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Transition metal dichalcogenides (TMDs) have long been thought to be alternatives for noble Pt/Ir metals as hydrogen evolution reaction electrocatalysts. However, sparse active sites and poor electrical property, two of the most formidable challenges for their electrocatalytic performance, can hardly be improved just by existing methods. Herein, tungsten (W)@tungsten disulfide (WS2) core–shell nanospheres (CSNSs) were synthesized via one-step laser-assisted strategy. Through introducing multifunctional CSNSs, metallic WS2 hierarchically curves on the W core with a curvature as high as 10−2 nm−1 make the interlayer spacing of WS2 broaden significantly and then expose more catalytic sites. Moreover, the electrical conductivity of the electrocatalyst rises 4.5 times via a highly electroconductive W core. The electrochemical surface area of WS2 is also greatly enlarged by forming a 3D nanospheres-aggregated nanoporous van der Waals heterostructure. Calculations indicate that CSNSs contribute to optimizing the hydrogen adsorption Gibbs free energy, and modulating the electronic occupation around the Fermi level. Among these, W sites on the curved shell emerge as the most active catalytic centers. Further experiments demonstrate that W@WS2 CSNSs can therefore exhibit superior catalytic activities featuring a small overpotential of 161 mV at 10 mA cm−2, an ultralong durability in acids (∼100 h) and most importantly, the smallest Tafel slope (34.5 mV dec−1) and the biggest electrical double-layer capacitance (62.2 mF cm−2) among WS2-based electrocatalysts. This study opens a pathway to develop site-rich and highly electroconductive TMDs, which not only act as high performance water electrolysis catalysts on a large scale, but can also be used for batteries, supercapacitors and electrochemical actuators.

Repairing osteochondral defects is a considerable challenge because it involves the breakdown of articular cartilage and underlying bone. Traditional hydrogels with a homogenized single-layer structure cannot fully restore the function of osteochondral cartilage tissue. In this study, a mussel-inspired hydrogel with a bilayer structure is developed to repair osteochondral defects. The hydrogel is synthesized by simultaneously polymerizing two layers using a one-pot method. The resulting upper and lower gelatin methacryloyl-polydopamine hydrogel layers are used as cartilage and subchondral bone repair layers, respectively. Polydopamine-induced hydroxyapatite in situ mineralization takes place in the lower layer to mimic the structure of subchondral bone. The bilayer hydrogel exhibits good mechanical properties for the synergistic effect of covalent and noncovalent bonds, as well as nanoreinforcement of mineralized hydroxyapatite. To improve the tissue-inducibility of hydrogels, transforming growth factor β3 is immobilized in the upper layer to induce cartilage regeneration, while bone morphogenetic protein 2 is immobilized in the lower layer to induce bone regeneration. Bone and cartilage repair performance of the hydrogel is examined by implantation into a full-thickness cartilage defect of a rabbit knee joint. The bilayer-structure hydrogel promotes regeneration of osteochondral tissue, thus providing a new option for repair of osteochondral defects.

Tough and conductive hydrogels are the promising materials for various applications. However, fabrication of these hydrogels at room or low temperatures, without external stimuli, is a challenge. H...

Adhesive hydrogels have gained popularity in biomedical applications, however, traditional adhesive hydrogels often exhibit short-term adhesiveness, poor mechanical properties and lack of antibacterial ability. Here, a plant-inspired adhesive hydrogel has been developed based on Ag-Lignin nanoparticles (NPs)triggered dynamic redox catechol chemistry. Ag-Lignin NPs construct the dynamic catechol redox system, which creates long-lasting reductive-oxidative environment inner hydrogel networks. This redox system, generating catechol groups continuously, endows the hydrogel with long-term and repeatable adhesiveness. Furthermore, Ag-Lignin NPs generate free radicals and trigger self-gelation of the hydrogel under ambient environment. This hydrogel presents high toughness for the existence of covalent and non-covalent interaction in the hydrogel networks. The hydrogel also possesses good cell affinity and high antibacterial activity due to the catechol groups and bactericidal ability of Ag-Lignin NPs. This study proposes a strategy to design tough and adhesive hydrogels based on dynamic plant catechol chemistry., Biomimetic catechol-based adhesives have attracted significant interest but can lose adhesion due to excessive oxidation. Here, the authors report on the addition of silver-Lignin nanoparticles as a dynamic catechol redox system to maintain catechol/quinone balance, making a reusable, antibacterial bioadhesive.

Gelatin methacryloyl (GelMA) hydrogels are widely used for tissue regeneration. Nonetheless, a pure GelMA hydrogel cannot efficiently serve for cartilage regeneration because of weak mechanical properties and brittleness. In this study, we established a mussel-inspired strategy for tuning the mechanical properties of GelMA hydrogels by intercalating oligomers of dopamine methacrylate (ODMA) into the chain of GelMA. After the ODMA intercalated, the hydrogel became tough and resilient. This is because ODMA intercalation reduces the high density of entangled GelMA chains and introduces additional sacrificial physical cross-linking into the hydrogel. Rheological analysis showed that the ODMA-GelMA hydrogel was mechanically stable at body temperature. The hydrogel also manifested a sustained protein release because of the ODMA catechol groups. Furthermore, the ODMA-GelMA hydrogel was found to have good biocompatibility and affinity for cells and tissues because of the catechol groups on ODMA. In vitro, the hydrogel promoted mesenchymal stem cell adhesion and growth, and in vivo, it promoted cartilage regeneration after loading with chondroitin sulfate or TGF-β3. The hydrogel can serve as a growth-factor-free scaffold for cartilage regeneration. This hydrogel not only provided a favorable microenvironment for cartilage repair but also could serve as a promising candidate material for repair of other tissues. This mussel-inspired strategy of introduction of reactive oligomers instead of polymers into a brittle hydrogel network may be extended to the development of other tough hydrogels for biomedical applications.

Conductive hydrogels (CHs) have gained significant attention for their wide applications in biomedical engineering owing to their structural similarity to soft tissues. However, designing CHs that combine biocompatibility with good mechanical and electrical properties is still challenging. Herein, we report a new strategy for the fabrication of tough CHs with excellent conductivity, superior mechanical properties, and good biocompatibility by using chitosan framework as molecular templates for controlling conducting polypyrrole (PPy) nanorods in situ formation inside the hydrogel networks. First, polyacrylamide/chitosan (CS) interpenetrating polymer network hydrogel was synthesized by UV photopolymerization; second, hydrophobic and conductive pyrrole monomers were absorbed and fixed on CS molecular templates and then polymerized with FeCl