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Bad Münster am Stein-Ebernburg, Germany

Seela F.,Center for Nanotechnology | Seela F.,University of Osnabruck | Pujari S.S.,Center for Nanotechnology | Pujari S.S.,University of Osnabruck | Schafer A.H.,NanoAnalytics GmbH
Tetrahedron | Year: 2011

Nucleoside hydrogels based on benzyl azide 'click' conjugates of 8-aza-7-deaza-2′-deoxyadenosine bearing 7-ethynyl, 7-octa-(1,7-diynyl), and 7-tri-prop-2-ynyl-amine side chains were synthesized (1, 3, 4). The cycloaddition adduct with the shortest linker (1) yields the most powerful hydrogelator forming stable gels at a concentration of 0.3 wt % of 1 in water. One molecule of 1 catches 7500 water molecules. Cycloaddition of the 8-aza-7-deaza-7-azido-2′-deoxyadenosine (9) and 3-phenyl-1-propyne (10) leads to the isomeric conjugate 2, with a C-N connectivity between the nucleobase and triazole moiety. This gel is less stable than that of the adduct 1. Both gels show a similar stability over a wide pH range (4.0-10.0). Xerogels of 1 and 2 studied by scanning electron microscopy (SEM) reveal that both click adducts (1 and 2) form long fibers spontaneously. © 2011 Elsevier Ltd. All rights reserved.

Borgognoni C.F.,University of Munster | Mormann M.,University of Munster | Qu Y.,University of Munster | Qu Y.,CAS National Center for Nanoscience and Technology | And 8 more authors.
Nanomedicine: Nanotechnology, Biology, and Medicine | Year: 2015

The cytokine secretion of primary cells of human macrophages during the interaction of TiO2 nanoparticles (with an average primary size of 100-120nm) is investigated down to concentration levels suggested to be relevant for in vivo conditions. We find that high TiO2 concentrations induce the cytokines Interleukin IL-1β, IL-6, and IL-10 secretion, while at low concentrations only IL-6 secretion is observed. To obtain further evidence on in vivo conditions we investigated the development and structure of the protein corona of the nanoparticles. We demonstrated that the surface of TiO2 particles attract preferably secondary modified proteins which then induce cytokine secretion of macrophages. Our results indicate that concentration of corona covered TiO2 particles below 1μg/ml induce IL-6 secretion which is reported to be responsible for the development of autoimmune diseases as well as for the secretion of acute phase proteins. © 2015 Elsevier Inc.

Ranganath K.V.S.,University of Munster | Kloesges J.,University of Munster | Schafer A.H.,NanoAnalytics GmbH | Glorius F.,University of Munster
Angewandte Chemie - International Edition | Year: 2010

Superficial success: A chiral N-heterocyclic carbene (NHC *) is used to modify Fe3O4/Pd nanoparticles, which then catalyze asymmetric α-arylations. This successful synthesis of a heterogeneous catalyst and its appliation in asymmetric catalysis is in stark contrast to the simple immobilization of an established chiral homogeneous catalyst. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dickschat A.T.,University of Munster | Behrends F.,University of Munster | Buhner M.,NanoAnalytics GmbH | Ren J.,University of Munster | And 3 more authors.
Chemistry - A European Journal | Year: 2012

The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction. Cooperative clicking: Bifunctional mesoporous silica particles were synthesized by orthogonal surface chemistry. A thiol-ene reaction, a copper-catalyzed 1,3-dipolar cycloaddition and a radical nitroxide exchange reaction were used as orthogonal processes for the introduction of the acid and base functionalities (see scheme). Catalytic activities of these bifunctionalized inorganic/organic hybrid materials were studied on the Henry reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kehr N.S.,University of Munster | Riehemann K.,University of Munster | El-Gindi J.,University of Munster | Schafer A.,NanoAnalytics GmbH | And 3 more authors.
Advanced Functional Materials | Year: 2010

Chemically functionalized self-assembled monolayers made by disk-shaped zeolite L nanocrystals are used as models for biocompatible surfaces to study cell-adhesion behavior. Different chemical groups lead to different cellular behavior and fluorescent-molecule-loaded zeolites allow the position of the cells to be determined. Furthermore, a patterned monolayer of asymmetrically functionalized zeolite L obtained by microcontact chemistry is used to grow cells. A spatial recognition of the cells, which proliferate only on the bioactivemolecule-functionalized stripes, is possible. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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