Publications by authors named "Andreas Walther"

195 Publications

Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues.

Polymers (Basel) 2021 May 20;13(10). Epub 2021 May 20.

Laboratory for Sensors, Institute of Microsystems Engineering IMTEK, University of Freiburg, 79110 Freiburg, Germany.

Soft tissues are commonly fiber-reinforced hydrogel composite structures, distinguishable from hard tissues by their low mineral and high water content. In this work, we proposed the development of 3D printed hydrogel constructs of the biopolymers chitosan (CHI) and cellulose nanofibers (CNFs), both without any chemical modification, which processing did not incorporate any chemical crosslinking. The unique mechanical properties of native cellulose nanofibers offer new strategies for the design of environmentally friendly high mechanical performance composites. In the here proposed 3D printed bioinspired CNF-filled CHI hydrogel biomaterials, the chitosan serves as a biocompatible matrix promoting cell growth with balanced hydrophilic properties, while the CNFs provide mechanical reinforcement to the CHI-based hydrogel. By means of extrusion-based printing (EBB), the design and development of 3D functional hydrogel scaffolds was achieved by using low concentrations of chitosan (2.0-3.0% ()) and cellulose nanofibers (0.2-0.4% ()). CHI/CNF printed hydrogels with good mechanical performance (Young's modulus 3.0 MPa, stress at break 1.5 MPa, and strain at break 75%), anisotropic microstructure and suitable biological response, were achieved. The CHI/CNF composition and processing parameters were optimized in terms of 3D printability, resolution, and quality of the constructs (microstructure and mechanical properties), resulting in good cell viability. This work allows expanding the library of the so far used biopolymer compositions for 3D printing of mechanically performant hydrogel constructs, purely based in the natural polymers chitosan and cellulose, offering new perspectives in the engineering of mechanically demanding hydrogel tissues like intervertebral disc (IVD), cartilage, meniscus, among others.
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http://dx.doi.org/10.3390/polym13101663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8160918PMC
May 2021

Short term cognitive function after sevoflurane anesthesia in patients suspect to obstructive sleep apnea syndrome: an observational study.

BMC Anesthesiol 2021 May 18;21(1):150. Epub 2021 May 18.

Philipps-University Marburg Department of Anesthesia and Intensive Care, University Hospital Giessen-Marburg, Marburg Campus, Baldingerstraße, 35033, Marburg, Germany.

Background: The obstructive sleep apnea syndrome (OSAS) is characterized by intermittent cerebral hypoxia which can cause cognitive alterations. Likewise, hypoxia induced neurocognitive deficits are detectable after general anesthesia using volatile anesthetics. The objective of this study was to evaluate the association between a moderate to high risk patients of OSAS and postoperative cognitive dysfunction after volatile anesthesia.

Methods: In this single center prospective, observational study between May 2013 and September 2013, 46 patients aged 55 to 80 years with an estimated hospital stay of at least 3 days undergoing surgery were enrolled. Patients were screened using the STOP-BANG test with score of 3 or higher indicating moderate to high risk of OSAS. The cognitive function was assessed using a neuropsychological assessment battery, including the DemTect test for cognitive impairment among other tests e.g. SKT memory, the day before surgery and within 2 days after extubation.

Results: Twenty-three of the 46 analyzed patients were identified with a moderate to high risk of OSAS. When comparing post- to preoperative phase a significant better performance for the SKT was found for both groups (p <  0.001). While the moderate to high risk group scores increased postoperative in the DemTect test, they decreased in the low risk group (p <  0.003). When comparing the changes between groups, the moderate to high risk patients showed significant better test result for DemTect testing after anaesthesia. This effect remained robust when adjusting for potential confounding variables using a two-factor ANOVA.

Conclusion: Compared to low risk, a moderate to high risk of OSAS based on the STOP-BANG score was associated with improved postoperative cognitive function measured by the DemTect test.

Trial Registration: The study was approved by the local Ethics committee (Ethikkommission der Medizinischen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany) (reference number: 87_12 B ) on 19.04.2012.
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http://dx.doi.org/10.1186/s12871-021-01363-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8130360PMC
May 2021

Spinodal decomposition of chemically fueled polymer solutions.

Soft Matter 2021 Jun;17(21):5401-5409

A3BMS Lab, Department of Chemistry, University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany. and Cluster of Excellence livMatS @ FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany.

Out-of-equilibrium phase transitions driven by dissipation of chemical energy are a common mechanism for morphological organization and temporal programming in biology. Inspired by this, dissipative self-assembly utilizes chemical reaction networks (CRNs) that consume high-energy molecules (chemical fuels) to generate transient structures and functionality. While a wide range of chemical fuels and building blocks are now available for chemically fueled systems, so far little attention has been paid to the phase-separation process itself. Herein, we investigate the chemically fueled spinodal decomposition of poly(norbornene dicarboxylic acid) (PNDAc) solution, which is driven by a cyclic chemical reaction network. Our analysis encompasses both the molecular level in terms of the CRN, but also the phase separation process. We investigate the morphology of formed domains, as well as the kinetics and mechanism of domain growth, and develop a kinetic/thermodynamic hybrid model to not only rationalize the dependence of the system on fuel concentration and pH, but also open pathways towards predictive design of future fueled polymer systems.
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http://dx.doi.org/10.1039/d1sm00515dDOI Listing
June 2021

A Modular Fluorescent Probe for Viscosity and Polarity Sensing in DNA Hybrid Mesostructures.

