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Author: Pich, Andrij × Type: Text × Publisher: Weinheim : Wiley-VCH ×

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Now showing 1 - 10 of 10
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    Pros and Cons : Supramolecular or Macromolecular : What Is Best for Functional Hydrogels with Advanced Properties?
    (Weinheim : Wiley-VCH, 2020) Eelkema, Rienk; Pich, Andrij
    Hydrogels are fascinating soft materials with unique properties. Many biological systems are based on hydrogel-like structures, underlining their versatility and relevance. The properties of hydrogels strongly depend on the structure of the building blocks they are composed of, as well as the nature of interactions between them in the network structure. Herein, gel networks made by supramolecular interactions are compared to covalent macromolecular networks, drawing conclusions about their performance and application as responsive materials. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Tuning the Volume Phase Transition Temperature of Microgels by Light
    (Weinheim : Wiley-VCH, 2021) Jelken, Joachim; Jung, Se-Hyeong; Lomadze, Nino; Gordievskaya, Yulia D.; Kramarenko, Elena Yu.; Pich, Andrij; Santer, Svetlana
    Temperature-responsive microgels find widespread applications as soft materials for designing actuators in microfluidic systems, as carriers for drug delivery or catalysts, as functional coatings, and as adaptable sensors. The key property is their volume phase transition temperature, which allows for thermally induced reversible swelling/deswelling. It is determined by the gel's chemical structure as well as network topology and cannot be varied easily within one system. Here a paradigm change of this notion by facilitating a light-triggered reversible switching of the microgel volume in the range between 32 and 82 °C is suggested. Photo-sensitivity is introduced by photosensitive azobenzene containing surfactant, which forms a complex with microgels consisting of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AAc) chains when assuming a hydrophobic trans-state, and prefers to leave the gel matrix in its cis-state. Using a similar strategy, it is demonstrated that at a fixed temperature, for example, 37 °C, one can reversibly change the microgel radius by a factor of 3 (7–21 µm) by irradiating either with UV (collapsed state) or green light (swollen state). It is envisaged that the possibility to deploy a swift external means of adapting the swelling behavior of microgels may impact and redefine the latter's application across all fields. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
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    Towards New Robust Zn(II) Complexes for the Ring-Opening Polymerization of Lactide Under Industrially Relevant Conditions
    (Weinheim : Wiley-VCH, 2019) Schäfer, Pascal M.; Dankhoff, Katja; Rothemund, Matthias; Ksiazkiewicz, Agnieszka N.; Pich, Andrij; Schobert, Rainer; Weber, Birgit; Herres-Pawlis, Sonja
    The synthesis of bio-based and biodegradable plastics is a hot topic in research due to growing environmental problems caused by omnipresent plastics. As a result, polylactide, which has been known for years, has seen a tremendous increase in industrial production. Nevertheless, the manufacturing process using the toxic catalyst Sn(Oct)2 is very critical. As an alternative, five zinc acetate complexes have been synthesized with Schiff base-like ligands that exhibit high activity in the ring-opening polymerization of non-purified lactide. The systems bear different side arms in the ligand scaffold. The influence of these substituents has been analyzed. For a detailed description of the catalytic activities, the rate constants kapp and kp were determined using in-situ Raman spectroscopy at a temperature of 150 °C. The polymers produced have molar masses of up to 71 000 g mol−1 and are therefore suitable for a variety of applications. Toxicity measurements carried out for these complexes proved the nontoxicity of the systems. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Undiscovered Potential: Ge Catalysts for Lactide Polymerization
    (Weinheim : Wiley-VCH, 2020) Rittinghaus, Ruth D.; Tremmel, Jakub; Růžička, Ales; Conrads, Christian; Albrecht, Pascal; Hoffmann, Alexander; Ksiazkiewicz, Agnieszka N.; Pich, Andrij; Jambor, Roman; Herres-Pawlis, Sonja
