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End date: 2023 × Start date: 2023 × DDC: 600 × Has files: Yes × WGL Institute: DWI ×

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Now showing 1 - 10 of 22
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    In-Gel Direct Laser Writing for 3D-Designed Hydrogel Composites That Undergo Complex Self-Shaping
    (Weinheim : Wiley-VCH, 2017) Nishiguchi, Akihiro; Mourran, Ahmed; Zhang, Hang; Möller, Martin
    Self-shaping and actuating materials inspired by biological system have enormous potential for biosensor, microrobotics, and optics. However, the control of 3D-complex microactuation is still challenging due to the difficulty in design of nonuniform internal stress of micro/nanostructures. Here, we develop in-gel direct laser writing (in-gel DLW) procedure offering a high resolution inscription whereby the two materials, resin and hydrogel, are interpenetrated on a scale smaller than the wavelength of the light. The 3D position and mechanical properties of the inscribed structures could be tailored to a resolution better than 100 nm over a wide density range. These provide an unparalleled means of inscribing a freely suspended microstructures of a second material like a skeleton into the hydrogel body and also to direct isotropic volume changes to bending and distortion motions. In the combination with a thermosensitive hydrogel rather small temperature variations could actuate large amplitude motions. This generates complex modes of motion through the rational engineering of the stresses present in the multicomponent material. More sophisticated folding design would realize a multiple, programmable actuation of soft materials. This method inspired by biological system may offer the possibility for functional soft materials capable of biomimetic actuation and photonic crystal application.
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    DNA Nanotechnology Enters Cell Membranes
    (Weinheim : Wiley-VCH, 2019) Huo, Shuaidong; Li, Hongyan; Boersma, Arnold J.; Herrmann, Andreas
    DNA is more than a carrier of genetic information: It is a highly versatile structural motif for the assembly of nanostructures, giving rise to a wide range of functionalities. In this regard, the structure programmability is the main advantage of DNA over peptides, proteins, and small molecules. DNA amphiphiles, in which DNA is covalently bound to synthetic hydrophobic moieties, allow interactions of DNA nanostructures with artificial lipid bilayers and cell membranes. These structures have seen rapid growth with great potential for medical applications. In this Review, the current state of the art of the synthesis of DNA amphiphiles and their assembly into nanostructures are first summarized. Next, an overview on the interaction of these DNA amphiphiles with membranes is provided, detailing on the driving forces and the stability of the interaction. Moreover, the interaction with cell surfaces in respect to therapeutics, biological sensing, and cell membrane engineering is highlighted. Finally, the challenges and an outlook on this promising class of DNA hybrid materials are discussed.
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    Porous PEDOT:PSS Particles and their Application as Tunable Cell Culture Substrate
    (Weinheim : Wiley, 2021) Rauer, Sebastian Bernhard; Bell, Daniel Josef; Jain, Puja; Rahimi, Khosrow; Felder, Daniel; Linkhorst, John; Wessling, Matthias
    Due to its biocompatibility, electrical conductivity, and tissue-like elasticity, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) constitutes a highly promising material regarding the fabrication of smart cell culture substrates. However, until now, high-throughput synthesis of pure PEDOT:PSS geometries was restricted to flat sheets and fibers. In this publication, the first microfluidic process for the synthesis of spherical, highly porous, pure PEDOT:PSS particles of adjustable material properties is presented. The particles are synthesized by the generation of PEDOT:PSS emulsion droplets within a 1-octanol continuous phase and their subsequent coagulation and partial crystallization in an isopropanol (IPA)/sulfuric acid (SA) bath. The process allows to tailor central particle characteristics such as crystallinity, particle diameter, pore size as well as electrochemical and mechanical properties by simply adjusting the IPA:SA ratio during droplet coagulation. To demonstrate the applicability of PEDOT:PSS particles as potential cell culture substrate, cultivations of L929 mouse fibroblast cells and MRC-5 human fibroblast cells are conducted. Both cell lines present exponential growth on PEDOT:PSS particles and reach confluency with cell viabilities above 95 vol.% on culture day 9. Single cell analysis could moreover reveal that mechanotransduction and cell infiltration can be controlled by the adjustment of particle crystallinity.
