TY - JOUR A1 - Zhang, Quanchao A1 - Sauter, Tilman A1 - Fang, Liang A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Shape-Memory Capability of Copolyetheresterurethane Microparticles Prepared via Electrospraying JF - Macromolecular materials and engineering N2 - Multifunctional thermo-responsive and degradable microparticles exhibiting a shapememory effect (SME) have attracted widespread interest in biomedicine as switchable delivery vehicles or microactuators. In this work almost spherical solid microparticles with an average diameter of 3.9 +/- 0.9 mm are prepared via electrospraying of a copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(e-caprolactone) (OCL) switching segments. The PDC microparticles are programmed via compression at different pressures and their shapememory capability is explored by off-line and online heating experiments. When a low programming pressure of 0.2 MPa is applied a pronounced thermally-induced shape-memory effect is achieved with a shape recovery ratio about 80%, while a high programming pressure of 100 MPa resulted in a weak shape-memory performance. Finally, it is demonstrated that an array of PDC microparticles deposited on a polypropylene (PP) substrate can be successfully programmed into a smart temporary film, which disintegrates upon heating to 60 degrees C. KW - biomaterials KW - microparticles KW - processing KW - stimuli-sensitive polymers KW - shape-memory effect Y1 - 2015 U6 - https://doi.org/10.1002/mame.201400267 SN - 1438-7492 SN - 1439-2054 VL - 300 IS - 5 SP - 522 EP - 530 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Secker, Christian A1 - Brosnan, Sarah M. A1 - Luxenhofer, Robert A1 - Schlaad, Helmut T1 - Poly(alpha-Peptoid)s Revisited: Synthesis, Properties, and Use as Biomaterial JF - Macromolecular bioscience N2 - Polypeptoids have been of great interest in the polymer science community since the early half of the last century; however, they had been basically forgotten materials until the last decades in which they have enjoyed an exciting revival. In this mini-review, we focus on the recent developments in polypeptoid chemistry, with particular focus on polymers synthesized by the ring-opening polymerization (ROP) of amino acid N-carboxyanhydrides (NCAs). Specifically, we will review traditional monomer synthesis (such as Leuchs, Katchalski, and Kricheldorf) and recent advances in polymerization methods to yield both linear, cyclic, and functional polymers, solution and bulk thermal properties, and preliminary results on the use of polypeptoids as biomaterials (i.e immunogenicity, biodistribution, degradability, and drug delivery). KW - amino acid N-carboxyanhydride (NCA) KW - biomaterials KW - peptides KW - properties KW - ring-opening polymerization Y1 - 2015 U6 - https://doi.org/10.1002/mabi.201500023 SN - 1616-5187 SN - 1616-5195 VL - 15 IS - 7 SP - 881 EP - 891 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Federico, Stefania A1 - Pierce, Benjamin F. A1 - Piluso, Susanna A1 - Wischke, Christian A1 - Lendlein, Andreas A1 - Neffe, Axel T. T1 - Design of Decorin-Based Peptides That Bind to CollagenI and their Potential as Adhesion Moieties in Biomaterials JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Mimicking the binding epitopes of protein-protein interactions by using small peptides is important for generating modular biomimetic systems. A strategy is described for the design of such bioactive peptides without accessible structural data for the targeted interaction, and the effect of incorporating such adhesion peptides in complex biomaterial systems is demonstrated. The highly repetitive structure of decorin was analyzed to identify peptides that are representative of the inner and outer surface, and it was shown that only peptides based on the inner surface of decorin bind to collagen. The peptide with the highest binding affinity for collagenI, LHERHLNNN, served to slow down the diffusion of a conjugated dye in a collagen gel, while its dimer could physically crosslink collagen, thereby enhancing the elastic modulus of the gel by one order of magnitude. These results show the potential of the identified peptides for the design of biomaterials for applications in regenerative medicine. KW - biomaterials KW - collagen KW - gels KW - peptides KW - protein-protein interactions Y1 - 2015 U6 - https://doi.org/10.1002/anie.201505227 SN - 1433-7851 SN - 1521-3773 