@article{RumschoettelKosmellaPrietzeletal.2016, author = {Rumsch{\"o}ttel, Jens and Kosmella, Sabine and Prietzel, Claudia Christina and Appelhans, Dietmar and Koetz, Joachim}, title = {Change in size, morphology and stability of DNA polyplexes with hyperbranched poly(ethyleneimines) containing bulky maltose units}, series = {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}, volume = {138}, journal = {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}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7765}, doi = {10.1016/j.colsurfb.2015.11.061}, pages = {78 -- 85}, year = {2016}, abstract = {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.}, language = {en} } @article{RumschoettelBausKosmellaetal.2017, author = {Rumsch{\"o}ttel, Jens and Baus, Susann and Kosmella, Sabine and Appelhans, Dietmar and Koetz, Joachim}, title = {Incorporation of DNA/PEI polyplexes into gelatin/chitosan hydrogel scaffolds}, series = {Composite interfaces}, volume = {25}, journal = {Composite interfaces}, number = {1}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1568-5543}, doi = {10.1080/09276440.2017.1302725}, pages = {1 -- 11}, year = {2017}, abstract = {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.}, language = {en} } @article{RumschoettelKosmellaPrietzeletal.2017, author = {Rumschoettel, Jens and Kosmella, Sabine and Prietzel, Claudia Christina and Appelhans, Dietmar and Koetz, Joachim}, title = {DNA polyplexes with dendritic glycopolymer-entrapped gold nanoparticles}, series = {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}, volume = {154}, journal = {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}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7765}, doi = {10.1016/j.colsurfb.2017.03.001}, pages = {74 -- 81}, year = {2017}, abstract = {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.}, language = {en} } @article{RojasKoetzKosmellaetal.2009, author = {Rojas, Oscar and Koetz, Joachim and Kosmella, Sabine and Tiersch, Brigitte and Wacker, Philipp and Kramer, Markus}, title = {Structural studies of ionic liquid-modified microemulsions}, issn = {0021-9797}, doi = {10.1016/j.jcis.2009.02.039}, year = {2009}, abstract = {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.}, language = {en} } @article{RajuKosmellaFribergetal.2017, author = {Raju, Rajarshi Roy and Kosmella, Sabine and Friberg, Stig E. and Koetz, Joachim}, title = {Pickering Janus emulsions and polyelectrolyte complex-stabilized Janus gels}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {533}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2017.08.022}, pages = {241 -- 248}, year = {2017}, abstract = {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.}, language = {en} } @article{NoteKosmellaKoetz2006, author = {Note, Carine and Kosmella, Sabine and Koetz, Joachim}, title = {Poly(ethyleneimine) as reducing and stabilizing agent for the formation of gold nanoparticles in w/o microemulsions}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {290}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, number = {1-3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2006.05.018}, pages = {150 -- 156}, year = {2006}, abstract = {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.}, language = {en} } @article{NoteKoetzKosmellaetal.2005, author = {Note, Carine and Koetz, Joachim and Kosmella, Sabine and Tiersch, Brigitte}, title = {Hydrophobically modified polyelectrolytes used as reducing and stabilizing agent for the formation of gold nanoparticles}, issn = {0303-402X}, year = {2005}, abstract = {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}, language = {en} } @article{NoteKoetzKosmella2006, author = {Note, Carine and Koetz, Joachim and Kosmella, Sabine}, title = {Structural changes in poly(ethyleneimine) modified microemulsion}, series = {Journal of colloid and interface science}, volume = {302}, journal = {Journal of colloid and interface science}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0021-9797}, doi = {10.1016/j.jcis.2006.06.071}, pages = {662 -- 668}, year = {2006}, abstract = {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.