TY - JOUR A1 - Blocki, Anna A1 - Löwenberg, Candy A1 - Jiang, Yi A1 - Kratz, Karl A1 - Neffe, Axel T. A1 - Jung, Friedrich A1 - Lendlein, Andreas T1 - Response of encapsulated cells to a gelatin matrix with varied bulk and microenvironmental elastic properties JF - Polymers for advanced technologies N2 - Gelatin-based hydrogels offer various biochemical cues that support encapsulated cells and are therefore suitable as cell delivery vehicles in regenerative medicine. However, besides the biochemical signals, biomechanical cues are crucial to ensure an optimal support of encapsulated cells. Hence, we aimed to correlate the cellular response of encapsulated cells to macroscopic and microscopic elastic properties of glycidylmethacrylate (GMA)-functionalized gelatin-based hydrogels. To ensure that different observations in cellular behavior could be attributed to differences in elastic properties, an identical concentration as well as degree of functionalization of biopolymers was utilized to form covalently crosslinked hydrogels. Elastic properties were merely altered by varying the average gelatin-chain length. Hydrogels exhibited an increased degree of swelling and a decreased bulk elastic modulus G with prolonged autoclaving of the starting solution. This was accompanied by an increase of hydrogel mesh size and thus by a reduction of crosslinking density. Tougher hydrogels retained the largest amount of cells; however, they also interfered with cell viability. Softer gels contained a lower cell density, but supported cell elongation and viability. Observed differences could be partially attributed to differences in bulk properties, as high crosslinking densities interfere with diffusion and cell spreading and thus can impede cell viability. Interestingly, a microscopic elastic modulus in the range of native soft tissue supported cell viability and elongation best while ensuring a good cell entrapment. In conclusion, gelatin-based hydrogels providing a soft tissue-like microenvironment represent adequate cell delivery vehicles for tissue engineering approaches. Copyright (c) 2016 John Wiley & Sons, Ltd. KW - mechanotransduction KW - hydrogel KW - gelatin KW - cell encapsulation KW - matrix elasticity Y1 - 2017 U6 - https://doi.org/10.1002/pat.3947 SN - 1042-7147 SN - 1099-1581 VL - 28 SP - 1245 EP - 1251 PB - Wiley CY - Hoboken ER - TY - THES A1 - Niedl, Robert Raimund T1 - Nichtlineare Kinetik und responsive Hydrogele für papierbasierte Schnelltestanwendungen T1 - Nonlinear kinetics and responsive hydrogels for paperbased point-of-care diagnostics N2 - Viele klinische Schnelltestsysteme benötigen vorpräparierte oder aufgereinigte Analyte mit frisch hergestellten Lösungen. Fernab standardisierter Laborbedingungen wie z.B. in Entwicklungsländern oder Krisengebieten sind solche Voraussetzungen oft nur unter einem hohen Aufwand herstellbar. Zusätzlich stellt die erforderliche Sensitivität die Entwicklung einfach zu handhabender Testsysteme vor große Herausforderungen. Autokatalytische Reaktionen, die sich mit Hilfe sehr geringer Initiatorkonzentrationen auslösen lassen, können hier eine Perspektive für Signalverstärkungsprozesse bieten. Aus diesem Grund wird im ersten Teil der vorliegenden Arbeit das Verhalten der autokatalytischen Arsenit-Jodat-Reaktion in einem mikrofluidischen Kanal untersucht. Dabei werden insbesondere die diffusiven und konvektiven Einflüsse auf die Reaktionskinetik im Vergleich zu makroskopischen Volumenmengen betrachtet. Im zweiten Teil werden thermoresponsive Hydrogele mit einem kanalstrukturierten Papiernetzwerk zu einem neuartigen, kapillargetriebenen, extern steuerbaren Mikrofluidik-System kombiniert. Das hier vorgestellte Konzept durch Hydrogele ein papierbasiertes LOC-System zu steuern, ermöglicht zukünftig die Herstellung von komplexeren, steuerbaren Point-Of-Care Testsystemen (POCT). Durch z.B. einen thermischen Stimulus, wird das Lösungsverhalten eines Hydrogels so verändert, dass die gespeicherte Flüssigkeit freigesetzt und durch die Kapillarkraft des Papierkanals ins