This study investigated the behavior of ferrofluids containing superparamagnetic iron oxide nanoparticles (SPION) of various compositions for potential applications in drug delivery and imaging. To ensure biocompatibility, the interaction of these SPION with two cell lines (adhesive and suspended) was also investigated using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The cell lines studied were primary mouse connective tissue cells (adhesive) and human leukemia cells (suspended). SPION were synthesized with a co-precipitation method under different stirring rates and NaOH molarities. The SPION demonstrated a range of magnetic saturations due to their different shapes, which included magnetite colloidal nanocrystal clusters (CNC’s), magnetic beads, and single-coated nanoparticles. All synthesized SPION maintained reasonable cell viability following exposure to cells. Flow cytometer tests showed that no apoptosis took place in cells exposed to SPION. A multiphysics numerica...