Adv Sci (Weinh) 2021 Mar 23;8(5):2003740. Epub 2020 Dec 23.

Institute for Macromolecular Chemistry University of Freiburg Stefan-Meier-Straße 31 Freiburg 79104 Germany.

There exists a critical need in biomedical molecular imaging and diagnostics for molecular sensors that report on slight changes to their local microenvironment with high spatial fidelity. Herein, a modular fluorescent probe, termed StyPy, is rationally designed which features i) an enormous and tunable Stokes shift based on twisted intramolecular charge transfer (TICT) processes with no overlap, a broad emission in the far-red/near-infrared (NIR) region of light and extraordinary quantum yields of fluorescence, ii) a modular applicability via facile -fluoro-thiol reaction (PFTR), and iii) a polarity- and viscosity-dependent emission. This renders StyPy as a particularly promising molecular sensor. Based on the thorough characterization on the molecular level, StyPy reports on the viscosity change in all-DNA microspheres and indicates the hydrophilic and hydrophobic compartments of hybrid DNA-based mesostructures consisting of latex beads embedded in DNA microspheres. Moreover, the enormous Stokes shift of StyPy enables one to detect multiple fluorophores, while using only a single laser line for excitation in DNA protocells. The authors anticipate that the presented results for multiplexing information are of direct importance for advanced imaging in complex soft matter and biological systems.
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http://dx.doi.org/10.1002/advs.202003740DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927630PMC
March 2021

pH Feedback Lifecycles Programmed by Enzymatic Logic Gates Using Common Foods as Fuels.

Angew Chem Int Ed Engl 2021 05 7;60(20):11398-11405. Epub 2021 Apr 7.

Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31, 79104, Freiburg, Germany.

Artificial temporal signaling systems, which mimic living out-of-equilibrium conditions, have made large progress. However, systems programmed by enzymatic reaction networks in multicomponent and unknown environments, and using biocompatible components remain a challenge. Herein, we demonstrate an approach to program temporal pH signals by enzymatic logic gates. They are realized by an enzymatic disaccharide-to-monosaccharide-to-sugar acid reaction cascade catalyzed by two metabolic chains: invertase-glucose oxidase and β-galactosidase-glucose oxidase, respectively. Lifetimes of the transient pH signal can be programmed from less than 15 min to more than 1 day. We study enzymatic kinetics of the reaction cascades and reveal the underlying regulatory mechanisms. Operating with all-food grade chemicals and coupling to self-regulating hydrogel, our system is quite robust to work in a complicated medium with unknown components and in a biocompatible fashion.
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http://dx.doi.org/10.1002/anie.202017003DOI Listing
May 2021

Electrical switching of high-performance bioinspired nanocellulose nanocomposites.

Nat Commun 2021 02 26;12(1):1312. Epub 2021 Feb 26.

Institute for Macromolecular Chemistry, University of Freiburg, Freiburg, Germany.

Nature fascinates with living organisms showing mechanically adaptive behavior. In contrast to gels or elastomers, it is profoundly challenging to switch mechanical properties in stiff bioinspired nanocomposites as they contain high fractions of immobile reinforcements. Here, we introduce facile electrical switching to the field of bioinspired nanocomposites, and show how the mechanical properties adapt to low direct current (DC). This is realized for renewable cellulose nanofibrils/polymer nanopapers with tailor-made interactions by deposition of thin single-walled carbon nanotube electrode layers for Joule heating. Application of DC at specific voltages translates into significant electrothermal softening via dynamization and breakage of the thermo-reversible supramolecular bonds. The altered mechanical properties are reversibly switchable in power on/power off cycles. Furthermore, we showcase electricity-adaptive patterns and reconfiguration of deformation patterns using electrode patterning techniques. The simple and generic approach opens avenues for bioinspired nanocomposites for facile application in adaptive damping and structural materials, and soft robotics.
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http://dx.doi.org/10.1038/s41467-021-21599-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7910463PMC
February 2021

Recyclable and Light-Adaptive Vitrimer-Based Nacre-Mimetic Nanocomposites.

ACS Nano 2021 03 25;15(3):5043-5055. Epub 2021 Feb 25.

Department of Chemistry, University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.

Nacre's natural design consists of a perfect hierarchical assembly that resembles a brick-and-mortar structure with synergistic stiffness and toughness. The field of bioinspired materials often provides attractive architecture and engineering pathways which allow to explore outstanding property areas. However, the study of nacre-mimetic materials should not be limited to the design of its architecture but ought to include the understanding, operation, and improvement of internal interactions between their components. Here, we introduce a vitrimer prepolymer system that, once integrated into the nacre-mimetic nanocomposites, cures and cross-links with the presence of Lewis acid catalyst and further manifests associative dynamic exchange reactions. Bond exchanges are controllable by molecular composition and catalyst content and characterized by creep, shear-lag, and shape-locking tests. We exploit the vitrimer properties by laminating 70 films into thick bulk materials, and characterize the flexural resistance and crack propagation. More importantly, we introduce recycling by grinding and hot-pressing. The recycling for highly reinforced nacre-mimetic nanocomposites is critically enabled by the vitrimer chemistry and improves the sustainability of bioinspired nanocomposites in cyclic economy. Finally, we integrate photothermal converters into the structures and use laser irradiation as external trigger to activate the vitrimer exchange reactions.
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http://dx.doi.org/10.1021/acsnano.0c10001DOI Listing
March 2021

Multivalency Pattern Recognition to Sort Colloidal Assemblies.

