Biocompatibility of a PLA-based composite containing hydroxyapatite derived from waste bones of dolphin Neophocaena asiaeorientalis

Abstract

Natural hydroxyapatite (HA), derived from waste bones of several animal species, has received much attention as a material for bone grafts and fillers and has a role as a coating for metal implants because of its biocompatibility and non-toxicity. To investigate the applicability of HA derived from waste bones of novel animal sources, the biocompatibility and toxicity of a poly-l-lactic acid (PLA)-based composite containing HA derived from the backbone of the dolphin Neophocaena asiaeorientalis (HANA) were examined in Sprague-Dawley (SD) rats. HANA powder showed X-ray diffraction peak patterns that corresponded to those of standard HA. Among five composites prepared from different combinations of PLA and HANA (7:3, 6:4, 5:5, 4:6, and 3:7), a PLA/HANA composite manufactured with a 6:4 PLA:HANA ratio had high surface roughness (453 nm), 10.3 N of maximum load, and 451.9 MPa of module elasticity. After implantation in the subcutaneous region of SD rats for 8 weeks, the amount of confluent, aggregated structures of multilayered cells on the PLA/HANA implant surface was greater than that on the PLA surface, although both implants were completely covered with adhesive cells. During the implant period, the initial intact form of the PLA/HANA composite broke into small fragments with few inflammatory cells in the contact region and no indication of significant toxicity. Taken together, the results suggest that HANA may have good biocompatibility and be non-toxic as it did not induce an immune response in SD rats.