    Polylactide (PLA) is a high potential bioplastic that can replace oil-based plastics in a number of applications. To date, in spite of its known toxicity, a tin catalyst is used on industrial scale which should be replaced by a benign catalyst in the long run. Germanium is known to be unharmful while having similar properties as tin. Only few germylene catalysts are known so far and none has shown the potential for industrial application. We herein present Ge complexes in combination with zinc and copper, which show amazingly high polymerization activities for lactide in bulk at 150 °C. By systematical variation of the complex structure, proven by single-crystal XRD and DFT calculations, structure–property relationships are found regarding the polymerization activity. Even in the presence of zinc and copper, germanium acts as the active site for polymerizing probably through the coordination–insertion mechanism to high molar mass polymers. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Zwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications
    (Weinheim : Wiley-VCH, 2021) Saha, Pabitra; Ganguly, Ritabrata; Li, Xin; Das, Rohan; Singha, Nikhil K.; Pich, Andrij
    Zwitterionic polymers by virtue of their unique chemical and physical attributes have attracted researchers in recent years. The simultaneous presence of positive and negative charges in the same repeat unit renders them of various interesting properties such as superhydrophilicity, which has significantly broadened their scope for being used in different applications. Among polyzwitterions of different architectures, micro- and/or nano-gels have started receiving attention only until recently. These 3D cross-linked colloidal structures show peculiar characteristics in context to their solution properties, which are attributable either to the comonomers present or the presence of different electrolytes and biological specimens. In this review, a concise yet detailed account is provided of the different synthetic techniques and application domains of zwitterion-based micro- and/or nanogels that have been explored in recent years. Here, the focus is kept solely on the “polybetaines,” which have garnered maximum research interest and remain the extensively studied polyzwitterions in literature. While their vast application potential in the biomedical sector is being detailed here, some other areas of scope such as using them as microreactors for the synthesis of metal nanoparticles or making smart membranes for water-treatment are discussed in this minireview as well.
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    Biadhesive Peptides for Assembling Stainless Steel and Compound Loaded Micro-Containers
    (Weinheim : Wiley-VCH, 2019) Apitius, Lina; Buschmann, Sven; Bergs, Christian; Schönauer, David; Jakob, Felix; Pich, Andrij; Schwaneberg, Ulrich
    Biadhesive peptides (peptesives) are an attractive tool for assembling two chemically different materials—for example, stainless steel and polycaprolactone (PCL). Stainless steel is used in medical stents and PCL is used as a biodegradable polymer for fabrication of tissue growth scaffolds and drug delivering micro-containers. Biadhesive peptides are composed of two domains (e.g., dermaseptin S1 and LCI) with different material-binding properties that are separated through a stiff peptide-spacer. The peptesive dermaseptin S1-domain Z-LCI immobilizes antibiotic-loaded PCL micro-containers on stainless steel surfaces. Immobilization is visualized by microscopy and field emission scanning electron microscopy analysis and released antibiotic from the micro-containers is confirmed through growth inhibition of Escherichia coli cells.
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    Synthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization
    (Weinheim : Wiley-VCH, 2020) Xu, Wenjing; Rudov, Andrey; Oppermann, Alex; Wypysek, Sarah; Kather, Michael; Schroeder, Ricarda; Richtering, Walter; Potemkin, Igor I.; Wöll, Dominik; Pich, Andrij
    Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli-responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus-like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self-assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus-like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Heterolepic β‐Ketoiminate Zinc Phenoxide Complexes as Efficient Catalysts for the Ring Opening Polymerization of Lactide
    (Weinheim : Wiley-VCH, 2019) Ghosh, Swarup; Schäfer, Pascal M.; Dittrich, Dennis; Scheiper, Christoph; Steiniger, Phillip; Fink, Gerhard; Ksiazkiewicz, Agnieszka N.; Tjaberings, Alexander; Wölper, Christoph; Gröschel, André H.; Pich, Andrij; Herres‐Pawlis, Sonja; Schulz, Stephan