VL - 54 IS - 37 SP - 10980 EP - 10984 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Vukicevic, Radovan A1 - Neffe, Axel T. A1 - Luetzow, Karola A1 - Pierce, Benjamin F. A1 - Lendlein, Andreas T1 - Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release JF - Macromolecular rapid communications N2 - 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. KW - ultrasound KW - polymers KW - microgels KW - lipase release KW - controlled release KW - thermoresponsive polymers KW - biomaterials Y1 - 2015 U6 - https://doi.org/10.1002/marc.201500311 SN - 1022-1336 SN - 1521-3927 VL - 36 IS - 21 SP - 1891 EP - 1896 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Braune, Steffen A1 - Walter, M. A1 - Schulze, F. A1 - Lendlein, Andreas A1 - Jung, Friedrich T1 - Changes in platelet morphology and function during 24 hours of storage JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - For in vitro studies assessing the interaction of platelets with implant materials, common and standardized protocols for the preparation of platelet rich plasma (PRP) are lacking, which may lead to non-matching results due to the diversity of applied protocols. Particularly, the aging of platelets during prolonged preparation and storage times is discussed to lead to an underestimation of the material thrombogenicity. Here, we study the influence of whole blood-and PRP-storage times on changes in platelet morphology and function. Whole blood PFA100 closure times increased after stimulation with collagen/ADP and collagen/epinephrine. Twenty four hours after blood collection, both parameters were prolonged pathologically above the upper limit of the reference range. Numbers of circulating platelets, measured in PRP, decreased after four hours, but no longer after twenty four hours. Mean platelet volumes (MPV) and platelet large cell ratios (P-LCR, 12 fL - 40 fL) decreased over time. Immediately after blood collection, no debris or platelet aggregates could be visualized microscopically. After four hours, first debris and very small aggregates occurred. After 24 hours, platelet aggregates and also debris progressively increased. In accordance to this, the CASY system revealed an increase of platelet aggregates (up to 90 mu m diameter)with increasing storage time. The percentage of CD62P positive platelets and PF4 increased significantly with storage time in resting PRP. When soluble ADP was added to stored PRP samples, the number of activatable platelets decreased significantly over storage time. The present study reveals the importance of a consequent standardization in the preparation of WB and PRP. Platelet morphology and function, particularly platelet reactivity to adherent or soluble agonists in their surrounding milieu, changed rapidly outside the vascular system. This knowledge is of crucial interest, particularly in the field of biomaterial development for cardiovascular applications, and may help to define common standards in the in vitro hemocompatibility testing of biomaterials. KW - Platelet KW - platelet function KW - platelet rich plasma KW - whole blood KW - platelet aging KW - platelet storage KW - hemocompatibility KW - biomaterials Y1 - 2014 U6 - https://doi.org/10.3233/CH-141876 SN - 1386-0291 SN - 1875-8622 VL - 58 IS - 1 SP - 159 EP - 170 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Degtyar, Elena A1 - Harrington, Matthew J. A1 - Politi, Yael A1 - Fratzl, Peter T1 - The mechanical role of metal ions in biogenic protein-based materials JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Protein-metal interactions-traditionally regarded for roles in metabolic processes-are now known to enhance the performance of certain biogenic materials, influencing properties such as hardness, toughness, adhesion, and self-healing. Design principles elucidated through thorough study of such materials are yielding vital insights for the design of biomimetic metallopolymers with industrial and biomedical applications. Recent advances in the understanding of the biological structure-function relationships are highlighted here with a specific focus on materials such as arthropod biting parts, mussel byssal threads, and sandcastle worm cement. KW - adhesives KW - biomaterials KW - metal coordination KW - sacrificial bonds KW - self-healing materials Y1 - 2014 U6 - https://doi.org/10.1002/anie.201404272 SN - 1433-7851 SN - 1521-3773 VL - 53 IS - 45 SP - 12026 EP - 12044 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Neffe, Axel T. A1 - von Rüsten-Lange, Maik A1 - Braune, Steffen A1 - Lützow, Karola A1 - Roch, Toralf A1 - Richau, Klaus A1 - Jung, Friedrich A1 - Lendlein, Andreas T1 - Poly(ethylene glycol) grafting to Poly(ether imide) membranes - influence on protein adsorption and Thrombocyte adhesion JF - Macromolecular bioscience N2 - The chain length and end groups of linear PEG grafted on smooth surfaces is known to influence protein adsorption and thrombocyte adhesion. Here, it is explored whether established structure function relationships can be transferred to application relevant, rough surfaces. Functionalization of poly(ether imide) (PEI) membranes by grafting with monoamino PEG of different chain lengths (M-n=1kDa or 10kDa) and end groups (methoxy or hydroxyl) is proven by spectroscopy, changes of surface hydrophilicity, and surface shielding effects. The surface functionalization does lead to reduction of adsorption of BSA, but not of fibrinogen. The thrombocyte adhesion is increased compared to untreated PEI surfaces. Conclusively, rough instead of smooth polymer or gold surfaces should be investigated as relevant models. KW - biomaterials KW - poly(ethylene glycol) KW - protein adsorption KW - surface functionalization KW - thrombocyte adhesion Y1 - 2013 U6 - https://doi.org/10.1002/mabi.201300309 SN - 1616-5187 SN - 1616-5195 VL - 13 IS - 12 SP - 1720 EP - 1729 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Junginger, Mathias A1 - Kübel, Christian A1 - Schacher, Felix H. A1 - Müller, Axel H. E. A1 - Taubert, Andreas T1 - Crystal structure and chemical composition of biomimetic calcium phosphate nanofibers N2 - Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 244 KW - air-water-interface KW - polycationic monolayer KW - mineralization beneath KW - block-copolymers KW - aqueous-solution KW - morphology KW - orthophosphates KW - biomaterials KW - nucleation KW - clusters Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95176 SP - 11301 EP - 11308 ER - TY - THES A1 - Santan, Harshal Diliprao T1 - Synthesis and characterization of thermosensitive hydrogels derived from polysaccharides N2 - In this work, thermosensitive hydrogels having tunable thermo-mechanical properties were synthesized. Generally the thermal transition of thermosensitive hydrogels is based on either a lower critical solution temperature (LCST) or critical micelle concentration/ temperature (CMC/ CMT). The temperature dependent transition from sol to gel with large volume change may be seen in the former type of thermosensitive hydrogels and is negligible in CMC/ CMT dependent systems. The change in volume leads to exclusion of water molecules, resulting in shrinking and stiffening of system above the transition temperature. The volume change can be undesired when cells are to be incorporated in the system. The gelation in the latter case is mainly driven by micelle formation above the transition temperature and further colloidal packing of micelles around the gelation temperature. As the gelation mainly depends on concentration of polymer, such a system could undergo fast dissolution upon addition of solvent. Here, it was envisioned to realize a thermosensitive gel based on two components, one responsible for a change in mechanical properties by formation of reversible netpoints upon heating without volume change, and second component conferring degradability on demand. As first component, an ABA triblockcopolymer (here: Poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEPE) with thermosensitive properties, whose sol-gel transition on the molecular level is based on micellization and colloidal jamming of the formed micelles was chosen, while for the additional macromolecular component crosslinking the formed micelles biopolymers were employed. The synthesis of the hydrogels was performed in two ways, either by physical mixing of compounds showing electrostatic interactions, or by covalent coupling of the components. Biopolymers (here: the polysaccharides hyaluronic acid, chondroitin sulphate, or pectin, as well as the protein gelatin) were employed as additional macromolecular crosslinker to simultaneously incorporate an enzyme responsiveness into the systems. In order to have strong ionic/electrostatic interactions between PEPE and polysaccharides, PEPE was aminated to yield predominantly mono- or di-substituted