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This article discusses the development of hydrogels that can adapt their properties and internal structure in response to external stimuli. The hydrogels contain redox-responsive and light-responsive units that can independently react to specific triggers, but also demonstrate adaptability and self-regulation in terms of stiffness when simultaneously addressed. The study describes the formation of hydrogels with a redox-sensitive disulfide-crosslinked network and light-sensitive ortho-nitrobenzyl units, which can quickly adjust their network properties. The hydrogels show potential for applications in drug delivery and tissue engineering. [Extracted from the article]

Summary Gels consist of a solid and a liquid phase interpenetrating each other. The liquid is thus immobilized. In the case of hydrogels, the liquid phase is water, and another liquid in the case of organogels. For the formation of the solid phase, natural or synthetic polymers, molecules or colloidal particles must be crosslinked by covalent bonds or non‐covalent interactions. In this article, different kinds of gels and network structures are introduced by the example of selected applications. [ABSTRACT FROM AUTHOR]

Wassermoleküle spielen eine wichtige Rolle für die Struktur, Funktion und Dynamik von (Bio‐) Materialien. Ein direkter Zugang zur Anzahl der Wassermoleküle in nanoskopischen Volumina kann daher neue molekulare Einblicke in Materialien geben und eine Feinabstimmung ihrer Eigenschaften in anspruchsvollen Anwendungen ermöglichen. Die Bestimmung des lokalen Wassergehalts wurde durch die Entdeckung möglich, dass H2O die Fluoreszenz von rot‐emittierenden Farbstoffen löscht. Da deuteriertes Wasser, D2O, keine signifikante Fluoreszenzlöschung hervorruft, lässt sich über Fluoreszenzlebensdauermessungen bei unterschiedlichen H2O/D2O‐Verhältnissen die lokale Wasserkonzentration bestimmen. Wir kombinierten diesen Effekt mit der vor Kurzem entwickelten Fluoreszenzlebensdauer‐Einzelmolekül‐Lokalisierungsmikroskopie (FL‐SMLM), um die lokale Wasserkonzentration in Mikrogelen, d. h. weichen Hydrogelpartikeln, die aus einem in Wasser gequollenen vernetzten Polymer bestehen, nanoskopisch zu bestimmen. Die Änderung des Wassergehalts von thermoresponsiven Mikrogelen beim Übergang von ihrem gequollenen Zustand bei Raumtemperatur zu einem kollabierten Zustand bei erhöhter Temperatur konnte analysiert werden. Es wurde eine deutliche Abnahme des Wassergehalts festgestellt, die zu unserer Überraschung über das gesamte Mikrogelvolumen recht gleichmäßig war. In der Peripherie der gequollenen Mikrogele war die Wasserkonzentration um den Farbstoff herum nur geringfügig größer als in deren Zentrum. [ABSTRACT FROM AUTHOR]

Lignin, ein komplexes und häufig vorkommendes Biopolymer, das aus pflanzlichen Zellwänden gewonnen wird, hat sich als vielversprechender Rohstoff für eine nachhaltige Materialentwicklung herausgestellt. Aufgrund des hohen Anteils an Phenylpropanoideinheiten, aromatischen Ringen und Hydroxylgruppen ist Lignin ein idealer Kandidat für die Erforschung verschiedener Materialanwendungen. Daher ist die Nachfrage nach der Ligninverwertung zur Entwicklung höherwertiger Produkte deutlich angestiegen. Dieser Kurzaufsatz gibt einen Überblick über die Ligninumwandlung, wobei der Schwerpunkt auf der Funktionalisierung durch chemische und enzymatische Verfahren und deren Anwendung in Polymerharzen, Hydrogelen und Nanomaterialien auf Ligninbasis liegt. Die Funktionalisierung von Ligninmolekülen mit verschiedenen chemischen Gruppen bietet maßgeschneiderte Eigenschaften und eine erhöhte Kompatibilität mit anderen Materialien und erweitert so seine potentiellen Anwendungen. Darüber hinaus führt die Bildung von Netzwerken auf Ligninbasis, entweder durch Vernetzung oder Mischung mit Polymeren, zu neuartigen Materialien mit verbesserten mechanischen, thermischen und Barriereeigenschaften. Es bestehen jedoch weiterhin Herausforderungen in der Optimierung der Funktionalisierungstechniken, dem Erhalt der inhärenten Komplexität von Lignin und der Skalierbarkeit für die industrielle Umsetzung. Das Potential von Lignin ist groß und noch lange nicht ausgeschöpft und man erhofft sich, dass Lignin den Wandel zu umweltfreundlicheren und ressourceneffizienteren Industrien einläuten kann. [ABSTRACT FROM AUTHOR]

