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- ItemPlasma-Assisted Immobilization of a Phosphonium Salt and Its Use as a Catalyst in the Valorization of CO2(Weinheim : Wiley-VCH, 2020) Hu, Yuya; Peglow, Sandra; Longwitz, Lars; Frank, Marcus; Epping, Jan Dirk; Breser, Volker; Werner, ThomasThe first plasma-assisted immobilization of an organocatalyst, namely a bifunctional phosphonium salt in an amorphous hydrogenated carbon coating, is reported. This method makes the requirement for prefunctionalized supports redundant. The immobilized catalyst was characterized by solid-state 13C and 31P NMR spectroscopy, SEM, and energy-dispersive X-ray spectroscopy. The immobilized catalyst (1 mol %) was employed in the synthesis of cyclic carbonates from epoxides and CO2. Notably, the efficiency of the plasma-treated catalyst on SiO2 was higher than those of the SiO2 support impregnated with the catalyst and even the homogeneous counterpart. After optimization of the reaction conditions, 13 terminal and four internal epoxides were converted with CO2 to the respective cyclic carbonates in yields of up to 99 %. Furthermore, the possibility to recycle the immobilized catalyst was evaluated. Even though the catalyst could be reused, the yields gradually decreased from the third run. However, this is the first example of the recycling of a plasma-immobilized catalyst, which opens new possibilities in the recovery and reuse of catalysts. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemSinglet-Oxygen-Induced Phospholipase A2 Inhibition: A Major Role for Interfacial Tryptophan Dioxidation(Weinheim : Wiley-VCH, 2021) Nasri, Zahra; Memari, Seyedali; Wenske, Sebastian; Clemen, Ramona; Martens, Ulrike; Delcea, Mihaela; Bekeschus, Sander; Weltmann, Klaus-Dieter; von Woedtke, Thomas; Wende, KristianSeveral studies have revealed that various diseases such as cancer have been associated with elevated phospholipase A2 (PLA2) activity. Therefore, the regulation of PLA2 catalytic activity is undoubtedly vital. In this study, effective inactivation of PLA2 due to reactive species produced from cold physical plasma as a source to model oxidative stress is reported. We found singlet oxygen to be the most relevant active agent in PLA2 inhibition. A more detailed analysis of the plasma-treated PLA2 identified tryptophan 128 as a hot spot, rich in double oxidation. The significant dioxidation of this interfacial tryptophan resulted in an N-formylkynurenine product via the oxidative opening of the tryptophan indole ring. Molecular dynamics simulation indicated that the efficient interactions between the tryptophan residue and phospholipids are eliminated following tryptophan dioxidation. As interfacial tryptophan residues are predominantly involved in the attaching of membrane enzymes to the bilayers, tryptophan dioxidation and indole ring opening leads to the loss of essential interactions for enzyme binding and, consequently, enzyme inactivation. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
- ItemSinglet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis(Weinheim : Wiley-VCH, 2020) Ingenbosch, Kim N.; Quint, Stephan; Dyllick-Brenzinger, Melanie; Wunschik, Dennis S.; Kiebist, Jan; Süss, Philipp; Liebelt, Ute; Zuhse, Ralf; Menyes, Ulf; Scheibner, Katrin; Mayer, Christian; Opwis, Klaus; Gutmann, Jochen S.; Hoffmann-Jacobsen, KerstinSinglet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen. © 2020 Wiley-VCH GmbH
- ItemSupercritical fluid extraction-supercritical fluid chromatography of saliva: Single-quadrupole mass spectrometry monitoring of caffeine for gastric emptying studies†(Weinheim : Wiley-VCH, 2021) Hofstetter, Robert K.; Schulig, Lukas; Bethmann, Jonas; Grimm, Michael; Sager, Maximilian; Aude, Philipp; Keßler, Rebecca; Kim, Simon; Weitschies, Werner; Link, AndreasSaliva is an attractive sampling matrix for measuring various endogenous and exogeneous substances but requires sample treatment prior to chromatographic analysis. Exploiting supercritical CO2 for both extraction and chromatography simplifies sample preparation, reduces organic solvent consumption, and minimizes exposure to potentially infectious samples, but has not yet been applied to oral fluid. Here, we demonstrate the feasibility and benefits of online supercritical fluid extraction coupled to supercritical fluid chromatography and single-quadrupole mass spectrometry for monitoring the model salivary tracer caffeine. A comparison of 13C- and 32S-labeled internal standards with external standard calibration confirmed the superiority of stable isotope-labeled caffeine over nonanalogous internal standards. As proof of concept, the validated method was applied to saliva from a magnetic resonance imaging study of gastric emptying. After administration of 35 mg caffeine via ice capsule, salivary levels correlated with magnetic resonance imaging data, corroborating caffeine's usefulness as tracer of gastric emptying (R2 = 0.945). In contrast to off-line methods, online quantification required only minute amounts of organic solvents and a single manual operation prior to online bioanalysis of saliva, thus demonstrating the usefulness of CO2-based extraction and separation techniques for potentially infective biomatrices.
