3D printing of ZnO-modified hydroxyapatite scaffolds with directional pore microstructure for enhanced mechanical properties and biocompatibility

Abstract

Hydroxyapatite (HA) exhibits multifunctionality and wide applications in biological tissues such as vertebrate bones and teeth, due to facial element substitutions and chemical modifications of active surfaces in crystal structures with various inorganic or organic additives. It is a challenge to achieve biocompatible scaffolds that combine both high strength and toughness for the repair and regeneration of bone and tooth defects. In this study, we developed ZnO-modified hydroxyapatite 3D scaffolds with microscopic directional pore structures (∼20 μm) using a directional freezing-assisted direct-ink-writing (DIW) 3D printing technique. The directional pore microstructure significantly enhanced the mechanical properties compared to the non-directional scaffolds. Moreover, both experimental and molecular dynamics simulation results demonstrated that the incorporation of ZnO nanoparticles improved the sintering process, maintaining the directional pore microstructure while significantly increasing the mechanical strength. Notably, the coated hydroxyapatite scaffolds demonstrated excellent antimicrobial activity with ∼99 % antimicrobial resistance and biocompatibility with ∼89.96 % cell survival. This study presents an innovative approach for constructing directional porous hydroxyapatite scaffolds with multifunctionality and high mechanical properties, providing a promising foundation for advancements in dental restoration, implantable medical devices, and bone tissue engineering.