PEPEs. The systems based on aminated PEPE physically mixed with HA showed an enhancement in the mechanical properties such as, elastic modulus (G′) and viscous modulus (G′′) and a decrease of the gelation temperature (Tgel) compared to the PEPE at same concentration. Furthermore, by varying the amount of aminated PEPE in the composition, the Tgel of the system could be tailored to 27-36 °C. The physical mixtures of HA with di-amino PEPE (HA·di-PEPE) showed higher elastic moduli G′ and stability towards dissolution compared to the physical mixtures of HA with mono-amino PEPE (HA·mono-PEPE). This indicates a strong influence of electrostatic interaction between –COOH groups of HA and –NH2 groups of PEPE. The physical properties of HA with di-amino PEPE (HA·di-PEPE) compare beneficially with the physical properties of the human vitreous body, the systems are highly transparent, and have a comparable refractive index and viscosity. Therefore,this material was tested for a potential biological application and was shown to be non-cytotoxic in eluate and direct contact tests. The materials will in the future be investigated in further studies as vitreous body substitutes. In addition, enzymatic degradation of these hydrogels was performed using hyaluronidase to specifically degrade the HA. During the degradation of these hydrogels, increase in the Tgel was observed along with decrease in the mechanical properties. The aminated PEPE were further utilised in the covalent coupling to Pectin and chondroitin sulphate by using EDC as a coupling agent. Here, it was possible to adjust the Tgel (28-33 °C) by varying the grafting density of PEPE to the biopolymer. The grafting of PEPE to Pectin enhanced the thermal stability of the hydrogel. The Pec-g-PEPE hydrogels were degradable by enzymes with slight increase in Tgel and decrease in G′ during the degradation time. The covalent coupling of aminated PEPE to HA was performed by DMTMM as a coupling agent. This method of coupling was observed to be more efficient compared to EDC mediated coupling. Moreover, the purification of the final product was performed by ultrafiltration technique, which efficiently removed the unreacted PEPE from the final product, which was not sufficiently achieved by dialysis. Interestingly, the final products of these reaction were in a gel state and showed enhancement in the mechanical properties at very low concentrations (2.5 wt%) near body temperature. In these hydrogels the resulting increase in mechanical properties was due to the combined effect of micelle packing (physical interactions) by PEPE and covalent netpoints between PEPE and HA. PEPE alone or the physical mixtures of the same components were not able to show thermosensitive behavior at concentrations below 16 wt%. These thermosensitive hydrogels also showed on demand solubilisation by enzymatic degradation. The concept of thermosensitivity was introduced to 3D architectured porous hydrogels, by covalently grafting the PEPE to gelatin and crosslinking with LDI as a crosslinker. Here, the grafted PEPE resulted in a decrease in the helix formation in gelatin chains and after fixing the gelatin chains by crosslinking, the system showed an enhancement in the mechanical properties upon heating (34-42 °C) which was reversible upon cooling. A possible explanation of the reversible changes in mechanical properties is the strong physical interactions between micelles formed by PEPE being covalently linked to gelatin. Above the transition temperature, the local properties were evaluated by AFM indentation of pore walls in which an increase in elastic modulus (E) at higher temperature (37 °C) was observed. The water uptake of these thermosensitive architectured porous hydrogels was also influenced by PEPE and temperature (25 °C and 37 °C), showing lower water up take at higher temperature and vice versa. In addition, due to the lower water uptake at high temperature, the rate of hydrolytic degradation of these systems was found to be decreased when compared to pure gelatin architectured porous hydrogels. Such temperature sensitive architectured porous hydrogels could be important for e.g. stem cell culturing, cell differentiation and guided cell migration, etc. Altogether, it was possible to demonstrate that the crosslinking of micelles by a macromolecular crosslinker increased the shear moduli, viscosity, and stability towards