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    Mitigating Water Crossover by Crosslinked Coating of Cation‐Exchange Membranes for Brine Concentration
    (Weinheim : Wiley, 2021) Rommerskirchen, Alexandra; Roth, Hannah; Linnartz, Christian J.; Egidi, Franziska; Kneppeck, Christian; Roghmans, Florian; Wessling, Matthias
    Undesired water crossover through ion-exchange membranes is a significant limitation in electrically driven desalination processes. The effect of mitigating water crossover is twofold: 1) The desalination degree is less reduced due to the unwanted removal of water, and 2) the brine concentration is increased due to decreased dilution by an unwanted crossover of water molecules. Hence, water crossover limits the desalination and concentration efficiency of the processes, while the energy demand to achieve a certain level of desalination or concentration increases. This effect is especially pronounced when treating high salinity solutions, which goes hand in hand with the crossover of many ions through the ion-exchange membranes. A crosslinked coating for cation-exchange membranes (CEMs) is presented in this work, which can significantly mitigate such undesired water crossover. The efficacy is demonstrated using the flow-electrode capacitive deionization process applied for desalination and concentration of saline brines at feed concentrations of 60 and 120 g L−1 NaCl. With just a single coated CEM, the water crossover was reduced by up to 54%.
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    Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering
    (Basel : MDPI, 2016) Hardy, John G.; Torres-Rendon, Jose Guillermo; Leal-Egaña, Aldo; Walther, Andreas; Schlaad, Helmut; Cölfen, Helmut; Scheibel, Thomas
    Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.
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    3D‐Printed Bioreactor with Integrated Impedance Spectroscopy for Cell Barrier Monitoring
    (Weinheim : Wiley, 2021) Linz, Georg; Rauer, Sebastian Bernhard; Kuhn, Yasmin; Wennemaring, Simon; Siedler, Laura; Singh, Smriti; Wessling, Matthias
    Cell culture experiments often suffer from limited commercial availability of laboratory-scale bioreactors, which allow experiments to be conducted under flow conditions and additional online monitoring techniques. A novel 3D-printed bioreactor with a homogeneously distributed flow field enabling epithelial cell culture experiments and online barrier monitoring by integrated electrodes through electrical impedance spectroscopy (EIS) is presented. Transparent and conductive indium tin oxide glass as current-injecting electrodes allows direct visualization of the cells, while measuring EIS simultaneously. The bioreactor's design considers the importance of a homogeneous electric field by placing the voltage pick-up electrodes in the electrical field. The device's functionality is demonstrated by the cultivation of the epithelial cell line Caco-2 under continuous flow and monitoring of the cell layer by online EIS. The collected EIS data were fitted by an equivalent electric circuit, resulting in the cell layer's resistance and capacitance. This data is used to monitor the cell layer's reaction to ethylene glycol-bis-(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid and forskolin. These two model substances show the power of impedance spectroscopy as a non-invasive way to characterize cell barriers. In addition, the bioreactor design is available as a print-ready file in the Appendix, enabling its use for other scientific institutions.
