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Abstract
Intervertebral disk pathology, including disk herniation and degeneration, is a major contributor to chronic low back pain, and when conservative treatment fails, surgical management often involves discectomy-based procedures that leave residual annulus fibrosus (AF) defects associated with reherniation and progressive degeneration. These limitations have motivated interest in regenerative strategies using biomaterial scaffolds; however, reproducing the hierarchical, angle-ply architecture of the AF remains challenging. Here, we present a single-step extrusion-based 3D-printing approach to fabricate polycaprolactone (PCL) scaffolds with aligned microscale surface grooves that promote AF-like organization. Patterned nozzles with circumferential peaks generated uniaxial concave microgrooves (10–17 µm wide) directly during printing, enabling formation of multilamellar angle-ply constructs. Human bone marrow-derived mesenchymal stem cells cultured on patterned scaffolds aligned longitudinally within concave grooves, forming end-to-end arrays that guided extracellular matrix deposition. Gene expression analysis showed that topographical cues governed cellular organization without significantly altering gene expression profiles, while TGF-β3 supplementation upregulated outer AF-associated markers, including COL1, COL12, SFRP2, MKX, MCAM, and SCX. TAGLN expression increased specifically on patterned scaffolds in the absence of TGF-β3, indicating an association between microgroove-guided cellular organization and TAGLN expression, warranting further investigation into potential tension-related mechanisms. This novel single-step extrusion-printing approach leverages custom nozzle geometry to impart concave microgrooves, facilitating scalable fabrication of multilamellar angle-ply scaffolds that induce aligned cellular organization and support potential applications in annulus fibrosus repair, as well as mechanobiological studies of anisotropic musculoskeletal tissues.

Abstract
In this study, a novel hybrid scaffold comprising 3D-printed porous polyhydroxybutyrate (PHB), dextran (Dex), and magnesium-doped whitlockite (WL) nanoparticles was developed, which were further enhanced with an electrospun nanofibrous coating composed of Dex and Pluronic F127 (F127) loaded with Sildenafil (Sil) for use in craniofacial regeneration. This design was intended to improve the solubility of sildenafil and enable controlled release. Scanning electron microscopy (SEM) revealed a well-integrated structure between the 3D-printed strands and electrospun nanofibers. The scaffold exhibited sustained release of Sil over 28 days, with mechanical testing showing a compressive strength of 3.70 ± 0.33 MPa and an elastic modulus of 49.04 ± 4.62 MPa. Non-toxicity was confirmed via MTT assay on the MG63 cell line, and qRT-PCR results indicated significantly higher expression levels of collagen I, RUNX2, osteocalcin, VEGF, and CD31 markers associated with osteogenesis and angiogenesis. Following implantation in a rat calvarial defect model, the scaffold demonstrated robust osteogenic activity and new bone tissue formation over an eight-week period. This innovative scaffold design offers a promising solution for overcoming the challenges in craniofacial defect repair by integrating bioactive materials with advanced drug delivery systems, leading to more effective tissue regeneration strategies.