Synthesis of magnetic Fe3O4 particles covered with a modifiable phospholipid coat

This work reports the synthesis of iron oxide cores by coprecipitation of Fe2+ and Fe3+, ions with NaHCO3 or NH3. Depending on the experimental conditions, particles of two different sizes (13 or 130 nm diameter) were produced. Xray diffractometry revealed Fe3O4 (magnetite) to be the main constituent. The smaller particles, which, in contrast to the larger ones, are superparamagnetic, were stabilized with a phospholipid bilayer consisting of a 9:1 molar ratio of dimyristoylphosphatidylcholine and dimyristoylpliosphatidylglycerol, thereby creating so-called magnetoliposomes. In a subsequent step, poly(ethylene glycol)-(PEG-) derivatized dipalmitoylphosphatidylethanolamine was introduced into the lipid envelope by incubating the magnetoliposomes with preformed sonicated vesicles containing the PEGylated lipid. The mechanism by which lipid transfer occurred was determined from the kinetic profiles. The relevance of these observations to a wide range of biomedical applications is briefly discussed.