Zelluläre Organismen verfügen über komplexe mechanoadaptive Systeme, die es ihnen ermöglichen, Kräfte zu spüren und sie mit (bio)chemischen Regelkreisläufen zur funktionellen Anpassung zu verarbeiten. Inspiriert durch solche Prozesse stellt diese Studie ein Hydrogelsystem vor, das zur mechanisch aktivierten und chemisch amplifizierten Selbstauflösung fähig ist. Die hierzu entwickelten Hydrogele können mechanisch Radikale erzeugen, die in einer sich selbst ausbreitenden radikalischen Entnetzungsreaktion verarbeitet und verstärkt werden, was letztendlich zu einer mechanisch ausgelösten Selbstauflösung führt. Wir setzen dieses System bei der mechanoinduzierten Ablösung und in einem Doppelschichtaktuator ein, bei dem die durch Schwellung verursachte Biegung ausreichend Kraft für den selektiven Abbau einer Schicht erzeugt, was zu einer autonomen Selbstregulierung im Zusammenhang mit der Entbiegung führt. Unsere Arbeit hilft bei der Definition von Designkriterien für molekular kontrollierte adaptive und selbstregulierende Materialien mit integrierter mechanochemischer Informationsverarbeitung und zeigt deren Potenzial für Adhäsive und die Soft Robotik auf. [ABSTRACT FROM AUTHOR]

In Hydrogele eingebrachte chemische Reaktionsnetzwerke können responsive Materialien zu komplexen, selbstregulierenden Materialien transformieren, die eine Rückkopplung auf externe Stimuli generieren können. Diese Arbeit präsentiert Hydrogele aus dem Wirt‐Gast‐Paar β‐Cyclodextrin und Ferrocen als supramolekulare Vernetzer. Ein redoxresponsives Verhalten des Systems wird induziert durch die Treibstoff‐Enzym‐Paare Meerrettich‐Peroxidase/H2O2 und Glucose‐Oxidase (GOx)/d‐Glucose. Das Hydrogel kann durch Variation der Konzentration des Reduktionstreibstoffs d‐Glucose von einem responsiven zu einem selbstregulierenden supramolekularen System umgewandelt werden. Gestartet wird das selbstregulierende Verhalten durch die Bildung eines Oxidationsmittels innerhalb des Gels durch das Cofaktor‐Intermediat GOx[FADH2]. UV/Vis‐Spektroskopie, Rheologie und kinetische Modellierung wurden angewendet, um dieses Nichtgleichgewichtsverhalten und die Programmierbarkeit der Rückkopplung des Hydrogels, unter anderem die Anpassung des Speichermoduls und die mögliche Anwendung als Glucose‐Sensor, zu beleuchten. [ABSTRACT FROM AUTHOR]

Responsive Materialien, wie z. B. schaltbare Hydrogele, wurden in den meisten Fällen dahingehend entworfen, eine maximale Änderung zwischen zwei Zuständen zu generieren. Im Gegensatz dazu zielen adaptive Systeme auf unterschiedliche funktionelle Plateaus zwischen diesen Maxima ab. In diesem Forschungsartikel zeigen wir daher, wie der photostationäre Zustand (PSS) eines E/Z‐Arylazopyrazol‐Photoschalters mit Hilfe der eingestrahlten Wellenlänge über ein breites Farbspektrum eingestellt werden kann, um die photodynamischen Eigenschaften von Hydrogelen auf der Grundlage von multivalenten, photoschaltbaren Wechselwirkungen zu beeinflussen. Wir präsentieren, dass sich diese Hydrogele an den wellenlängenabhängigen PSS und an die Anzahl der Arylazopyrazol‐Einheiten durch programmierbare Beziehungen anpassen. Unser Materialdesign ermöglicht daher die einfache Einstellung der mechanischen Eigenschaften ohne eine zeitaufwändige Synthese. Das Konzept geht über das klassische Schalten zwischen Zustand A und B hinaus und zeigt Wege für eine wellenlängenabhängige Adaption der Hydrogeleigenschaften auf, die für Weiterentwicklungen in der Zellkultivierung oder in der Soft‐Robotik nützlich sein werden. [ABSTRACT FROM AUTHOR]

Immobilization of compartmentalized microscale objects in 3D hydrogels provides a step towards the modular assembly of soft functional materials with tunable architectures and distributed functionalities. Herein, we report the use of a combination of micro‐compartmentalization, immobilization, and modularization to fabricate and assemble hydrogel‐based microreactor assemblies comprising millions of functionalized polysaccharide–polynucleotide coacervate droplets. The heterogeneous hydrogels can be structurally fused by interfacial crosslinking and coupled as input and output modules to implement a UV‐induced photocatalytic/peroxidation nanoparticle/DNAzyme reaction cascade that generates a spatiotemporal fluorescence read‐out depending on the droplet number density, intensity of photoenergization, and chemical flux. Our approach offers a route to heterogeneous hydrogels with endogenous reactivity and reconfigurable architecture, and provides a step towards the development of soft modular materials with programmable functionality. [ABSTRACT FROM AUTHOR]