- ItemOral SARS-CoV-2 reduction by local treatment: A plasma technology application?(Weinheim : Wiley-VCH, 2022) von Woedtke, Thomas; Gabriel, Gülsah; Schaible, Ulrich E.; Bekeschus, SanderThe SARS-CoV-2 pandemic reemphasized the importance of and need for efficient hygiene and disinfection measures. The coronavirus' efficient spread capitalizes on its airborne transmission routes via virus aerosol release from human oral and nasopharyngeal cavities. Besides the upper respiratory tract, efficient viral replication has been described in the epithelium of these two body cavities. To this end, the idea emerged to employ plasma technology to locally reduce mucosal viral loads as an additional measure to reduce patient infectivity. We here outline conceptual ideas of such treatment concepts within what is known in the antiviral actions of plasma treatment so far.
- ItemPlasma Spraying of Kaolinite for Preparing Reactive Alumino-Silicate Glass Coatings(Weinheim : Wiley-VCH, 2022) Warr, Laurence N.; Wolff, Thorben; Testrich, Holger; Grathoff, Georg; Kruth, Angela; Foest, RüdigerThermally treated kaolinite is used to develop a range of alumino-silicate-based precursor materials but its behavior during plasma spraying has not been well-researched. In this study, two types of kaolinite samples were investigated in the form of low defect (KGa-1b) and high defect (KGa-2) varieties. The extreme temperatures of the plasma stream (up to 20 000 K) induced flash melting to produce a highly porous alumino-silicate glass without any crystallization of new Al−Si oxide minerals. The glass is comprised largely of intact or deformed spheres (average diameters 1.14–1.44 μm), which indicates rapid quenching and solidification before impact. The subspherical structures contain up to 40 % closed pore space caused by the rapid escape of water during melting. The low-density, porous alumino-silicate glass coatings with predicted specific surface areas (>0.95 m2/g) and hardnesses >1.8 GPa represent a potentially reactive but physically stable substrate ideal for further chemical functionalization.
- ItemElectrically Conductive and 3D-Printable Oxidized Alginate-Gelatin Polypyrrole: PSS Hydrogels for Tissue Engineering(Weinheim : Wiley-VCH, 2021) Distler, Thomas; Polley, Christian; Shi, Fukun; Schneidereit, Dominik; Ashton, Mark D.; Friedrich, Oliver; Kolb, Jürgen F.; Hardy, John G.; Detsch, Rainer; Seitz, Hermann; Boccaccini, Aldo R.Electroactive hydrogels can be used to influence cell response and maturation by electrical stimulation. However, hydrogel formulations which are 3D printable, electroactive, cytocompatible, and allow cell adhesion, remain a challenge in the design of such stimuli-responsive biomaterials for tissue engineering. Here, a combination of pyrrole with a high gelatin-content oxidized alginate-gelatin (ADA-GEL) hydrogel is reported, offering 3D-printability of hydrogel precursors to prepare cytocompatible and electrically conductive hydrogel scaffolds. By oxidation of pyrrole, electroactive polypyrrole:polystyrenesulfonate (PPy:PSS) is synthesized inside the ADA-GEL matrix. The hydrogels are assessed regarding their electrical/mechanical properties, 3D-printability, and cytocompatibility. It is possible to prepare open-porous scaffolds via bioplotting which are electrically conductive and have a higher cell seeding efficiency in scaffold depth in comparison to flat 2D hydrogels, which is confirmed via multiphoton fluorescence microscopy. The formation of an interpenetrating polypyrrole matrix in the hydrogel matrix increases the conductivity and stiffness of the hydrogels, maintaining the capacity of the gels to promote cell adhesion and proliferation. The results demonstrate that a 3D-printable ADA-GEL can be rendered conductive (ADA-GEL-PPy:PSS), and that such hydrogel formulations have promise for cell therapies, in vitro cell culture, and electrical-stimulation assisted tissue engineering. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH