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- ItemPorous 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, MatthiasDue 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.
- ItemBiocompatible Micron-Scale Silk Fibers Fabricated by Microfluidic Wet Spinning(Weinheim : Wiley-VCH, 2021) Lüken, Arne; Geiger, Matthias; Steinbeck, Lea; Joel, Anna-Christin; Lampert, Angelika; Linkhorst, John; Wessling, MatthiasFor successful material deployment in tissue engineering, the material itself, its mechanical properties, and the microscopic geometry of the product are of particular interest. While silk is a widely applied protein-based tissue engineering material with strong mechanical properties, the size and shape of artificially spun silk fibers are limited by existing processes. This study adjusts a microfluidic spinneret to manufacture micron-sized wet-spun fibers with three different materials enabling diverse geometries for tissue engineering applications. The spinneret is direct laser written (DLW) inside a microfluidic polydimethylsiloxane (PDMS) chip using two-photon lithography, applying a novel surface treatment that enables a tight print-channel sealing. Alginate, polyacrylonitrile, and silk fibers with diameters down to 1 µm are spun, while the spinneret geometry controls the shape of the silk fiber, and the spinning process tailors the mechanical property. Cell-cultivation experiments affirm bio-compatibility and showcase an interplay between the cell-sized fibers and cells. The presented spinning process pushes the boundaries of fiber fabrication toward smaller diameters and more complex shapes with increased surface-to-volume ratio and will substantially contribute to future tailored tissue engineering materials for healthcare applications. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH
- ItemMitigating 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, MatthiasUndesired 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%.
- ItemReconstruction of Ultra-thin Alveolar-capillary Basement Membrane Mimics(Weinheim : Wiley-VCH, 2021) Jain, Puja; Nishiguchi, Akihiro; Linz, Georg; Wessling, Matthias; Ludwig, Andreas; Rossaint, Rolf; Möller, Martin; Singh, SmritiAlveolar-capillary basement membrane (BM) is ultra-thin (<2 µm) extracellular matrix that maintains integral epithelial-endothelial cell layers. In vitro reconstructions of alveolar-capillary barrier supported on synthetic scaffolds closely resembling the fibrous and ultra-thin natural BM are essential in mimicking the lung pathophysiology. Although BM topology and dimensions are well known to significantly influence cellular behavior, conventionally used BM mimics fail to recreate this natural niche. To overcome this, electrospun ultra-thin 2 µm poly(caprolactone) (PCL) nanofibrous mesh is used to establish an alveolar-capillary barrier model of lung endothelial/epithelial cells. Transepithelial electrical resistance (TEER) and permeability studies reveal integral tight junctions and improved mass transport through the highly porous PCL meshes compared to conventional dense membranes with etched pores. The chemotaxis of neutrophils is shown across the barrier in presence of inflammatory response that is naturally impeded in confined regions. Conventional requirement of 3 µm or larger pore size can lead to barrier disruption due to epithelial/endothelial cell invasion. Despite high porosity, the interconnected BM mimic prevents barrier disruption and allows neutrophil transmigration, thereby demonstrating the physiological relevance of the thin nanofibrous meshes. It is envisioned that these bipolar cultured barriers would contribute to an organ-level in vitro model for pathological disease, environmental pollutants, and nanotoxicology. © 2021 The Authors. Advanced Biology published by Wiley-VCH GmbH
- ItemPolymeric Membranes With Sufficient Thermo‐Mechanical Stability to Deploy Temperature Enhanced Backwash(Weinheim : Wiley-VCH, 2021) Aumeier, Benedikt M.; Vollmer, Fabian; Lenfers, Simon; Yüce, Süleyman; Wessling, MatthiasThe alternative membrane cleaning method Temperature Enhanced Backwash exploits elevated temperatures of typically 125 °C to realize high shear rate. This exceeds usual operating temperatures by far. Therefore, the thermo-mechanical properties of polymeric membranes were investigated. A repeated load cycle testing was suited and sensitive to detect the failure of membrane material and potting. All tested PES membranes showed to be stable during the repeated load cycle testing. The potting adhesive may be decisive, thus, a tensile test at 125 °C is proposed. © 2021 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH
- ItemA scalable bubble-free membrane aerator for biosurfactant production(New York, NY : Wiley, 2021) Bongartz, Patrick; Bator, Isabel; Baitalow, Kristina; Keller, Robert; Tiso, Till; Blank, Lars Mathias; Wessling, MatthiasThe bioeconomy is a paramount pillar in the mitigation of greenhouse gas emissions and climate change. Still, the industrialization of bioprocesses is limited by economical and technical obstacles. The synthesis of biosurfactants as advanced substitutes for crude-oil-based surfactants is often restrained by excessive foaming. We present the synergistic combination of simulations and experiments towards a reactor design of a submerged membrane module for the efficient bubble-free aeration of bioreactors. A digital twin of the combined bioreactor and membrane aeration module was created and the membrane arrangement was optimized in computational fluid dynamics studies with respect to fluid mixing. The optimized design was prototyped and tested in whole-cell biocatalysis to produce rhamnolipid biosurfactants from sugars. Without any foam formation, the new design enables a considerable higher space-time yield compared to previous studies with membrane modules. The design approach of this study is of generic nature beyond rhamnolipid production.
