We report the
polyethyleneimine (PEI)-enabled synthesis and functionalization of
manganese oxide (
Mn3O4) nanoparticles (NPs) for targeted
tumor magnetic resonance (MR) imaging in vivo. In this work, monodispersed PEI-coated
Mn3O4 NPs were formed by decomposition of
acetylacetone manganese via a solvothermal approach. The
Mn3O4 NPs with PEI coating were sequentially conjugated with
fluorescein isothiocyanate,
folic acid (FA)-linked
polyethylene glycol (PEG), and PEG monomethyl
ether. Followed by final acetylation of the remaining PEI surface
amines, multifunctional
Mn3O4 NPs were formed and well characterized. We show that the formed multifunctional
Mn3O4 NPs with a mean diameter of 8.0 nm possess good water-dispersibility, colloidal stability, and cytocompatibility and hemocompatibility in the given concentration range. Flow cytometry and confocal microscopic observation reveal that the multifunctional
Mn3O4 NPs are able to target FA receptor-overexpressing
cancer cells in vitro. Importantly, the FA-targeted
Mn3O4 NPs can be used as a nanoprobe for efficient T1-weighted MR imaging of
cancer cells in vitro and the xenografted
tumor model in vivo via an active FA-mediated targeting pathway. With the facile PEI-enabled formation and functionalization, the developed PEI-coated
Mn3O4 NPs may be modified with other biomolecules for different biomedical imaging applications.