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- ItemPros and Cons : Supramolecular or Macromolecular : What Is Best for Functional Hydrogels with Advanced Properties?(Weinheim : Wiley-VCH, 2020) Eelkema, Rienk; Pich, AndrijHydrogels 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
- ItemTuning 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, SvetlanaTemperature-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
- ItemUndiscovered 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, SonjaPolylactide (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.
- ItemMechanoresponsive diselenide-crosslinked microgels with programmed ultrasound-triggered degradation and radical scavenging ability for protein protection(Cambridge : RSC Publishing, 2022) Kharandiuk, Tetiana; Tan, Kok Hui; Xu, Wenjing; Weitenhagen, Fabian; Braun, Susanne; Göstl, Robert; Pich, AndrijIn the context of controlled delivery and release, proteins constitute a delicate class of cargo requiring advanced delivery platforms and protection. We here show that mechanoresponsive diselenide-crosslinked microgels undergo controlled ultrasound-triggered degradation in aqueous solution for the release of proteins. Simultaneously, the proteins are protected from chemical and conformational damage by the microgels, which disintegrate to water-soluble polymer chains upon sonication. The degradation process is controlled by the amount of diselenide crosslinks, the temperature, and the sonication amplitude. We demonstrate that the ultrasound-mediated cleavage of diselenide bonds in these microgels facilitates the release and activates latent functionality preventing the oxidation and denaturation of the encapsulated proteins (cytochrome C and myoglobin) opening new application possibilities in the targeted delivery of biomacromolecules.
- ItemZwitterionic 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, AndrijZwitterionic 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.
- ItemDual Stimuli-Responsive Self-Assembly Behavior of a Tailor-Made ABC-Type Amphiphilic Tri-Block Copolymer(Hoboken, NJ [u.a.] : Wiley, 2020) Pal, Sanjay; Kather, Michael; Banerjee, Sovan Lal; Saha, Pabitra; Pich, Andrij; Singha, Nikhil K.This investigation describes the synthesis of a dual stimuli-responsive, amphiphilic ABC tri-block copolymer (BCP) based on the functional monomers via RAFT polymerization. In this case, ABC-type BCP was prepared based on N-isopropylacrylamide, n-butyl acrylate, and 4-vinylpyridine in DMF solvent using cyanomethyl dodecyl trithiocarbonate as the RAFT agent and azobisisobutyronitrile as a thermal initiator in a subsequent macro-RAFT approach, respectively. The BCPs were characterized by SEC, 1H-NMR, FTIR spectroscopy, and DSC analyses. Temperature and pH-dependent properties of the smart BCP micelles in aqueous medium were investigated using dynamic light scattering. Transmission electron microscopic images were taken at cryogenic and dry conditions to study the morphology of molecular assemblies of block copolymers in an aqueous medium. The phase and topographical images were captured by atomic force microscopy to understand the assembly of block copolymers in solvents of different polarities. The morphology of BCP micelles was transformed from flower-like to spherical in the presence of solvents with different polarities (H2O or CHCl3). © 2020 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc.
- ItemSynthesis 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, AndrijControlling 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.
- ItemImpact 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, AndrijMechanical 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
- ItemThermoresponsive zwitterionic poly(phosphobetaine) microgels: Effect of macro-RAFT chain length and cross-linker molecular weight on their antifouling properties(New York, NY : Wiley, 2021) Saha, Pabitra; Palanisamy, Anand Raj; Santi, Marta; Ganguly, Ritabrata; Mondal, Somashree; Singha, Nikhil K.; Pich, AndrijAdsorption of proteins on biological surfaces is a detrimental phenomenon that reduces the work-life of the implants in various biomedical applications. Here, we synthesized a new class of thermoresponsive zwitterionic poly(phosphobetaine) (PMPC) microgel with excellent surface antifouling property by macro-RAFT mediated thiol-epoxy click reaction. End-group modified zwitterionic PMPC homopolymers with well-defined molecular weight and narrow dispersity were grafted onto poly(N-vinylcaprolactam-co-glycidyl methacrylate) (PVG) copolymer backbone followed by addition of a cross-linker, leading to microgel formation. While no upper critical solution temperature (UCST) was found in poly(N-vinylcaprolactam-co-glycidyl methacrylate-g-2-methacryloyloxyethyl phosphorylcholine) (PVGP) graft copolymers, the corresponding microgels exhibited both UCST and lower critical solution temperature (LCST) transitions, related to the swelling and collapse of PMPC and poly (N-vinylcaprolactam) (PVCL) components respectively. An increase in the molecular chain length of the PMPC increased the shifting of UCST and LCST of the microgels to higher temperatures, due to the ability of zwitterionic groups to coordinate a large number of water molecules. The effect of the variation in the molecular weights of amphiphilic poly(ethylene glycol) diamine (PEG-NH2) cross-linker was also reflected in both temperature and salt responsiveness of the microgels. The efficacy of the microgels as potential antifouling materials was further studied by fluorescence microscopy and XPS analysis on microgel coatings treated with FITC-BSA solution and pure BSA solution respectively. Lower protein adsorption was observed for microgels grafted with higher molecular chain length of PMPC, whereas, the microgels synthesized using higher molecular weight PEG-NH2 diamine cross-linker displayed greater protein adsorption on their surfaces.