Preparation and Characterization of Poly(PEGMA) Modified Superparamagnetic Nanogels Used as Potential MRI Contrast Agents

Anovel synthesis method of biocompatible polymers-coated magnetic nanogels was developed. Poly(PEGMA) modified superparamagnetic nanogels were synthesized by in-situ polymerization using poly(ethylene glycol) methacrylate (PEGMA) as monomer and N,N -methylene-bis-(acrylamide) (MBA) as cross-linking agent in magnetite aqueous suspension under UV irradiation. The surface functional groups, structure, particle size, Zeta potential and magnetic property were characterized, respectively. The Fourier transform infrared spectroscopy (FTIR) results indicated that the poly(PEGMA) modified magnetic nanogels were synthesized successfully under UV irradiation. The analyses of transmission electron microscopy (TEM) and photon correlation spectroscopy (peS) indicated that the poly(PEGMA) modified magnetic nanogels were essentially monodisperse, nearly spherical in shape, the mean diameter in aqueous solution wai: 68.4 nm, and the size distribution was narrow. The thermogravimetric analyzer (TGA) result indicated that there was a high Fe304 content of 53.4% in the magnetic nanogels, which endowed the magnetic nanogels with a strong magnetic response under external magnetic field. Magnetic measurement revealed that the saturated magnetization of the poly(PEGMA) magnetic nanogels reached 58.6 emu/g and the nanogels showed the characteristics of superparamagnetic. The Zeta potential was -17.3 mV at physiological pH (pH 7.4) which helped maintain stability in blood. The transverse relaxation time (T2) was also performed for potential use of magnetic resonance imaging (MRI) contrast agents. The preliminary experiment verified the feasibility of the magnetic nanogels for potential MRI contrast agents.