Fig. 1

SPION size-isolation via sequential centrifugation. Schematic overview of the centrifugation protocol to obtain monodispersed SPION with different hydrodynamic diameters from a crude mixture of polydisperse SPION. The polydisperse SPION sample (C) was transferred into 1.5 ml Eppendorf tubes and centrifuged at 14,000 rpm for 20 min. The resulting 1 ml of supernatant was collected (C1). 0.1 ml of the bottom compartment in the Eppendorf tube was resuspended in water and again centrifuged, and the top 1 ml was collected (C2). These steps were repeated multiple times, with optimized centrifugation times and speeds, to obtain three additional fractions of monodisperse SPION samples (C3–C5). The different fractions were subsequently analyzed for magnetic resonance imaging (MRI), magnetic particle imaging (MPI) and magnetic fluid hyperthermia (MFH) performance, and compared to the crude sample (C), to Resovist® and to Sinerem®