Iron oxide-loaded liposomes for MR imaging

In this study a liposome cell labeling system was developed for non-target-specific labeling of glioma cells with superparamagnetic iron oxide nanoparticles for magnetic resonance imaging (MRI). A high non-target-specific uptake is ideal for in vitro labeling of cells and subsequently for cell tracking and visualization of phagocytic cells in vivo. The preparation of iron oxide-loaded liposomes was optimized and the biological properties of the liposomes were investigated. Cytotoxicity and cell viability were examined and showed limited cytotoxic effects. Non-target-specific labeling of glioma cells in vitro for subsequent specific labeling of molecules for MR imaging was tested by T2*-weighted MRI at 3T. The glioma cells showed a strong initial uptake of the iron oxide liposomes and the uptake was not saturable within 24 h exposure. The uptake of liposomes was superior to non-coated magnetite nanoparticles. Using PEG-ylated liposomes, the non-specific uptake could be decreased fundamentally (86% lower) in comparison to conventional liposomes. Furthermore, the ability of liposomes as contrast agents for MR imaging was investigated. Cells labeled with iron oxide nanoparticles by treatment with liposomes showed a negative contrast in MRI and consequently successful cellular labeling. Thus, iron oxide-loaded liposomes are well suited for non-target-specific cell labeling for MR imaging.