@article{KyriakosPhilippLinetal.2016, author = {Kyriakos, Konstantinos and Philipp, Martine and Lin, Che-Hung and Dyakonova, Margarita and Vishnevetskaya, Natalya and Grillo, Isabelle and Zaccone, Alessio and Miasnikova, Anna and Laschewsky, Andre and Mueller-Buschbaum, Peter and Papadakis, Christine M.}, title = {Quantifying the Interactions in the Aggregation of Thermoresponsive Polymers: The Effect of Cononsolvency}, series = {Macromolecular rapid communications}, volume = {37}, journal = {Macromolecular rapid communications}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201500583}, pages = {420 -- 425}, year = {2016}, abstract = {The aggregation kinetics of thermoresponsive core-shell micelles with a poly(N-isopropyl acrylamide) shell in pure water or in mixtures of water with the cosolvents methanol or ethanol at mole fractions of 5\% is investigated during a temperature jump across the respective cloud point. Characteristically, these mixtures give rise to cononsolvency behavior. At the cloud point, aggregates are formed, and their growth is followed with time-resolved small-angle neutron scattering. Using the reversible association model, the interaction potential between the aggregates is determined from their growth rate in dependence on the cosolvents. The effect of the cosolvent is attributed to the interaction potential on the structured layer of hydration water around the aggregates. It is surmised that the latter is perturbed by the cosolvent and thus the residual repulsive hydration force between the aggregates is reduced. The larger the molar volume of the cosolvent, the more pronounced is the effect. This framework provides a molecular-level understanding of solvent-mediated effective interactions in polymer solutions and new opportunities for the rational control of self-assembly in complex soft matter systems.}, language = {en} } @phdthesis{Behm2019, author = {Behm, Laura Vera Johanna}, title = {Thermoresponsive Zellkultursubstrate f{\"u}r zeitlich-r{\"a}umlich gesteuertes Auswachsen neuronaler Zellen}, doi = {10.25932/publishup-43619}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436196}, school = {Universit{\"a}t Potsdam}, pages = {VII, 105}, year = {2019}, abstract = {Ein wichtiges Ziel der Neurowissenschaften ist das Verst{\"a}ndnis der komplexen und zugleich faszinierenden, hochgeordneten Vernetzung der Neurone im Gehirn, welche neuronalen Prozessen, wie zum Beispiel dem Wahrnehmen oder Lernen wie auch Neuropathologien zu Grunde liegt. F{\"u}r verbesserte neuronale Zellkulturmodelle zur detaillierten Untersuchung dieser Prozesse ist daher die Rekonstruktion von geordneten neuronalen Verbindungen dringend erforderlich. Mit Oberfl{\"a}chenstrukturen aus zellattraktiven und zellabweisenden Beschichtungen k{\"o}nnen neuronale Zellen und ihre Neuriten in vitro strukturiert werden. Zur Kontrolle der neuronalen Verbindungsrichtung muss das Auswachsen der Axone zu benachbarten Zellen dynamisch gesteuert werden, zum Beispiel {\"u}ber eine ver{\"a}nderliche Zug{\"a}nglichkeit der Oberfl{\"a}che. In dieser Arbeit wurde untersucht, ob mit thermoresponsiven Polymeren (TRP) beschichtete Zellkultursubstrate f{\"u}r eine dynamische Kontrolle des Auswachsens neuronaler Zellen geeignet sind. TRP k{\"o}nnen {\"u}ber die Temperatur von einem zellabweisenden in einen zellattraktiven Zustand geschaltet werden, womit die Zug{\"a}nglichkeit der Oberfl{\"a}che f{\"u}r Zellen dynamisch gesteuert werden kann. Die TRP-Beschichtung wurde mikrostrukturiert, um einzelne oder wenige neuronale Zellen zun{\"a}chst auf der Oberfl{\"a}che anzuordnen und das Auswachsen der Zellen und Neuriten {\"u}ber definierte TRP-Bereiche in Abh{\"a}ngigkeit der Temperatur zeitlich und r{\"a}umlich zu kontrollieren. Das Protokoll wurde mit der neuronalen Zelllinie SH-SY5Y etabliert und auf humane induzierte Neurone {\"u}bertragen. Die Anordnung der Zellen konnte bei Kultivierung im zellabweisenden Zustand des TRPs f{\"u}r bis zu 7 Tage aufrecht erhalten werden. Durch Schalten des TRPs in den zellattraktiven Zustand konnte das Auswachsen der Neuriten und Zellen zeitlich und r{\"a}umlich induziert werden. Immunozytochemische F{\"a}rbungen und Patch-Clamp-Ableitungen der Neurone demonstrierten die einfache Anwendbarkeit und Zellkompatibilit{\"a}t der TRP-Substrate. Eine pr{\"a}zisere r{\"a}umliche Kontrolle des Auswachsens der