Small 2021 Feb 15;17(5):e2005668. Epub 2021 Jan 15.

Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Strasse 31, 79104, Freiburg, Germany.

Multivalent interaction is an important principle for self-assembly and has been widely used to assemble colloids. However, surface binding partners are statistically distributed, which falls short of the interaction possibilities arising from geometrically controlled multivalency patterns as seen in viruses. Herein, the precision provided by 3D DNA origami is exploited to introduce multivalency pattern recognition via designing geometrically precise interaction patterns at patches of patchy nanocylinders. This gives rise to self-sorting of colloidal assemblies despite having the same type and number of supramolecular binding motifs-solely based on the pattern located on a 20 × 20 nm cross-section. The degree of sorting can be modulated by the geometric overlap of patterns and homo; mixed and alternating supracolloidal polymerizations are demonstrated. Multivalency patterns are able to provide an additional information layer to organize soft matter, important towards engineering of biological responses and functional materials design.
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http://dx.doi.org/10.1002/smll.202005668DOI Listing
February 2021

Modular functionalization and hydrogel formation red-shifted and self-reporting [2+2] cycloadditions.

Chem Commun (Camb) 2021 Jan;57(6):805-808

Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany. and Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg, Germany and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany and Cluster of Excellence livMatS @ FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, D-79110 Freiburg, Germany and A3BMS Lab, Department of Chemistry, University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.

We present a modularly applicable, red-shifted and self-reporting photodynamic covalent crosslinker, abbreviated qStyPy, that performs [2+2] cycloadditions upon irradiation with 470 nm in water. The rational design of qStyPy increases its hydrophilicity due to a permanent charge and features a broad emission in the far-red/near-infrared regime as a readout for the cycloadduct formation, rendering qStyPy suitable for biomedical applications.
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http://dx.doi.org/10.1039/d0cc07429bDOI Listing
January 2021

Room-Temperature Phosphorescence Enabled through Nacre-Mimetic Nanocomposite Design.

Adv Mater 2021 Feb 21;33(5):e2005973. Epub 2020 Dec 21.

A3BMS Lab-Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, Freiburg, 79104, Germany.

A generic, facile, and waterborne strategy is introduced to fabricate flexible, low-cost nanocomposite films with room-temperature phosphorescence (RTP) by incorporating waterborne RTP polymers into self-assembled bioinspired polymer/nanoclay nanocomposites. The excellent oxygen barrier of the lamellar nanoclay structure suppresses the quenching effect from ambient oxygen (k ) and broadens the choice of polymer matrices towards lower glass transition temperature (T ), while providing better mechanical properties and processability. Moreover, the oxygen permeation and diffusion inside the films can be fine-tuned by varying the polymer/nanoclay ratio, enabling programmable retention times of the RTP signals, which is exploited for transient information storage and anti-counterfeiting materials. Additionally, anti-interception materials are showcased by tracing the interception-induced oxygen history that interferes with the preset self-erasing time. Merging bioinspired nanocomposite design with RTP materials contributes to overcoming the inherent limitations of molecular design of organic RTP compounds, and allows programmable temporal features to be added into RTP materials by controlled mesostructures. This will assist in paving the way for practical applications of RTP materials as novel anti-counterfeiting materials.
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http://dx.doi.org/10.1002/adma.202005973DOI Listing
February 2021

Chemically Fueled Volume Phase Transition of Polyacid Microgels.

Angew Chem Int Ed Engl 2021 03 24;60(13):7117-7125. Epub 2021 Feb 24.

A3BMS Lab, Department of Chemistry, University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany.

Microgels are soft colloids that show responsive behavior and are easy to functionalize for applications. They are considered key components for future smart colloidal material systems. However, so far microgel systems have almost exclusively been studied in classical responsive switching settings using external triggers, while internally organized, autonomous control mechanisms as found in supramolecular chemistry and DNA nanotechnology relying on fuel-driven out-of-equilibrium concepts have not been implemented into microgel systems. Here, we introduce chemically fueled transient volume phase transitions (VPTs) for poly(methacrylic acid) (PMAA) microgels, where the collapsed hydrophobic state can be programmed using the fuel concentration in a cyclic reaction network. We discuss details of the system behavior as a function of pH and fuel amount, unravel kinetically trapped regions and showcase transient encapsulation and time-programmed release as a first application.
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http://dx.doi.org/10.1002/anie.202014417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048534PMC
March 2021

Fuel-Driven Transient DNA Strand Displacement Circuitry with Self-Resetting Function.

J Am Chem Soc 2020 12 2;142(50):21102-21109. Epub 2020 Dec 2.

Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany.

Toehold-mediated DNA strand displacement (DSD) is a powerful strategy to engineer dynamics in DNA-based devices and for molecular computing. However, facile strategies for autonomously self-resettable DSD cascades with programmable lifetimes are still missing. Here, we concatenate an ATP-powered ligation/restriction network with toehold-mediated DSD reactions realizing ATP-driven transient DSD with self-resetting behavior. The ATP-fueled ligation biases strand displacement reactions by increasing the toehold length and increasing the local concentration by covalent fixation, while the concurrent endonuclease restriction eliminates this bias, allowing to reset the system. The lifetimes and adaptive dynamic steady states for the DSD are engineered by the ATP-fueled uphill-driven nonequilibrium ligation/restriction system. By programming the toeholds for downstream DSD reaction networks, we realize ATP-fueled transient DSD cascades. A higher level of fuel-driven automaton is achieved by combining two subsystems for the transient DSD, where the expelled strands are each other's input strands and the restriction-induced double-stranded DNA melting resets the systems.
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http://dx.doi.org/10.1021/jacs.0c09681DOI Listing
December 2020

The Influence of Workload and Work Flexibility on Work-Life Conflict and the Role of Emotional Exhaustion.

