Biocompatible superparamagnetic iron oxide nanoparticle dispersions stabilized with poly(ethylene glycol)-oligo(aspartic acid) hybrids.

Methoxypoly(ethylene glycol)-oligo(aspartic acid) (MPEG-Asp(n)-NH(2), n = 2-5) hybrid block copolymers were synthesized and used as stabilizers to prepare superparamagnetic Fe(3)O(4) nanoparticles with magnetite as the inner core and and poly(ethylene glycol) as the hydrophilic outer shell. The aqueous dispersions of the nanoparticles were stable at pH 2-11 and in 1M NaCl solution, when repeat number, n, was 3 or more. Transmission electron microscopy showed that the nanoparticles, stabilized with MPEG-Asp(3)-NH(2), were about 14 nm in diameter.