Publikationen

We idealise dendrite growth in a ceramic electrolyte by climb of a thick edge dislocation. Growth of the dendrite occurs at constant chemical potential of Li+ at the dendrite tip: the free-energy to fracture and wedge open the electrolyte is provided by the flux of Li+ from the electrolyte into the dendrite tip. This free-energy is dependent on the Li+ overpotential at the dendrite tip and is thereby related to the imposed charging current density. The predicted critical current density agrees with measurements for Li/LLZO/Li symmetric cells: the critical current density decreases with increasing initial length of the dendrite and with increasing electrode/electrolyte interfacial ionic resistance. The simulations also reveal that a void on the cathode/electrolyte interface locally enhances the Li+ overpotential and significantly reduces the critical current density for the initiation of dendrite growth.

The ability to generate programmable vertically aligned 1D nanoscale substrate topography has spurred advances in five fields of cellular nanotechnology: nanoelectrode-based electrophysiology, intracellular delivery, biosensing, mechanotransduction, and – the focus of this review – understanding the key parameters that govern nanostructure-mediated electroporation for diverse cellular manipulations. The integration of 1D nanostructures into conventional cell manipulation and interrogation systems, based on electroporation, has engendered significant interest over the past decade. We evaluate the latest and most influential studies on engineered nanostructure-mediated electroporation platforms, focusing on the use of tuneable, vertically configured nanostructures – in particular, vertically aligned nanowire, nanostraw, and nanotube arrays – to orchestrate cellular processes such as intracellular delivery, biomolecular extraction, and action potential probing, via both experimental and theoretical studies.

Human bone becomes increasingly brittle with ageing. Bones also fracture differently under slow and fast loadings, being ductile and brittle, respectively. The effects of a combination of these two factors have never been examined before. Here we show that cortical bone is most fracture-resistant at the physiologically prevalent intermediate strain rates of 10−3 s−1 to 10−2 s−1 such as they occur in walking or running, slightly weaker at slower quasistatic and much weaker at fast impact loading rates. In young cortical bone (15 years of age) the ductile-to-brittle transition (DBT) occurs at strain rates of 10−2 s−1, in old cortical bone (85 yrs) at speeds lower by a factor of 10 to 40. Other research has shown that the energy required to break bone (per unit of fracture surface) drops as much as 60% between these two ages. Therefore, DBT seems to compound the well-known phenomenon of ‘brittle old bones’. Old bones can only cope with slow movement, young ones with both slow and fast movement. These observed material characteristics of (i) a shift of the DBT and (ii) a reduced energy absorption capacity appear to contribute at least as much to the loss of bone quality as the various quantity based (lowered bone density and mineral content) explanations of the past. They also provide a new powerful paradigm, which allows us to demonstrate mechanically, and uniquely, how human bone becomes increasingly brittle with age.

Abstract Adhesive hydrogels are widely applied for biological and medical purposes; however, they are generally unable to adhere to tissues under wet/underwater conditions. Herein, described is a class of novel dynamic hydrogels that shows repeatable and long-term stable underwater adhesion to various substrates including wet biological tissues. The hydrogels have Fe3+-induced hydrophobic surfaces, which are dynamic and can undergo a self-hydrophobization process to achieve strong underwater adhesion to a diverse range of dried/wet substrates without the need for additional processes or reagents. It is also demonstrated that the hydrogels can directly adhere to biological tissues in the presence of under sweat, blood, or body fluid exposure, and that the adhesion is compatible with in vivo dynamic movements. This study provides a novel strategy for fabricating underwater adhesive hydrogels for many applications, such as soft robots, wearable devices, tissue adhesives, and wound dressings.

Developing a versatile probe for targeting the lysosomes of specific cancer cells and subsequently detecting glutathione (GSH) levels is critical in disclosing the roles of GSH in the lysosomal oxidative stress of cancer cells. Herein, we demonstrate an efficient strategy for the preparation of a dual-targeting (both cancer cell- and lysosome-targeting) fluorescence nanoprobe (DTFN) that enables the imaging of GSH in the lysosomes of specific cancer cells. The nanoprobe (DTFN) is obtained by combining folic acid (FA)-modified photostable aggregation-induced emission dots with GSH-responsive manganese dioxide (MnO2) nanosheets via electrostatic interactions. DTFN has outstanding characteristics of good water dispersity, delightful photostability, shorter responsive time (∼5 min) and wide pH-response range. Intracellular experiments showed that the as-prepared DTFN could be preferentially internalized into a folate receptor (FR)-positive cancer cells via the FR-mediated endocytosis. Subsequently, with the aid of the positively charged amino moiety of the nanoprobe, DTFN can selectively accumulate in lysosomes and successfully achieve the real-time imaging of the lysosomal GSH levels in FR-positive cancer cells. This study highlights a strategy to design a versatile dual-targeting fluorescence probe for enhanced cancer imaging.

