Exosomes derived from human adipose-derived stem cells (hADSCs-Exos) have shown potential as an effective therapeutic tool for repairing bone defects. Although metal-organic framework (MOF) scaffolds are promising strategies for bone tissue regeneration, their potential use for exosome loading remains unexplored. In this study, motivated by the potential advantages of hADSCs-Exos and Mg-GA MOF, we designed and synthesized an exosome-functionalized cell-free PLGA/Mg-GA MOF (PLGA/Exo-Mg-GA MOF) scaffold, taking using of the benefits of hADSCs-Exos, Mg²⁺, and gallic acid (GA) to construct unique nanostructural interfaces to enhance osteogenic, angiogenic and anti-inflammatory capabilities simultaneously. Our in vitro work demonstrated the beneficial effects of PLGA/Exo-Mg-GA MOF composite scaffolds on the osteogenic effects in human bone marrow-derived mesenchymal stem cells (hBMSCs) and angiogenic effects in human umbilical endothelial cells (HUVECs). Slowly released hADSCs-Exos from composite scaffolds were phagocytosed by co-cultured cells, stabilized the bone graft environment, ensured blood supply, promoted osteogenic differentiation, and accelerated bone reconstruction. Furthermore, our in vivo experiments with rat calvarial defect model showed that PLGA/Exo-Mg-GA MOF scaffolds promoted new bone formation and satisfactory osseointegration. Overall, we provide valuable new insights for designing exosome-coated nanocomposite scaffolds with enhanced osteogenesis property.

This paper aims to use ${}^{29}\mathrm{Si}$ nuclear magnetic resonance (NMR) for investigating the effect of nanofillers on the C-S-H gel structure of hardened cement paste, analyze the modification mechanism of nanofillers from a microscopic perspective, and then provide fundamentals for controlling the macroscopic properties of cement-based materials. Different curing temperatures (25°C and 90°C) and nanofiller types [including $\mathrm{nano}\text{-}{\mathrm{SiO}}_2$ , $\mathrm{nano}\text{-}{\mathrm{ZrO}}_2$ , $\mathrm{nano}\text{-}{\mathrm{TiO}}_2$ , carbon nanotubes (CNTs), nano-boron nitride (nano-BN), and multilayer graphenes (MLGs)] are considered as the influencing factors. Three characterization parameters [polymerization degree, mean molecular chain length (MCL), and hydration degree] are calculated and used as the evaluation indexes. Experimental results show that the incorporation of most types of nanofillers can cause increases in all of these three parameters. With the increase of curing temperature, the polymerization degree of C-S-H gel is further enhanced, because the layered or even spatial network structures of silicate tetrahedron occur in the C-S-H gel. The composites with MLGs present the maximum increase values of polymerization degree, MCL, and hydration degree, by 786.2%, 166.5%, and 27.4% compared with control cement paste, respectively, which is mainly attributed to the nanofiller morphology (unique two-dimensional stacked flake structure) and the functional group (carboxyl-functionalized) on the surface of nanofillers. Fluctuations of polymerization degree and MCL appear in composites with $\mathrm{nano}\text{-}{\mathrm{TiO}}_2$ and with CNTs, relative to the particle sizes, crystal phases, and surface modification of nanofillers. The effect mechanisms of nanofillers on C-S-H gel can be attributed to two main aspects: (1) the nucleation effect and pozzolanic effect (just for $\mathrm{nano}\text{-}{\mathrm{SiO}}_2$ ) of nanofillers facilitate the cement hydration; (2) the high water absorption capability of nanofillers reduces the proton water inside C-S-H gel, and shortens the distance between the structural groups of Ca, O, and Si atoms. The chemical bonds (ionic bonds and covalent bonds) between these groups are enhanced and the values of polymerization degree and MCL are therefore increased.

Hydrogels are considered to be one of the promising candidates for wearable sensors due to their ideal designability and excellent mechanical flexibility. Nevertheless, the preparation of ion-conductive hydrogels with excellent mechanical properties by simple methods remains a great challenge. Herein, a unique hierarchical cross-linked network is fabricated in a polyacrylamide–hyaluronic acid (PAM–HA) hybrid hydrogel, achieving a dramatic improvement in the overall mechanical properties of the system. This hydrogel has been shown to have ideal transmittance (>90%), super stretchability (with a breaking elongation of 3040%), high mechanical strength (breaking strength up to 317.8 kPa), satisfactory toughness (3.07 MJ m⁻³), and excellent fatigue resistance. Furthermore, the hybrid hydrogel also shows remarkable self-adhesive performance on different substrates, including ceramics, glass, metals, plastics, and pigskin, and maintains a stable repeat adhesion strength. Attractively, the hydrogel-based strain sensor shows an amazing detection range of over 1000% and a lower detection limit of 1%, which enables it to accurately capture and monitor large and subtle human motions. This work can provide a new method for the construction of hydrogels with ideal comprehensive mechanical properties and promote the application of hydrogels in the field of wearable sensors.

The interfacial bond strength and field-induced storage modulus of magnetorheological elastomers can be enhanced by using flower-like active particles.