To optimize the iron oxide nanoparticles as T1-weight contrast for in vivo magnetic resonance imaging (MRI), numbers of macromolecule ligands have been explored with considerable effort. However, reports refer to the comparison of the T1-weight contrast performances of iron oxide nanoparticles modified with natural and artificial macromolecule ligands are still limited. In this work, we used a typical natural protein macromolecule (bovine serum albumin, BSA) and an artificial macromolecule (poly(acrylic acid)-poly(methacrylic acid), PMAA-PTTM) as surface ligands to fabricate Fe3O4-BSA and Fe3O4-PMAA-PTTM nanoparticles with similar size and magnetization by the coprecipitation method and compared their MRI performances. In vitro and in vivo experiments revealed that Fe3O4-BSA with lower cytotoxicity exhibited higher r2/r1 ratio in solution and darkening contrast enhancement for liver and kidney sites of mice under T1-weight imaging, while Fe3O4-PMAA-PTTM displayed much lower r2/r1 ratio in solution and brighter contrast enhancement for liver and kidney sites. These remarkably different MRI behaviors demonstrated that the surface ligands play an important role for optimizing the MRI performance of Fe3O4 nanoparticles. We expect these results may facilitate the design of macromolecule ligands for developing an iron oxide–based T1-weight contrast agent.
Small functionalized iron oxide nanoparticles for dual brain magnetic resonance imaging and fluorescence imaging
