TY - JOUR A1 - Rumschöttel, Jens A1 - Kosmella, Sabine A1 - Prietzel, Claudia Christina A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Change in size, morphology and stability of DNA polyplexes with hyperbranched poly(ethyleneimines) containing bulky maltose units JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - Polyplexes between Salmon DNA and non-modified hyperbranched poly(ethyleneimines) of varying molar mass, i.e., PEI(5 k) with 5000 g/mol and PEI(25 k) with 25,000 g/mol, and modified PEI(5 k) with maltose units (PEI-Mal) were investigated in dependence on the molar N/P ratio by using dynamic light scattering (DLS), zeta potential measurements, micro differential scanning calorimetry (mu-DSC), scanning-transmission electron microscopy (STEM), and cryo-scanning electron microscopy (cryo-SEM). A reloading of the polyplexes can be observed by adding the unmodified PEI samples of different molar mass. In excess of PEI a morphological transition from core-shell particles (at N/P 8) to loosely packed onion-like polyplexes (at N/P 40) is observed. The shift of the DSC melting peak from 88 degrees C to 76 degrees C indicates a destabilization of the DNA double helix due to the complexation with the unmodified PEI. Experiments with the maltose-modified PEI show a reloading already at a lower N/P ratio. Due to the presence of the sugar units in the periphery of the polycation electrostatic interactions between DNA become weaker, but cooperative H-bonding forces are reinforced. The resulting less-toxic, more compact polyplexes in excess of the PEI-Mal with two melting points and well distributed DNA segments are of special interest for extended gene delivery experiments. (C) 2015 Elsevier B.V. All rights reserved. KW - DNA complexation KW - Polyplexes KW - Maltose-modified poly(ethyleneimine) KW - Morphology Y1 - 2016 U6 - https://doi.org/10.1016/j.colsurfb.2015.11.061 SN - 0927-7765 SN - 1873-4367 VL - 138 SP - 78 EP - 85 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rumschöttel, Jens A1 - Baus, Susann A1 - Kosmella, Sabine A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Incorporation of DNA/PEI polyplexes into gelatin/chitosan hydrogel scaffolds BT - a mu-DSC study JF - Composite interfaces N2 - Polyplexes between a double-stranded Salmon DNA and hyperbranched poly(ethyleneimine) (PEI) as well as a maltosylated PEI-Mal were incorporated into a gelatin/chitosan hydrogel scaffold. Calorimetric experiments of the polyplexes show a decrease of the melting temperature in presence of PEI and a peak splitting in presence of PEI-Mal, which can be interpreted to a partial compaction of the DNA strands in presence of PEI-Mal. When the polyplexes are incorporated into a gelatin/chitosan scaffold in the swollen state, the DNA melting peaks at 90 and 93 degrees C, respectively, indicate in both cases the release of the DNA at the surface of the hydrogel scaffold in a more compact form. Specific interactions between the PEI-Mal shell and gelatin are responsible for the tuning of the release properties in presence of the maltose units in the hyperbranched PEI. KW - DNA-PEI polyplexes KW - maltosylated poly(ethyleneimine) KW - mu-DSC KW - DNA release KW - gelatin/chitosan hydrogel scaffold Y1 - 2017 U6 - https://doi.org/10.1080/09276440.2017.1302725 SN - 1568-5543 VL - 25 IS - 1 SP - 1 EP - 11 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Rumschoettel, Jens A1 - Kosmella, Sabine A1 - Prietzel, Claudia Christina A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - DNA polyplexes with dendritic glycopolymer-entrapped gold nanoparticles JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - Polyplexes, composed of Salmon DNA and very small gold nanoparticles embedded into a dendritic glycopolymer architecture of sugar-modified poly(ethyleneimine) (PEI-Mal) with a molar mass of about 25,000 g/mol, were characterized by dynamic light scattering (DLS), zeta potential measurements, micro differential scanning calorimetry (mu-DSC) and transmission electron microscopy (TEM). The PEI-Mal-entrapped gold nanoparticles of about 2 nm in diameter influence the polyplex formation of the hyperbranched PEI containing bulky maltose, and in consequence the DNA is more compactized in the inner part of spherical polyplex particles of about 150 nm in diameter. The resulting more compact core shell polyplex particles with embedded gold nanoparticles in the outer polymer shell will be used as components in forthcoming gene delivery experiments. (C) 2017 Elsevier