    Zinc phenoxide complexes L1ZnOAr 1–4 (L1=Me2NC2H4NC(Me)CHC(Me)O) and L2ZnOAr 5–8 (L2=Me2NC3H6NC(Me)CHC(Me)O) with donor-functionalized β-ketoiminate ligands (L1/2) and OAr substituents (Ar=Ph 1, 5; 2,6-Me2-C6H3 2, 6; 3,5-Me2-C6H3 3, 7; 4-Bu-C6H4 4, 8) with tuneable electronic and steric properties were synthesized and characterized. 1–8 adopt binuclear structures in the solid state except for 5, while they are monomeric in CDCl3 solution. 1–8 are active catalysts for the ring opening polymerization (ROP) of lactide (LA) in CH2Cl2 at ambient temperature and the catalytic activity is controlled by the electronic and steric properties of the OAr substituent, yielding polymers with high average molecular weight (Mn) and moderately controlled molecular weight distribution (MWDs). 1 and 5 showed a living polymerization character and kinetic studies on the ROP of L–LA with 1 and 5 proved first order dependencies on the monomer concentration. Homonuclear decoupled 1H-NMR analyses of polylactic acid (PLA) formed with rac-LA proved isotactic enrichment of the PLA microstructure. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Trypsin-Free Cultivation of 3D Mini-Tissues in an Adaptive Membrane Bioreactor
    (Weinheim : Wiley-VCH, 2020) Djeljadini, Suzana; Lohaus, Theresa; Gausmann, Marcel; Rauer, Sebastian; Kather, Michael; Krause, Bernd; Pich, Andrij; Möller, Martin; Wessling, Matthias
    The production of large scaffold-free tissues is a key challenge in regenerative medicine. Nowadays, temperature-responsive polymers allow intact tissue harvesting without needing proteolytic enzymes. This method is limited to tissue culture plastic with limited upscaling capacity and plain process control. Here, a thermoresponsive hollow fiber membrane bioreactor is presented to produce large scaffold-free tissues. Intact tissues, rich in cell-to-cell connections and ECM, are harvested from a poly(N-vinylcaprolactam) microgel functionalized poly(ether sulfone)/poly(vinylpyrrolidone) hollow fiber membrane by a temperature shift. The harvested 3D tissues adhere in successive cultivation and exhibit high vitality for several days. The facile adsorptive coating waives the need for extensive surface treatment. The research is anticipated to be a starting point for upscaling the production of interconnected tissues enabling new opportunities in regenerative medicine, large-scale drug screening on physiological relevant tissues, and potentially opening new chances in cell-based therapies. © 2020 The Authors. Advanced Biosystems published by Wiley-VCH GmbH
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    Impact of Reactive Amphiphilic Copolymers on Mechanical Properties and Cell Responses of Fibrin-Based Hydrogels
    (Weinheim : Wiley-VCH, 2020) Al Enezy-Ulbrich, Miriam Aischa; Malyaran, Hanna; de Lange, Robert Dirk; Labude, Norina; Plum, René; Rütten, Stephan; Terefenko, Nicole; Wein, Svenja; Neuss, Sabine; Pich, Andrij
    Mechanical properties of hydrogels can be modified by the variation of structure and concentration of reactive building blocks. One promising biological source for the synthesis of biocompatible hydrogels is fibrinogen. Fibrinogen is a glycoprotein in blood, which can be transformed enzymatically to fibrin playing an important role in wound healing and clot formation. In the present work, it is demonstrated that hybrid hydrogels with their improved mechanical properties, tunable internal structure, and enhanced resistance to degradation can be synthesized by a combination of fibrinogen and reactive amphiphilic copolymers. Water-soluble amphiphilic copolymers with tunable molecular weight and controlled amounts of reactive epoxy side groups are used as reactive crosslinkers to reinforce fibrin hydrogels. In the present work, copolymers that can influence the mechanical properties of fibrin-based hydrogels are used. The reactive copolymers increase the storage modulus of the hydrogels from 600 Pa to 30 kPa. The thickness of fibrin fibers is regulated by the copolymer concentration. It could be demonstrated that the fibrin-based hydrogels are biocompatible and support cell proliferation. Their degradation rate is considerably slower than that of native fibrin gels. In conclusion, fibrin-based hydrogels with tunable elasticity and fiber thickness useful to direct cell responses like proliferation and differentiation are produced. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim