Fig. 1 Characterization of FVIOs and SPIOs. TEM images of the negatively stained (a) FVIOs and (b) SPIOs. The marked surface layer (~ 5 nm thick) corresponds to the anti-His antibodies and DHCA coating. Scale bars, 20 nm. (c) Powder X-ray diffraction patterns of the SPIOs and FVIOs. (d) Room temperature magnetization curves constructed for SPIOs and FVIOs. (e) Temperature changes in the SPIO and FVIO solutions at various Fe concentrations (0.05, 0.15, and 0.30 mg/mL) under AMF exposure (H = 20 mT and f = 275 kHz). (f) The specific absorption rate (SAR) was calculated from the rate of temperature increase of the SPIO and FVIO solutions. The data are presented as the mean ± S.D.; n = 3 independent experiments for each sample.