first practical result, three-dimensional swimming trajectories of the cypris larva of the barnacle Semibalanus balanoides are recorded in the vicinity of a glass surface and close to PEG2000-OH and C11NMe3 +Cl- terminated self-assembled monolayers. Although less frequently used in biofouling experiments due to its short reproductive season, the selected model species [Marechal and Hellio (2011), Int Biodeterior Biodegrad, 65(1):92-101] has been used following a number of recent investigations on the settlement behavior on chemically different surfaces [Aldred et al. (2011), ACS Appl Mater Interfaces, 3(6):2085-2091]. Experiments were scheduled to match the availability of cyprids off the north east coast of England so that natural material could be used. In order to demonstrate the biological applicability of the system, analysis of parameters such as swimming direction, swimming velocity and swimming angle are performed. © The Author(s) 2012.
    view abstract10.1007/s13758-012-0050-x
  • biofouling

  • cell adhesion

  • hydrophobic and hydrophilic interactions

  • surfaces

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