}, language = {en} } @article{LutterKoetzTierschetal.2009, author = {Lutter, Stefanie and Koetz, Joachim and Tiersch, Brigitte and Kosmella, Sabine}, title = {Polymer-modified bicontinuous microemulsions used as a template for the formation of nanorods}, issn = {0193-2691}, doi = {10.1080/01932690802643113}, year = {2009}, abstract = {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.}, language = {en} } @article{KovachKosmellaPrietzeletal.2015, author = {Kovach, Ildyko and Kosmella, Sabine and Prietzel, Claudia Christina and Bagdahn, Christian and Koetz, Joachim}, title = {Nano-porous calcium phosphate balls}, series = {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}, volume = {132}, journal = {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}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7765}, doi = {10.1016/j.colsurfb.2015.05.021}, pages = {246 -- 252}, year = {2015}, abstract = {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.}, language = {en} } @article{KosmellaVenusHahnetal.2014, author = {Kosmella, Sabine and Venus, Jane and Hahn, Jennifer and Prietzel, Claudia Christina and Koetz, Joachim}, title = {Low-temperature synthesis of polyethyleneimine-entrapped CdS quantum dots}, series = {Chemical physics letters}, volume = {592}, journal = {Chemical physics letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2614}, doi = {10.1016/j.cplett.2013.12.019}, pages = {114 -- 119}, year = {2014}, abstract = {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.}, language = {en} } @article{KosmellaKoetzShirahamaetal.1998, author = {Kosmella, Sabine and Koetz, Joachim and Shirahama, K. and Liu, J.}, title = {The cooperative nature of complex formation in mixed polyelectrolyte-surfactant systems}, year = {1998}, language = {en} } @article{KosmellaKoetzShirahama1999, author = {Kosmella, Sabine and Koetz, Joachim and Shirahama, K.}, title = {Binding of dodecylpyridinium chloride to anionic co-polymers and their complexes}, year = {1999}, language = {en} } @article{KosmellaKoetzFribergetal.1996, author = {Kosmella, Sabine and Koetz, Joachim and Friberg, Stig E. and Mackay, R. A.}, title = {Interactions of polyelectrolytes with the lyotropic liquid crystalline system - hexadecyltrimethylammonium bromide / decanol / water}, issn = {0927-7757}, year = {1996}, language = {en} } @article{KosmellaKoetzFribergetal.1996, author = {Kosmella, Sabine and Koetz, Joachim and Friberg, Stig E. and Mackay, R. A}, title = {Interactions of polyelectrolytes with the lyotropic liquid crystalline system Na-dodecylsulfate / decanol / water}, year = {1996}, language = {en} } @article{KosmellaKlemkeHaeusleretal.2019, author = {Kosmella, Sabine and Klemke, Bastian and H{\"a}usler, Ines and Koetz, Joachim}, title = {From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {570}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2019.03.017}, pages = {331 -- 338}, year = {2019}, abstract = {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.}, language = {en} } @article{KoetzKosmellaKulickeetal.2002, author = {Koetz, Joachim and Kosmella, Sabine and Kulicke, Werner-Michael and Heinze, Thomas}, title = {Zum Einfluss des L{\"o}sungszustandes von Carboxymethylcellulosen auf das Strukturbildungsverhalten in kolloidalen Systemen}, year = {2002}, language = {de} } @article{KoetzKosmellaBruehl1996, author = {Koetz, Joachim and Kosmella, Sabine and Br{\"u}hl, Iris}, title = {Self-assembly of liquid crystalline lamellar surfactant-polyelectrolyte systems}, year = {1996}, language = {en} } @article{KoetzKosmellaBeitz2001, author = {Koetz, Joachim and Kosmella, Sabine and Beitz, Toralf}, title = {Self-assembled Polyelectrolyte Systems}, year = {2001}, language = {en} } @article{KoetzKosmella2002, author = {Koetz, Joachim and Kosmella, Sabine}, title = {Interactions of Polyelectrolytes with Clay Surfaces}, isbn = {0-8247-0633-1}, year = {2002}, language = {en} }