TY - JOUR A1 - Preller, Tobias A1 - Runge-Borchert, Gundula A1 - Zellmer, Sabrina A1 - Menzel, Dirk A1 - Saein, Saeid Azimi A1 - Peters, Jan A1 - Raatz, Annika A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Garnweitner, Georg T1 - Particle-reinforced and functionalized hydrogels for SpineMan, a soft robotics application JF - Journal of materials science N2 - SpineMan is designed as a prototype of a soft robotic manipulator that is constructed of alternating hard and soft segments similar to the human spine. Implementing such soft segments allows to surpass the rigidity of conventional robots and ensures safer workspaces where humans and machines can work side by side with less stringent safety restrictions. Therefore, we used a hydrogel as viscoelastic material consisting of poly(vinyl alcohol) and borax. The mechanical properties of the hydrogel were tailored by embedding silica particles of various particles sizes as well as in different mass fractions. Increased mass contents as well as larger particle sizes led to strongly enhanced rigidity with a more than doubled storage modulus of the composite compared to the pure hydrogel. Furthermore, specific functionalities were induced by the incorporation of superparamagnetic Fe3O4 nanoparticles that can in principle be used for sensing robotic motion and detecting malfunctions. Therefore, we precisely adjusted the saturation magnetization of the soft segments using defined mass contents of the nanoparticles. To ensure long-time shape stability and prevention of atmospheric influences on the prepared composites, a silicone skin of specific shore hardness was used. The composites and the soft segments were characterized by oscillation measurements, cryo-SEM, bending tests and SQUID measurements, which give insights into the properties in the passive and in the moving state of SpineMan. The utilization of tailored composites led to highly flexible, reinforced and functional soft segments, which ensure stability, easy movability by springs of the shape memory alloy nitinol and prevention of total failure. Y1 - 2018 U6 - https://doi.org/10.1007/s10853-018-3106-6 SN - 0022-2461 SN - 1573-4803 VL - 54 IS - 5 SP - 4444 EP - 4456 PB - Springer CY - New York ER - TY - JOUR A1 - Frasca, Stefano A1 - Rojas, Oscar A1 - Salewski, Johannes A1 - Neumann, Bettina A1 - Stiba, Konstanze A1 - Weidinger, Inez M. A1 - Tiersch, Brigitte A1 - Leimkühler, Silke A1 - Koetz, Joachim A1 - Wollenberger, Ursula T1 - Human sulfite oxidase electrochemistry on gold nanoparticles modified electrode JF - Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society N2 - The present study reports a facile approach for sulfite biosensing, based on enhanced direct electron transfer of a human sulfite oxidase (hSO) immobilized on a gold nanoparticles modified electrode. The spherical core shell AuNPs were prepared via a new method by reduction of HAuCl4 with branched poly(ethyleneimine) in an ionic liquids resulting particles with a diameter less than 10 nm. These nanoparticles were covalently attached to a mercaptoundecanoic acid modified Au-electrode where then hSO was adsorbed and an enhanced interfacial electron transfer and electrocatalysis was achieved. UV/Vis and resonance Raman spectroscopy, in combination with direct protein voltammetry, are employed for the characterization of the system and reveal no perturbation of the structural integrity of the redox protein. The proposed biosensor exhibited a quick steady-state current response, within 2 s, a linear detection range between 0.5 and 5.4 mu M with a high sensitivity (1.85 nA mu M-1). The investigated system provides remarkable advantages in the possibility to work at low applied potential and at very high ionic strength. Therefore these properties could make the proposed system useful in the development of bioelectronic devices and its application in real samples. KW - Direct electron transfer KW - Gold nanoparticle KW - Human sulfite oxidase KW - Ionic liquid KW - Sulfite biosensor Y1 - 2012 U6 - https://doi.org/10.1016/j.bioelechem.2011.11.012 SN - 1567-5394 VL - 87 SP - 33 EP - 41 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Jyotishkumar, P. A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Strehmel, Veronika A1 - oezdilek, Ceren A1 - Moldenaers, Paula A1 - Hässler, Rüdiger A1 - Thomas, Sabu T1 - Complex phase separation in poly(acrylonitrile-butadiene-styrene)-modified epoxy/4,4 '-diaminodiphenyl sulfone blends : generation of new micro- and nanosubstructures N2 - The epoxy system containing diglycidyl ether of bisphenol A and 4,4'-diaminodiphenyl sulfone is modified with poly(acrylonitrile-butadiene-styrene) (ABS) to explore the effects of the ABS content on the phase morphology, mechanism of phase separation, and viscoelastic properties. The amount of ABS in the blends was 5, 10, 15, and 20 parts per hundred of epoxy resin (phr). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to investigate the final morphology of ABS-modified epoxy blends. Scanning electron microscopic studies of 15 phr ABS-modified epoxy blends reveal a bicontinuous structure in which both epoxy and ABS are continuous, with substructures of the ABS phase dispersed in the continuous epoxy phase and substructures of the epoxy phase dispersed in the continuous ABS phase. TEM micrographs of 15 phr ABS-modified epoxy blends confirm the results observed by SEM. TEM micrographs reveal the existence of nanosubstructures of ABS in 20 phr ABS-modified epoxy blends. To the best of our knowledge, to date, nanosubstructures have never been reported in any epoxy/thermoplastic blends. The influence of the concentration of the thermoplastic on the generated morphology as analyzed by SEM and TEM was explained in detail. The evolution and mechanism of phase separation was investigated in detail by optical microscopy (OM) and small-angle laser light scattering (SALLS). At concentrations lower than 10 phr the system phase separates through nucleation and growth (NG). However, at higher concentrations, 15 and 20 phr, the blends phase separate through both NG and spinodal decomposition mechanisms. On the basis of OM and SALLS, we conclude that the phenomenon of complex substructure formation in dynamic asymmetric blends is due to the combined effect of hydrodynamics and viscoelasticity. Additionally, dynamic mechanical analysis was carried out to evaluate the viscoelastic behavior of the cross-linked epoxy/ABS blends. Finally, apparent weight fractions of epoxy and ABS components in epoxy- and ABS-rich phases were evaluated from T-g analysis. Y1 - 2009 UR - http://pubs.acs.org/journal/jpcbfk U6 - https://doi.org/10.1021/Jp8094566 SN - 1520-6106 ER - TY - JOUR A1 - Wöhl-Bruhn, Stefanie A1 - Badar, Muhammad A1 - Bertz, Andreas A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Menzel, Henning A1 - Müller, Peter P. A1 - Bunjes, Heike T1 - Comparison of in vitro and in vivo protein release from hydrogel systems JF - Journal of controlled release N2 - Hydrogel systems based on hydroxyethyl