Self‐assembly of peptide‐based building units into supramolecular nanostructures creates an important class of biomaterials with robust mechanical properties and improved resistance to premature degradation. Yet, upon aggregation, substrate–enzyme interactions are often compromised because of the limited access of macromolecular proteins to the peptide substrate, leading to either a reduction or loss of responsiveness to biomolecular cues. Reported here is the supramolecular design of unsymmetric reverse bolaamphiphiles (RBA) capable of exposing a matrix metalloproteinase (MMP) substrate on the surface of their filamentous assemblies. Upon addition of MMP‐2, these filaments rapidly break into fragments prior to reassembling into spherical micelles. Using 3D cell culture, it is shown that drug release is commensurate with cell density, revealing more effective cell killing when more cancer cells are present. This design platform could serve as a cell‐responsive therapeutic depot for local chemotherapy. [ABSTRACT FROM AUTHOR]

Inspired by biology, one current goal in supramolecular chemistry is to control the emergence of new functionalities arising from the self‐assembly of molecules. In particular, some peptides can self‐assemble and generate exceptionally catalytically active fibrous networks able to underpin hydrogels. Unfortunately, the mechanical fragility of these materials is incompatible with process developments, relaying this exciting field to academic curiosity. Here, we show that this drawback can be circumvented by enzyme‐assisted self‐assembly of peptides initiated at the walls of a supporting porous material. We applied this strategy to grow an esterase‐like catalytically active supramolecular hydrogel (CASH) in an open‐cell polymer foam, filling the whole interior space. Our supported CASH material is highly efficient towards inactivated esters and enables the kinetic resolution of racemates. This hybrid material is robust enough to be used in continuous flow reactors, and is reusable and stable over months. [ABSTRACT FROM AUTHOR]

Guanosine‐5′‐hydroxamic acid (3) forms hydrogels when mixed with guanosine (1) and KCl. The 5′‐hydroxamic acid (HA) unit is pH‐responsive and also chelates Fe3+. When gels are prepared under basic conditions, the 5′‐HA groups are deprotonated and the anionic hydrogel binds cationic thiazole orange (TO), signaled by enhanced fluorescence. The HA nucleoside 3, when immobilized in the G‐quartet gel, acts as a supramolecular siderophore to form red complexes with Fe3+. We patterned the hydrogel's surface with FeCl3, by hand and by using a 3D printer. Patterns form instantly, are visible by eye, and can be erased using vitamin C. This hydrogel, combining self‐assembled G‐quartet and siderophore–Fe3+ motifs, is strong, can be molded into different shapes, and is stable on the bench or under salt water. [ABSTRACT FROM AUTHOR]

Stem‐cell behavior is regulated by the material properties of the surrounding extracellular matrix, which has important implications for the design of tissue‐engineering scaffolds. However, our understanding of the material properties of stem‐cell scaffolds is limited to nanoscopic‐to‐macroscopic length scales. Herein, a solid‐state NMR approach is presented that provides atomic‐scale information on complex stem‐cell substrates at near physiological conditions and at natural isotope abundance. Using self‐assembled peptidic scaffolds designed for nervous‐tissue regeneration, we show at atomic scale how scaffold‐assembly degree, mechanics, and homogeneity correlate with favorable stem cell behavior. Integration of solid‐state NMR data with molecular dynamics simulations reveals a highly ordered fibrillar structure as the most favorable stem‐cell scaffold. This could improve the design of tissue‐engineering scaffolds and other self‐assembled biomaterials. [ABSTRACT FROM AUTHOR]

Many living organisms have amazing control over their color, shape, and morphology for camouflage, communication, and even reproduction in response to interplay between environmental stimuli. Such interesting phenomena inspire scientists to develop smart soft actuators/robotics via integrating color‐changing functionality based on polymer films or elastomers. However, there has been no significant progress in synergistic color‐changing and shape‐morphing capabilities of life‐like material systems such as hydrogels. Herein, we reported a new class of bioinspired synergistic fluorescence‐color‐switchable polymeric hydrogel actuators based on supramolecular dynamic metal–ligand coordination. Artificial hydrogel apricot flowers and chameleons have been fabricated for the first time, in which simultaneous color‐changing and shape‐morphing behaviors are controlled by the subtle interplay between acidity/alkalinity, metal ions, and temperature. This work has made color‐changeable soft machines accessible and is expected to hold wide potential applications in biomimetic soft robotics, biological sensors, and camouflage. [ABSTRACT FROM AUTHOR]

Integrating 2D culture of adherent mammalian cells with single‐cell western blotting (in situ scWB) uses microfluidic design to eliminate the requirement for trypsin release of cells to suspension, prior to single‐cell isolation and protein analysis. To assay HeLa cells from an attached starting state, we culture adherent cells in fibronectin‐functionalized microwells formed in a thin layer of polyacrylamide gel. To integrate the culture, lysis, and assay workflow, we introduce a one‐step copolymerization process that creates protein‐decorated microwells. After single‐cell culture, we lyse each cell in the microwell and perform western blotting on each resultant lysate. We observe cell spreading after overnight microwell‐based culture. scWB reports increased phosphorylation of MAP kinases (ERK1/2, p38) under hypertonic conditions. We validate the in situ scWB with slab‐gel western blot, while revealing cell‐to‐cell heterogeneity in stress responses. [ABSTRACT FROM AUTHOR]

