@article{DolyaRojasKosmellaetal.2013, author = {Dolya, Natalya and Rojas, Oscar and Kosmella, Sabine and Tiersch, Brigitte and Koetz, Joachim and Kudaibergenov, Sarkyt}, title = {"One-Pot" in situ frmation of Gold Nanoparticles within Poly(acrylamide) Hydrogels}, series = {Macromolecular chemistry and physics}, volume = {214}, journal = {Macromolecular chemistry and physics}, number = {10}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201200727}, pages = {1114 -- 1121}, year = {2013}, abstract = {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.}, language = {en} } @article{KoetzAndresKosmellaetal.2006, author = {Koetz, Joachim and Andres, S. and Kosmella, Sabine and Tiersch, Brigitte}, title = {BaSO4 nanorods produced in polymer-modified bicontinuous microemulsions}, issn = {0927-6440}, doi = {10.1163/156855406777408629}, year = {2006}, abstract = {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}, 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{KoetzJagielskiKosmellaetal.2006, author = {Koetz, Joachim and Jagielski, Nicole and Kosmella, Sabine and Friedrich, Alwin and Kleinpeter, Erich}, title = {CdS nanocubes formed in phosphatidylcholin-based template phases}, volume = {288}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2006.01.013}, pages = {43 -- 1-3}, year = {2006}, abstract = {The paper is focused on the characterization and use of phosphatidylcholine (PC)-based inverse microemulsions as a template phase for the CdS nanoparticle formation. The optically clear, isotropic phase in the oil corner was identified as a "classical{\"o} water-in-oil microemulsion by means of NMR-diffusion measurements. Because of the very small dimensions of the water droplets, the isotropic phase shows a Newtonian-like flow behavior, and adequate amounts of bulk water cannot be detected by DSC. It is demonstrated that this w/o microemulsion can be used successfully as a nanoreactor for the formation of CdS nanoparticles with diameters of 4-5 nm. During the following process of solvent evaporation the individual small CdS nanoparticles aggregate to significant larger cubic nanoparticles, with an edge length of 2-40 nm, arranged in well-defined mosaic-like superstructures. In presence of SDS the nanocubes were stable up to 800 °C. It has to be stated here that polyelectrolytes prevent the formation of such well-ordered superstructures.}, language = {en} } @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{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{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{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{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{KoetzKosmella1994, author = {Koetz, Joachim and Kosmella, Sabine}, title = {Interactions between Poly(diallyldimethylammonium Chloride) and Poly(Acrylic Acid) in dependence on polymer concentration}, year = {1994}, language = {en} }