Novel magnetic iron oxide nanoparticles coated with poly(ethylene imine)-g-poly(ethylene glycol) for potential biomedical application: Synthesis, stability, cytotoxicity and MR imaging

Magnetic iron oxide nanoparticles have found application as contrast agents for magnetic resonance imaging (MRI) and as switchable drug delivery vehicles. Their stabilization as colloidal carriers remains a challenge. The potential of poly(ethylene imine)-g-poly(ethylene glycol) (PEGPEI) as stabilizer for iron oxide (gamma-Fe2O3) nanoparticles was studied in comparison to branched poly(ethylene imine) (PEI). Carrier systems consisting of gamma-Fe2O3-PEI and gamma-Fe2O3-PEGPEI were prepared and characterized regarding their physicochemical properties including magnetic resonance relaxometry. Colloidal stability of the formulations was tested in several media and cytotoxic effects in adenocarcinomic epithelial cells were investigated. Synthesized gamma-Fe2O3 cores showed superparamagnetism and high degree of crystallinity. Diameters of polymer-coated nanoparticles gamma-Fe2O3-PEI and gamma-Fe2O3-PEGPEI were found to be 38.7 +/- 1.0 nm and 40.4 +/- 1.6 nm, respectively. No aggregation tendency was observable for gamma-Fe2O3-PEGPEI over 12 h even in high ionic strength media. Furthermore, IC50 values were significantly increased by more than 10-fold when compared to gamma-Fe2O3-PEI. Formulations exhibited r(2) relaxivities of high numerical value, namely around 160 mM(-1) s(-1). In summary, novel carrier systems composed of gamma-Fe2O3-PEGPEI meet key quality requirements rendering them promising for biomedical applications, e.g. as MRI contrast agents. (C) 2011 Elsevier B.V. All rights reserved.