Effective PEGylation of Fe3O4 Nanomicelles for In Vivo MR Imaging

A practical and effective strategy for synthesizing PEGylated Fe3O4 nanomicelles is established. In this strategy, a magnetic fluid of the Fe3O4 nanomicelles was synthesized with amphiphilic PEGylated phospholipid as surfactant and soybean oil as stabilizer under simple mechanical stirring and subsequent ultrasonication. Transmission electron microscope (TEM) measurement indicated that the sample is monodisperse spherical Fe3O4 nanoparticles with internal core size of 9 nm and external nanomicelle shell thickness of 1.5 nm. The final hydrodynamic size of the sample is 19.5 nm and its zeta potential is - 38.5 mV, suggesting good stability of the magnetic nanomicelles in water. To assess the ability of magnetic nanomicelles to escape reticuloendothelial system (RES) uptake, in vitro cell phagocytosis experiments were conducted using murine macrophages (RAW264.7). The results indicated that the PEGylation can effectively prevent the uptake of the nanomicelles by the macrophages. Using a mouse model of 4T1 breast cancer, the nanomicelles provided a good magnetic resonance imaging (MRI) capability to sensitively detect tumor by enhanced permeability and retention (EPR) effect. The PEGylated monodisperse magnetic nanomicelles would become a potential contrast agent for passive targeting diagnosis of tumor by MR imaging.