Liposome-Mediated Transfer Can Improve the Efficacy of Islet Labeling With Superparamagnetic Iron Oxide

An in vivo method for islet visualization using magnetic resonance imaging (MRI), using superparamagnetic iron oxide (SPIO), has been described. Herein we have developed a protocol that uses cationic liposomes to increase the efficiency of islet cell labeling by SPIO in vitro. Fresh islet cells were incubated in RPMI-1640 medium, to which had been added a range of concentrations of ferucarbotran, a SPIO contrast agent. At each SPIO concentration, duplicate samples were incubated with versus without addition of cationic liposomes. We measured intracellular iron concentration, cell viability, and insulin-release function after labeling. We observed that the amount of iron bound to islet cells increased as the concentration of added SPIO increased. The presence of liposomes increased labeling efficiency at each SPIO concentration. In vitro MRI confirmed the effect of liposomes to improve labeling efficiency of islet cells by SPIO.