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    Porous PVDF Monoliths with Templated Geometry
    (Weinheim : Wiley, 2021) Djeljadini, Suzana; Bongartz, Patrick; Alders, Michael; Hartmann, Nils; Oing, Alexander; Cornelissen, Christian; Hesselmann, Felix; Arens, Jutta; Steinseifer, Ulrich; Linkhorst, John; Wessling, Matthias
    Additive manufacturing of complex porous polymer geometries is a new field of advanced materials processing. Such new geometries can be used to fabricate porous polymer monoliths serving as a support for other material functions. Here, a novel fabrication technology to manufacture tailored 3D porous monoliths via additive manufacturing and templating is presented. The method is based on replicating a 3D-printed mold with a polymer solution of polyvinylidenfluorid-triethyl phosphate (PVDF-TEP) and induce phase separation of the polymer solution subsequently. In a second step, the mold is removed without affecting the porous PVDF phase. As a result, porous monoliths with a templated 3D architecture are successfully fabricated. The manufacturing process is successfully applied to complex structures and can be applied to any conceivable geometry. Coating the porous 3D monoliths with another PVDF solution allows applying a skin layer yielding an asymmetric membrane monolith. As a showcase, a polydimethylsiloxane coating even leads to a smooth and dense layer of micrometer size. The methodology enables a new generation of complex porous polymer monoliths with tailored surface coatings. For the combination of poly(dimethylsiloxane) on a porous support, gas/liquid mass transfer is used in blood oxygenation with reduced diffusion limitation is within reach.
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    On the Dynamical Regimes of Pattern-Accelerated Electroconvection
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2016) Davidson, Scott M.; Wessling, Matthias; Mani, Ali
    Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.
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    Direct Observation of Deformation in Microgel Filtration
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2019) Linkhorst, John; Rabe, Jonas; Hirschwald, Lukas T.; Kuehne, Alexander J. C.; Wessling, Matthias
    Colloidal filtration processes using porous membranes suffer from productivity loss due to colloidal matter retention and continuous build-up by the retained matter. Especially during filtration of soft matter, the deformation of the individual colloids that make up the filter cake may be significant; however, this deformation and its impact remain unresolved so far. Yet, understanding the deformation on the single colloid level as well as on the ensemble level is important to be able to deconvolute filter cake properties from resistance increase of the membrane either by simultaneous internal adsorption or blocking of pores. Here, we report on the compression of a filter cake by filtrating soft microgels in a microfluidic channel in front of a model membrane. To study the single colloid deformation amorphous and crystalline domains were built up in front of the membrane and visualized on-line using confocal fluorescence microscopy while adjusting the degree of permeation, i.e., the transmembrane flux. Results show locally pronounced asymmetric deformation in amorphous domains, while the microgels in colloidal crystals approached regular polyeder shape. Increasing the flux beyond the maximum colloid deformation results in non-isochoric microgel behavior. The presented methodology enables a realistic description of complex colloidal matter deposits during filtration.
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    Electron transfer pathways in a light, oxygen, voltage (LOV) protein devoid of the photoactive cysteine
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2017) Kopka, Benita; Magerl, Kathrin; Savitsky, Anton; Davari, Mehdi D.; Röllen, Katrin; Bocola, Marco; Dick, Bernhard; Schwaneberg, Ulrich; Jaeger, Karl-Erich; Krauss, Ulrich
    Blue-light absorption by the flavin chromophore in light, oxygen, voltage (LOV) photoreceptors triggers photochemical reactions that lead to the formation of a flavin-cysteine adduct. While it has long been assumed that adduct formation is essential for signaling, it was recently shown that LOV photoreceptor variants devoid of the photoactive cysteine can elicit a functional response and that flavin photoreduction to the neutral semiquinone radical is sufficient for signal transduction. Currently, the mechanistic basis of the underlying electron- (eT) and proton-transfer (pT) reactions is not well understood. We here reengineered pT into the naturally not photoreducible iLOV protein, a fluorescent reporter protein derived from the Arabidopsis thaliana phototropin-2 LOV2 domain. A single amino-acid substitution (Q489D) enabled efficient photoreduction, suggesting that an eT pathway is naturally present in the protein. By using a combination of site-directed mutagenesis, steady-state UV/Vis, transient absorption and electron paramagnetic resonance spectroscopy, we investigate the underlying eT and pT reactions. Our study provides strong evidence that several Tyr and Trp residues, highly conserved in all LOV proteins, constitute the eT pathway for flavin photoreduction, suggesting that the propensity for photoreduction is evolutionary imprinted in all LOV domains, while efficient pT is needed to stabilize the neutral semiquinone radical.