B.V. All rights reserved. KW - DNA polyplexes KW - Gold nanoparticles KW - Maltose-modified poly(ethyleneimine) KW - TEM KW - mu-DSC Y1 - 2017 U6 - https://doi.org/10.1016/j.colsurfb.2017.03.001 SN - 0927-7765 SN - 1873-4367 VL - 154 SP - 74 EP - 81 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 - Raju, Rajarshi Roy A1 - Kosmella, Sabine A1 - Friberg, Stig E. A1 - Koetz, Joachim T1 - Pickering Janus emulsions and polyelectrolyte complex-stabilized Janus gels JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Janus emulsions, containing olive oil (OO) and silicone oil (SiO), were formed in presence of polyelectrolyte complex particles, i.e., gelatin-sodium polyacrylate (NaPAA) complexes. The diameter of completely engulfed Janus droplets can be tuned between 50 and 200 mu m by varying the gelatin/NaPAA complex particle size between 200 and 400 nm. The gelatin/NaPAA complex particles adsorbed at the olive oil interface decrease the interfacial tension and stabilize the resulting completely engulfed Pickering Janus emulsions. Long-term stable Janus gels can be synthesized in presence of gelatin/sodium carboxymethylcellulose (NaCMC) mixtures. In that case Coulombic forces are of relevance with regard to the stabilization of the Janus droplets embedded in a gelatin/NaCMC gel matrix. Janus gels show elastic reological behavior and thixotropic properties. KW - Pickering Janus emulsions KW - Janus gels KW - Interfacial tension KW - Ring tensiometry KW - Gelatin-NaCMC KW - Gelatin-NaPAA composites Y1 - 2017 U6 - https://doi.org/10.1016/j.colsurfa.2017.08.022 SN - 0927-7757 SN - 1873-4359 VL - 533 SP - 241 EP - 248 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Note, Carine A1 - Kosmella, Sabine A1 - Koetz, Joachim T1 - Poly(ethyleneimine) as reducing and stabilizing agent for the formation of gold nanoparticles in w/o microemulsions JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - This paper is focused on the use of branched poly(ethyleneimine) (PEI) as reducing as well as stabilizing agent for the formation of gold nanoparticles in different media. The process of nanoparticle formation was investigated, in the absence of any other reducing agents, in microemulsion template phase in comparison to the nucleation process in aqueous polymer solution. On the one hand, it was shown that the polyelectrolyte can be used for the controlled single-step synthesis and stabilization of gold nanoparticles via a nucleation reaction and particles with an average diameter of 7.1 nm can be produced. On the other hand, it was demonstrated that the polymer can also act as reducing and stabilizing agent in much more complex systems, i.e. in water-in-oil (w/o) microemulsion droplets. The reverse microemulsion droplets of the quaternary system sodium dodecylsulfate (SDS)/toluene-pentanol (1:1)/water were successfully used for the synthesis of gold nanoparticles. The polymer, incorporated in the droplets, exhibits reducing properties, adsorbs on the surface of the nanoparticles and prevents their aggregation. Consequently, nanoparticles of 8.6 nm can be redispersed after solvent evaporation without a change of their size. Nevertheless, the polymer acts already as a "template" during the formation of the nanoparticles in water and in microemulsion, so that an additional template effect of the microemulsion is not observed. The particle formation for both methods is checked by means of UV-vis spectroscopy and the particle size and size distribution are investigated via dynamic light scattering and transmission electron microscopy (TEM). (c) 2006 Elsevier B.V. All rights reserved. KW - polyelectrolyte KW - microemulsion KW - gold nanoparticles Y1 - 2006 U6 - https://doi.org/10.1016/j.colsurfa.2006.05.018 SN - 0927-7757 VL - 290 IS - 1-3 SP - 150 EP - 156 PB - Elsevier CY - Amsterdam 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 - Note, Carine A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Structural changes in poly(ethyleneimine) modified microemulsion JF - Journal of colloid and interface science N2 - The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer. KW - polyelectrolyte KW - microemulsion KW - bicontinuous phase Y1 - 2006 U6 - https://doi.org/10.1016/j.jcis.2006.06.071 SN - 0021-9797 VL - 302 SP - 662 EP - 668 PB - Elsevier CY - Amsterdam 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 - Kovach, Ildyko A1 - Kosmella, Sabine A1 - Prietzel, Claudia Christina A1 - Bagdahn, Christian A1 - Koetz, Joachim T1 - Nano-porous calcium phosphate