dissolution of CMC-based gels. This effect could be likewise be realized by covalent or non-covalent mechanisms such as, micelle interactions, physical interactions of gelatin chains and physical interactions between gelatin chains and micelles. Moreover, the covalent grafting of PEPE will create additional net-points which also influence the mechanical properties of thermosensitive architectured porous hydrogels. Overall, the physical and chemical interactions and reversible physical interactions in such thermosensitive architectured porous hydrogels gave a control over the mechanical properties of such complex system. The hydrogels showing change of mechanical properties without a sol-gel transition or volume change are especially interesting for further study with cell proliferation and differentiation. N2 - In der vorliegenden Arbeit wurden thermosensitive Hydrogele mit einstellbaren thermo-mechanischen Eigenschaften synthetisiert. Im Allgemeinen basiert der thermische Übergang thermosensitiver Gele auf einer niedrigsten kritischen Löslichkeitstemperatur (LCST) oder kritischer Mizellkonzentration bzw. –temperatur(CMC/ CMT). Der temperaturabhängige Übergang von Sol zu Gel mit großer Volumenänderung wurde im ersten Fall bei thermosensitiven Hydrogelen beobachtet und ist vernachlässigbar für CMC/ CMT abhängige Systeme. Die Änderung des Volumens führt zum Ausschluss von Wassermolekülen, was zum Schrumpfen und Versteifen des Systems oberhalb der Übergangstemperatur führt. Die Volumenänderung kann unerwünscht sein, wenn Zellen in das Gel eingeschlossen werden sollen. Die Gelierung im zweiten Fall beruht hauptsächlich auf der Mizellbildung oberhalb der Übergangstemperatur und weiterem kolloidalem Packen von Mizellen im Bereich der Gelierungstemperatur. Weil die Gelierung hauptsächlich von der Polymerkonzentration abhängt, kann sich das Gel bei Zugabe von Lösungsmittel leicht wieder lösen. Hier sollten thermosensitive Gele entwickelt werden, die auf zwei Komponenten beruhen. Eine Komponente sollte aus einem ABA-Triblockcopolymer mit thermosensitiven Eigenschaften bestehen, dem Poly(ethylen glycol)-b-Poly(propylenglycol)-b-Poly(ethylen glycol) (PEPE), dessen Sol-Gel-Übergang auf Mizellierung und kolloidalem Jamming der gebildeten Mizellen basiert, und einer weiteren makromolekularen Komponente, einem Biopolymer, dass die Mizellen vernetzt. Auf diese Weise sollten thermosensitive Gele realisiert werden, die keine oder nur eine kleine Volumenänderung während der Änderung der mechanischen Eigenschaften zeigen, die stabiler gegenüber Verdünnung sein sollten als klassische Hydrogele mit einem CMC-basierten Übergang und die jedoch gezielt abgebaut werden können. Die Hydrogele wurden auf zwei Arten vernetzt, entweder durch physikalisches Vermischen, bei dem die Vernetzung durch elektrostatische Wechselwirkungen erfolgte, oder durch kovalente Kopplung der beiden Komponenten. Als makromolekulare Komponente zur Vernetzung der Mizellen wurden Biopolymere (hier: die Polysaccharide Hyaluronsäure (HA), Chondroitinsulfat oder Pektin oder das Protein Gelatin) verwendet, um die Hydrogele enzymatisch abbaubar zu gestalten. Um eine starke ionische/elektrostatische Wechselwirkung zwischen dem PEPE und den Polysachariden zu erzielen, wurde PEPE aminiert, um hauptsächlich monoaminiertes bzw. diaminiertes PEPE einsetzen zu können. Die Gele, die auf der physikalischen Mischung von aminierten PEPE mit HA bestehen, zeigten im Vergleich zu PEPE bei gleicher Konzentration eine Zunahme der mechanischen Eigenschaften, wie beispielsweise dem elastischem Modulus (G′) und dem Viskositätsmodulus (G′′) bei gleichzeitiger Abnahme der Gelierungstemperatur (Tgel). Durch Variation des Gehalts an aminierten PEPE-, konnte die Tgel in einem Bereich von 27-36 °C eingestellt werden. Interessanterweise zeigten die physikalischen Mischungen mit diaminierten PEPE (HA·di-PEPE) höhere mechanische Eigenschaften (elastischer Modulus G′) und eine höhere Stabilität gegenüber Verdünnungseffekten als Mischungen mit monoaminiertem PEPE (HA·mono-PEPE). Dies zeigt den starken Einfluss der elektrostatischen Wechselwirkungen zwischen der Carboxylgruppe der HA und der Amingruppe von PEPE. Die physikalischen Eigenschaften HA·di-PEPE sind vergleichbar mit den physikalischen Eigenschaften des Glaskörpers im Auge hinsichtlich Transparenz, Brechungsindex und Viskosität. Deswegen wurde das Material hinsichtlich seiner biologischen