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- ItemControlling Optical and Catalytic Activity of Genetically Engineered Proteins by Ultrasound(Weinheim : Wiley-VCH, 2021) Zhou, Yu; Huo, Shuaidong; Loznik, Mark; Göstl, Robert; Boersma, Arnold J.; Herrmann, AndreasUltrasound (US) produces cavitation-induced mechanical forces stretching and breaking polymer chains in solution. This type of polymer mechanochemistry is widely used for synthetic polymers, but not biomacromolecules, even though US is biocompatible and commonly used for medical therapy as well as in vivo imaging. The ability to control protein activity by US would thus be a major stepping-stone for these disciplines. Here, we provide the first examples of selective protein activation and deactivation by means of US. Using GFP as a model system, we engineer US sensitivity into proteins by design. The incorporation of long and highly charged domains enables the efficient transfer of force to the protein structure. We then use this principle to activate the catalytic activity of trypsin by inducing the release of its inhibitor. We expect that this concept to switch “on” and “off” protein activity by US will serve as a blueprint to remotely control other bioactive molecules. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemActivation of the Catalytic Activity of Thrombin for Fibrin Formation by Ultrasound(Weinheim : Wiley-VCH, 2021) Zhao, Pengkun; Huo, Shuaidong; Fan, Jilin; Chen, Junlin; Kiessling, Fabian; Boersma, Arnold J.; Göstl, Robert; Herrmann, AndreasThe regulation of enzyme activity is a method to control biological function. We report two systems enabling the ultrasound-induced activation of thrombin, which is vital for secondary hemostasis. First, we designed polyaptamers, which can specifically bind to thrombin, inhibiting its catalytic activity. With ultrasound generating inertial cavitation and therapeutic medical focused ultrasound, the interactions between polyaptamer and enzyme are cleaved, restoring the activity to catalyze the conversion of fibrinogen into fibrin. Second, we used split aptamers conjugated to the surface of gold nanoparticles (AuNPs). In the presence of thrombin, these assemble into an aptamer tertiary structure, induce AuNP aggregation, and deactivate the enzyme. By ultrasonication, the AuNP aggregates reversibly disassemble releasing and activating the enzyme. We envision that this approach will be a blueprint to control the function of other proteins by mechanical stimuli in the sonogenetics field. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemMulticolor Mechanofluorophores for the Quantitative Detection of Covalent Bond Scission in Polymers(Weinheim : Wiley-VCH, 2021) Baumann, Christoph; Stratigaki, Maria; Centeno, Silvia P.; Göstl, RobertThe fracture of polymer materials is a multiscale process starting with the scission of a single molecular bond advancing to a site of failure within the bulk. Quantifying the bonds broken during this process remains a big challenge yet would help to understand the distribution and dissipation of macroscopic mechanical energy. We here show the design and synthesis of fluorogenic molecular optical force probes (mechanofluorophores) covering the entire visible spectrum in both absorption and emission. Their dual fluorescent character allows to track non-broken and broken bonds in dissolved and bulk polymers by fluorescence spectroscopy and microscopy. Importantly, we develop an approach to determine the absolute number and relative fraction of intact and cleaved bonds with high local resolution. We anticipate that our mechanofluorophores in combination with our quantification methodology will allow to quantitatively describe fracture processes in materials ranging from soft hydrogels to high-performance polymers. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- 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
- ItemMechanochemical Release of Non-Covalently Bound Guests from a Polymer-Decorated Supramolecular Cage(Weinheim : Wiley-VCH, 2021) Küng, Robin; Pausch, Tobias; Rasch, Dustin; Göstl, Robert; Schmidt, Bernd M.Supramolecular coordination cages show a wide range of useful properties including, but not limited to, complex molecular machine-like operations, confined space catalysis, and rich host–guest chemistries. Here we report the uptake and release of non-covalently encapsulated, pharmaceutically-active cargo from an octahedral Pd cage bearing polymer chains on each vertex. Six poly(ethylene glycol)-decorated bipyridine ligands are used to assemble an octahedral PdII6(TPT)4 cage. The supramolecular container encapsulates progesterone and ibuprofen within its hydrophobic nanocavity and is activated by shear force produced by ultrasonication in aqueous solution entailing complete cargo release upon rupture, as shown by NMR and GPC analyses. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemMethods for Exerting and Sensing Force in Polymer Materials Using Mechanophores(Weinheim : Wiley-VCH, 2020) Stratigaki, Maria; Göstl, RobertIn recent years, polymer mechanochemistry has evolved as a methodology to provide insights into the action-reaction relationships of polymers and polymer-based materials and composites in terms of macroscopic force application (stress) and subsequent deformation (strain) through a mechanophore-assisted coupling of mechanical and chemical phenomena. The perplexity of the process, however, from the viewpoint of mechanophore activation via a molecular-scaled disruption of the structure that yields a macroscopically detectable optical signal, renders this otherwise rapidly evolving field challenging. Motivated by this, we highlight here recent advancements of polymer mechanochemistry with particular focus on the establishment of methodologies for the efficient activation and quantification of mechanophores and anticipate to aptly pinpoint unresolved matters and limitations of the respective approaches, thus highlighting possible developments. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemGoing with the Flow : Tunable Flow-Induced Polymer Mechanochemistry(Weinheim : Wiley-VCH, 2020) Willis-Fox, Niamh; Rognin, Etienne; Baumann, Christoph; Aljohani, Talal A.; Göstl, Robert; Daly, RonanMechanical forces can drive chemical transformations in polymers, directing reactions along otherwise inaccessible pathways, providing exciting possibilities for developing smart, responsive materials. The state-of-the-art test for solution-based polymer mechanochemistry development is ultrasonication. However, this does not accurately model the forces that will be applied during device fabrication using processes such as 3D printing or spray coating. Here, a step is taken toward predictably translating mechanochemistry from molecular design to manufacturing by demonstrating a highly controlled nozzle flow setup in which the shear forces being delivered are precisely tuned. The results show that solvent viscosity, fluid strain rate, and the nature of the breaking bond can be individually studied. Importantly, it is shown that the influence of each is different to that suggested by ultrasonication (altered quantity of chain breakage and critical polymer chain length). Significant development is presented in the understanding of polymer bond breakage during manufacturing flows to help guide design of active components that trigger on demand. Using an anthracene-based mechanophore, the triggering of a fluorescence turn-on is demonstrated through careful selection of the flow parameters. This work opens the avenue for programmed chemical transformations during inline manufacturing processes leading to tunable, heterogeneous final products from a single source material. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim