Development of Polylactic Acid/Hydroxyapatite Composite Filaments for 3D Printing of Bone Tissue Engineering Scaffolds

This study addresses the development of novel composite filaments tailored for 3D printing applications in bone tissue engineering. The granules were fabricated by blending polylactic acid with commercial hydroxyapatite (HA) at different weight ratios of 10, 20, 30, and 40% (i.e., PLA/HA_10, PLA/HA_20, PLA/HA_30, and PLA/HA_40), using twin-screw extrusion. The resulting granules were subsequently processed into filaments through single-screw extrusion. The as-obtained filaments were comprehensively characterized in terms of thermal stability, morphological features, mechanical properties, and biological performance. It should be emphasized that the variation in HA concentration played a critical role in optimizing both the mechanical and biological performance of the composite filaments. Mechanical testing demonstrated increased elastic modulus for PLA/HA_10 and PLA/HA_20 composites. However, higher HA concentrations adversely affected the tensile strength, likely due to particle agglomeration and poor interfacial adherence between the polymer matrix and ceramic phase. In vitro biological evaluation revealed that low-to-moderate HA concentrations (i.e., 10 and 20%) improved cytocompatibility and promoted cell attachment. These findings underscore the importance of carefully tailoring the HA content to develop functional composite materials suitable for bone scaffold fabrication, with promising implications for future clinical applications in bone tissue engineering.