Anwendung getestet und zeigte sich sowohl im Überstand als auch im direkten Kontakt als nichtzytotoxisch. Zukünftig wird dieses Material in weiteren Untersuchungen bezüglich seiner Eignung als Glaskörperersatz geprüft werden. Zusätzlich konnte der enzymatische Abbau der Hydrogele mit Hyaluronidase gezeigt werden, die spezifisch HA abbaut. Beim Abbau der Hydrogele stieg Tgel bei gleichzeitiger Abnahme der mechanischen Eigenschaften. Aminiertes PEPE wurde zusätzlich zur kovalenten Bindung unter Verwendung von EDC als Aktivator an Pektin und Chondroitinsulfat eingesetzt. Tgel konnte auf 28 – 33 °C eingestellt werden durch Variation der Pfropfungsdichte am Biopolymer bei gleichzeitiger Zunahme der thermischen Stabilität. Die Pec-g-PEPE Hydrogele waren enzymatisch abbaubar, was zu einer leichten Erhöhung von Tgel und zu einer Abnahme von G′ führte. Die kovalente Bindung der aminierten PEPE an HA erfolgte unter Verwendung von DMTMM als Aktivator, der sich in diesem Fall als effektiver als EDC herausstellte. Die Reinigung mittels Ultrafiltration führte zu einer deutlich besseren Aufreinigung des Produkts als mittels Dialyse. Die gegrafteten Systeme waren in Nähe der Körpertemperatur bereits im Gelstadium und zeigten eine Erhöhung der mechanischen Eigenschaften bereits bei sehr geringen Konzentrationen von 2.5Gew.%. Die höheren mechanischen Eigenschaften dieser Hydrogele erklären sich durch die Kombination der Mizellbildung (physikalische Wechselwirkung) des PEPE und der Bildung kovalenter Netzpunkte zwischen PEPE und HA. PEPE bzw. entsprechende physikalische Mischungen derselben Komponenten zeigten kein thermosensitives Verhalten bei einer Konzentration unterhalb von 16 Gew%. Diese thermosensitiven Hydrogele zeigten auch eine Löslichkeit auf Abruf durch enzymatischen Abbau. Das Konzept der Thermosensitivität wurde in 3D strukturierte, poröse Hydrogele (TArcGel)eingeführt, bei dem PEPE kovalent an Gelatin gebunden wurde und mit LDI vernetzt wurde. Das gepfropfte PEPE führte zu einer Erniedrigung der Helixbildung der Gelatinketten. Nach Fixierung der Gelatinketten durch Vernetzung zeigte das System eine Erhöhung der mechanischen Eigenschaften bei Erwärmung (34-42 °C). Dieses Phänomen war reversibel beim Abkühlen. Eine mögliche Erklärung der reversiblen Änderungen bezüglich der mechanischen Eigenschaften sind die starken physikalischen Wechselwirkungen zwischen den Mizellen des PEPE, die kovalent an Gelatin gebunden wurden. Ferner wurde durch AFM Untersuchungen festgestellt, dass bei Temperaturerhöhung (37 °C) die örtlichen elastischen Moduli (E) der Zellwände zugenommen haben. Zusätzlich wurde die Wasseraufnahme der TArcGele durch PEPE und die Temperatur (25 °C und 37 °C) beeinflusst und zeigte eine niedrigere Wasseraufnahme bei höherer Temperatur und umgekehrt. Durch die niedrigere Wasseraufnahme bei hohen Temperaturen erniedrigte sich die Geschwindigkeit des hydrolytischen Abbaus im Vergleich zu dem strukturierten Hydrogel aus reiner Gelatin. Diese temperatursensitiven ArcGele könnten bedeutsam sein für Anwendungen im Bereich Stammzellkultivierung, Zelldifferenzierung und gerichteter Zellmigration. Zusammenfassend konnte bei den thermosensitiven Hydrogelen gezeigt werden, dass die Vernetzung von Mizellen mit einem makromolekularen Vernetzer die Schermoduli, Viskosität und Löslichkeitsstabilität im Vergleich zu reinen ABATriblockcopolymeren mit CMC-Übergang erhöht. Dieser Effekt konnte durch kovalente und nichtkovalente Mechanismen, wie beispielsweise Mizell- Wechselwirkungen, physikalische Interaktionen von Gelatinketten und physikalische Interaktionen von Gelatinketten und Mizellen, realisiert werden. Das Pfropfen von PEPE führte zu zusätzlichen Netzpunkten, die die mechanischen Eigenschaften der thermosensitiven architekturisierten, porösen Hydrogele beeinflussten. Insgesamt ermöglichten die physikalischen und chemischen Bindungen und die reversiblen physikalischen Wechselwirkungen in den strukturierten, porösen Hydrogelen eine Kontrolle der mechanischen Eigenschaften in diesem sehr komplexen System. Die Hydrogele, die eine Veränderung ihrer mechanischen Eigenschaften ohne Volumenänderung oder Sol-Gel-Übergang zeigen sind besonders interessant für Untersuchungen bezüglich Zellproliferation und –differenzierung. KW - thermosensitive KW - hydrogels KW - biomaterials KW - biopolymers KW - sol-gel Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-69793 ER -