Determination of properties of individual liposomes by capillary electrophoresis with postcolumn laser-induced fluorescence detection

Individual liposome measurements by capillary electrophoresis with postcolu mn laser-induced fluorescence detection facilitated the determination of li posome property distributions, two-dimensional plots, and an improved chara cterization of a liposomal preparation. This advancement in liposome analys is was feasible by using a high-sensitivity postcolumn laser-induced fluore scence detector wired for millisecond response. For each individual liposom e containing fluorescein, peak height and migration time were determined. F rom these measurements the individual entrapped volumes and electrophoretic mobilities were determined. Distribution analysis of these properties faci litated comparison of various liposome dilutions and indicated that the met hod is reproducible and unaffected by the density of liposomes (10(7)-10(9) liposomes/ml) in the suspension. Furthermore, liposomes showed entrapped v olumes that vary from 0.3 to 13 fL with apparent radius varying from 370 nm to 1.8 mum. Two-dimensional plots of reduced mobility versus kappaR (Debye parameter x liposome radius) revealed that the liposomes resuspended from a dried film of phospholipids are heterogeneous in regard to the surface ch arge density of individual liposomes. The described method has the potentia l of becoming a new tool for characterization of commercial liposomal prepa rations and theoretical studies.