starch-polyethylene glycol methacrylate (HES-P(EG)(6)MA) or hydroxyethyl starch methacrylate (HES-MA) were used to assess the protein release behavior. Here, we analyzed the in vitro release of FITC-anti-human antibodies incorporated in either HES-P(EG)(6)MA or HES-MA hydrogel delivery systems in PBS or human serum. In addition, hydrogel disks and microparticles prepared from the two polymers were subcutaneously implanted in BALB/c mice. The in vivo release of FITC-IgG was non-invasively monitored by an in vivo imaging system (IVIS 200) over a time period of up to 3 months. The imaging system allowed to asses individual animals over time, therefore only a small number of animals was required to obtain high quality data. The reduction in fluorescence intensity at the site of administration was compared to in vitro release profiles. These investigations demonstrated a sustained release from HES-MA hydrogel disks compared to rapidly degrading HES-P(EG)(6)MA disks and microparticles. The sustained release from HES-MA disks could be further optimized by using increased polymer concentrations. Human serum as in vitro release medium reflected better the in vivo release from HES-P(EG)(6)MA systems than PBS, suggesting that the presence of organic substances like proteins or lipids may play a significant role for the release kinetics. KW - In vivo imaging system (IVIS) KW - Hydrogel disks KW - Hydrogel microparticles KW - Release KW - In vivo-in vitro correlation KW - Hydroxyethyl starch (HES) Y1 - 2012 U6 - https://doi.org/10.1016/j.jconrel.2012.05.049 SN - 0168-3659 VL - 162 IS - 1 SP - 127 EP - 133 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bertz, Andreas A1 - Wöhl-Bruhn, Stefanie A1 - Miethe, Sebastian A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Hust, Michael A1 - Bunjes, Heike A1 - Menzel, Henning T1 - Encapsulation of proteins in hydrogel carrier systems for controlled drug delivery influence of network structure and drug size on release rate JF - Journal of biotechnology N2 - Novel hydrogels based on hydroxyethyl starch modified with polyethylene glycol methacrylate (HES-P(EG)(6)MA) were developed as delivery system for the controlled release of proteins. Since the drug release behavior is supposed to be related to the pore structure of the hydrogel network the pore sizes were determined by cryo-SEM, which is a mild technique for imaging on a nanometer scale. The results showed a decreasing pore size and an increase in pore homogeneity with increasing polymer concentration. Furthermore, the mesh sizes of the hydrogels were calculated based on swelling data. Pore and mesh size were significantly different which indicates that both structures are present in the hydrogel. The resulting structural model was correlated with release data for bulk hydrogel cylinders loaded with FITC-dextran and hydrogel microspheres loaded with FITC-IgG and FITC-dextran of different molecular size. The initial release depended much on the relation between hydrodynamic diameter and pore size while the long term release of the incorporated substances was predominantly controlled by degradation of the network of the much smaller meshes. KW - Hydrogel KW - Hydrogel microspheres KW - Network structure KW - Release studies KW - Protein delivery KW - Mesh size Y1 - 2013 U6 - https://doi.org/10.1016/j.jbiotec.2012.06.036 SN - 0168-1656 VL - 163 IS - 2 SP - 243 EP - 249 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rojas, Oscar A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Tiersch, Brigitte A1 - Wacker, Philipp A1 - Kramer, Markus T1 - Structural studies of ionic liquid-modified microemulsions N2 - This work is focused on the influence of an ionic liquid (IL), i.e. ethyl-methylimidazolium hexylsulfate, on the spontaneous formation of microemulsions with ionic surfactants. The influence of the ionic liquid on Structure formation in the optically clear phase region in water/toluene/pentanol mixtures in presence of the cationic surfactant CTAB was studied in more detail. The results show a significant increase of the transparent phase region by adding the ionic liquid. Conductometric investigations demonstrate that adding the ionic liquid can drastically reduce the droplet- droplet interactions in the L-2 phase. H-1 nuclear magnetic resonance (H-1 NMR) diffusion coefficient measurements in combination with dynamic light scattering measurements clearly show that inverse microemulsion droplets still exist, but the droplet size is decreased to 2 nm. A more detailed characterisation of the isotropic phase channel by means of conductivity measurements, dynamic light scattering (DLS), H-1 NMR and cryo-scanning electron microscopy (SEM), allows the identification of a bicontinuous sponge phase between the L-1 and L-2 phase. When the poly(ethyleneimine) is added, the isotropic phase range is reduced drastically, but the inverse microemulsion range still exists. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00219797 U6 - https://doi.org/10.1016/j.jcis.2009.02.039 SN - 0021-9797 ER - TY - JOUR A1 - Rojas, Oscar A1 - Tiersch, Brigitte A1 - Rabe, Christian A1 - Stehle, Ralf A1 - Hoell, Armin A1 - Arlt, Bastian A1 - Koetz, Joachim T1 - Nonaqueous Microemulsions Based on N,N '-Alkylimidazolium Alkylsulfate Ionic Liquids JF - Langmuir N2 - The ternary system composed of the ionic liquid surfactant (IL-S) 1-butyl-3-methylimidazolium dodecylsulfate ([Bmim][DodSO(4)]), the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]), and toluene has been investigated. Three major mechanisms guiding the structure of the isotropic phase were identified by means of conductometric experiments, which have been correlated to the presence of oil-in-IL, bicontinuous, and IL-in-oil microemulsions. IL-S forms micelles in toluene, which swell by adding RTIL as to be shown by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) experiments. Therefore, it is possible to form water free IL-in-oil reverse microemulsions <= 10 nm in size as a new type of nanoreactor. Y1 - 2013 U6 - https://doi.org/10.1021/la401080q SN - 0743-7463 VL - 29 IS - 23 SP - 6833 EP - 6839 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Dolya, Natalya A1 - Rojas, Oscar A1 - Kosmella, Sabine A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Kudaibergenov, Sarkyt T1 - "One-Pot" in situ frmation of Gold Nanoparticles within Poly(acrylamide) Hydrogels JF - Macromolecular chemistry and physics N2 - This paper focuses on two different strategies to incorporate gold nanoparticles (AuNPs) into the matrix of polyacrylamide (PAAm) hydrogels. Poly(ethyleneimine) (PEI) is used as both reducing and stabilizing agent for the formation of AuNPs. In addition, the influence of an ionic liquid (IL) (i.e., 1-ethyl-3-methylimidazolium ethylsulfate) on the stability of the nanoparticles and their immobilization in the hydrogel is investigated The results show that AuNPs surrounded by a shell containing PEI and IL, synthesized according to the one-pot approach, are much better immobilized within the PAAm hydrogel. Hereby, the