The effect of magnetic targeting on the uptake of magnetic-fluid-loaded liposomes by human prostatic adenocarcinoma cells

Interactions of magnetic-fluid-loaded liposomes (MFL) with human adenocarcinoma prostatic cell line PC3 were investigated in vitro. MFL consisted of unilamellar phosphatidylcholine vesicles (mean hydrodynamic diameter close to 180 nm) encapsulating 8-nm nanocrystals of maghemite (γ-Fe2O3) and sterically stabilized by introducing 5 mol.% of distearylphosphatidylcholine poly(ethylene glycol)2000 (DSPE-PEG2000) in the vesicle bilayer. The association processes with living cells, including binding and effective internalization, were followed versus time at two levels. On one hand, the lipid vesicles labeled by 1 mol.% of rhodamine-marked phosphatidylethanolamine were imaged by confocal fluorescence microscopy. On the other hand, the iron oxide particles associated with cells were independently quantified by magnetophoresis. This allowed modeling of MFL uptake kinetics as a two-step process involving first binding adsorption onto the outer cell membrane followed by subsequent internalization. Capture efficiency was significantly improved by guiding MFL in the near vicinity of the cells by means of a 0.29-T external magnet developing a magnetic field gradient close to 30 mT/mm. Double detection of lipids by fluorescence tracking and of iron oxide by magnetophoresis showed excellent correlation. This demonstrated that MFL associate with tumor cells as intact vesicle structures which conserve their internal content.