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- ItemReversibly Photo-Modulating Mechanical Stiffness and Toughness of Bioengineered Protein Fibers(Weinheim : Wiley-VCH, 2020) Sun, Jing; Ma, Chao; Maity, Sourav; Wang, Fan; Zhou, Yu; Portale, Giuseppe; Göstl, Robert; Roos, Wouter H.; Zhang, Hongjie; Liu, Kai; Herrmann, AndreasLight-responsive materials have been extensively studied due to the attractive possibility of manipulating their properties with high spatiotemporal control in a non-invasive fashion. This stimulated the development of a series of photo-deformable smart devices. However, it remained a challenge to reversibly modulate the stiffness and toughness of bulk materials. Here, we present bioengineered protein fibers and their optomechanical manipulation by employing electrostatic interactions between supercharged polypeptides (SUPs) and an azobenzene (Azo)-based surfactant. Photo-isomerization of the Azo moiety from the E- to Z-form reversibly triggered the modulation of tensile strength, stiffness, and toughness of the bulk protein fiber. Specifically, the photo-induced rearrangement into the Z-form of Azo possibly strengthened cation–π interactions within the fiber material, resulting in an around twofold increase in the fiber's mechanical performance. The outstanding mechanical and responsive properties open a path towards the development of SUP-Azo fibers as smart stimuli-responsive mechano-biomaterials. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemModular and Versatile Trans-Encoded Genetic Switches(Weinheim : Wiley-VCH, 2020) Paul, Avishek; Warszawik, Eliza M.; Loznik, Mark; Boersma, Arnold J.; Herrmann, AndreasCurrent bacterial RNA switches suffer from lack of versatile inputs and are difficult to engineer. We present versatile and modular RNA switches that are trans-encoded and based on tRNA-mimicking structures (TMSs). These switches provide a high degree of freedom for reengineering and can thus be designed to accept a wide range of inputs, including RNA, small molecules, and proteins. This powerful approach enables control of the translation of protein expression from plasmid and genome DNA. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
- ItemFour-Dimensional Deoxyribonucleic Acid–Gold Nanoparticle Assemblies(Weinheim : Wiley-VCH, 2020) Luo, Ming; Xuan, Mingjun; Huo, Shuaidong; Fan, Jilin; Chakraborty, Gurudas; Wang, Yixi; Zhao, Hui; Herrmann, Andreas; Zheng, LifeiOrganization of gold nanoobjects by oligonucleotides has resulted in many three-dimensional colloidal assemblies with diverse size, shape, and complexity; nonetheless, autonomous and temporal control during formation remains challenging. In contrast, living systems temporally and spatially self-regulate formation of functional structures by internally orchestrating assembly and disassembly kinetics of dissipative biomacromolecular networks. We present a novel approach for fabricating four-dimensional gold nanostructures by adding an additional dimension: time. The dissipative character of our system is achieved using exonuclease III digestion of deoxyribonucleic acid (DNA) fuel as an energy-dissipating pathway. Temporal control over amorphous clusters composed of spherical gold nanoparticles (AuNPs) and well-defined core–satellite structures from gold nanorods (AuNRs) and AuNPs is demonstrated. Furthermore, the high specificity of DNA hybridization allowed us to demonstrate selective activation of the evolution of multiple architectures of higher complexity in a single mixture containing small and larger spherical AuNPs and AuNRs. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
- ItemAtomic layer deposition for efficient oxygen evolution reaction at Pt/Ir catalyst layers(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2020) Schlicht, Stefanie; Percin, Korcan; Kriescher, Stefanie; Hofer, André; Weidlich, Claudia; Wessling, Matthias; Bachmann, JulienWe provide a direct comparison of two distinct methods of Ti felt surface treatment and Pt/Ir electrocatalyst deposition for the positive electrode of regenerative fuel cells and vanadium-air redox flow batteries. Each method is well documented in the literature, and this paper provides a direct comparison under identical experimental conditions of electrochemical measurements and in identical units. In the first method, based on classical engineering, the bimetallic catalyst is deposited by dip-coating in a precursor solution of the salts followed by their thermal decomposition. In the alternative method, more academic in nature, atomic layer deposition (ALD) is applied to the felts after anodization. ALD allows for a controlled coating with ultralow noble-metal loadings in narrow pores. In acidic electrolyte, the ALD approach yields improved mass activity (557 A·g-1 as compared to 80 A·g-1 at 0.39 V overpotential) on the basis of the noble-metal loading, as well as improved stability. © 2020 Schlicht et al.