IL is responsible for structural changes in the hydrogel as well as the improved stabilization and embedding of the AuNPs into the polymer gel matrix. KW - gold nanoparticles KW - immobilization KW - ionic liquids KW - poly(acrylamide) hydrogels Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200727 SN - 1022-1352 VL - 214 IS - 10 SP - 1114 EP - 1121 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Koetz, Joachim A1 - Bahnemann, Jennifa A1 - Lucas, Gordon A1 - Tiersch, Brigitte A1 - Kosmella, Sabine T1 - Polyelectrolyte-modified microemulsions as new templates for the formation of nanoparticles N2 - The paper is focused on the formation and redispersion of monodisperse BaSO4 nanoparticles in polyelectrolyte- modified microemulsions. It is shown that a cationic polyelectrolyte of low molar mass, e.g. poly(dially1dimethylammonium chloride) (PDADMAC), can be incorporated into the individual inverse microemulsion droplets (L2 phase) consisting of heptanol, water, and an amphoteric surfactant with a sulfobetaine head group. These PDADMAC- filled microemulsion droplets can be successfully used as a template phase for the nanoparticle formation. The monodisperse BaSO4 nanoparticles are produced by a simple mixing procedure and can be redispersed after solvent evaporation without a change in particle dimensions. Dynamic and electrophoretical light scattering in combination with sedimentation experiments in the analytical Ultracentrifuge of the redispersed powder show polyelectrolyte-stabilized nanoparticles with diameters of about 6 nm. The polyelectrolyte shows a "size control effect", which can be explained by the polyelectrolyte-surfactant interactions in relation to the polyelectrolyte-nanoparticle interactions during the particle growth, solvent evaporation and redispersion process. However, the approach used here opens away to produce different types of polyelectrolyte-stabilized nanoparticles (including rare metals, semiconductors, carbonates or oxides) of very small dimensions. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0927-7757 ER - TY - JOUR A1 - Koetz, Joachim A1 - Andres, S. A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - BaSO4 nanorods produced in polymer-modified bicontinuous microemulsions N2 - The influence of the water soluble polymer poly(ethylene glycol) (PEG) on structure formation in the quasiternary system sodium dodecylsulfate (SDS)/pentanol-xylene/water was checked by means of conductometry, rheology, and micro differential calorimetry. The polymer induces the formation of an isotropic phase channel between the o/w and w/o microemulsion. The transition from the normal as well as from the inverse micellar to the bicontinuous phase range can be detected by conductometry, rheology as well as micro-DSC. As a result of polymer-surfactant interactions, the spontaneous curvature of the surfactant film is changed and a sponge phase is formed. The bicontinuous phase is characterized by a moderate shear viscosity, a Newtonian flow behaviour, and the disappearence of interphasal water in the heating curve of the micro-DSC. When the polymer-modified bicontinuous phase is used as a template phase for the nanoparticle formation, spherical BaSO4 nanoparticles were formed. During the following solvent evaporation process the primarily formed spherical nanoparticles aggregate to nanorods and triangular structures due to the non-restriction of the bicontinuous template phase in longitudinal direction Y1 - 2006 UR - http://www.ingentaconnect.com/content/vsp/ci U6 - https://doi.org/10.1163/156855406777408629 SN - 0927-6440 ER - TY - JOUR A1 - Note, Carine A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Hydrophobically modified polyelectrolytes used as reducing and stabilizing agent for the formation of gold nanoparticles N2 - This paper is focused on the synthesis and characterization of hydrophobically modified polyelectrolytes and their use as reducing as well as stabilizing agents for the formation of gold nanoparticles. Commercially available poly(acrylic acid) has been hydrophobically modified with various degrees of grafting of butylamine introduced randomly along the chain. Different analytical methods are performed, i.e., IR and H-1-NMR spectroscopy in combination with elemental analysis to determine the degree of grafting. The modified polymers can successfully be used for the controlled single-step synthesis and stabilization of gold nanoparticles. The process of nanoparticle formation is investigated by means of UV-vis spectroscopy. The size and shape of the particles obtained in the presence of unmodified or modified polyelectrolytes are characterized by dynamic light scattering, zeta potential measurements and transmission electron microscopy. The polyelectrolytes were involved in the crystallization process of the nanoparticles, and in the presence of hydrophobic microdomains at the particle surface, a better stabilization at higher temperature can be observed Y1 - 2005 SN - 0303-402X ER - TY - JOUR A1 - Robertson, Daniela A1 - Hellweg, Thomas A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Polymer-induced structural changes in lecithin/sodium dodecyl sulfate-based multilamellar vesicles N2 - Aqueous concentrated lecithin mixtures (asolectin from soybean) show typical lamellar liquid crystalline behavior and the individual lamellae tend to form spherical supramolecular structures, i.e., multilamellar vesicles. When part of the lecithin is replaced by the anionic surfactant sodium dodecyl sulfate (SIDS), the compact multilamellar vesicles disappear and the viscosity decreases. By adding oly(diallyldimethylammonium chloride) (PDADMAC) to the lecithin/SDS system, the formation of multilamellar vesicles can be induced again and the viscosity increases. However, one characteristic feature of these polymer-modified systems is a temperature-dependent phase transition from a compact multilamellar vesicle phase to a more swollen liquid crystalline phase. The polymer-modified multilamellar compact vesicles are of interest for utilization as new thermosensitive drug delivery systems. (C) 2003 Elsevier Inc. All rights reserved Y1 - 2004 SN - 0021-9797 ER - TY - JOUR A1 - Robertson, Daniela A1 - Hellweg, Thomas A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Polymer induced structural changes in lecithin/SDS-based multilamellar vesicles Y1 - 2004 SN - 0021-9797 ER - TY - JOUR A1 - Couturier, Jean-Philippe A1 - Wischerhoff, Erik A1 - Bernin, Robert A1 - Hettrich, Cornelia A1 - Koetz, Joachim A1 - Sutterlin, Martin A1 - Tiersch, Brigitte A1 - Laschewsky, Andre T1 - Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols JF - Langmuir N2 - Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers’ cloud point, or the induced changes of the hydrogels’ swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b00803 SN - 0743-7463 VL - 32 SP - 4333 EP - 4345 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vargas-Ruiz, Salome A1 - Schulreich, Christoph A1 - Kostevic, Angelika A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Kakorin, Sergej A1 - von Klitzing, Regine A1 - Jung, Martin A1 - Hellweg, Thomas A1 - Wellert, Stefan T1 - Extraction of model contaminants from solid surfaces by environmentally compatible microemulsions JF - Journal of colloid and interface science N2 - In the present contribution, we evaluate the efficiency of eco-friendly microemulsions to decontaminate solid surfaces by monitoring the extraction of non-toxic simulants of sulfur mustard out of model surfaces. The extraction process of the non-toxic simulants has been monitored by means of spectroscopic and chromatographic techniques. The kinetics of the removal process was analyzed by different empirical models. Based on the analysis of the kinetics, we can assess the influence of the amounts of oil and water and the microemulsion structure on the extraction process. (C) 2016 Elsevier Inc. All rights reserved. KW - Microemulsions KW - Decontamination KW - Surface removal KW - Kinetic analysis KW - Extraction Y1 - 2016 U6 - https://doi.org/10.1016/j.jcis.2016.03.006 SN - 0021-9797 SN - 1095-7103 VL - 471 SP - 118 EP - 126 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Großkopf, Sören A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Mix, Andreas A1 - Hellweg, Thomas T1 - Shear-Induced Transformation of Polymer-Rich Lamellar Phases to Micron-Sized Vesicles JF - Langmuir N2 - In the present work, we study the shear-induced transformation of polymer-rich lamellar phases into vesicles. The evolution of vesicle size is studied by different scattering techniques, rheology, and microscopy methods. The lamellar phase found in the system D2O/o-xylene/Pluronic PE9400/C(8)TAB can be fully transformed to multilamellar vesicles (MLVs) by applying shear. The size of the MLVs is proportional to the inverse square root of the shear rate. Hence, the polymer based quaternary system behaves similar to lamellar phases based on small surfactant molecules. Additionally, we found a growth effect leading to a size increase of the vesicles after shearing was stopped. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.8602786 SN - 0743-7463 VL - 35 IS - 8 SP - 3048 EP - 3057 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Perez-Anes, Alexandra A1 - Rodrigues, Fernanda A1 - Caminade, Anne-Marie A1 - Stefaniu, Cristina A1 - Tiersch, Brigitte A1 - Turrin, Cedric-Olivier A1 - Blanzat, Muriel T1 - Influence of structural parameters on the self-association properties of anti-HIV catanionic dendrimers JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The self-association properties of anti-HIV catanionic dendrimers as multivalent galactosylceramide (GalCer)-derived inhibitors are presented. The study was designed to elucidate the origin of the relatively high cytotoxicity values of these antiHIV catanionic dendrimers, which have previously been found to exhibit in vitro anti-HIV activity in the submicromolar range. The physicochemical properties of these catanionic dendrimers were studied to tentatively correlate the structural parameters with self-association and biological properties. We can conclude from this study that the absence of correlation between the hydrophobicity and the cytotoxicity of the catanionic systems could be explained by the partial segregation of the different partners of the catanionic entities. KW - anti-HIV KW - catanionic surfactants KW - dendrimers KW - galactosylceramide KW - glycolipids Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500484 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 16 SP - 3433 EP - 3437 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Rusu, Viorel Marin A1 - Ng, C. H. A1 - Wilke, Max A1 - Tiersch, Brigitte A1 - Fratzl, Peter A1 - Peter, Martin G. T1 - Size-controlled hydroxyapatite nanoparticles as self-organized organic-in organic composite materials N2 - This paper presents some results concerning the size-controlled hydroxyapatite nanoparticles obtained in aqueous media in a biopolymer matrix from soluble precursors salts. Taking the inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite was investigated. A stepwise co-precipitation approach was used to obtain different types of composites by means of different ratio between components. The synthesis of hydroxyapatite was carried out in the chitosan matrix from calcium chloride and sodium dihydrogenphosphate in alkaline solutions at moderate pH of 10-11 for 24 h. Our research is focused on studying and understanding the structure of this class of composites, aiming at the development of novel materials, controlled at the nanolevel scale. The X-ray diffraction technique was employed in order to study the kinetic of hydroxyapatite formation in the chitosan matrix as well as to determine the HAp crystallite sizes in the composite samples. The hydroxyapatite synthesized using this route was found to be nano-sized (15-50nm). Moreover, applying an original approach to analyze the (002) XRD diffraction peak profile of hydroxyapatite by using a sum of two Gauss functions, the bimodal distribution of nanosized hydroxyapatite within the chitosan matrix was revealed. Two types of size distribution domains such as cluster-like (between 200 and 400 nm), which are the habitat of "small" hydroxyapatite nanocrystallites and scattered-like, which are the habitat of "large" hydroxyapatite nanocrystallites was probed by TEM and CSLM. The structural features of composites suggest that self-assembly processes might be involved. The composites contain nanosized hydroxyapatite with structural features close to those of biological apatites that make them attractive for bone tissue engineering applications. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0142-9612 ER - TY - GEN A1 - Koetz, Joachim A1 - Reichelt, S. A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Recovery of nanoparticles produced in phosphatidylcholine-based template phases N2 - This paper focuses on the characterization and use of polymer-modified phosphatidylcholine (PC)/sodium dodecyl sulfate (SDS)-based inverse microemulsions as a template phase for BaSO4 nanoparticle formation. The area of the optically clear inverse microemulsion phase in the isooctane/hexanol/water/PC/SDS system is not significantly changed by adding polyelectrolytes, i.e., poly(diallyldimethylammonium chloride) (PDADMAC), or amphoteric copolymers of diallyldimethylammonium chloride and maleamid acid to the SDS-modified inverse microemulsion. Shear experiments show non- Newtonian flow behavior and oscillation experiments show a frequency-dependent viscosity increase (dilatant behavior) of the microemulsions. Small amounts of bulk water were identified by means of differential scanning calorimetry. One can conclude that the macromolecules are incorporated into the individual droplets, and polymer-filled microemulsions are formed. The polymer-filled microemulsions were used as a template phase for the synthesis of BaSO4 nanoparticles. After solvent evaporation the nanoparticles were redispersed in water and