Assessments of polycaprolactone/hydroxyapatite composite scaffold with enhanced biomimetic mineralization by exposure to hydroxyapatite via a 3D-printing system and alkaline erosion

In the 3D-printed polycaprolactone/hydroxyapatite composite scaffold, hydroxyapatite particles are usually covered by a thin-film of polycaprolactone because of the rheological characteristics of the extrusion process. This phenomenon could disrupt the original bioactive characteristics of hydroxyapatite particles. In this study, to expose the hydroxyapatite particles covered by a thin-film of polycaprolactone, an alkaline erosion method was proposed. Moreover, to investigate the cell activity and biomimetic mineralization influenced by hydroxyapatite exposure, polycaprolactone scaffolds, polycaprolactone scaffolds with alkaline erosion, and polycaprolactone/ hydroxyapatite scaffolds were fabricated as control groups and compared with the polycaprolactone/hydroxyapatite scaffolds with alkaline erosion. Furthermore, to characterize the 3D-printed composite scaffold in terms of hydroxyapatite exposure, several assessments were made including morphology, pore size, porosity, mechanical compressive modulus, surface roughness, water absorption. Consequently, the proposed alkaline erosion for hydroxyapatite particle exposure had little effect on the structure of the fabricated scaffolds via the 3D-printing system including the designed pore size, porosity, and mechanical properties. Moreover, mechanical properties of the polycaprolactone/hydroxyapatite scaffolds were increased by the high dispersion of hydroxyapatite in the polycaprolactone matrix. Additionally, we verified that the exposure of hydroxyapatite particles by alkaline erosion improves cell proliferation and biomimetic mineralization, because calcium and phosphate ions were rapidly deposited on the scaffold.