Solvent-free atom transfer radical polymerization for the preparation of poly(poly(ethyleneglycol) monomethacrylate)-grafted Fe3O4 nanoparticles:: Synthesis, characterization and cellular uptake

Poly(poly(ethyleneglycol) monomethacrylate) (P(PEGMA))-grafted magnetic nanoparticles (MNPs) were successfully prepared via a solvent-free atom transfer radical polymerization (ATRP) method. The macroinitiators were immobilized on the surface of 6.4 +/- 0.8 nm Fe3O4 nanoparticles via effective ligand exchange of oleic acid with 3-chloropropionic acid (CPA), which rendered the nanoparticles soluble in the PEGMA monomer. The so-obtained P(PEGMA)-grafted MNPs have a uniform hydrodynamic particle size of 36.0 +/- 1.2 nm. The successful grafting of P(PEGMA) on the MNP surface was ascertained from FTIR and XPS analyses. The uptake of the MNPs by macrophage cells is reduced by two-orders of magnitude to < 2 pg Fe/cell after surface grafting with P(PEGMA). Furthermore, the morphology and viability of the macrophage cells cultured in a medium containing 0.2 mg/mL of P(PEGMA)-grafted MNPs were found similar to those of cells cultured without nanoparticles, indicating an absence of significant cytotoxicity effects. T-2-weighted magnetic resonance imaging (MRI) of P(PEGMA)-grafted MNPs showed that the magnetic resonance signal is enhanced significantly with increasing nanoparticle concentration in water. The R-1 and R-2 values per millimole Fe, and R-2/R-1 value of the P(PEGMA)-grafted MNPs were calculated to be 8.8 mM(-1) s(-1), 140 mM(-1) s(-1), and 16, respectively. These results indicate that the P(PEGMA)-grafted MNPs have great potential for application in MRI of specific biotargets. (C) 2007 Elsevier Ltd. All rights reserved.