Zellen sollte durch lokales Schalten der TRP-Beschichtung erreicht werden. Daf{\"u}r wurden Mikroheizchips mit Mikroelektroden zur lokalen Jouleschen Erw{\"a}rmung der Substratoberfl{\"a}che entwickelt. Zur Evaluierung der generierten Temperaturprofile wurde eine Temperaturmessmethode entwickelt und die erhobenen Messwerte mit numerisch simulierten Werten abgeglichen. Die Temperaturmessmethode basiert auf einfach zu applizierenden Sol-Gel-Schichten, die den temperatursensitiven Fluoreszenzfarbstoff Rhodamin B enthalten. Sie erm{\"o}glicht oberfl{\"a}chennahe Temperaturmessungen in trockener und w{\"a}ssriger Umgebung mit hoher Orts- und Temperaturaufl{\"o}sung. Numerische Simulationen der Temperaturprofile korrelierten gut mit den experimentellen Daten. Auf dieser Basis konnten Geometrie und Material der Mikroelektroden hinsichtlich einer lokal stark begrenzten Temperierung optimiert werden. Ferner wurden f{\"u}r die Kultvierung der Zellen auf den Mikroheizchips eine Zellkulturkammer und Kontaktboard f{\"u}r die elektrische Kontaktierung der Mikroelektroden geschaffen. Die vorgestellten Ergebnisse demonstrieren erstmalig das enorme Potential thermoresponsiver Zellkultursubstrate f{\"u}r die zeitlich und r{\"a}umlich gesteuerte Formation geordneter neuronaler Verbindungen in vitro. Zuk{\"u}nftig k{\"o}nnte dies detaillierte Studien zur neuronalen Informationsverarbeitung oder zu Neuropathologien an relevanten, humanen Zellmodellen erm{\"o}glichen.}, language = {de} } @article{VukicevicNeffeLuetzowetal.2015, author = {Vukicevic, Radovan and Neffe, Axel T. and Luetzow, Karola and Pierce, Benjamin F. and Lendlein, Andreas}, title = {Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release}, series = {Macromolecular rapid communications}, volume = {36}, journal = {Macromolecular rapid communications}, number = {21}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201500311}, pages = {1891 -- 1896}, year = {2015}, abstract = {Triggering the release of cargo from a polymer network by ultrasonication as an external, non-invasive stimulus can be an interesting concept for on-demand release. Here, it is shown that, in pH-and thermosensitive microgels, the ultrasound sensitivity of the polymer network depends on the external conditions. Crosslinked poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] microgels showed a volume phase transition temperature (VPTT) of 25-50 degrees C, which increases with decreasing pH. Above the VPTT the polymer chains are collapsed, while below VPTT they are extended. Only in the case of maximum observed swelling, where the polymer chains are expanded, the microgels are mechanically fragmented through ultrasonication. In contrast, when the polymer chains are partially collapsed it is not possible to manipulate the microgels by ultrasound. Additionally, the ultrasound-induced on-demand release of wheat germ lipase from the microgels could be demonstrated successfully. The principle of conditional ultrasound sensitivity is likely to be general and can be used for selection of matrix-cargo combinations.}, language = {en} } @article{AdelsbergerMetwalliDiethertetal.2012, author = {Adelsberger, Joseph and Metwalli, Ezzeldin and Diethert, Alexander and Grillo, Isabelle and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump}, series = {Macromolecular rapid communications}, volume = {33}, journal = {Macromolecular rapid communications}, number = {3}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1022-1336}, doi = {10.1002/marc.201100631}, pages = {254 -- 259}, year = {2012}, abstract = {Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems.}, language = {en} } @article{InalKoelschChiappisietal.2013, author = {Inal, Sahika and Koelsch, Jonas D. and Chiappisi, Leonardo and Kraft, Mario and Gutacker, Andrea and Janietz, Dietmar and Scherf, Ullrich and Gradzielski, Michael and Laschewsky, Andr{\´e} and Neher, Dieter}, title = {Temperature-Regulated Fluorescence Characteristics of Supramolecular Assemblies Formed By a Smart Polymer and a Conjugated Polyelectrolyte}, series = {MACROMOLECULAR CHEMISTRY AND PHYSICS}, volume = {214}, journal = {MACROMOLECULAR CHEMISTRY AND PHYSICS}, number = {4}, publisher = {WILEY-V C H VERLAG GMBH}, address = {WEINHEIM}, issn = {1022-1352}, doi = {10.1002/macp.201200493}, pages = {435 -- 445}, year = {2013}, abstract = {Aqueous mixtures of a