Behav Sci (Basel) 2020 Nov 16;10(11). Epub 2020 Nov 16.

Clinical Psychology and Psychotherapy, Department of Psychology, University of Zurich, 8006 Zürich, Switzerland.

The purpose of this study is to examine the relationship between contextual work-related factors in terms of job demands (workload-) and job resources (work flexibility-), work-life conflict () and the burnout dimension emotional exhaustion () in a large population-based sample. Building on the job demands resources model (JDRM), we have developed the hypothesis that has an indirect effect on that is mediated by We conducted a secondary analysis using data from the Dresden Burnout Study (DBS, = 4246, mean age (SD) = 42.7 years (10.5); 36.4% male). Results from structural equation modelling revealed that is positively associated with (β = 0.15, = 0.001) and negatively associated with (β = -0.13, = 0.001), also after accounting for potential confounding variables (demography, depressive symptoms, and lifetime diagnosis of burnout). Both effects are mediated by ( = 0.18; = 0.001 and = 0.08; = 0.001, respectively) highlighting the important role of in employee health. In summary, may help to reduce burnout symptoms in employees, whereas may increase them. Study results suggest that both associations depend on levels.
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http://dx.doi.org/10.3390/bs10110174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697797PMC
November 2020

Wavelength-Gated Adaptation of Hydrogel Properties via Photo-Dynamic Multivalency in Associative Star Polymers.

Angew Chem Int Ed Engl 2021 02 21;60(8):4358-4367. Epub 2020 Dec 21.

A3BMS Lab-Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104, Freiburg, Germany.

Responsive materials, such as switchable hydrogels, have been largely engineered for maximum changes between two states. In contrast, adaptive systems target distinct functional plateaus between these maxima. Here, we demonstrate how the photostationary state (PSS) of an E/Z-arylazopyrazole photoswitch can be tuned by the incident wavelength across a wide color spectrum, and how this behavior can be exploited to engineer the photo-dynamic mechanical properties of hydrogels based on multivalent photoswitchable interactions. We show that these hydrogels adapt to the wavelength-dependent PSS and the number of arylazopyrazole units by programmable relationships. Hence, our material design enables the facile adjustment of the mechanical properties without laborious synthetic efforts. The concept goes beyond the classical switching from state A to B, and demonstrates pathways for a truly wavelength-gated adaptation of hydrogel properties potentially useful to engineer cell fate or in soft robotics.
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http://dx.doi.org/10.1002/anie.202011592DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898538PMC
February 2021

A simple experimental method for measuring the thermal sensitivity of single-mode fibers.

Rev Sci Instrum 2020 Oct;91(10):105114

Department of Physics, Lund University, P.O. Box 118, SE-22100 Lund, Sweden.

We present a simple technique to experimentally determine the optical-path length change with temperature for optical single-mode fibers. Standard single-mode fibers act as natural low-finesse cavities, with the Fresnel reflection of the straight cleaved surfaces being ∼3%, for the laser light coupled to them. By measuring the intensity variations due to interference of light reflected from the fiber front and end surfaces, while ramping the ambient temperature, the thermal sensitivity of the optical-path length of the fiber can be derived. Light was generated by a narrow linewidth, low drift laser. With our fairly short test fibers, we found that it was possible to reach a relative precision of the temperature sensitivity, compared to a reference fiber, on the 0.4%-2% scale and an absolute precision of 2%-5%, with the potential to improve both by an order of magnitude. The results for single-acrylate, dual-acrylate, and copper- and aluminum-coated fibers are presented. Values are compared with analytic models and results from a finite element method simulation. With the aid of these measurements, a simple fiber-interferometer, which is insensitive to thermal drifts, could be constructed.
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http://dx.doi.org/10.1063/5.0020913DOI Listing
October 2020

Autonomous Transient pH Flips Shaped by Layered Compartmentalization of Antagonistic Enzymatic Reactions.

Angew Chem Int Ed Engl 2021 02 16;60(7):3619-3624. Epub 2020 Dec 16.

A3BMS Lab-Active Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31, 79104, Freiburg, Germany.

Transient signaling orchestrates complex spatiotemporal behaviour in living organisms via (bio)chemical reaction networks (CRNs). Compartmentalization of signal processing is an important aspect for controlling such networks. However, artificial CRNs mostly focus on homogeneous solutions to program autonomous self-assembling systems, which limits their accessible behaviour and tuneability. Here, we introduce layered compartments housing antagonistic pH-modulating enzymes and demonstrate that transient pH signals in a supernatant solution can be programmed based on spatial delays. This overcomes limitations of activity mismatches of antagonistic enzymes in solution and allows to flexibly program acidic and alkaline pH lifecycles beyond the possibilities of homogeneous solutions. Lag time, lifetime, and the pH minima and maxima can be precisely programmed by adjusting spatial and kinetic conditions. We integrate these spatially controlled pH flips with switchable peptides, furnishing time-programmed self-assemblies and hydrogel material system.
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http://dx.doi.org/10.1002/anie.202009542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898518PMC
February 2021

Self-Assembled Bioinspired Nanocomposites.