- ItemEnlightening Materials with Photoswitches(Weinheim : Wiley-VCH, 2020) Goulet-Hanssens, Alexis; Eisenreich, Fabian; Hecht, StefanIncorporating molecular photoswitches into various materials provides unique opportunities for controlling their properties and functions with high spatiotemporal resolution using remote optical stimuli. The great and largely still untapped potential of these photoresponsive systems has not yet been fully exploited due to the fundamental challenges in harnessing geometrical and electronic changes on the molecular level to modulate macroscopic and bulk material properties. Herein, progress made during the past decade in the field of photoswitchable materials is highlighted. After pointing to some general design principles, materials with an increasing order of the integrated photoswitchable units are discussed, spanning the range from amorphous settings over surfaces/interfaces and supramolecular ensembles, to liquid crystalline and crystalline phases. Finally, some potential future directions are pointed out in the conclusion. In view of the exciting recent achievements in the field, the future emergence and further development of light-driven and optically programmable (inter)active materials and systems are eagerly anticipated. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemWet-Spinning of Biocompatible Core–Shell Polyelectrolyte Complex Fibers for Tissue Engineering(Weinheim : Wiley-VCH, 2020) Cui, Qing; Bell, Daniel Josef; Rauer, Sebastian Bernhard; Wessling, MatthiasPolyelectrolyte complex fibers (PEC fibers) have great potential with regard to biomedical applications as they can be fabricated from biocompatible and water-soluble polyelectrolytes under mild process conditions. The present publication describes a novel method for the continuous fabrication of PEC fibers in a water-based wet-spinning process by interfacial complexation within a core–shell spinneret. This process combines the robustness and flexibility of nonsolvent-induced phase separation (NIPS) spinning processes conventionally used in the membrane industry with the complexation between oppositely charged polyelectrolytes. The produced fibers demonstrate a core–shell structure with a low-density core and a highly porous polyelectrolyte complex shell of ≈800 μm diameter. In the case of chitosan and polystyrene sulfonate (PSS), mechanical fiber properties could be enhanced by doping the PSS with poly(ethylene oxide) (PEO). The resulting CHI/PSS-PEO fibers present a Young modulus of 3.78 GPa and a tensile strength of 165 MPa, which is an excellent combination of elongation at break and break stress compared to literature. The suitability of the CHI/PSS-PEO fibers as a scaffold for cell culture applications is verified by a four-day cultivation of human HeLa cells on PEO-reinforced fibers with a subsequent analysis of cell viability by fluorescence-based live/dead assay. © 2020 The Authors. Published by Wiley-VCH GmbH
- 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
- ItemHow Much Physical Guidance is Needed to Orient Growing Axons in 3D Hydrogels?(Weinheim : Wiley-VCH, 2020) Rose, Jonas C.; Gehlen, David B.; Omidinia-Anarkoli, Abdolrahman; Fölster, Maaike; Haraszti, Tamás; Jaekel, Esther E.; De Laporte, LauraDirecting cells is essential to organize multi-cellular organisms that are built up from subunits executing specific tasks. This guidance requires a precisely controlled symphony of biochemical, mechanical, and structural signals. While many guiding mechanisms focus on 2D structural patterns or 3D biochemical gradients, injectable material platforms that elucidate how cellular processes are triggered by defined 3D physical guiding cues are still lacking but crucial for the repair of soft tissues. Herein, a recently developed anisotropic injectable hybrid hydrogel (Anisogel) contains rod-shaped microgels that orient in situ by a magnetic field and has propelled studying 3D cell guidance. Here, the Anisogel is used to investigate the dependence of axonal guidance on microgel dimensions, aspect ratio, and distance. While large microgels result in high material anisotropy, they significantly reduce neurite outgrowth and thus the guidance efficiency. Narrow and long microgels enable strong axonal guidance with maximal outgrowth including cell sensing over distances of tens of micrometers in 3D. Moreover, nerve cells decide to orient inside the Anisogel within the first three days, followed by strengthening of the alignment, which goes along with oriented fibronectin deposition. These findings demonstrate the potential of the Anisogel to tune structural and mechanical parameters for specific applications. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemDigitally Fabricated and Naturally Augmented In Vitro Tissues(Weinheim : Wiley-VCH, 2020) Duarte Campos, Daniela F.; De Laporte, LauraHuman in vitro tissues are extracorporeal 3D cultures of human cells embedded in biomaterials, commonly hydrogels, which recapitulate the heterogeneous, multiscale, and architectural environment of the human body. Contemporary strategies used in 3D tissue and organ engineering integrate the use of automated digital manufacturing methods, such as 3D printing, bioprinting, and biofabrication. Human tissues and organs, and their intra- and interphysiological interplay, are particularly intricate. For this reason, attentiveness is rising to intersect materials science, medicine, and biology with arts and informatics. This report presents advances in computational modeling of bioink polymerization and its compatibility with bioprinting, the use of digital design and fabrication in the development of fluidic culture devices, and the employment of generative algorithms for modeling the natural and biological augmentation of in vitro tissues. As a future direction, the use of serially linked in vitro tissues as human body-mimicking systems and their application in drug pharmacokinetics and metabolism, disease modeling, and diagnostics are discussed. © 2020 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH
- ItemSelective hydrogenation of fluorinated arenes using rhodium nanoparticles on molecularly modified silica(London : RSC Publ., 2020) Kacem, Souha; Emondts, Meike; Bordet, Alexis; Leitner, WalterThe production of fluorinated cyclohexane derivatives is accomplished through the selective hydrogenation of readily available fluorinated arenes using Rh nanoparticles on molecularly modified silica supports (Rh@Si-R) as highly effective and recyclable catalysts. The catalyst preparation comprises grafting non-polar molecular entities on the SiO2 surface generating a hydrophobic environment for controlled deposition of well-defined rhodium particles from a simple organometallic precursor. A broad range of fluorinated cyclohexane derivatives was shown to be accessible with excellent efficacy (0.05-0.5 mol% Rh, 10-55 bar H2, 80-100 °C, 1-2 h), including industrially relevant building blocks. Addition of CaO as scavenger for trace amounts of HF greatly improves the recyclability of the catalytic system and prevents the risks associated to the presence of HF, without compromising the activity and selectivity of the reaction. © The Royal Society of Chemistry.