System transportiert wird. Die Eigenschaften dieses Gelnetzwerks können dabei so eingestellt werden, dass eine Freisetzung von Flüssigkeiten sogar bei Körpertemperatur möglich wäre und damit eine Anwendung gänzlich ohne weitere Hilfsmittel denkbar ist. Für die Anwendung notwendige Chemikalien oder Enzyme lassen sich hierbei bequem in getrocknetem Zustand im Papiersubstrat vorlagern und bei Bedarf in Lösung bringen. Im abschließenden dritten Teil der Arbeit wird ein durch Hydrogele betriebener, Antikörper-basierter Mikroorganismenschnelltest für Escherichia coli präsentiert. Darüber hinaus wird weiterführend eine einfache Methode zur Funktionalisierung eines Hydrogels mit Biomolekülen über EDC/NHS-Kopplung vorgestellt. N2 - Many test systems for clinical applications require well-prepared or purified analytes. Far away from a laboratory environment, for example in developing countries or crisis regions, such prerequisites are often difficult to establish. Furthermore, the required sensitivity poses a considerable challenge for the development of easy-to-use test systems. . Autocatalytic reactions, which are which are highly sensitive to small initiator concentrations, may offer promising solutions to this problem. For this reason, in the first part of this thesis, the behavior of the autocatalytic arsenit-iodate-clock reaction is studied in a microfluidic environment. Especially the influence of diffusive and convective effects on the kinetics of the reaction were examined and compared to reaction conditions in macroscopic volumes. In the second part thermoresponsive hydrogels and a microstructured papersubstrate are combined to a externally controllable, new microfluidic system driven by capillary force. This offers new opportunities to integrate more complex analytic procedures in small point-of-care devices. For example, initiated by a thermal stimulus, the solubility of the hydrogel network is changed, so that the stored liquid is released and transported into the paper device, driven by capillary forces. The properties of thermoresponsive hydrogels can be tuned in such a way that the liquid release is triggered already by body temperature, so that no pumps or tubings are required anymore for usage. Furthermore chemicals and enzymes can be stored in the paper channels under dried conditions for a long time. Upon operation of the device, they can be taken up by the liquid released from the hydrogel reservoirs when needed. Finally, in the third part of this work, a rapid, easy-to-use hydrogel-driven test system for Escherichia coli is presented, based on an antibody assay. Futhermore a simple method for biofunctionalization of a hydrogel of a hydrogel based on EDC/NHS coupling will be introduced. KW - Hydrogel KW - papierbasiert KW - Mikrofluidik KW - HPµF KW - POCT KW - Pathogenerkennung KW - thermoresponsive KW - hydrogel KW - paperbased KW - POCT KW - nonlinear KW - chemical clock KW - biomolecule KW - functionalization Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-77735 ER - TY - JOUR A1 - Dey, Pradip A1 - Adamovski, Miriam A1 - Friebe, Simon A1 - Badalyan, Artavazd A1 - Mutihac, Radu-Cristian A1 - Paulus, Florian A1 - Leimkühler, Silke A1 - Wollenberger, Ursula A1 - Haag, Rainer T1 - Dendritic polyglycerol-poly(ethylene glycol)-based polymer networks for biosensing application JF - ACS applied materials & interfaces N2 - This work describes the formation of a new dendritic polyglycerol-poly(ethylene glycol)-based 3D polymer network as a matrix for immobilization of the redox enzyme periplasmatic aldehyde oxidoreductase to create an electrochemical biosensor. The novel network is built directly on the gold surface, where it simultaneously stabilizes the enzyme for up to 4 days. The prepared biosensors can be used for amperometric detection of benzaldehyde in the range of 0.8-400 mu M. KW - biosensors KW - hydrogel KW - amperometry KW - dendritic Y1 - 2014 U6 - https://doi.org/10.1021/am502018x SN - 1944-8244 VL - 6 IS - 12 SP - 8937 EP - 8941 PB - American Chemical Society CY - Washington ER -