Acc Chem Res 2020 11 29;53(11):2622-2635. Epub 2020 Sep 29.

A3BMS Lab-Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany.

Bioinspired materials engineering impacts the design of advanced functional materials across many domains of sciences from wetting behavior to optical and mechanical materials. In all cases, the advances in understanding how biology uses hierarchical design to create failure and defect-tolerant materials with emergent properties lays the groundwork for engaging into these topics. Biological mechanical materials are particularly inspiring for their unique combinations of stiffness, strength, and toughness together with lightweightness, as assembled and grown in water from a limited set of building blocks at room temperature. Wood, nacre, crustacean cuticles, and spider silk serve as some examples, where the correct arrangement of constituents and balanced molecular energy dissipation mechanisms allows overcoming the shortcomings of the individual components and leads to synergistic materials performance beyond additive behavior. They constitute a paradigm for future structural materials engineering-in the formation process, the use of sustainable building blocks and energy-efficient pathways, as well as in the property profiles-that will in the long term allow for new classes of high-performance and lightweight structural materials needed to promote energy efficiency in mobile technologies.This Account summarizes our efforts of the past decade with respect to designing self-assembling bioinspired materials aiming for both mechanical high-performance structures and new types of multifunctional property profiles. The Account is set out to first give a definition of bioinspired nanocomposite materials and self-assembly therein, followed by an in-depth discussion on the understanding of mechanical performance and rational design to increase the mechanical performance. We place a particular emphasis on materials formed at high fractions of reinforcements and with tailor-made functional polymers using self-assembly to create highly ordered structures and elucidate in detail how the soft polymer phase needs to be designed in terms of thermomechanical properties and sacrificial supramolecular bonds. We focus on nanoscale reinforcements such as nanoclay and nanocellulose that lead to high contents of internal interfaces and intercalated polymer layers that experience nanoconfinement. Both aspects add fundamental challenges for macromolecular design of soft phases using precision polymer synthesis. We build upon those design criteria and further develop the concepts of adaptive bioinspired nanocomposites, whose properties are switchable from the outside using molecularly defined triggers with light. In a last section, we discuss how new types of functional properties, in particular flexible and transparent gas barrier materials or fire barrier materials, can be reached on the basis of the bioinspired nanocomposite design strategies. Additionally, we show new types of self-assembled photonic materials that can even be evolved into self-assembling lasers, hence moving the concept of mechanical nanocomposite design to other functionalities.The comparative discussion of different bioinspired nanocomposite architectures with nematic, fibrillar, and cholesteric structures, as based on different reinforcing nanoparticles, aims for a unified understanding of the design principles and shall aid researchers in the field in the more elaborate design of future bioinspired nanocomposite materials based on molecular control principles. We conclude by addressing challenges, in particular also the need for a transfer from fundamental molecular materials science into scalable engineering materials of technological and societal relevance.
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http://dx.doi.org/10.1021/acs.accounts.0c00448DOI Listing
November 2020

Glass Transition Temperature Regulates Mechanical Performance in Nacre-Mimetic Nanocomposites.

Macromol Rapid Commun 2020 Oct 9;41(20):e2000380. Epub 2020 Sep 9.

A 3BMS Lab-Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31, 79104, Freiburg, Germany.

Although research in bioinspired nanocomposites is delivering mechanically superior nanocomposite materials, there remain gaps in understanding some fundamental design principles. This article discusses how the mechanical properties of nacre-mimetic polymer/nanoclay nanocomposites with nanoconfined polymer layers are controlled by the thermo-mechanical polymer properties, that is, glass transition temperature, T using a series of poly(ethylene glycol methyl ether methacrylate-co-N,N-dimethylacrylamide) copolymers with tunable T from 130 to -55 °C. It is elucidated that both the type of copolymer and the nanoconfined polymer layer thickness control energy dissipation and inelastic deformation at high fractions of reinforcements in such bioinspired nanocomposites.
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http://dx.doi.org/10.1002/marc.202000380DOI Listing
October 2020

Scalable One-Pot-Liquid-Phase Oligonucleotide Synthesis for Model Network Hydrogels.

J Am Chem Soc 2020 09 16;142(39):16610-16621. Epub 2020 Sep 16.

A3BMS Lab, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Strasse 31, 79104 Freiburg, Germany.

Solid-phase oligonucleotide synthesis (SPOS) based on phosphoramidite chemistry is currently the most widespread technique for DNA and RNA synthesis but suffers from scalability limitations and high reagent consumption. Liquid-phase oligonucleotide synthesis (LPOS) uses soluble polymer supports and has the potential of being scalable. However, at present, LPOS requires 3 separate reaction steps and 4-5 precipitation steps per nucleotide addition. Moreover, long acid exposure times during the deprotection step degrade sequences with high A content (adenine) due to depurination and chain cleavage. In this work, we present the first one-pot liquid-phase DNA synthesis technique which allows the addition of one nucleotide in a one-pot reaction of sequential coupling, oxidation, and deprotection followed by a single precipitation step. Furthermore, we demonstrate how to suppress depurination during the addition of adenine nucleotides. We showcase the potential of this technique to prepare high-purity 4-arm PEG-T (T = thymine) and 4-arm PEG-A building blocks in multigram scale. Such complementary 4-arm PEG-DNA building blocks reversibly self-assemble into supramolecular model network hydrogels and facilitate the elucidation of bond lifetimes. These model network hydrogels exhibit new levels of mechanical properties (storage modulus, bond lifetimes) in DNA bonds at room temperature (melting at 44 °C) and thus open up pathways to next-generation DNA materials programmable through sequence recognition and available for macroscale applications.
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http://dx.doi.org/10.1021/jacs.0c05488DOI Listing
September 2020

Functional and morphological adaptation in DNA protocells via signal processing prompted by artificial metalloenzymes.

