Biocompatibility of metal-ion-substituted hydroxyapatite as orthopaedic/dental implant

Abstract

Metal ions substitution in hydroxyapatite crystal structure is expected to improve biocompatibility and osseointegration to prosthetic implants. Mn(II) and Fe(III) ions substituted hydroxyapatite were synthesized by wet chemical method and ion exchange mechanism with atomic substitution concentration ranged from 1% - 10% and 1% - 5%, respectively. All samples were single-phased and non-stoichiometric, as indicated by various characterization methods including XRD, FTIR, EDX and ICP. Biocompatibility testings were done by using human osteoblast ATCC cell line hFOB 1.19. Cytotoxicity test by extraction method and MTT assay showed that Mn(II) and Fe(III) ions had no cytotoxic effect on the osteoblast cells. In addition, it was established that both Mn(II) and Fe(III) ions improve osteoblast proliferation and activity (confirmed by ALP assay). The optimum ionic substitution concentration was observed to be 5% for both Mn(II) and Fe(III) ions. It was believed that higher metallic ions content led to smaller and less perfect crystal, although not shown in FESEM images among the atomic substitution percentage here. Significant increase in filopodia formation was observed surrounding osteoblast cells which were seeded on both 5% Mn(II) and Fe(III)-ion-substituted hydroxyapatite pellets, indicating good cell-substrate attachment, good intercellular interaction, and improved cell viability.