coumarin-labeled non-ionic thermoresponsive copolymer and a cationic polythiophene exhibit marked changes in their fluorescence properties upon heating. At room temperature, emission from the label is significantly quenched due to energy transfer to the conjugated polyelectrolyte. Heating the mixture reduces the energy-transfer efficiency markedly, resulting in a clearly visible change of the emission color. Although the two macromolecules associate strongly at room temperature, the number of interacting sites is largely reduced upon the phase transition. Crucially, the intermolecular association does not suppress the responsiveness of the smart polymer, meaning that this concept should be applicable to chemo- or bioresponsive polymers with optical read-out, for example, as a sensor device.}, language = {en} } @phdthesis{Hildebrand2016, author = {Hildebrand, Viet}, title = {Twofold switchable block copolymers based on new polyzwitterions}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-101372}, school = {Universit{\"a}t Potsdam}, pages = {xvi, 170, LXXX}, year = {2016}, abstract = {In complement to the well-established zwitterionic monomers 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate ("SPE") and 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate ("SPP"), the closely related sulfobetaine monomers were synthesized and polymerized by reversible addition-fragmentation chain transfer (RAFT) polymerization, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar mass were characterized with respect to their solubility in water, deuterated water, and aqueous salt solutions. These poly(sulfobetaine)s show thermoresponsive behavior in water, exhibiting upper critical solution temperatures (UCST). Phase transition temperatures depend notably on the molar mass and polymer concentration, and are much higher in D2O than in H2O. Also, the phase transition temperatures are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed structure of the zwitterionic side chain, on the other hand. For the polymers with the same zwitterionic side chain, it is found that methacrylamide-based poly(sulfobetaine)s exhibit higher UCST-type transition temperatures than their methacrylate analogs. The extension of the distance between polymerizable unit and zwitterionic groups from 2 to 3 methylene units decreases the UCST-type transition temperatures. Poly(sulfobetaine)s derived from aliphatic esters show higher UCST-type transition temperatures than their analogs featuring cyclic ammonium cations. The UCST-type transition temperatures increase markedly with spacer length separating the cationic and anionic moieties from 3 to 4 methylene units. Thus, apparently small variations of their chemical structure strongly affect the phase behavior of the polyzwitterions in specific aqueous environments. Water-soluble block copolymers were prepared from the zwitterionic monomers and the non-ionic monomer N-isopropylmethacrylamide ("NIPMAM") by the RAFT polymerization. Such block copolymers with two hydrophilic blocks exhibit twofold thermoresponsive behavior in water. The poly(sulfobetaine) block shows an UCST, whereas the poly(NIPMAM) block exhibits a lower critical solution temperature (LCST). This constellation induces a structure inversion of the solvophobic aggregate, called "schizophrenic micelle". Depending on the relative positions of the two different phase transitions, the block copolymer passes through a molecularly dissolved or an insoluble intermediate regime, which can be modulated by the polymer concentration or by the addition of salt. Whereas, at low temperature, the poly(sulfobetaine) block forms polar aggregates that are kept in solution by the poly(NIPMAM) block, at high temperature, the poly(NIPMAM) block forms hydrophobic aggregates that are kept in solution by the poly(sulfobetaine) block. Thus, aggregates can be prepared in water, which switch reversibly their "inside" to the "outside", and vice versa.}, language = {en} } @misc{InalKoelschChiappisietal.2013, author = {Inal, Sahika and K{\"o}lsch, Jonas D. and Chiappisi, Leonardo and Janietz, Dietmar and Gradzielski, Michael and Laschewsky, Andr{\´e} and Neher, Dieter}, title = {Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95379}, pages = {6603 -- 6612}, year = {2013}, abstract = {We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.}, language = {en} }