Coaxial electrohydrodynamic printing of core–shell microfibrous scaffolds with layer-specific growth factors release for enthesis regeneration

The rotator cuff tear has emerged as a significant global health concern.However,existing therapies fail to fully restore the intricate bone-to-tendon gradients,resulting in compromised biomechanical functionalities of the reconstructed enthesis tissues.Herein,a tri-layered core–shell microfibrous scaffold with layer-specific growth factors(GFs)release is developed using coaxial electrohydrodynamic(EHD)printing for in situ cell recruitment and differentiation to facilitate gradient enthesis tissue repair.Stromal cell-derived factor-1(SDF-1)is loaded in the shell,while basic fibroblast GF,transforming GF-beta,and bone morphogenetic protein-2 are loaded in the core of the EHD-printed microfibrous scaffolds in a layer-specific manner.Correspondingly,the tri-layered microfibrous scaffolds have a core–shell fiber size of(25.7±5.1)μm,with a pore size sequentially increasing from(81.5±4.6)μm to(173.3±6.9)μm,and to(388.9±6.9μm)for the tenogenic,chondrogenic,and osteogenic instructive layers.A rapid release of embedded GFs is observed within the first 2 d,followed by a faster release of SDF-1 and a slightly slower release of differentiation GFs for approximately four weeks.The coaxial EHD-printed microfibrous scaffolds significantly promote stem cell recruitment and direct their differentiation toward tenocyte,chondrocyte,and osteocyte phenotypes in vitro.When implanted in vivo,the tri-layered core–shell microfibrous scaffolds rapidly restored the biomechanical functions and promoted enthesis tissue regeneration with native-like bone-to-tendon gradients.Our findings suggest that the microfibrous scaffolds with layer-specific GFs release may offer a promising clinical solution for enthesis regeneration.

Highly strengthening and toughening biomimetic ceramic structures fabricated via a novel coaxially printing

Additive manufacturing technology,by manipulating and emulating inherent multiscale,multi-material,and multifunctional structures found in nature,has created new opportunities for constructing heterogeneous structures associated with special properties and achieving ultra-high mechanical performance and reliability in ceramic composite materials.In this study,we have developed an innovative fabrication method designated as coaxial 3D printing for the synchronous construction of two constituents into ceramic composites with a tooth enamel biomimetic microstructure.Herein,the stiff silicate and flexible epoxy served as a strengthening bridge and toughening layer,respectively.The method differed from the traditional approach of randomly dispersing reinforcing components within a ceramic matrix.It allowed for the direct creation of an internally effective three-dimensional reinforcement network structure in ceramic composites.This process facilitated synergistic deformation and simultaneous enhancement of multiple materials and hierarchical structures.Owing to the uniform distribution of internal stress and effective block of microcrack propagation,the biomimetically structured silicate/epoxy ceramic composite has demonstrated much significant enhancement in mechanical properties,includingcompressive strength(48.8±3.12MPa),flexuralstrength(10.39±1.23MPa),andflexuraltoughness(218.7±54.6kJ/m^(3)),which was 0.5,2.1,and 47.5 times as high as those of the intrinsic brittle silicate ceramics,respectively.In-situ characterization and multiscale finite element simulation of microstructural evolution during three-point bending deformation further validated multiple-step features of the fracture process(silicate bridge fracture,interface detachment,epoxy extraction,and rupture),which benefited from interpenetrating structural features achieved by coaxial printing to accomplish with the complex propagating routines of the crack deflection in silicate ceramic composites.This coaxial 3D printing method paves the way for tailored toughening-strengthening designs for other brittle engineering ceramic materials.

Innovative coaxial high-temperature thin-film sensor with core-shell structure surpassing traditional multilayer films

High-temperature thin-film sensors(TFSs)often suffer from inadequate tolerance to elevated temperatures.In this study,an innovative approach is presented to fabricate in situ integrated TFSs with a core-shell structure on alloy components using coaxial multi-ink printing technique.This method replaces traditional layerby-layer(LbL) deposition and LbL sintering processes and achieves simplified one-step manufacturing.The coaxial TFS includes a conductive Pt core for conducting and sensing and a dielectric shell for electrical isolation and high-temperature protection.The coaxial Pt resistance grid demonstrates excellent high-temperature stability,with a resistance drift rate of only 0.08%·h^(-1) at 800 ℃,significantly lower than traditional Pt TFSs.By employing this method,a Pt thin-film strain gauge(TFSG) is fabricated that boasts remarkable high-temperature electromechanical properties.This effectively addresses the problem of sensitivity degradation experienced by traditional LbL Pt TFSGs when subjected to high temperatures.We demonstrate the system integration potential of the technique by printing and verifying the functionality of a long-path thinfilm resistance grid on turbine blades,which can withstand butane flame up to ~1300℃.These results showcase the potential of core-shell structure of the coaxial TFS for high-temperature applications,providing a novel approach to develop high-performance TFS beyond traditional multilayer structure.

Coaxial-printed small-diameter polyelectrolyte-based tubes with an electrostatic self-assembly of heparin and YIGSR peptide for antithrombogenicity and endothelialization

Low patency ratio of small-diameter vascular grafts remains a major challenge due to the occurrence of thrombosis formation and intimal hyperplasia after transplantation.Although developing the functional coating with release of bioactive molecules on the surface of small-diameter vascular grafts are reported as an effective strategy to improve their patency ratios,it is still difficult for current functional coatings cooperating with spatiotemporal control of bioactive molecules release to mimic the sequential requirements for antithrombogenicity and endothelialization.Herein,on basis of 3D-printed polyelectrolyte-based vascular grafts,a biologically inspired release system with sequential release in spatiotemporal coordination of dual molecules through an electrostatic self-assembly was first described.A series of tubes with tunable diameters were initially fabricated by a coaxial extrusion printing method with customized nozzles,in which a polyelectrolyte ink containing of ε-polylysine and sodium alginate was used.Further,dual bioactive molecules,heparin with negative charges and Tyr-Ile-Gly-Ser-Arg(YIGSR)peptide with positive charges were layer-by-layer assembled onto the surface of these 3D-printed tubes.Due to the electrostatic interaction,the sequential release of heparin and YIGSR was demonstrated and could construct a dynamic microenvironment that was thus conducive to the antithrombogenicity and endothelialization.This study opens a new avenue to fabricate a small-diameter vascular graft with a biologically inspired release system based on electrostatic interaction,revealing a huge potential for development of small-diameter artificial vascular grafts with good patency.