Nat Nanotechnol 2020 11 7;15(11):914-921. Epub 2020 Sep 7.

A3BMS Lab, Institute for Macromolecular Chemistry, University of Freiburg, Freiburg, Germany.

For life to emerge, the confinement of catalytic reactions within protocellular environments has been proposed to be a decisive aspect to regulate chemical activity in space. Today, cells and organisms adapt to signals by processing them through reaction networks that ultimately provide downstream functional responses and structural morphogenesis. Re-enacting such signal processing in de novo-designed protocells is a profound challenge, but of high importance for understanding the design of adaptive systems with life-like traits. We report on engineered all-DNA protocells harbouring an artificial metalloenzyme whose olefin metathesis activity leads to downstream morphogenetic protocellular responses with varying levels of complexity. The artificial metalloenzyme catalyses the uncaging of a pro-fluorescent signal molecule that generates a self-reporting fluorescent metabolite designed to weaken DNA duplex interactions. This leads to pronounced growth, intraparticular functional adaptation in the presence of a fluorescent DNA mechanosensor or interparticle protocell fusion. Such processes mimic chemically transduced processes found in cell adaptation and cell-to-cell adhesion. Our concept showcases new opportunities to study life-like behaviour via abiotic bioorthogonal chemical and mechanical transformations in synthetic protocells. Furthermore, it reveals a strategy for inducing complex behaviour in adaptive and communicating soft-matter microsystems, and it illustrates how dynamic properties can be upregulated and sustained in micro-compartmentalized media.
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http://dx.doi.org/10.1038/s41565-020-0761-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7610402PMC
November 2020

ATP-Responsive and ATP-Fueled Self-Assembling Systems and Materials.

Adv Mater 2020 Oct 2;32(42):e2002629. Epub 2020 Sep 2.

A3BMS Lab - Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, Freiburg, 79104, Germany.

Adenosine triphosphate (ATP) is a central metabolite that plays an indispensable role in various cellular processes, from energy supply to cell-to-cell signaling. Nature has developed sophisticated strategies to use the energy stored in ATP for many metabolic and non-equilibrium processes, and to sense and bind ATP for biological signaling. The variations in the ATP concentrations from one organelle to another, from extracellular to intracellular environments, and from normal cells to cancer cells are one motivation for designing ATP-triggered and ATP-fueled systems and materials, because they show great potential for applications in biological systems by using ATP as a trigger or chemical fuel. Over the last decade, ATP has been emerging as an attractive co-assembling component for man-made stimuli-responsive as well as for fuel-driven active systems and materials. Herein, current advances and emerging concepts for ATP-triggered and ATP-fueled self-assemblies and materials are discussed, shedding light on applications and highlighting future developments. By bringing together concepts of different domains, that is from supramolecular chemistry to DNA nanoscience, from equilibrium to non-equilibrium self-assembly, and from fundamental sciences to applications, the aim is to cross-fertilize current approaches with the ultimate aim to bring synthetic ATP-dependent systems closer to living systems.
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http://dx.doi.org/10.1002/adma.202002629DOI Listing
October 2020

Granular Cellulose Nanofibril Hydrogel Scaffolds for 3D Cell Cultivation.

Macromol Rapid Commun 2020 Sep 11;41(18):e2000191. Epub 2020 Aug 11.

DWI-Leibniz-Institute for Interactive Materials, Forckenbeckstr. 50, D-52074, Aachen, Germany.

The replacement of diseased and damaged organs remains an challenge in modern medicine. However, through the use of tissue engineering techniques, it may soon be possible to (re)generate tissues and organs using artificial scaffolds. For example, hydrogel networks made from hydrophilic precursor solutions can replicate many properties found in the natural extracellular matrix (ECM) but often lack the dynamic nature of the ECM, as many covalently crosslinked hydrogels possess elastic and static networks with nanoscale pores hindering cell migration without being degradable. To overcome this, macroporous colloidal hydrogels can be prepared to facilitate cell infiltration. Here, an easy method is presented to fabricate granular cellulose nanofibril hydrogel (CNF) scaffolds as porous networks for 3D cell cultivation. CNF is an abundant natural and highly biocompatible material that supports cell adhesion. Granular CNF scaffolds are generated by pre-crosslinking CNF using calcium and subsequently pressing the gel through micrometer-sized nylon meshes. The granular solution is mixed with fibroblasts and crosslinked with cell culture medium. The obtained granular CNF scaffold is significantly softer and enables well-distributed fibroblast growth. This cost-effective material combined with this efficient and facile fabrication technique allows for 3D cell cultivation in an upscalable manner.
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http://dx.doi.org/10.1002/marc.202000191DOI Listing
September 2020

Switchable supracolloidal 3D DNA origami nanotubes mediated through fuel/antifuel reactions.

