This study reports the development of a bilayered scaffold with aligned channels produced via a sequential coextrusion and unidirectional freezing process to facilitate upward bone-marrow stem-cell migration. The biomimetic scaffold with collagen and biphasic calcium phosphate (BCP) layers is successfully fabricated with matching of the cartilage and bone layers. The aligned structure results in an enhancement of the compressive strength, and the channels enable tight anchoring of the collagen layers on the BCP scaffolds compared with a randomly structured porous scaffold. An in vitro evaluation demonstrates that the aligned channels guide the cells to attach on the surface in highly stretched shapes and migrate upward faster than the random structure. In addition, in vivo assessment reveals that the aligned channels yield superior osteochondral tissue regeneration compared with the random structure. Moreover, the channel diameter greatly affects the tissue regeneration, and the scaffold with a channel diameter of ≈270 µm exhibits the optimal regeneration because of sufficient nutrient supply and adequate tissue ingrowth. These findings indicate that the introduction of aligned channels to a bilayered scaffold provides an effective approach for osteochondral tissue regeneration.

Poly(lactic acid) (PLA) is the most utilized biodegradable polymer in orthopedic implant applications because of its ability to replace regenerated bone tissue via continuous degradation over time. However, the poor osteoblast affinity for PLA results in a high risk of early implant failure, and this issue remains one of the most difficult challenges with this technology. In this study, we demonstrate the use of a new technique in which plasma immersion ion implantation (PIII) is combined with a conventional DC magnetron sputtering. This technique, referred to as sputtering-based PIII (S-PIII), makes it possible to produce a tantalum (Ta)-implanted PLA surface within 30 s without any tangible degradation or deformation of the PLA substrate. Compared to a Ta-coated PLA surface, the Ta-implanted PLA showed twice the surface roughness and substantially enhanced adhesion stability in dry and wet conditions. The strong hydrophobic surface properties and biologically relatively inert chemical structure of PLA were ameliorated by Ta S-PIII treatment, which produced a moderate hydrophilic surface and enhanced cell−material interactions. Furthermore, in an in vivo evaluation in a rabbit distal femur implantation model, Ta-implanted PLA demonstrated significantly enhanced osseointegration and osteogenesis compared with bare PLA. These results indicate that the Ta-implanted PLA has great potential for orthopedic implant applications.

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Inspired by the anisotropic structure of natural menisci, porous and densified layers of glycerol phosphate (gp)‐conjugated polyurethane (PU) and hydroxyapatite (HA), abbreviated PUH, are alternately stacked to fabricate a biomimetic multilayered scaffold. Densification is used to better match the mechanical properties of the composites to those of natural menisci for load‐bearing applications. The porosity is easily controlled (30%, 10%, and 7%) during the densification process by adjusting the applied heat and pressure. The strength and elastic modulus of the densified PUH are significantly higher than those of the porous PUH because HA is trapped as fillers inside the densified PU matrix. Multi‐layered PUH is successfully fabricated after stacking the densified and porous layers alternately. And each layer is highly attached, resulting in good interfacial stability. In addition, the scaffold is stiff along the x‐ and y‐directions and more flexible along the z‐axis (the stacking direction), as designed.