isooctane, respectively. The polymers incorporated into the microemulsion are involved in the redispersion process and influence the size and shape of the redispersed BaSO4 particles in a specific way. The crystallization process mainly depends on the type of solvent and the polymer component added. In the presence of the cationic polyelectrolyte PDADMAC the crystallization to larger cubic crystals is inhibited, and layers consisting of polymer-stabilized spherical nanoparticles of BaSO4 (6 nm in size) will be observed. (c) 2004 Elsevier Inc. All rights reserved Y1 - 2005 SN - 0021-9797 ER - TY - JOUR A1 - Koetz, Joachim A1 - Brühl, Iris A1 - Kosmella, Sabine A1 - Reiche, Jürgen A1 - Tiersch, Brigitte T1 - Polyelectrolyte Complex Formation in Lamellar Liquid Crystalline Systems N2 - The influence of polyelectrolytes on structure formation in liquid crystalline Na-dodecylsulfate/decanol/water systems was investigated by means of small angle X-ray diffraction, rheology, NMR spectroscopy, and microscopy. By adding Na-polyacrylate (PAA) into the mesophase, the one-phase region is left and phenomena of phase separation into a solvent-rich and a polymer/surfactantrich phase occurs. By incoporating an anionic and cationic polyelectrolyte step by step the tendency of phase separation is increased drastically. The self-organization process can be regulated directly by varying the water content of the system. However, at a water content of 30% the properties of the resulting liquid crystal were changed drastically. X-ray diffraction shows a multitude of Bragg peaks, NMR shows a peak-splitting, and rheology shows a change from non-Newtonian to Newtonian-flow behavior. On the basis of the experimental results an ordered multilayer associate structure can be assumed. Y1 - 1997 ER - TY - JOUR A1 - Lutter, Stefanie A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Kosmella, Sabine T1 - Polymer-modified bicontinuous microemulsions used as a template for the formation of nanorods N2 - This article is focused on the characterization of the poly(ethylene glycol) (PEG)-induced bicontinuous microemulsion of the pseudo-ternary system sodium dodecylsulfate (SDS)/xylene-pentanol/water by means of differential scanning calorimetry, rheology, and conductometry. The influence of the polymer concentration (cp) and the molecular weight (Mw) on the microstructure of the microemulsion was investigated using Cryo scanning electron microscopy. It was found that an increase of cp influences the structure of the sponge-like phase significantly. These polymer-modified microemulsions can be used as a template phase for the formation of BaSO4 nanorods, where individual nanoparticles (5nm in size) are ordered along the polymer backbone. Y1 - 2009 UR - http://www.informaworld.com/openurl?genre=journal&issn=0193-2691 U6 - https://doi.org/10.1080/01932690802643113 SN - 0193-2691 ER - TY - JOUR A1 - Grobosch, Thomas A1 - Schilde, Uwe A1 - Tiersch, Brigitte T1 - Abtrennung von Arsen und anderer Schwermetalle mit imprägnierten Adsorberpolymeren - teil 2: Abtrennung von Blei, Kupfer, Nickel und Zink Y1 - 2006 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/60500203/ U6 - https://doi.org/10.1002/cite.200500171 SN - 0009-286X ER - TY - JOUR A1 - Koetz, Joachim A1 - Beitz, Toralf A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Polymer-modified microemulsions Y1 - 2000 ER - TY - JOUR A1 - Bechthold, Nina A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Friberg, Stig E. T1 - Structure Formation in polymer-modified liquid crystals Y1 - 1999 ER - TY - JOUR A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Hartmann, Jürgen T1 - Structural Analysis of the influence of polymers on lyotropic liquid-crystal systems Y1 - 1997 ER - TY - JOUR A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Bogen, Iris T1 - Polyelectrolyte induced vesicle-formation in lamellar liquid crystalline model systems Y1 - 2000 ER - TY - JOUR A1 - Koetz, Joachim A1 - Beitz, Toralf A1 - Tiersch, Brigitte T1 - Self assembled polymer-surfactant systems Y1 - 1999 ER - TY - JOUR A1 - Bressel, Katharina A1 - Prevost, Sylvain A1 - Appavou, Marie-Sousai A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Gradzielski, Michael T1 - Phase behaviour and structure of zwitanionic mixtures of perfluorocarboxylates and tetradecyldimethylamine oxide-dependence on chain length of the perfluoro surfactant JF - Soft matter N2 - Phase behaviour and the mesoscopic structure of zwitanionic surfactant mixtures based on the zwitterionic tetradecyldimethylamine oxide (TDMAO) and anionic lithium perfluoroalkyl carboxylates have been investigated for various chain lengths of the perfluoro surfactant with an emphasis on spontaneously forming vesicles. These mixtures were studied at a constant total concentration of 50 mM and characterised by means of dynamic light scattering (DLS), electric conductivity, small-angle neutron scattering (SANS), viscosity, and cryo-scanning electron microscopy (Cryo-SEM). No vesicles are formed for relatively short perfluoro surfactants. The extension of the vesicle phase becomes substantially larger with increasing chain length of the perfluoro surfactant, while at the same time the size of these vesicles increases. Head group interactions in these systems play a central role in the ability to form vesicles, as already protonating 10 mol% of the TDMAO largely enhances the propensity for vesicle formation. The range of vesicle formation in the phase diagram is not only substantially enlarged but also extends to shorter perfluoro surfactants, where without protonation no vesicles would be formed. The size and polydispersity of the vesicles are related to the chain length of the perfluoro surfactant, the vesicles becoming smaller and more monodisperse with increasing perfluoro surfactant chain length. The ability of the mixed systems to form well-defined unilamellar vesicles accordingly can be controlled by the length of the alkyl chain of the perfluorinated surfactant and depends strongly on the charge conditions, which can be tuned easily by pH-variation. Y1 - 2011 U6 - https://doi.org/10.1039/c1sm05618b SN - 1744-683X VL - 7 IS - 23 SP - 11232 EP - 11242 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schulze, Nicole A1 - Appelhans, D. A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Morphological transformation of vesicles into tubular structures by adding polyampholytes or dendritic glycopolymers JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - For the first time tubulating properties of spherical dendritic glycopolymers and linear alternating polyampholytes against non-uniform negatively charged giant vesicles are proven by light microscopy and cryo-scanning electron microscopy study. Real time observation of the morphological transformation from giant vesicles to tubular structures, simulating morphogenesis in living cells, is given by using the cationic and H-bond active dendritic glycopolymer accompanied by reducing the size of the giant vesicles and the evidence of vesicle-vesicle