A nanosized delivery system of superparamagnetic iron oxide for tumor MR imaging.

Superparamagnetic iron oxide (SPIO) nanoparticles have been intensively investigated as MRI probes due to the noninvasive detection of in vivo pathological changes. In the study, a nanosized system for SPIO delivery to a tumor was prepared to overcome the common challenges of SPIO nanoparticles such as insufficient uptake of SPIO by specific cells due to instability, short half-life by macrophage, and low efficiency of internalization. SPIO with ca. 6 nm sizes as a MRI probe and PLA-PEG (5K-2K) as a biocompatible stable system were prepared. The hydrophobic modified SPIO were loaded into the core of micelles and showed a stable dispersion with 140-170 nm particle sizes. The SPIO loading micelles showed higher relaxivity coefficients and increases of T(2) relaxation in vivo MR imaging. This SPIO delivery system with high stability and sensitivity can be a promising imaging formulation as MRI T(2) probes for tumor detection.