Engineered dual-scale poly (ε-caprolactone) scaffolds using 3D printing and rotational electrospinning for bone tissue regeneration

Large bone defects due to trauma or disease present a significant clinical challenge with limited efficacy of current therapies. A key aim is to develop biomimetic scaffolds that reflect the native tissue structure with 3D printing being an important enabling technology. However, the incorporation of multiple length scales and anisotropic features, mimicking the native architecture, is difficult with current processes. In this study, we propose a simple and versatile hybrid printing process using a screw-assisted additive manufacturing technique combined with rotational electrospinning to fabricate dual-scale anisotropic scaffolds. 3D microscale porous polycaprolactone (PCL) structures with highly aligned nanoscale fibres were successfully produced layer-by-layer. The scaffolds were morphological, mechanical and biological characterised. Human adipose-derived stem cells (hADSCs) were seeded on the hybrid scaffold to evaluate the effects of structural and anisotropic topographic cues on cell attachment, proliferation and osteogenesis differentiation. Results show that the 3D printed microscale structures have uniform and well-defined geometries and the alignment of nanoscale electrospun fibres increases by increasing the electrospinning rotational velocity. Mechanical results show that there is no significant difference between 3D printed scaffolds with or without electrospun meshes. In vitro results show higher cell seeding efficiency and proliferation in dual-scale scaffolds with high density electrospun meshes. A more stretched and elongated cell morphology was observed in aligned nanofibre scaffolds showing higher anisotropic cytoskeletal organization than 3D printed PCL scaffolds without electrospun meshes. The dual-scale scaffolds present improved overall osteogenic markers expressions (COL-1, ALP and OCN). However, no statistical difference between normalised osteogenic marker expressions were observed between dual-scale scaffolds and 3D printed scaffolds. This might be attributed to the poor bioactivity of the substrate material, PCL, suggesting topographical cues might not be sufficient to stimulate cell fate towards to an osteogenic linage. The results suggest that the proposed fabrication strategy is a promising approach for the design of novel bone scaffolds to modulate cell fates by integrating the topographic cue reported in this paper with biochemical cues associated to the use of more bioactive materials.