Sponges, Neofibularia nolitangere, can regenerate spontaneously after being broken down into small pieces, and the regenerated structure maintains the original appearance and function. Synthetic materials with such capabilities are highly desired but hardly achieved. Presented here is a sponge‐inspired self‐regenerative powder from a double‐network (DN) tough hydrogel. Hydrogels are regenerated from their powder form, by addition of water, with preservation of the original appearance and mechanical properties. The powder‐hydrogel‐powder cycle can be repeated multiple times with little loss in mechanical properties, analogous to the regeneration of sponges. These DN hydrogels can be conveniently stored and easily shaped upon regeneration. This work may have implications in the development of regenerative materials for coatings and adhesives. [ABSTRACT FROM AUTHOR]

Using peptide assemblies with emergent properties to achieve elaborate functions has attracted increasing attention in recent years. Besides tailoring the self‐assembly of peptides in vitro, peptide research is advancing into a new and exciting frontier: the rational design of peptide assemblies (or their derivatives) for biological functions in a complex environment. This Minireview highlights recent developments in peptide assemblies and their applications in biological systems. After introducing the unique merits of peptide assemblies, we discuss the recent progress in designing peptides (or peptide derivatives) for self‐assembly with conformational control. Then, we describe biological functions of peptide assemblies, with an emphasis on approach‐instructed assembly for spatiotemporal control of peptide assemblies, in the cellular context. Finally, we discuss the future promises and challenges of this exciting area of chemistry. [ABSTRACT FROM AUTHOR]

There is a growing interest in materials that can dynamically change their properties in the presence of cells to study mechanobiology. Herein, we exploit the 365 nm light mediated [4+4] photodimerization of anthracene groups to develop cytocompatible PEG‐based hydrogels with tailorable initial moduli that can be further stiffened. A hydrogel formulation that can stiffen from 10 to 50 kPa, corresponding to the stiffness of a healthy and fibrotic heart, respectively, was prepared. This system was used to monitor the stiffness‐dependent localization of NFAT, a downstream target of intracellular calcium signaling using a reporter in live cardiac fibroblasts (CFbs). NFAT translocates to the nucleus of CFbs on stiffening hydrogels within 6 h, whereas it remains cytoplasmic when the CFbs are cultured on either 10 or 50 kPa static hydrogels. This finding demonstrates how dynamic changes in the mechanical properties of a material can reveal the kinetics of mechanoresponsive cell signaling pathways that may otherwise be missed in cells cultured on static substrates. [ABSTRACT FROM AUTHOR]

Despite the tremendous efforts devoted to the structural analysis of hydrogel microspheres (microgels), many details of their structures remain unclear. Reported in this study is that thermoresponsive poly(N‐isopropyl acrylamide) (pNIPAm)‐based microgels exhibit not only the widely accepted core–shell structures, but also inhomogeneous decanano‐sized non‐thermoresponsive spherical domains within their dense cores, which was revealed by temperature‐controlled high‐speed atomic force microscopy (TC‐HS‐AFM). Based on a series of experiments, it is concluded that the non‐thermoresponsive domains are characteristic for pNIPAm microgels synthesized by precipitation polymerization, and plausible structures for microgels prepared by other polymerization techniques are proposed. [ABSTRACT FROM AUTHOR]

Inspired by the anti‐freezing mechanisms found in nature, ionic compounds (ZnCl2/CaCl2) are integrated into cellulose hydrogel networks to enhance the freezing resistance. In this work, cotton cellulose is dissolved by a specially designed ZnCl2/CaCl2 system, which endows the cellulose hydrogels specific properties such as excellent freeze‐tolerance, good ion conductivity, and superior thermal reversibility. Interestingly, the rate of cellulose coagulation could be promoted by the addition of extra water or glycerol. This new type of cellulose‐based hydrogel may be suitable for the construction of flexible devices used at temperature as low as −70 °C. [ABSTRACT FROM AUTHOR]

Soft colloidal particles such as hydrogel microspheres assemble at air/water or oil/water interfaces, where the soft colloids are highly deformed and their surface polymer chains are highly entangled with each other. Herein, we report the formation of robust one‐dimensional, string‐like colloidal assemblies through self‐organization of hydrogel microspheres with shape anisotropy at the air/water interface of sessile droplets. Shape‐anisotropic hydrogel microspheres were synthesized via two‐step polymerization, whereby a hydrogel shell was formed onto preformed rigid microellipsoids. The shape anisotropy of the hydrogel microspheres was confirmed by transmission electron microscopy and high‐speed atomic force microscopy as well as by light‐scattering measurements. The present findings are crucial for the understanding of natural self‐organization phenomena, where "softness" influences microscopic assembled structures such as those of Nostoc bacteria. [ABSTRACT FROM AUTHOR]

