Novel method for synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) coated with polyethylenimine (PEI) and modified with poly(ethylene glycol) methyl ether (MPEG), MPEG-PEI-SPIONs, was developed. PEI-SPIONs were successfully prepared in aqueous system via photochemistry, and their surface was modified with poly(ethylene glycol) methyl ether (MPEG). The so-obtained MPEG-PEI-SPIONs had a uniform hydrodynamic particle size of 34 nm. The successful coating of MPEG-PEI on the SPIONs was ascertained from FT-IR analysis, and the PEI and MPEG fractions in MPEG-PEI-SPIONs were calculated to account for 31% and 12%, respectively. Magnetic measurement revealed that the saturated magnetization of MPEG-PEI-SPIONs reached 46 emu/g and the nanoparticles showed the characteristic of being superparamagnetic. The stability experiment revealed that the MPEG-PEI modification improved the nanoparticles stability greatly.T2 relaxation measurements showed that MPEG-PEI-SPIONs show similarR2 value to the PEI-SPIONs. TheT2-weighted magnetic resonance imaging (MRI) of MPEG-PEI-SPIONs showed that the magnetic resonance signal was enhanced significantly with increasing nanoparticle concentration in water. These results indicated that the MPEG-PEI-SPIONs had great potential for application in MRI.
Core–Shell Structure of Monodisperse Poly(ethylene glycol)-Grafted Iron Oxide Nanoparticles Studied by Small-Angle X-ray Scattering
