Imaging liposomes at electron microscopic level: encapsulated colloidal iron as an electrondense marker for liposome-cell interactions.

Colloidal iron was encapsulated into liposomes prepared by different methods to provide an electrondense marker for easy identification of liposomes in cell and tissue culture. Stable colloidal iron solution can be prepared at virtually any concentration. The diameters of more than 75 per cent of the iron particles measured between 1 and 5 nm. Liposomes with a distinct electrondense core were evident at a colloidal iron solution concentration of 0.6 g/l. The colloidal iron labelled liposomes were easily identified in cells after incubation by routine electron microscopic procedures. Liposomes could be found in lysosomes or endosomes of human M21 melanoma cells. Intact, as well as partially degraded liposomes were present after two hours of incubation.