Synthesis, Characterization and In Vitro Bioactivity of Magnetite Nanoparticles Obtained by Co-Precipitation.

Magnetite (Fe3O4) nanoparticles have been explored for biomedical applications. Their surface behavior in physiological-like environments has not been fully established. Fe3O4 nanoparticles obtained by chemical co-precipitation were exposed to simulated body fluid (SBF) for up to 28 days, and in vitro bioactivity was examined. Structural and surface changes were investigated using XRD, FTIR-ATR, SEM/EDS and thermal analysis, while pH and electrical conductivity measurements were used to monitor changes at the particle-solution interface. Magnetite was the main crystalline phase, and the main crystalline structure was preserved during SBF exposure within the detection limits. Progressive surface transformations occurred, including hydration/hydroxylation and formation of calcium-phosphate-containing surface deposits. Changes in pH and variations in electrical conductivity were interpreted as complementary indicators of interfacial processes. Cytotoxicity tests on L929 fibroblast cells showed that Fe3O4_14SBF was well tolerated at 25-50 µg/mL, whereas higher concentrations reduced cell viability. These findings suggest that Fe3O4-based magnetic materials may be further considered for biomedical applications, provided that concentration-dependent cytocompatibility is considered.