Synthesis and in vitro properties of iron oxide nanoparticles grafted with brushed phosphorylcholine and polyethylene glycol

Polyethylene glycol (PEG) is an established grafting agent for engineered materials deployed in aqueous environments including biological systems. Phosphorylcholine (PC) has shown promise as a viable strategy for enhancing the biofunctionality of surfaces and structures. Here we developed a new and facile strategy for grafting superparamagnetic iron oxide nanoparticles (IONPs) by phosphonic acid terminated poly(2-(methacryloyloxy)ethyl phosphorylcholine) brushes, synthetized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Properties of covalently bound IONPs with PC, PEG or PEG:PC brush-like structures via a "grafting onto" approach through robust bidentate Fe-O-P bonds were compared. The presence of modified polymers on the functionalized IONP surfaces was proved using both ATR-FTIR and TGA. The resultant synthesized IONPs were characterized for their physicochemical and biological aspects. Interestingly, compared with PEG combs, specifically, PC brushes rendered comparable or enhanced suspendability, stability, biocompatibility and cellular distribution. We attribute these characteristics to the biomimetic nature and larger polarity of PC in contrast to the synthetic and hydrophilic PEG. These synthesis strategies and characterizations may prove beneficial to the design and applications of IONPs in nanobiotechnology and nanomedicine.