A direct surface modification of iron oxide nanoparticles with various poly(amino acid)s for use as magnetic resonance probes.

Water soluble and biocompatible iron oxide nanoparticles coated with poly(aspartic acid) (PAsp), poly(asparagines) (PAsn), poly(2-hydroxy-ethyl L-aspartamide) (PHEA), and poly-α,β-(N-2-dimethylaminoethyl L-aspartamide) (PDMAEA) were prepared by hydrophobic interaction between hydrophobic iron oxide nanoparticles and each amphiphilic poly(amino acid)s graft polymer. The octadecyl side chain grafted poly(succinimide)(PSI-g-C(18)), used as a precursor polymer, was easily aminolyzed with nucleophilic compounds to form various poly(amino acid)s graft polymer (PAsp-g-C(18), PAsn-g-C(18), PHEA-g-C(18), PDMAEA-g-C(18),) and simultaneously stabilize the dispersion of iron oxide nanoparticles in aqueous solution. The diameters of the poly(amino acid)s coated iron oxide nanoparticles (PAIONs) were smaller than 30 nm in aqueous solution, extremely stable in aqueous solutions with a wide range of pH and salt concentrations. Further, all the PAIONs showed excellent MR signal intensities (high r(2) values) and the cellular uptake property of the PAIONs was also evaluated.