Ultrasmall Superparamagnetic Iron Oxide Nanoparticle for T₂-Weighted Magnetic Resonance Imaging

A facile method to synthesize ultrasmall-sized supermagnetic iron oxide nanoparticles with good monodispersity and high relaxivity is desired for magnetic resonance imaging (MRI) technology. Herein, we have developed a one-step method to direct the formation of superparamagnetic iron oxide nanoparticle (uBSPIO) using albumin under mild conditions. The resulting uBSPIO possess ultrasmall size (4.78 ± 0.55 nm) and super high MR relaxivity (444.56 ± 8.82 mM^-1 s^-1). After grafted by the luteinizing hormone release hormone peptide (LHRH), the uBSPIO could targeted and accumulated in the tumor site. Finally, the uBSPIOs had good stability and did not induce cytotoxicity in vitro or major organ toxicity in vivo. The uBSPIOs are promising contrast agents for MRI.