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Recently, metal‐free, heteroatom‐doped carbon nanomaterials have emerged as promising electrocatalysts for the oxygen evolution reaction (OER), but their synthesis is a tedious process involving energy‐wasting calcination. Molecular electrocatalysts offer attractive catalysts for the OER. Here, phytic acid (PA) was selected to investigate the OER activity of carbons in organic molecules by DFT calculations and experiments. Positively charged carbons on PA were very active towards the OER. The PA molecules were fixed into a porous, conductive hydrogel with a superhydrophilic surface. This outperformed most metal‐free electrocatalysts. Besides the active sites on PA, the high OER activity was also related to the porous and conductive networks on the hydrogel, which allowed fast charge and mass transport during the OER. Therefore, this work provides a metal‐free, organic‐molecule‐based electrocatalyst to replace carbon nanomaterials for efficient OER. [ABSTRACT FROM AUTHOR]

The self‐healing of zinc‐ion batteries (ZIBs) will not only significantly improve the durability and extend the lifetime of devices, but also decrease electronic waste and economic cost. A poly(vinyl alcohol)/zinc trifluoromethanesulfonate (PVA/Zn(CF3SO3)2) hydrogel electrolyte was fabricated by a facile freeze/thaw strategy. PVA/Zn(CF3SO3)2 hydrogels possess excellent ionic conductivity and stable electrochemical performance. Such hydrogel electrolytes can autonomously self‐heal by hydrogen bonding without any external stimulus. All‐in‐one integrated ZIBs can be assembled by incorporating the cathode, separator, and anode into hydrogel matrix since the fabrication of PVA/Zn(CF3SO3)2 hydrogel is a process of converting the liquid to quasi‐solid state. The ZIBs show an outstanding self‐healing and can recover electrochemical performance completely even after several cutting/healing cycles. [ABSTRACT FROM AUTHOR]

The ability to control the degradation of a material is critical to various applications. The purpose of this study was to demonstrate a concept of controlling degradation by using a double‐locked domain (DLD). DLDs are molecular structures with two functional units that work cooperatively under environmental stimulation. One unit is triggered to transform without cleavage in the presence of the first stimulus, but this transformation enables the activation of the other unit for cleavage in the presence of the second stimulus. A DLD is presented that is activated to transform through intramolecular reconfiguration when exposed to light. After this transformation, the light‐triggered DLD can undergo rapid cleavage under acid treatment. When this DLD is used as the crosslinkers of hydrogels, hydrogels undergo rapid degradation after sequential exposure to light irradiation and acid treatment. Reversing the order of light irradiation and acid treatment or only using individual stimulation does not lead to comparable degradation. Thus, this study has successfully demonstrated the great potential of using DLDs to achieve programmable degradation of materials. [ABSTRACT FROM AUTHOR]

Hydrogel microparticles are important in materials engineering, but their applications remain limited owing to the difficulties associated with their manipulation. Herein, we report the self‐orientation of crescent‐shaped hydrogel microparticles and elucidate its mechanism. Additionally, the microparticles were used, for the first time, as micro‐buckets to carry living cells. In aqueous solution, the microparticles spontaneously rotated to a preferred orientation with the cavity facing up. We developed a geometric model that explains the self‐orienting behavior of crescent‐shaped particles by minimizing the potential energy of this specific morphology. Finally, we selectively modified the particles' cavities with RGD peptide and exploited their preferred orientation to load them with living cells. Cells could adhere, proliferate, and be transported and released in vitro. These micro‐buckets hold a great potential for applications in smart materials, cell therapy, and biological engineering. [ABSTRACT FROM AUTHOR]

The development of new material platforms can improve our ability to study biological processes. Here, we developed a water‐compatible variant of a click‐like polymerization between alkynoates and secondary amines to form β‐aminoacrylate synthetic polyethylene glycol (PEG) based hydrogels. These materials are easy to access—PEG alkynoate was synthesized on a 100 gram scale and the amines were available commercially; these materials are also operationally simple to formulate—gel formation occurred upon simple mixing of precursor solutions without the need for initiators, catalysts, nor specialized equipment. Three‐dimensional cell culture experiments also indicated cytocompatibility of these gels with >90 % viability retained in THP‐1 and NIH/3T3 cells after 72 hours in culture. This hydrogel system therefore represents an alternative platform to other click and click‐like hydrogels with improved accessibility and user‐friendliness for biomaterials application. [ABSTRACT FROM AUTHOR]

Peristaltic crawling, which is the moving mechanism of earthworm‐like limbless creatures in narrow spaces, is a challenging target to mimic by using soft materials. Here we report an unprecedented hydrogel actuator that enables not only a peristaltic crawling motion but also reversing its direction. Our cylindrically processed hydrogel contains gold nanoparticles for photothermal conversion, a thermoresponsive polymer network for switching the electrical permittivity of the gel interior, and cofacially oriented 2D electrolytes (titanate nanosheets; TiNSs) to synchronously change their anisotropic electrostatic repulsion. When a hydrogel, which was designed to include cofacially oriented TiNSs along the cylindrical gel axis, is pointwisely photoirradiated with a visible‐light laser, it spatiotemporally expands immediately (<0.5 s) and largely (80 % of its original length) in an isovolumetric manner. When the irradiation spot is moved along the cylindrical gel axis, the hydrogel undergoes peristaltic crawling due to quick and sequential elongation/contraction events and moves oppositely toward the laser scanning direction. Thus, when the scanning direction is switched, the crawling direction is reversed. When gold nanorods are used in place of gold nanoparticles, the hydrogel becomes responsive to a near‐infrared light, which can deeply penetrate into bio tissues. [ABSTRACT FROM AUTHOR]

Photodegradable hydrogels have emerged as useful platforms for research on cell function, tissue engineering, and cell delivery as their physical and chemical properties can be dynamically controlled by the use of light. The photo‐induced degradation of such hydrogel systems is commonly based on the integration of photolabile o‐nitrobenzyl derivatives to the hydrogel backbone, because such linkers can be cleaved by means of one‐ and two‐photon absorption. Herein we describe a cytocompatible click‐based hydrogel containing o‐nitrobenzyl ester linkages between a hyaluronic acid backbone, which is photodegradable in the presence of cells. It is demonstrated for the first time that by using a cyclic benzylidene ketone‐based small molecule as photosensitizer the efficiency of the two‐photon degradation process can be improved significantly. Biocompatibility of both the improved two‐photon micropatterning process as well as the hydrogel itself is confirmed by cell culture studies. [ABSTRACT FROM AUTHOR]

There is significant current interest in identifying new combination therapies that synergize to treat disease, and it is becoming increasingly clear that the temporal resolution of their administration greatly impacts efficacy. To facilitate effective delivery, a multicompartment hydrogel material was developed that is composed of spherical vesicles interlaced within a self‐assembled peptide‐based network of physically crosslinked fibrils that allows time‐resolved independent co‐delivery of small molecules. This material architecture effectively delivers the EGFR kinase inhibitor Erlotinib (ERL) and Doxorubicin (DOX, DNA intercalator) in an ERL→DOX sequential manner to synergistically kill glioblastoma, the most aggressive form of brain cancer. [ABSTRACT FROM AUTHOR]

Abstract: In our previous work, we have shown that “electrostatic forces”, when generated anisotropically in aqueous media by 2D electrolytes upon cofacial orientation, enable the formation of a hydrogel with an anisotropic parameter, as defined by the ratio of elastic moduli E⊥/E∥, of 3.0. Herein, we successfully developed the design strategy for a hydrogel with an anisotropic parameter of no less than 85. This value is not only 28 times greater than that of our previous anisotropic hydrogel but also 6 times larger than the current champion record in synthetic hydrogels (E⊥/E∥∼15). Firstly, we simply lowered ionic contaminants in the hydrogel and were able to enhance the anisotropic parameter from 3.0 to 18. Then, we chose a supporting polymer network allowing the hydrogel to carry a higher interior permittivity. Consequently, the anisotropic parameter was further enhanced from 18 to 85. Owing to the enhanced mechanical anisotropy, our new hydrogel displayed a superb ability of seismic isolation. [ABSTRACT FROM AUTHOR]

Die intramolekulare Kraftkompensation stellt ein neuartiges Verfahren dar, mit dem die Ansprechzeit von chemischen Sensoren auf Hydrogelbasis verkürzt werden kann. Bei dieser Art der Kraftkompensation sind sowohl Sensor- als auch Aktorfunktion in einem einzigen Hydrogel kombiniert. Dieser Beitrag legt die Messmethode, das hierzu notwendige bisensitive Hydrogel und einen entsprechenden Sensoraufbau dar. Die Ergebnisse zeigen, dass sowohl die gewünschte Bisensitivität des Sensors als auch eine Verkürzung der Ansprechzeit erreicht werden konnten. The method of intramolecular force compensation forms a new approach for reducing the response time of hydrogel-based chemical sensors. The principle is based on a bisensitive hydrogel, that fulfills both the function of a sensor and an actuator. This paper presents the measurement principle, the required bisensitive hydrogel and a sensor setup. The results show the desired bisensitivity of the sensor as well as the successfull reduction of the response time. [ABSTRACT FROM AUTHOR]

Abstract: Hydrophobic reduced graphene oxides (rGOs) were generated in agarose hydrogel beads (AgarBs) by NaBH4 reduction of graphene oxides (GOs) initially loaded in the AgarBs. The resulting rGO‐loaded AgarBs were able to effectively adsorb organic compounds in water as a result of the attractive hydrophobic force between the rGOs in the AgarBs and the organic compounds dissolved in aqueous media. The adsorption capacity of the rGOs was fairly high even toward reasonably water‐soluble organic compounds such as rhodamine B (321.7 mg g−1) and aspirin (196.4 mg g−1). Yet they exhibited salinity‐enhanced adsorption capacity and preferential adsorption of organic compounds with lower solubility in water. Such peculiar adsorption behavior highlights the exciting possibility for adopting an adsorption strategy, driven by hydrophobic forces, in practical wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Abstract: Controlling supramolecular growth at solid surfaces is of great importance to expand the scope of supramolecular materials. A dendritic benzene‐1,3,5‐tricarboxamide peptide conjugate is described in which assembly can be triggered by a pH jump. Stopped‐flow kinetics and mathematical modeling provide a quantitative understanding of the nucleation, elongation, and fragmentation behavior in solution. To assemble the molecule at a solid–liquid interface, we use proton diffusion from the bulk. The latter needs to be slower than the lag phase of nucleation to progressively grow a hydrogel outwards from the surface. Our method of surface‐assisted self‐assembly is generally applicable to other gelators, and can be used to create structured supramolecular materials. [ABSTRACT FROM AUTHOR]