interaction which was only postulated in a previous study. Similar morphogenesis of non-uniform giant vesicles into tubular network structure can be observed by using a polyampholyte in the stretched conformation at pH 9. Pearl necklace and tubular network structure formation are also observed by applying anionic vesicles of significant smaller dimensions with average size dimensions of 35 nm, after adding the polyampholyte at pH 9. However, the fitting accuracy between the functional groups along the backbone chain of the polyampholyte on one side and the vesicle surface on the other side is of high importance for the transformation process by using polyampholytes. The resulting tubular and network structures offer new fields of application as microfluidic transport channels or template phases for the shape controlled formation of nanoparticles. (C) 2014 Elsevier B.V. All rights reserved. KW - Alternating polyampholytes KW - Maltose-modified PEI KW - Network structure KW - Template phase KW - Cryo-SEM KW - DLS Y1 - 2014 U6 - https://doi.org/10.1016/j.colsurfa.2014.06.007 SN - 0927-7757 SN - 1873-4359 VL - 457 SP - 326 EP - 332 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wellert, Stefan A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Richardt, Andre A1 - Lapp, Alain A1 - Holderer, Olaf A1 - Gaeb, Juergen A1 - Blum, Marc-Michael A1 - Schulreich, Christoph A1 - Stehle, Ralf A1 - Hellweg, Thomas T1 - The DFPase from Loligo vulgaris in sugar surfactant-based bicontinuous microemulsions structure, dynamics, and enzyme activity JF - European biophysics journal : with biophysics letters ; an international journal of biophysics N2 - The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris is of great interest because of its ability to catalyze the hydrolysis of highly toxic organophosphates. In this work, the enzyme structure in solution (native state) was studied by use of different scattering methods. The results are compared with those from hydrodynamic model calculations based on the DFPase crystal structure. Bicontinuous microemulsions made of sugar surfactants are discussed as host systems for the DFPase. The microemulsion remains stable in the presence of the enzyme, which is shown by means of scattering experiments. Moreover, activity assays reveal that the DFPase still has high activity in this complex reaction medium. To complement the scattering experiments cryo-SEM was also employed to study the microemulsion structure. KW - Dynamic light scattering KW - Neutron spin echo KW - Microemulsion KW - Enzyme catalysis KW - SANS KW - Protein structure Y1 - 2011 U6 - https://doi.org/10.1007/s00249-011-0689-0 SN - 0175-7571 VL - 40 IS - 6 SP - 761 EP - 774 PB - Springer CY - New York ER - TY - JOUR A1 - Koeth, Anja A1 - Tiersch, Brigitte A1 - Appelhans, Dietmar A1 - Gradzielski, Michael A1 - Cölfen, Helmut A1 - Koetz, Joachim T1 - Synthesis of Core-Shell Gold Nanoparticles with Maltose-Modified Poly(Ethyleneimine) JF - Journal of dispersion science and technology N2 - The synthesis of ultrafine gold nanoparticles in presence of maltose-modified hyperbranched poly(ethyleneimines) (PEI) is described. The polymer acted as both a reducing and stabilising agent in the particle formation process. The nanoparticles were characterized by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), small-angle x-ray scattering (SAXS), and small-angle neutron scattering (SANS). The mechanism of nanoparticle formation can be described in two steps. The reduction process of the Au3+ ions located in the inner coil region of the hyperbranched PEI led to the formation of a compact gold core, and is accompanied by a collapse of the polymer coil. Therefore, in the subsequent reduction process a gold-polymer hybrid shell is formed. By using the PEI of higher molar mass, core-shell gold nanoparticles of about 3.6 nm size with a more narrow size distribution and special fluorescence behavior could be synthesized. KW - Gold nanoparticles KW - gold-polymer hybrid shell KW - maltose-modified poly(ethyleneimine) Y1 - 2012 U6 - https://doi.org/10.1080/01932691.2010.530084 SN - 0193-2691 VL - 33 IS - 1-3 SP - 52 EP - 60 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Weber, Nancy A1 - Tiersch, Brigitte A1 - Unterlass, Miriam M. A1 - Heilig, Anneliese A1 - Tauer, Klaus T1 - "Schizomorphic" Emulsion Copolymerization Particles JF - Macromolecular rapid communications N2 - Cryo-electron microscopy, atomic force microscopy, and light microscopy investigations provide experimental evidence that amphiphilic emulsion copolymerization particles change their morphology in dependence on concentration. The shape of the particles is spherical at solids content above 1%, but it changes to rod-like, ring-like, and web-like structures at lower concentrations. In addition, the shape and morphology of these particles at low concentrations are not fixed but very flexible and vary with time between spheres, flexible pearlnecklace structures, and stretched rods. KW - amphiphilic particles KW - emulsion polymerization KW - morphology Y1 - 2011 U6 - https://doi.org/10.1002/marc.201100491 SN - 1022-1336 VL - 32 IS - 23 SP - 1925 EP - 1929 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Koeth, Anja A1 - Appelhans, Dietmar A1 - Robertson, Daniela A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Use of weakly cationic dendritic glycopolymer for morphological transformation of phospholipid vesicles into tube-like networks JF - Soft matter N2 - Using cationic polyelectrolytes with different molecular architectures, only hyperbranched poly(ethyleneimine) with maltose shell is suited to tailor the morphological transformation of anionic vesicles into tube-like networks. The interaction features of those materials partly mimic biological features of tubular proteins in nature. Y1 - 2011 U6 - https://doi.org/10.1039/c1sm06439h SN - 1744-683X VL - 7 IS - 22 SP - 10581 EP - 10584 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Asawapirom, Udom A1 - Bulut, F. A1 - Farrell, Tony A1 - Gadermaier, C. A1 - Gamerith, S. A1 - Güntner, Roland A1 - Kietzke, Thomas A1 - Patil, S. A1 - Piok, T. A1 - Montenegro, Rivelino V. D. A1 - Stiller, Burkhard A1 - Tiersch, Brigitte A1 - Landfester, Katharina A1 - List, E. J. W. A1 - Neher, Dieter A1 - Torres, C. S. A1 - Scherf, Ullrich T1 - Materials for polymer electronics applications semiconducting polymer thin films and nanoparticles N2 - The paper presents two different approaches to nanostructured semiconducting polymer materials: (i) the generation of aqueous semiconducting polymer dispersions (semiconducting polymer nanospheres SPNs) and their processing into dense films and layers, and (ii) the synthesis of novel semiconducting polyfluorene-block-polyaniline (PF-b-PANI) block copolymers composed of conjugated blocks of different redox potentials which form nanosized morphologies in the solid state Y1 - 2004 SN - 1022-1360 ER - TY - JOUR A1 - Secker, Christian A1 - Voelkel, Antje A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-Induced Aggregation and Crystallization of Block Copolypeptoids in Water JF - Macromolecules : a publication of the American Chemical Society N2 - Block copolypeptoids comprising a thermosensitive, crystallizable poly(N-(n-propyl)glycine) block and a watersoluble poly(N-methylglycine) block, P70My (y = 23, 42, 76, 153, and 290), were synthesized bY ring-opening polymerization of the corresponding N-alkylglycine N-carboxyanhydrides (NCAs) and examined according to their thermo-induced aggregation and crystallization in water by turbidimetty, micro-differential scanning calorimetry (micro-DSC); cryogenic scanning electron microscopy (cryo-SEM), analytical ultracentrifugation (AUC), and static light scattering (SLS). At a temperature above the cloud point temperature, the initially formed micellar aggregates started to crystallize and grow into larger complex assemblies of about 100-500 nm, exhibiting flower-like (P70M23), ellipsoidal (P70M42 and P70M72) or irregular shapes (P70M153 and.P70M290). Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.5b02481 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 979 EP - 985 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Diehl, Christina A1 - Cernoch, Peter A1 - Zenke, Ingrid A1 - Runge, Heike A1 - Pitschke, Rona A1 - Hartmann, Juergen A1 - Tiersch, Brigitte A1 - Schlaad, Helmut T1 - Mechanistic study of the phase separation/crystallization process of poly(2-isopropyl-2-oxazoline) in hot water N2 - The kinetics of the crystallization of thermoresponsive poly(2-isopropyl-2-oxazoline) in water and the time- dependent evolution of the morphology were examined using wide-angle X-ray scattering and conventional and cryogenic scanning electron microscopy. Results indicate that a temperature-induced phase separation produces a bicontinuous polymer network-like structure, which with the onset of crystallization collapses into individual particles (1-2 mu m in diameter) composed of a porous fiber mesh. Nanofibers then preferentially form at the particle surface, thus wrapping the microspheres like a ball of wool. The particle morphology is severely affected by changes in temperature and less by the initial polymer concentration. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/sm/index.asp U6 - https://doi.org/10.1039/C0sm00114g SN - 1744-683X ER - TY - JOUR A1 - Bourgat, Yannick A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Menzel, Henning T1 - Enzyme degradable polymersomes from chitosan-g-[poly-l-lysine-block-epsilon-caprolactone] copolymer JF - Macromolecular bioscience N2 - The scope of this study includes the synthesis of chitosan-g-[peptide-poly-epsilon-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-epsilon-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation. KW - chitosan KW - click chemistry KW - drug delivery system KW - enzyme KW - polymersomes KW - poly‐ ε ‐ caprolactone Y1 - 2020 U6 - https://doi.org/10.1002/mabi.202000259 SN - 1616-5187 SN - 1616-5195 VL - 21 IS - 1 SP - 1 EP - 9 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wegener, Michael A1 - Wirges, Werner A1 - Tiersch, Brigitte T1 - Porous polytetrafluoroethylene (PTFE) electret films : porosity and time dependent charging behaviour of the free surface N2 - Electrically charged porous polytetrafluoroethylene (PTFE) films are often discussed as active layers for electromechanical transducers. Here, the electric charging behavior of open-porous PTFE films with different porosities is investigated. Optimized electric charging of porous PTFE films is determined by variation of charging parameters such as electric fields and charging times. Maximum surface potentials are depending on the porosity of the PTFE films. Suitable charging leads to high surface potentials observed on non-stretched or slightly stretched porous PTFE films. Further increase of charging fields yields decreasing values of the surface potential accompanied with an increase of conductivity. Y1 - 2006 UR - http://www.springerlink.com/content/601u86x365560515/ U6 - https://doi.org/10.1007/s10934-006-9015-0 ER - TY - JOUR A1 - Haase, Martin F. A1 - Grigoriev, Dmitry A1 - Moehwald, Helmuth A1 - Tiersch, Brigitte A1 - Shchukin, Dmitry G. T1 - Encapsulation of amphoteric substances in a pH-sensitive pickering emulsion N2 - Oil-in-water (o/w) Pickering emulsions stabilized with silica nanoparticles were prepared. Droplets of diethyl phthalate (oil phase) act as reservoirs for 8-hydroxyquinoline (8-HQ), which is used as (a) the hydrophobizing agent for the silica particles and (b) an encapsulated corrosion inhibitor for application in active feedback coatings. The hydrophobization of silica nanoparticles with 8-HQ is determined by the amount of this agent adsorbed on the nanoparticle surface. The latter is governed by the 8-HQ concentration in the aqueous phase, which in turn depends on the degree of protonation and fir ally on the pH. We observe three ranges of 8-HQ adsorption value with respect to nanoparticle hydophobization: (I) insufficient, (2) sufficient, and (3) excessive adsorption by the formation of an 8-HQ bilayer, where only case 2 leads to the necessary nanoparticle hydrophobization. Hence emulsions stable in a narrow pH window between pH 5.5 and 4.4 follow. Here functional molecules are sufficiently charged to compensate for the charges on silica nanoparticles to make them interfacially active and thus able to stabilize an emulsion but they are still to a large extent uncharged and thereby remain in the oil phase. The emulsification is reversible upon changing the pH to a value beyond the stability region. Y1 - 2010 UR - http://pubs.acs.org/journal/jpccck U6 - https://doi.org/10.1021/Jp104052s SN - 1932-7447 ER - TY - JOUR A1 - Haase, Martin F. A1 - Grigoriev, Dmitry A1 - Moehwald, Helmuth A1 - Tiersch, Brigitte A1 - Shchukin, Dmitry G. T1 - Nanoparticle modification by weak polyelectrolytes for pH-sensitive pickering emulsions JF - Langmuir N2 - The affinity of weak polyelectrolyte coated oxide particles to the oil-water interface can be controlled by the degree of dissociation and the thickness of the weak polyelectrolyte layer. Thereby the oil in water (o/w) emulsification ability of the particles can be enabled. We selected the weak polyacid poly(methacrylic acid sodium salt) and the weak polybase poly(allylamine hydrochloride) for the surface modification of oppositely charged alumina and silica colloids, respectively. The isoelectric point and the pH range of colloidal stability of both particle-polyelectrolyte composites depend on the thickness of the weak polyelectrolyte layer. The pH-dependent wettability of a weak polyelectrolyte-coated oxide surface is characterized by contact angle measurements. The o/w emulsification properties of both particles for the nonpolar oil dodecane and the more polar oil diethylphthalate are investigated by measurements of the droplet size distributions. Highly stable emulsions can be obtained when the degree of dissociation of the weak polyelectrolyte is below 80%. Here the average