Toward biomimetic porous poly(ε-caprolactone) scaffolds: Structural evolution and morphological control during solid phase extrusion

Abstract

Two-dimensional oriented scaffolds bear spatial limitation to regenerate three-dimensional (3D) tissues despite showing the ability to guide cell alignment and elongation. By combining solid phase extrusion (SPE) of co-continuous blends with phase removal, we prepared an interconnected 3D porous poly(ε-caprolactone) (PCL) scaffold with oriented pores. To better regulate structure of these distinctive scaffolds, structural evolution of co-continuous blends in the convergent die during SPE was investigated in this study. Morphological observation manifested that the elongation deformation of co-continuous blends proceeded along the extrusion direction in the converging die continuously. Due to the extrusion temperature below the melting point of the matrices, the aligned co-continuous phase was maintained to form the uniformly oriented pores after phase extraction. Unlike consecutive deformation of phase morphology, the change in the crystalline structure of PCL involved two stages divided by the critical deformation distance (∼10 mm). At stage I (<10 mm), spherical crystals of PCL transformed into ellipsoidal shape owing to plastic deformation. At stage II (>10 mm), organized PCL lamellae formed along the extrusion direction as a result of crystal fragmentation and rearrangement. On the basis of anterior cognition, effects of processing parameters on porous morphology were further explored. It was revealed that extrusion draw ratio and annealing time were more effective to regulate pore orientation and size of aligned porous scaffolds than extrusion temperature. The tunable morphological structure of biomimetic scaffolds is of vital importance to broaden their applications for tissue repair.