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The repair of cartilage injuries and defects in the knee presents a significant challenge in the field of human joint surgery. A promising solution involves the synergy of three-dimensional printing and articular cartilage tissue engineering. This research primarily focuses on the formulation of composite hydrogels comprising gelatin methacryloyl (GelMA), silk fibroin (SF) and hydroxyapatites (Haps), with a thorough examination of their morphology and mechanical properties. We also conducted tests on stacking height and grid area to assess the 3D printability of GM/SF/Haps inks. To evaluate the suitability of GM/SF/Haps scaffolds in cartilage regeneration, we performed 2D culture with mouse chondrocytes (ATDC5) inoculated on hydrogel surface and 3D culture with ATDC5 mixed in printing scaffolds. The assessment involved various techniques, such as Live/Dead staining, Cell Counting Kit-8 (CCK-8) assay, immunofluorescence staining and cytoskeleton staining. The outcomes of this investigation revealed that the inclusion of Haps significantly enhanced cell viability, cell proliferation and the differentiation of chondrocytes within the composite scaffolds. Consequently, this study underscores the promising potential of GM/SF/Haps scaffolds in the domain of cartilage regeneration. [ABSTRACT FROM AUTHOR]

Osteochondral defect caused by trauma or osteoarthritis exhibits a major challenge in clinical treatment with limited symptomatic effects at present. The regeneration and remodeling of subchondral bone play a positive effect on cartilage regeneration and further promotes the repair of osteochondral defects. Making use of the strengths of each preparation method, the combination of 3D printing and electrospinning is a promising method for designing and constructing multi-scale scaffolds that mimic the complexity and hierarchical structure of subchondral bone at the microscale and nanoscale, respectively. In this study, the 3D printed-electrospun poly(ɛ-caprolactone)/nano-hydroxyapatites/multi-walled carbon nanotubes (PCL/nHA/MWCNTs) scaffolds were successfully constructed by the combination of electrospinning and layer-by-layer 3D printing. The resulting dual-scale scaffold consisted of a dense layer of disordered nanospun fibers and a porous microscale 3D scaffold layer to support and promote the ingrowth of subchondral bone. Herein, the biomimetic PCL/nHA/MWCNTs scaffolds enhanced cell seeding efficiency and allowed for higher cell–cell interactions that supported the adhesion, proliferation, activity, morphology and subsequently improved the osteogenic differentiation of bone marrow mesenchymal stem cells in vitro. Together, this study elucidates that the construction of 3D printed-electrospun PCL/nHA/MWCNTs scaffolds provides an alternative strategy for the regeneration of subchondral bone and lays a foundation for subsequent in vivo studies. [ABSTRACT FROM AUTHOR]

Micro-supercapacitors (MSCs) with excellent electrochemical behaviours and flexibility possess great promise for portable and wearable electronic devices. A novel type of hybrid-dimensional Fe2O3/graphene/Ag ink is developed and extruded into MSC electrodes through the direct ink writing-based three-dimensional (3D) printing. The optimal solid-state MSC device exhibits a maximum areal capacitance of 412.3 mF cm−2 at 2 mA cm−2, a correspondingly high energy density of 65.4 μWh cm−2 and 89% capacitance retention for over 5000 charge and discharge cycles. The superior electrochemical performance is profited by the high electron transport synergistically boosted by two-dimensional graphene nanosheets and one-dimensional Ag nanowires, and the high pseudocapacitive behaviours of Fe2O3 nanoparticles. The 3D printed MSC exhibits reliable flexibility with remarkable retention of 90.2% of its original capacitance after 500 bending cycles. The current 3D printing fabrication demonstrates an efficient route for advanced miniaturised electrochemical energy storage. [ABSTRACT FROM AUTHOR]