droplet size depends on the degree of dissociation, and a minimum can be found when 15 to 45% of the monomer units are dissociated. The thickness of the adsorbed polyelectrolyte layer strongly influences the droplet size of dodecane/water emulsion droplets but has a less pronounced impact on the diethylphthalate/water droplets. We explain the dependency of the droplet size on the emulsion pH value and the polyelectrolyte coating thickness with arguments based on the particle-wetting properties, the particle aggregation state, and the oil phase polarity. Cryo-SEM visualization shows that the regularity of the densely packed particles on the oil-water interface correlates with the degree of dissociation of the corresponding polyelectrolyte. Y1 - 2011 U6 - https://doi.org/10.1021/la1027724 SN - 0743-7463 VL - 27 IS - 1 SP - 74 EP - 82 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Navarro, Salvador A1 - Shkilnyy, Andriy A1 - Tiersch, Brigitte A1 - Taubert, Andreas A1 - Menzel, Henning T1 - Preparation, characterization, and thermal gelation of amphiphilic alkyl-poly(ethyleneimine) N2 - Amphiphilic alkyl-poly(ethyleneimine)s (alkyl-PEI) with different degrees of polymerization have been produced by alkaline hydrolysis of alkyl-poly(2-methyl-2-oxazoline). Potentiometric titration of the alkyl-PEI shows the influence of the alkyl chain and the degree of polymerization on the titration curves and hence on the polymer conformation. Karl Fischer titration has been used to determine the water content in the polymers. Subsequent X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements prove the existence of different hydration states of the PEI even under dry storage conditions. Upon cooling from hot aqueous Solutions, hydrogels form. The gelation concentration decreases with increasing degree of polymerization of the PEI segment. Scanning electron microscopy (SEM and cryo-SEM) of the hydrogels reveal an alkyl-PEI fibrous network composed of fan-like units. DSC shows that the percentages of bound and free water in the hydrogels depend on the concentration of polar amino groups. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La9013569 SN - 0743-7463 ER - TY - JOUR A1 - Neumann, Mike A1 - Noeske, Robert A1 - Taubert, Andreas A1 - Tiersch, Brigitte A1 - Strauch, Peter T1 - Highly structured, biomorphous beta-SiC with high specific surface area from Equisetaceae JF - Journal of materials chemistry N2 - Mesoporous, highly structured silicon carbide (beta-SiC) was synthesised from renewable plant materials (two Equisetaceae species) in a one-step carbothermal process at remarkably low temperatures down to 1200 degrees C. The SiC precursor is a silicon-carbon mixture with finely dispersed carbon prepared by pyrolysis of the organic plant matrix. Yields are 3 to 100% (omega(Si/Si) related to the silicon deposited in the plant material), depending on reaction temperature and time. IR spectroscopy, X-ray diffraction, and nitrogen sorption prove the formation of high-purity beta-SiC with minor inorganic impurities after purification and a high specific surface area of up to 660 m(2) g(-1). Scanning electron microscopy shows that the plant morphology is maintained in the final SiC. Sedimentation analysis finds a mean particle size (diameters d(50)) of 20 mu m. Y1 - 2012 U6 - https://doi.org/10.1039/c2jm30253e SN - 0959-9428 VL - 22 IS - 18 SP - 9046 EP - 9051 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Bourgat, Yannick A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Menzel, Henning T1 - Enzyme degradable polymersomes from chitosan-g-[poly-l-lysine-block-epsilon-caprolactone] copolymer T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The scope of this study includes the synthesis of chitosan-g-[peptide-poly-epsilon-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-epsilon-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1382 KW - chitosan KW - click chemistry KW - drug delivery system KW - enzyme KW - polymersomes KW - poly‐ ε ‐ caprolactone Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-566584 SN - 1866-8372 IS - 1 ER - TY - JOUR A1 - Hornemann, Andrea A1 - Eichert, Diane Madeleine A1 - Hoehl, Arne A1 - Tiersch, Brigitte A1 - Ulm, Gerhard A1 - Ryadnov, Maxim G. A1 - Beckhoff, Burkhard T1 - Investigating Membrane-Mediated Antimicrobial Peptide Interactions with Synchrotron Radiation Far-Infrared Spectroscopy JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - Synchrotron radiation-based Fourier transform infrared spectroscopy enables access to vibrational information from mid over far infrared to even terahertz domains. This information may prove critical for the elucidation of fundamental bio-molecular phenomena including folding-mediated innate host defence mechanisms. Antimicrobial peptides (AMPs) represent one of such phenomena. These are major effector molecules of the innate immune system, which favour attack on microbial membranes. AMPs recognise and bind to the membranes whereupon they assemble into pores or channels destabilising the membranes leading to cell death. However, specific molecular interactions responsible for antimicrobial activities have yet to be fully understood. Herein we probe such interactions by assessing molecular specific variations in the near-THz 400-40 cm(-1) range for defined helical AMP templates in reconstituted phospholipid membranes. In particular, we show that a temperature-dependent spectroscopic analysis, supported by 2D correlative tools, provides direct evidence for the membrane-induced and folding-mediated activity of AMPs. The far-FTIR study offers a direct and information-rich probe of membrane-related antimicrobial interactions. KW - antimicrobial peptides KW - electrostatic interactions KW - IR spectroscopy KW - phospholipid membranes KW - protein folding Y1 - 2022 U6 - https://doi.org/10.1002/cphc.202100815 SN - 1439-4235 SN - 1439-7641 VL - 23 IS - 4 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wegener, Michael A1 - Wirges, Werner A1 - Fohlmeister, Jens Bernd A1 - Tiersch, Brigitte A1 - Gerhard, Reimund T1 - Two-step inflation of cellular polypropylene films: Void-thickness increase and enhanced electromechanical properties N2 - In cellular, electromechanically active polymer films, the so-called ferroelectrets, the cell size and shape distributions can be varied through a controlled inflation process. Up to now, high-pressure treatments were usually performed at elevated temperatures. There are, however, significant experimental limitations and complications if the pressure and temperature treatments are performed at the same time. Here, we demonstrate the controlled inflation of cellular polypropylene films by means of sepal-ate pressure and temperature treatments. Separate procedures are Much easier to implement. Excellent electromechanical properties were achieved with Such a two-step inflation process. The technique has significant potential for inflating large-area transducer films for electromechanical and electroacoustical applications Y1 - 2004 ER -