Nanoscale 2020 Aug;12(32):16995-17004

A3BMS Lab - Active, Adaptive and Autonomous Bioinspired Material Systems, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany. and Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany and Cluster of Excellence livMatS @ FIT, 79110 Freiburg, Germany.

3D DNA origami provide access to the de novo design of monodisperse and functional bio(organic) nanoparticles, and complement structural protein engineering and inorganic and organic nanoparticle synthesis approaches for the design of self-assembling colloidal systems. We show small 3D DNA origami nanoparticles, which polymerize and depolymerize reversibly to nanotubes of micrometer lengths by applying fuel/antifuel switches. 3D DNA nanocylinders are engineered as a basic building block with different numbers of overhang strands at the open sides to allow for their assembly via fuel strands that bridge both overhangs, resulting in the supracolloidal polymerization. The influence of the multivalent interaction patterns and the length of the bridging fuel strand on efficient polymerization and nanotube length distribution is investigated. The polymerized multivalent nanotubes disassemble through toehold-mediated rehybridization by adding equimolar amounts of antifuel strands. Finally, Förster resonance energy transfer yields in situ insights into the kinetics and reversibility of the nanotube polymerization and depolymerization.
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http://dx.doi.org/10.1039/d0nr04209aDOI Listing
August 2020

Into the looking glass: Post-viral syndrome post COVID-19.

Med Hypotheses 2020 11 27;144:110055. Epub 2020 Jun 27.

The School of Medicine and Manchester Academic Health Sciences Centre, Manchester University, UK; Department of Endocrinology and Diabetes, Salford Royal Hospital, Salford, UK. Electronic address:

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http://dx.doi.org/10.1016/j.mehy.2020.110055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7320866PMC
November 2020

ATP-powered molecular recognition to engineer transient multivalency and self-sorting 4D hierarchical systems.

Nat Commun 2020 07 21;11(1):3658. Epub 2020 Jul 21.

A3BMS Lab, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104, Freiburg, Germany.

Biological systems organize multiple hierarchical structures in parallel, and create dynamic assemblies and functions by energy dissipation. In contrast, emerging artificial non-equilibrium self-assembling systems have remained relatively simplistic concerning hierarchical design, and non-equilibrium multi-component systems are uncharted territory. Here we report a modular DNA toolbox allowing to program transient non-equilibrium multicomponent systems across hierarchical length scales by introducing chemically fueled molecular recognition orchestrated by reaction networks of concurrent ATP-powered ligation and cleavage of freely programmable DNA building blocks. Going across hierarchical levels, we demonstrate transient side-chain functionalized nucleic acid polymers, and further introduce the concept of transient cooperative multivalency as a key to bridge length scales to pioneer fuel-driven encapsulation, self-assembly of colloids, and non-equilibrium transient narcissistic colloidal self-sorting on a systems level. The fully programmable and functionalizable DNA components pave the way to design chemically fueled 4D (3 space, 1 time) molecular multicomponent systems and autonomous materials.
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http://dx.doi.org/10.1038/s41467-020-17479-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7374688PMC
July 2020

Biodegradation of Crystalline Cellulose Nanofibers by Means of Enzyme Immobilized-Alginate Beads and Microparticles.

Polymers (Basel) 2020 Jul 9;12(7). Epub 2020 Jul 9.

Institute of Microsystems Engineering IMTEK, Laboratory for Sensors, University of Freiburg, 79110 Freiburg, Germany.

Recent advances in nanocellulose technology have revealed the potential of crystalline cellulose nanofibers to reinforce materials which are useful for tissue engineering, among other functions. However, the low biodegradability of nanocellulose can possess some problems in biomedical applications. In this work, alginate particles with encapsulated enzyme cellulase extracted from were prepared for the biodegradation of crystalline cellulose nanofibers, which carrier system could be incorporated in tissue engineering biomaterials to degrade the crystalline cellulose nanoreinforcement in situ and on-demand during tissue regeneration. Both alginate beads and microparticles were processed by extrusion-dropping and inkjet-based methods, respectively. Processing parameters like the alginate concentration, concentration of ionic crosslinker Ca, hardening time, and ionic strength of the medium were varied. The hydrolytic activity of the free and encapsulated enzyme was evaluated for unmodified (CNFs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) in suspension (heterogeneous conditions); in comparison to solubilized cellulose derivatives (homogeneous conditions). The enzymatic activity was evaluated for temperatures between 25-75 °C, pH range from 3.5 to 8.0 and incubation times until 21 d. Encapsulated cellulase in general displayed higher activity compared to the free enzyme over wider temperature and pH ranges and for longer incubation times. A statistical design allowed optimizing the processing parameters for the preparation of enzyme-encapsulated alginate particles presenting the highest enzymatic activity and sphericity. The statistical analysis yielded the optimum particles characteristics and properties by using a formulation of 2% (w/v) alginate, a coagulation bath of 0.2 M CaCl and a hardening time of 1 h. In homogeneous conditions the highest catalytic activity was obtained at 55 °C and pH 4.8. These temperature and pH values were considered to study the biodegradation of the crystalline cellulose nanofibers in suspension. The encapsulated cellulase preserved its activity for several weeks over that of the free enzyme, which latter considerably decreased and practically showed deactivation after just 10 d. The alginate microparticles with their high surface area-to-volume ratio effectively allowed the controlled release of the encapsulated enzyme and thereby the sustained hydrolysis of the cellulose nanofibers. The relative activity of cellulase encapsulated in the microparticles leveled-off at around 60% after one day and practically remained at that value for three weeks.
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http://dx.doi.org/10.3390/polym12071522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407417PMC
July 2020

Male-Specific Metabolic Considerations Concerning the Prescription of Second-Generation Antipsychotics to Adolescents.