Abstract Developing a novel strategy to synthesize photoresponsive polymers is of significance owing to their potential applications. We report a photoinduced strain-assisted synthesis of main-chain stiff-stilbene polymers by using ring-opening metathesis polymerization (ROMP), activating a macrocyclic π-bond connected to a stiff-stilbene photoswitch through a linker. Since the linker acts as an external constraint, the photoisomerization to the E-form leads to the stiff-stilbene being strained and thus reactive to ROMP. The photoisomerization of Z-form to E-form was investigated using time-dependent NMR studies and UV/Vis spectroscopy. The DFT calculation showed that the E-form was less stable due to a lack of planarity. By the internal strain developed due to the linker constraint through photoisomerization, the E-form underwent ROMP by a second generation Grubbs catalyst. In contrast, Z-form did not undergo polymerization under similar conditions. The MALDI-TOF spectrum of E-form after polymerization showed the presence of oligomers of >5.2 kDa.

Abstract In recent years, various hydrogels with a wide range of functionalities have been developed. However, owing to the two major drawbacks of hydrogels—air-drying and water-swelling—hydrogels developed thus far have yet to achieve most of their potential applications. Herein, a bioinspired, facile, and versatile method for fabricating hydrogels with high stability in both air and water is reported. This method includes the creation of a bioinspired homogeneous fusion layer of a hydrophobic polymer and oil in the outermost surface layer of the hydrogel via a double-hydrophobic-coating produced through quenching. As a proof-of-concept, this method is applied to a polyacrylamide hydrogel without compromising its mechanical properties. The coated hydrogel exhibits strong resistance to both drying in air and swelling in multiple aqueous environments. Furthermore, the versatility of this method is demonstrated using different types of hydrogels and oils. Because this method is easy to apply and is not dependent on hydrogel surface chemistry, it can significantly broaden the scope of next-generation hydrogels for real-world applications in both wet and dry environments.

Physical entanglement of polymer chains is an interaction that is believed to be too weak to build polymer networks for hydrogelation. Herein, we report a cluster strategy for preparing a class of fundamentally new hydrogels that are crosslinked by only entanglement interaction of polymer chains. The entanglement cluster is created by in situ polymerization of the monomer (acrylamide) in polyacrylamide nanogels to form long inter-connected polyacrylamide chains passing through nanogels. The as-prepared hydrogels can swell high content of water to achieve very low polymer fractions (∼1 wt%). Although they contain an ultrahigh water content and possess an ultra-soft nature (low to ∼10 Pa storage modulus), these physical entanglement hydrogels (PEH) are tough and stretchable (>6 times) due to the free-sliding dynamics of the entanglement-cluster crosslinking interaction. Moreover, this free-sliding nature allows PEH to fully recover their mechanical properties after lyophilization–rehydration treatment. Because of their novel properties, PEH should be promising for various applications.

The design of novel ratiometric nanoprobes with two well-resolved fluorescence bands for accurate imaging of lysosomal hypochlorous acid (HClO) is significant to understand its biological and pathological behaviors. Herein, we develop a single-dye-doped self-referenced ratiometric nanoprobe (SSRN) for imaging of HClO in lysosomes under a single-wavelength excitation (λex = 405 nm). The referenced unit (benzothiazole moiety) and HClO-responsive unit (rhodamine B) are integrated into the single dye (HB-Py) to achieve the self-referenced ratiometric effect. The well-dispersed SSRN are prepared by a simple coprecipitation of the morpholine moiety modified amphiphilic polymers (CO-720-MA) and HB-Py. Of note, the two well-resolved fluorescence bands (∼130 nm) of SSRN could provide accurate imaging of analyte in live cells. Additionally, other distinct merits with SSRN are also simultaneously realized, including high water solubility, high sensitivity (detection limit: 52 nM), excellent selectivity, good biocompatibility and excellent photostability. Significantly, benefiting from the morpholine moiety, this nanoprobe SSRN can specially locate lysosomes and enable ratiometric imaging of exogenous/endogenous HClO in lysosomes.

Disulfide bonds are commonly exploited as dynamic crosslinks to fabricate degradable self-healing hydrogels. However, the low energy dissipation capability and low density of disulfide crosslinks in the hydrogel networks give these hydrogels poor mechanical properties, slow and non-autonomous self-healing, and incomplete polymer degradation. This paper reports a strategy for synthesizing multifunctional hydrogels by copolymerizing 2,3-dimercapto-1-propanol and meso-2,3-dimercaptosuccinic acid, yielding a dynamic poly(disulfide) backbone and numerous rapidly reversible physical crosslinks (H-bonds and ionic interactions). The high-density disulfide bonds and multiphysical crosslinkers synergistically provide the hydrogels with extremely fast self-healing in air and underwater, extraordinary stretchability, and complete and fast degradability. The hydrogels show various functionalities including three-dimensional printability in air and underwater, good electrical conductivity, non-cytotoxicity and bio-tissue adhesion. This strategy opens a new route for exploiting degradable self-healing multifunctional hydrogels with extraordinary features for biomedical and engineering applications.