Size control of ferrimagnetic iron oxide nanocubes to achieve optimum static dephasing regime r2 relaxivity for in vivo MRI

Ferrimagnetic nanoparticles have been limited in in vivo application because nanoparticles aggregate due to its remanent magnetization. Uniform-sized ferromagnetic iron oxide nanocubes with similar value of bulk saturated magnetization were synthesized. Control of nanocubes’ size minimized their remanence. PEG-phospholipid encapsulation enabled spacing to prevent the aggregation. As a result, water-dispersed single core ferrimagnetic iron oxide nanocubes were successfully prepared and their r2 relaxivity was 761 s-1mM-1. It was very close to theoretical calculated value 800 s-1mM-1 in static dephasing regime. in vivo MR images were obtained after intravenous injection of 22 nm nanoparticles to a mouse. The MR signal of tumor site changed significantly. In this research, synthesized ferrimagnetic iron oxide nanocubes showed a superior T2 contrast effect and it would be able to improve the quality of early diagnosis and detection of tumor.