J Child Adolesc Psychopharmacol 2021 02 30;31(1):53-55. Epub 2020 Jun 30.

Clinical Psychology and Psychotherapy, University of Zurich, Zurich, Switzerland.

Although males and females gain comparable weight when prescribed second-generation antipsychotics (SGAs), males may be uniquely vulnerable to an array of endocrinological, inflammatory, and psychosocial adverse drug effects. This opinion piece reviews work in each of these three areas for consideration. Androgens may decrease both through hypothalamic-pituitary-gonadal axis dysregulation and as a consequence of increased adiposity. Testosterone has anti-inflammatory properties, and declining levels as well as many other factors may influence overall immunological functioning. Psychosocial stressors are gender specific in obesity, and SGA-induced obesity may affect males in unique and severe ways. This opinion piece supports the framework of the World Federation of Societies of Biological Psychiatry's Task Force on Men's Mental Health to advocate for further studies concerning the adverse drug effects of SGAs as unique manifested in male children, adolescents, and young men.
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http://dx.doi.org/10.1089/cap.2020.0052DOI Listing
February 2021

Polymer Transformers: Interdigitating Reaction Networks of Fueled Monomer Species to Reconfigure Functional Polymer States.

Angew Chem Int Ed Engl 2020 10 13;59(41):18161-18165. Epub 2020 Aug 13.

A3BMS Lab-Active, Adaptive and Autonomous Bioinspired Materials, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Straße 31, 79104, Freiburg, Germany.

Adaptivity is an essential trait of life. One type of adaptivity is the reconfiguration of a functional system states by correlating sensory inputs. We report polymer transformers, which can adaptively reconfigure their composition from a state of a mixed copolymer to being enriched in either monomer A or B. This is achieved by embedding and hierarchically interconnecting two chemically fueled activation/deactivation enzymatic reaction networks for both monomers via a joint activation pathway (network level) and an AB linker monomer reactive to both A and B (species level). The ratio of enzymes governing the individual deactivation pathways (our external signals) control the enrichment behavior in the dynamic state. The method shows high programmability of the reconfigured state, rejuvenation of transformation cycles, and quick in situ adaptation. As a proof-of-concept, we showcase this dynamic reconfiguration for colloidal surface functionalities.
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http://dx.doi.org/10.1002/anie.202006526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7590193PMC
October 2020

Biodegradable Laser Arrays Self-Assembled from Plant Resources.

Adv Mater 2020 Jul 14;32(29):e2002332. Epub 2020 Jun 14.

A3BMS Lab, Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31, Freiburg, 79104, Germany.

The transition toward future sustainable societies largely depends on disruptive innovations in biobased materials to substitute nonsustainable advanced functional materials. In the field of optics, advanced devices (e.g., lasers or metamaterial devices) are typically manufactured using top-down engineering and synthetic materials. This work breaks with such concepts and switchable lasers self-assembled from plant-based cellulose nanocrystals and fluorescent polymers at room temperature and from water are shown. Controlled structure formation allows laser-grade cholesteric photonic bandgap materials, in which the photonic bandgap is matched to the fluorescence emission to function as an efficient resonator for low threshold multimode lasing. The lasers can be switched on and off using humidity, and can be printed into pixelated arrays. Additionally, the materials exhibit stiffness above typical thermoplastic polymers and biodegradability in soil. The concept showcases that highly advanced functions can be encoded into biobased materials, and opens the design space for future sustainable optical devices of unprecedented function.
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http://dx.doi.org/10.1002/adma.202002332DOI Listing
July 2020

Hierarchical cross-linking for synergetic toughening in crustacean-mimetic nanocomposites.

Nanoscale 2020 Jun 11;12(24):12958-12969. Epub 2020 Jun 11.

Institute for Macromolecular Chemistry, Stefan-Meier-Strasse 31, University of Freiburg, 79104 Freiburg, Germany.

The twisted plywood structure as found in crustacean shells possesses excellent mechanical properties with high stiffness and toughness. Synthetic mimics can be produced by evaporation-induced self-assembly of cellulose nanocrystals (CNCs) with polymer components into bulk films with a cholesteric liquid crystal structure. However, these are often excessively brittle and it has remained challenging to make materials combining high stiffness and toughness. Here, we describe self-assembling cholesteric CNC/polymer nanocomposites with a crustacean-mimetic structure and tunable photonic band gap, in which we engineer combinations of thermo-activated covalent and supramolecular hydrogen-bonded crosslinks to tailor the energy dissipation properties by precise molecular design. Toughening occurs upon increasing the polymer fractions in the nanocomposites, and, critically, combinations of both molecular bonding mechanisms lead to a considerable synergetic increase of stiffness and toughness - beyond the common rule of mixtures. Our concept following careful molecular design allows one to enter previously unreached areas of mechanical property charts for cholesteric CNC-based nanocomposites. The study shows that the subtle engineering of molecular energy dissipation units using sophisticated chemical approaches enables efficient enhancing of the properties of bioinspired CNC/polymer nanocomposites, and opens the design space for future molecular enhancement using tailor-made interactions.
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http://dx.doi.org/10.1039/d0nr02228dDOI Listing
June 2020