Magnetite-loaded fluorine-containing polymeric micelles for magnetic resonance imaging and drug delivery

Magnetite (Fe ₃O ₄) - loaded polymer micelles (denoted as " magnetomicelles" ) are produced by self-assembly of fluorine-containing amphiphilic poly(HFMA-g-PEGMA) copolymers with oleic acid modified Fe ₃O ₄ nanoparticles in an aqueous medium. The oleic acid modified Fe ₃O ₄ nanoparticles form small clusters in the poly(HFMA-g-PEGMA) micelles with a mean diameter of 100nm and the magnetomicelles show high stability in an aqueous medium due to the high hydrophobic fluorine segments in graft copolymers enhance the stability of the micelles. The magnetomicelles also show good cytocompatibility based on the MTT cytotoxicity assay and possess paramagnetic properties with saturation magnetization of 17.14 emu/g.Their good stability, cytocompatibility, and paramagnetic properties render the materials attractive in drug delivery and invivo magnetic resonance imaging (MRI) applications. Controlled release of hydrophobic drug-5-fluorouracil is achieved from the magnetomicelles with a loading efficiency of 20.94wt%. The magnetomicelles have transverse relaxivity rates (r ₂) of 134.27mM ^-1s ^-1 and exhibit high efficacy as a negative MRI agent in T ₂-weighted imaging. Invivo MRI studies demonstrate that the contrast between liver and spleen is enhanced by the magnetomicelles. These favorable properties suggest clinical use as nanocarriers in drug delivery applications and contrast agents in MRI. © 2011 Elsevier Ltd.