In vivo und in vitro Synthesen von Oxidkeramiken
Zusammenfassung der Projektergebnisse
In this project we investigated the possibility to apply living organisms for the synthesis of technically relevant ceramics. We studied three different organisms, the bacterium Halomonas halophila, the green alga Scenedesmus obliquus and the marine alga Emiliania huxleyi. We first established media with appropriate amounts of zinc for every test organism. Since zinc is toxic, the organisms use detoxification mechanisms to survive this treatment. We could show that these three model organisms use different strategies for the detoxification of zinc: The bacterium H. halophila and the freshwater alga S. obliquus accumulate the zinc ions on their cell wall, S. obliquus additionally transport the zinc ions into the cell interior to detoxify the environment and the cell wall. Subsequently, the algae build the untoxic chelate zinc phosphate in the cytoplasm. Our results show that the marine alga E. huxleyi incorporates the zinc ions in the coccoliths and also in the interior of the cells. We successfully developed Tb containing media, in which the algae survive and produce new coccoliths. First analyses with photoluminescence spectrometer showed characteristic peaks belonging to the Tb spectrum, which represents an important result regarding the generation of components of inorganic functional materials, i.e. CaCO3:Tb, by living organisms. Furthermore, the microorganisms built diverse materials through extracellular and intracellular biomineralization processes. Extracellular biomineralization: When zinc is present in the media, H. halophila produces vaterite and monohydrocalcite and S. obliquus precipitates aragonite instead of calcite, which is precipitated in media without zinc. Intracellular biomineralization: In a second experimental setup using a different medium with zinc, S. obliquus produces zinc-phosphate-based nano needles. We used SEM, STEM/XEDS, XRD and fluorescence microscopy to analyze the obtained materials. Based on these studies, a comprehensive understanding of the detoxification mechanism of the investigated organisms as well as the structure of the obtained materials is now available. In order to identify zinc oxide (ZnO) binding peptides, we established the phage display technology. From several isolated peptides, the binding of the two most abundant peptides were analyzed in detail. The binding affinity of the peptides to ZnO was determined with a phage-based binding assay and the peptides molecular binding sides to the ZnO were determined by NMR. As the binding partners of ZnO, serine and histidine could be identified. In this project, analysis by phage display and NMR was exemplarily combined for ZnO-binding peptides; this protocol can be used also for other target substances. Subsequently, three ZnO-binding peptides with different isoelectric points were used for in vitro mineralization experiments. We could show that the Ostwald rule of stages is the key for understanding the precipitation mechanism of ZnO under mild conditions. Metastable phases are represented by layered basic zinc salts and α-hydroxide. We could also reveal, that the crystal growths are inhibited by ZnO-binding peptides through selective adsorption on the surfaces. Additionally, we examined mineralization and particle growths kinetics of ZnO under moderate conditions in presence of gelatin B 225. The particles were examined by XRD and SEM and their growth using in situ DLS. When gelatin is added, the activation energy of particle growth is lowered. Furthermore, the XRD measurement showed that the precipitation procedure is according to Ostwald rule of stages with a dissolution-recrystallization mechanism, where zinc hydroxide acts as an intermediate product. The ZnO mineralization in presence of tobacco mosaic viruses (TMV) was investigated. TMV function as mineralization inducing and structure directing template. We could generate well defined TMV-ZnO nanorods which can function as field effect transistors devices (FET). Our results clearly reveal that beside the function of TMV as a structural scaffold, they also influence the semiconducting layer, indicating an electron injection capability of the TMV templates. Subsequently, two genetically modified TMV mutants were used for ZnO mineralization experiments. We could show that FET devices fabricated with these mutants had different properties in comparison to the wild type TMV.
Projektbezogene Publikationen (Auswahl)
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Virus-Templated Synthesis of ZnO Nanostructures and Formation of Field-Effect Transistors. Advanced Materials (2011)
Petia Atanasova, Dirk Rothenstein, Jörg J. Schneider, Rudolf C. Hoffmann, Stefan Dilfer, Sabine Eiben, Christina Wege, Holger Jeske and Joachim Bill
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Bio-inspired mineralization of zinc oxide in presence of ZnO-binding peptides, Biointerface research in applied chemistry 2, 380-391 (2012)
Johannes Baier, Torsten Naumburg, Nina J. Blumenstein, Lars P. H. Jeurgens, Udo Welzel, Tuan A. Do, Jürgen Pleiss, Joachim Bill
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Biomineralization of Zinc-Phosphate-Based Nano Needles by Living Microalgae, Journal of Biomaterials and Nanobiotechnology 3 (3), 362-370 (2012)
Giulia Santomauro, Vesna Srot, Birgit Bussmann, Peter A. van Aken, Franz Brümmer, Horst Strunk, Joachim Bill
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Formation of calcium carbonate polymorphs induced by living microalgae, Journal of Biomaterials and Nanobiotechnology 3 (4), 413-420 (2012)
Giulia Santomauro, Johannes Baier, Wanjing Huang, Stefan Pezold, Joachim Bill
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Isolation of ZnO-binding 12-mer peptides and determination of their binding epitopes by NMR spectroscopy, Journal of the American Chemical Society, 134 (30), pp 12547–12556 (2012)
Dirk Rothenstein, Birgit Claasen, Beatrice Omiecienski, Patricia Lammel, and Joachim Bill
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Mineralization and particle growth kinetics of ZnO in the presence of gelatine, Biointerface research in applied chemistry 2, 339-349 (2012)
Johannes Baier, Robin Strumberger, Frank Berger, Petia Atanasova, Udo Welzel, Joachim Bill