Abstract: Micro‐ and nanomotors and their use for biomedical applications have recently received increased attention. However, most designs use top‐down methods to construct inorganic motors, which are labour‐intensive and not suitable for biomedical use. Herein, we report a high‐throughput design of an asymmetric hydrogel microparticle with autonomous movement by using a microfluidic chip to generate asymmetric, aqueous, two‐phase‐separating droplets consisting of poly(ethylene glycol) diacrylate (PEGDA) and dextran, with the biocatalyst placed in the PEGDA phase. The motor is propelled by enzyme‐mediated decomposition of fuel. The speed of the motors is influenced by the roughness of the PEGDA surface after diffusion of dextran and was tuned by using higher molecular weight dextran. This roughness allows for easier pinning of oxygen bubbles and thus higher speeds of the motors. Pinning of bubbles occurs repeatedly at the same location, thereby resulting in constant circular or linear motion. [ABSTRACT FROM AUTHOR]

Abstract: Self‐healing solid‐state aqueous rechargeable NiCo||Zn batteries are inherently safe and have a high energy density and mechanical robustness. However, the self‐healability of solid‐state batteries has only been realized by a few studies in which electron/ion‐inactive self‐healable substrates are utilized. This arises from the lack of self‐healable electrolytes. Now an intrinsically self‐healing battery has been designed that utilizes a new electrolyte that is intrinsically self‐healable. Sodium polyacrylate hydrogel chains are crosslinked by ferric ions to promote dynamic reconstruction of an integral network. These non‐covalent crosslinkers can form ionic bonds to reconnect damaged surfaces when the hydrogel is cut off, providing an ultimate solution to the intrinsic self‐healability problem of batteries. As a result, this NiCo||Zn battery with this hydrogel electrolyte can be autonomically self‐healed with over 87 % of capacity retained after 4 cycles of breaking/healing. [ABSTRACT FROM AUTHOR]

Abstract: Macroscopic supramolecular assembly (MSA) is a recent development in supramolecular chemistry to associate visible building blocks through non‐covalent interactions in a multivalent manner. Although various substrates (e.g. hydrogels, rigid materials) have been used, a general design rule of building blocks in MSA systems and interpretation of the assembly mechanism are lacking and are required. Herein we design three model systems with varied elastic modulus and correlated the MSA probability with the elasticity. Based on the effects of substrate deformability on multivalency, we have proposed an elastic‐modulus‐dependent rule that building blocks below a critical modulus of 2.5 MPa can achieve MSA for the used host/guest system. Moreover, this MSA rule applies well to the design of materials for fast underwater adhesion: Soft substrates (0.5 MPa) can achieve underwater adhesion within 10 s with one order of magnitude higher strength than that of rigid substrates (2.5 MPa). [ABSTRACT FROM AUTHOR]

Abstract: Oligopeptide‐based supramolecular hydrogels hold promise in a range of applications. The gelation of these systems is hard to control, with minor alterations in the peptide sequence significantly influencing the self‐assembly process. We explored three pentapeptide sequences with different charge distributions and discovered that they formed robust, pH‐responsive hydrogels. By altering the concentration and charge distribution of the peptide sequence, the stiffness of the hydrogels could be tuned across two orders of magnitude (2–200 kPa). Also, through reassembly of the β‐sheet interactions the hydrogels could self‐heal and they demonstrated shear‐thin behavior. Using spectroscopic and cryo‐imaging techniques, we investigated the relationship between peptide sequence and molecular structure, and how these influence the mechanical properties of the hydrogel. These pentapeptide hydrogels with tunable morphology and mechanical properties have promise in tissue engineering, injectable delivery vectors, and 3D printing applications. [ABSTRACT FROM AUTHOR]

Abstract: Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to −70 °C and are stable under ambient conditions or even vacuum. [ABSTRACT FROM AUTHOR]

