Low-temperature fabrication of calcium deficient hydroxyapatite bone scaffold by optimization of 3D printing conditions

Abstract

We herein propose a novel low-temperature fabrication process of calcium deficient hydroxyapatite (CDHA) 3D scaffolds for bone tissue regeneration through a combination of material extrusion type 3D printing process and bone cement chemistry. The CDHA scaffolds with high porosity of 70% showed excellent mechanical property of 25 MPa (compressive strength), without any sintering process after 3D printing. By using this method, the final structures do not show size shrinkage, which must be considered in conventional ceramic sintering processes. We could therefore achieve both size- and 3D architecture-controlled porous CDHA scaffolds with high accuracy. In addition, the resulting ceramic cement scaffolds were not brittle and could be machined without chipping or fracturing the scaffold. The complete process takes place at physiological conditions (37 °C, pH=7), and heat sensitive drugs and biomolecules could be directly loaded onto the raw powder and achieve homogeneous distribution throughout the CDHA scaffold. In this study, we discuss various key factors to complete this low-temperature 3D printing fabrication of calcium phosphate, such as the pre-treatment conditions of particles, liquid-to-powder ratio, relationships between strut sizes, infill of structures, setting temperatures and the properties of 3D printed scaffolds. The low-temperature fabrication process of calcium phosphate scaffolds developed in this study has excellent potential for use in bone tissue engineering.