balls JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - By dropping a NaH2PO4 center dot H2O precursor solution to a CaCl2 solution at 90 degrees C under continuous stirring in presence of two biopolymers, i.e. gelatin (G) and chitosan (C), supramolecular calcium phosphate (CP) card house structures are formed. Light microscopic investigations in combination with scanning electron microscopy show that the GC-based flower-like structure is constructed from very thin CP platelets. Titration experiments indicate that H-bonding between both biopolymers is responsible for the synergistic effect in presence of both polymers. Gelatin chitosan water complexes play an important role with regard to supramolecular ordering. FTIR spectra in combination with powder X-ray diffraction show that after burning off all organic components (heating up >600 degrees C) dicalcium and tricalcium phosphate crystallites are formed. From high resolution transmission electron microscopy (HR-TEM) it is obvious to conclude, that individual crystal platelets are dicalcium phosphates, which build up ball-like supramolecular structures. The results reveal that the GC guided crystal growth leads to nano-porous supramolecular structures, potentially attractive candidates for bone repair. (c) 2015 Elsevier B.V. All rights reserved. KW - Calcium phosphates KW - Bone repair material KW - Biomineralization KW - Supramolecular ball structure Y1 - 2015 U6 - https://doi.org/10.1016/j.colsurfb.2015.05.021 SN - 0927-7765 SN - 1873-4367 VL - 132 SP - 246 EP - 252 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kosmella, Sabine A1 - Venus, Jane A1 - Hahn, Jennifer A1 - Prietzel, Claudia Christina A1 - Koetz, Joachim T1 - Low-temperature synthesis of polyethyleneimine-entrapped CdS quantum dots JF - Chemical physics letters N2 - This Letter is focused on the one-pot formation of CdS nanoparticles in aqueous medium in presence of polyethyleneimine (PEI). Quantum dots can be obtained by adding a pre-cooled aqueous Na2S solution to a pre-cooled aqueous CdCl2 solution dropwise in presence of PEI. Field flow fractionation in combination with TEM experiments show a time dependent agglomeration of individual quantum dots from 1.6 nm up to 3.2 nm in size. The hyperbranched PEI of moderate molar mass (>20000 g/mol) is an excellent polymer to prevent a further increase of the particle size. Therefore, stable fluorescent PEI-capped CdS quantum dots are available. Y1 - 2014 U6 - https://doi.org/10.1016/j.cplett.2013.12.019 SN - 0009-2614 SN - 1873-4448 VL - 592 SP - 114 EP - 119 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Shirahama, K. A1 - Liu, J. T1 - The cooperative nature of complex formation in mixed polyelectrolyte-surfactant systems Y1 - 1998 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Shirahama, K. T1 - Binding of dodecylpyridinium chloride to anionic co-polymers and their complexes Y1 - 1999 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Friberg, Stig E. A1 - Mackay, R. A. T1 - Interactions of polyelectrolytes with the lyotropic liquid crystalline system - hexadecyltrimethylammonium bromide / decanol / water Y1 - 1996 SN - 0927-7757 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Friberg, Stig E. A1 - Mackay, R. A T1 - Interactions of polyelectrolytes with the lyotropic liquid crystalline system Na-dodecylsulfate / decanol / water Y1 - 1996 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Klemke, Bastian A1 - Häusler, Ines A1 - Koetz, Joachim T1 - From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained. KW - Pickering emulsions KW - Pluronics KW - Magnetite and gold nanoparticles KW - Ring tensiometry KW - Cryo-SEM KW - HRTEM KW - Magnetization measurements Y1 - 2019 U6 - https://doi.org/10.1016/j.colsurfa.2019.03.017 SN - 0927-7757 SN - 1873-4359 VL - 570 SP - 331 EP - 338 PB - Elsevier Science CY - Amsterdam ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Kulicke, Werner-Michael A1 - Heinze, Thomas T1 - Zum Einfluss des Lösungszustandes von Carboxymethylcellulosen auf das Strukturbildungsverhalten in kolloidalen Systemen Y1 - 2002 ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Brühl, Iris T1 - Self-assembly of liquid crystalline lamellar surfactant-polyelectrolyte systems Y1 - 1996 ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Beitz, Toralf T1 - Self-assembled Polyelectrolyte Systems Y1 - 2001 ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Interactions of Polyelectrolytes with Clay Surfaces Y1 - 2002 SN - 0-8247-0633-1 ER -