Abstract: α‐Synuclein (α‐Syn) aggregation is associated with Parkinson's disease (PD) pathogenesis. In PD, the role of oligomers versus fibrils in neuronal cell death is debatable, but recent studies suggest oligomers are a proximate neurotoxin. Herein, we show that soluble α‐Syn monomers undergo a transformation from a solution to a gel state on incubation at high concentration. Detailed characterization of the gel showed the coexistence of monomers, oligomers, and short fibrils. In vitro, the gel was highly cytotoxic to human neuroblastoma cells. The individual constituents of the gel are short‐lived species but toxic to the cells. They comprise a structurally heterogeneous population of α‐helical and β‐sheet‐rich oligomers and short fibrils with the cross‐β motif. Given the recent evidence of the gel‐like state of the protein associated with neurodegenerative diseases, the gel state of α‐Syn in this study represents a mechanistic and structural model for the in vivo toxicity of α‐Syn in PD. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we report that assemblies of nucleopeptides selectively sequester ATP in complex conditions (for example, serum and cytosol). We developed assemblies of nucleopeptides that selectively sequester ATP over ADP. Counteracting enzymes interconvert ATP and ADP to modulate the nanostructures formed by the nucleopeptides and the nucleotides. The nucleopeptides, sequestering ATP effectively in cells, slow down efflux pumps in multidrug‐resistant cancer cells, thus boosting the efficacy of doxorubicin, an anticancer drug. Investigation of 11 nucleopeptides (including d‐ and l‐enantiomers) yields five more nucleopeptides that differentiate ATP and ADP through either precipitation or gelation. As the first example of assemblies of nucleopeptides that interact with ATP and disrupt intracellular ATP dynamics, this work illustrates the use of supramolecular assemblies to interact with small and essential biological molecules for controlling cell behavior. [ABSTRACT FROM AUTHOR]

Abstract: Gelation mechanism is of utmost importance to the rational design of supramolecular hydrogelators. Although both kinetic and thermodynamic controlled self‐assembly processes have been widely studied in hydrogels, the formation relationship between crystalline and amorphous gel networks still remains ambiguous. Herein, a gelation transformation from a kinetic to a thermodynamic process was achieved by balancing the rigidity and flexibility of the inorganic–organic co‐assemblies. By using polyoxometalates and zwitterionic amphiphiles, the transition morphologies between crystalline and amorphous hydrogel networks were evidenced for the first time, as ordered wormlike micelles. Given the versatile applications of hydrogels in biological systems and materials science, these findings may highlight the potential of inorganic–organic binary supramolecular hydrogelators and fill in the blank between kinetic and thermodynamic controlled gelation processes. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogele gelten wegen ihrer wasserreichen Strukturen, die denjenigen von biologischen Geweben ähneln, seit langem als vielversprechende Trägermaterialien für künstliche Gewebe und Organe. Allerdings unterscheiden sich die meisten synthetischen Hydrogele hinsichtlich der strukturellen Anisotropie erheblich von biologischen Systemen. Synthetische Hydrogele sind üblicherweise aus zufällig ausgerichteten, dreidimensionalen Polymernetzwerken zusammengesetzt. Demgegenüber nehmen biologische Systeme anisotrope Strukturen mit hierarchisch strukturierten Baueinheiten an. Solche anisotropen Strukturen spielen bei biologischen Systemen oft eine entscheidende Rolle für die Ausübung bestimmter Funktionen. In diesem Zusammenhang eröffnen anisotrope Hydrogele einen Zugang zur Erforschung biomimetischer Hydrogelanwendungen. In letzter Zeit haben Untersuchungen anisotroper Hydrogele zugenommen. Dieser Kurzaufsatz beleuchtet die Anwendung und die Perspektiven dieser anisotropen Hydrogele unter besonderer Berücksichtigung ihrer Herstellung und Strukturen. [ABSTRACT FROM AUTHOR]

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Abstract: Cellulose nanocrystals (CNCs) with >2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross‐linkers, as well as covalently embedded nanofillers for nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape‐persistent and free‐standing 3D structured objects were printed with a mono‐functional methacrylate, showing a superior swelling capacity and improved mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Solid‐state electrolytes have emerged as a promising alternative to existing liquid electrolytes for next generation Li‐ion batteries for better safety and stability. Of various types of solid electrolytes, composite polymer electrolytes exhibit acceptable Li‐ion conductivity due to the interaction between nanofillers and polymer. Nevertheless, the agglomeration of nanofillers at high concentration has been a major obstacle for improving Li‐ion conductivity. In this study, we designed a three‐dimensional (3D) nanostructured hydrogel‐derived Li0.35La0.55TiO3 (LLTO) framework, which was used as a 3D nanofiller for high‐performance composite polymer Li‐ion electrolyte. The systematic percolation study revealed that the pre‐percolating structure of LLTO framework improved Li‐ion conductivity to 8.8×10−5 S cm−1 at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: We herein describe the tandem molecular self‐assembly of a peptide derivative (1) that is controlled by a combination of enzymatic and chemical reactions. In phosphate‐buffered saline (PBS), compound 1 self‐assembles first into nanoparticles by phosphatase and then into nanofibers by glutathione. Liver cancer cells exhibit higher concentrations of both phosphatase and GSH than normal cells. Therefore, the tandem self‐assembly of 1 also occurs in the liver cancer cell lines HepG2 and QGY7703; compound 1 first forms nanoparticles around the cells and then forms nanofibers inside the cells. Owing to this self‐assembly mechanism, compound 1 exhibits large ratios for cellular uptake and inhibition of cell viability between liver cancer cells and normal liver cells. We envision that using both extracellular and intracellular reactions to trigger tandem molecular self‐assembly could lead to the development of supramolecular nanomaterials with improved performance in cancer diagnostics and therapy. [ABSTRACT FROM AUTHOR]