Increased osteoblast functions in the presence of hydroxyapatite-coated iron oxide nanoparticles

Hydroxyapatite (HA) has been widely used in the biomedical community, especially for orthopedic applications (such as reversing osteoporosis). In order to use HA as injectable nanoparticles that can be directed at will to various locations in the body to treat bone defects, HA was coated onto iron oxide nanoparticles in this study. Specifically, magnetite (Fe3O4) nanoparticles were synthesized and coated with HA. The resulting nanoparticles were treated hydrothermally to control the crystalline properties of the coating. Nanoparticles were characterized via transmission electron microscopy (TEM), dynamic light scattering, X-ray diffraction, Ζeta potential and vibrating sample magnetometry. Nanoparticle uptake by osteoblasts was studied using TEM. Osteoblast density was measured after 1, 3 and 5 days in the presence of Fe3O4 nanoparticles alone and HA-coated Fe3O4 magnetic nanoparticles. Long-term osteoblast experiments demonstrated greater alkaline phosphatase activity, total protein synthesis, collagen synthesis and calcium deposition after 7, 14 and 21 days in the presence of greater concentrations (up to 200 μg ml−1) of HA-coated iron oxide nanoparticles. In summary, the results of this study showed that HA-coated magnetic iron oxide nanoparticles should be further studied for various orthopedic applications in which such particles could be injected, their location controlled using an external magnetic source and bone growth promoted.