Synthesis of Biocompatible Poly[2-(methacryloyloxy)ethyl phosphorylcholine]-Coated Magnetite Nanoparticles

Abstract

A well-defined, double-hydrophilic diblock copolymer comprising poly[2-(methacryloyloxy)ethyl phosphorylcholine]-block-(glycerol monomethacrylate) (PMPC₃₀−PGMA₃₀, where the numbers represent the average degrees of polymerization for each block) was evaluated for the synthesis of colloidally stable ultrafine magnetite sols. Sterically stabilized paramagnetic sols were prepared in aqueous solution by chemical coprecipitation of ferric and ferrous salts in the presence of this block copolymer. The PMPC₃₀−PGMA₃₀-stabilized magnetite sol had a mean transmission electron microscopy (TEM) diameter of 9.4 ± 1.7 nm and a mean hydrodynamic diameter of 34 nm. This sol exhibited improved colloidal stability with respect to long-term storage and pH variation compared with magnetite sols prepared in the presence of alternative water-soluble homopolymers and diblock copolymers. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry, electron spectroscopy imaging (ESI), and ζ potential studies indicate that the PMPC₃₀−PGMA₃₀ diblock copolymer was adsorbed onto the surface of the sol via the PGMA₃₀ block, with the PMPC₃₀ chains acting as the stabilizing block. Such sterically stabilized sols are expected to be improved contrast agents for magnetic resonance imaging (MRI) applications.