Preparation and In Vivo Biodistribution of Ultra-Small Superparamagnetic Iron Oxide Nanoparticles with High Magnetic Targeting Response

The ultra-small superparamagnetic iron oxide (USPIO) particles with high saturation magnetization and good superparamagnetism were prepared by reverse micro-emulsions using novel C₁₆E₁₅ as surfactant, which can reduce magnetic dipole–dipole interaction, hence decreasing the critical blocking temperature (T_B ). Powder X-ray diffraction (XRD), Infrared spectrum (FT-IR), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Vibrating sample magnetometer (VSM) were used to characterize the magnetic particles. The higher ratio of Fe²⁺/Fe³⁺ caused redundant FeO on the USPIO surface. An in vitro approach model for simulating target delivery of USPIO particles to sites of interest was developed to illustrate the relationship between magnetic fluid retention rate and pole distance. In Vivo targeted interception and magnetic targeting bio-distribution of superparamagnetic particles were also investigated simultaneously. The results indicated that the USPIO had high ability for magnetic focusing in mimetic surrounding tissue surrounding blood vessels under the action of pulsed magnetic field. The USPIO nanoparticles will be fundamental in biomedical applications.