- ItemWet-Spun PEDOT/CNT Composite Hollow Fibers as Flexible Electrodes for H2O2 Production(Weinheim : Wiley-VCH, 2021) Cui, Qing; Bell, Daniel Josef; Wang, Siqi; Mohseni, Mojtaba; Felder, Daniel; Lölsberg, Jonas; Wessling, MatthiasThe electrochemical synthesis of hydrogen peroxide (H2O2) using the oxygen reduction reaction (ORR) requires highly catalytic active, selective, and stable electrode materials to realize a green and efficient process. The present publication shows for the first time the application of a facile one-step bottom-up wet-spinning approach for the continuous fabrication of stable and flexible tubular poly(3,4-ethylene dioxythiophene) (PEDOT : PSS) and PEDOT : PSS/carbon nanotube (CNT) hollow fibers. Additionally, electrochemical experiments reveal the catalytic activity of acid-treated PEDOT : PSS and its composites in the ORR forming hydrogen peroxide for the first time. Under optimized conditions, the composite electrodes with 40 wt % CNT loading could achieve a high production rate of 0.01 mg/min/cm2 and a current efficiency of up to 54 %. In addition to the high production rate, the composite hollow fiber has proven its long-term stability with 95 % current retention after 20 h of hydrogen peroxide production. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH
- ItemRecycling and Separation of Homogeneous Catalyst from Aqueous Multicomponent Mixture by Organic Solvent Nanofiltration(Basel : MDPI, 2021) Schnoor, J.-Kilian; Bettmer, Jens; Kamp, Johannes; Wessling, Matthias; Liauw, Marcel A.Organic solvent nanofiltration (OSN) has evolved to an established recycling method for homogeneous catalysts. However, commercial availability has not circumvented the need for classification and the scoping of possible applications for specific solvent mixtures. Therefore, Evonik’s DuraMem® 300 was assessed for the recycling of magnesium triflate at two transmembrane pressures from a mixture of ethanol, ethyl acetate and water. Catalyst retention up to 98% and permeability of up to 4.44·10−1∙L∙bar−1∙m−2∙h−1 were possible when less than 25% ethyl acetate was in the mixture. The retention of some of the components in the ternary mixture was observed while others were enriched, making the membrane also suitable for fractioning thereof.
- ItemWetting-Induced Polyelectrolyte Pore Bridging(Basel : MDPI, 2021) Kalde, Anna; Kamp, Johannes; Evdochenko, Elizaveta; Linkhorst, John; Wessling, MatthiasActive layers of ion separation membranes often consist of charged layers that retain ions based on electrostatic repulsion. Conventional fabrication of these layers, such as polyelectrolyte deposition, can in some cases lead to excess coating to prevent defects in the active layer. This excess deposition increases the overall membrane transport resistance. The study at hand presents a manufacturing procedure for controlled polyelectrolyte complexation in and on porous supports by support wetting control. Pre-wetting of the microfiltration membrane support, or even supports with larger pore sizes, leads to ternary phase boundaries of the support, the coating solution, and the pre-wetting agent. At these phase boundaries, polyelectrolytes can be complexated to form partially freestanding selective structures bridging the pores. This polyelectrolyte complex formation control allows the production of membranes with evenly distributed polyelectrolyte layers, providing (1) fewer coating steps needed for defect-free active layers, (2) larger support diameters that can be bridged, and (3) a precise position control of the formed polyelectrolyte multilayers. We further analyze the formed structures regarding their position, composition, and diffusion dialysis performance.
- ItemAutomated tangential-flow diafiltration device(Amsterdam : Elsevier, 2021) Lüken, Arne; Bruckhaus, Maike; Kosfeld, Udo; Emondts, Meike; Wessling, MatthiasTangential flow filtration (TFF) is a chemical unit operation used to purify and concentrate liquid suspensions of colloids, proteins, or cells. The solution flows tangentially across a membrane, such that a selective part of the fluid permeates the membrane while the filtrated matter is retained, increasing its concentration. TFF is a mild mechanical purification method that does not interact chemically with the filtrate. It is applied in sensitive separation tasks in protein chemistry, microbiology, or immunology. It is a fast alternative for dialysis applications, also applicable in the field of colloid purification. However, the costs of automated lab-scale devices (30,000 €) and the consumable membrane modules (100–600 €) make TFF currently hardly accessible for lab-scale polymer researchers. Therefore, we built a low-cost TFF system (2400 €) partly automated by an Arduino microcontroller and optimized for diafiltration buffer exchange and concentration processes in soft matter colloid research. We use medical hemodialysis membrane modules that only cost a share (20–50 €) of alternative TFF modules, and we demonstrate the functionality of the system for an exemplary colloidal microgel purification process.