Hyperbranched lipopolymer-folate-stabilized manganese ferrite nanoparticles for the water-soluble targeted MRI contrast agent

A powerful T2-weighted magnetic resonance imaging (MRI) contrast agent with targetability has been fabricated by encapsulating manganese ferrite (MnFe2O4) nanoparticles (NPs) into biocompatible L-α-phosphatidylethanolamine-hyperbranched polyglycidol (PE–HBPG) bioconjugates covalently functionalized with folic acid (FA). The PE–HBPG is synthesized by anionic ring-opening multibranching polymerization of glycidol using soy-based PE as an initiator. FA is then conjugated onto the periphery of PE–HBPG for targeting tumor cells which have over-expressed the folate receptor. The highly monodisperse MnFe2O4 NPs with uniform size (7–10 nm) stabilized by oleylamine are labeled with the PE–HBPG–FA by ligand exchange reaction to fabricate the water-soluble and biocompatible hybrid NPs, MnFe2O4@ PE–HBPG–FA, showing targetability through receptor-mediated cellular binding and uptake. The transverse relaxivity value of MnFe2O4@PE–HBPG–FA is 140.56 mM−1 s−1, higher than those of conventional superparamagnetic iron oxide particle contrast agents.