abstract
- At the nanoscale, bones are made up of collagen fibrils, the mineralization of bones takes place when ions of calcium and phosphate form hydroxyapatite (HAP) crystals. HAP due to its osteogenic and biocompatible properties has been widely used in conventional bone tissue engineering. 3D and 4D printing techniques have been explored to manufacture unique HAP scaffolds according to each patient's needs, although the clinical use is not yet ready, and the techniques are still being developed. The incorporation of different biomolecules like growth factors, peptides, drug molecules and nanomaterials etc. improves the biocompatibility and bio-functionality of these printed scaffolds. This critical review describes the evolution of HAP in conventional bone tissue engineering, and summarizes the new approaches, clinical applications and future perspectives of HAP in 3D-4D printing techniques. The synergistic potential and future clinical prospects for bone tissue engineering offered by various functionalization of hydroxyapatite-incorporated 3D and 4D printed scaffolds has been discussed. © 2024 Elsevier Ltd and Techna Group S.r.l.