Structural and biological characterization of Fe₃O₄-loaded spherical and tubular liposomes for use in drug delivery systems

Magnetic liposomes containing Fe₃O₄ nanoparticles were prepared using colipids [1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC_8,9PC)] and mixtures of the colipids with an anionic lipid [1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG)] or a cationic lipid [cetyltrimethylammonium bromide (CTAB)]. Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) analysis showed that the magnetic liposomes containing DC_8,9PC and DOPC were tubular and spherical in structure, respectively. The effects of an external magnetic field and the structure of the liposomes on cellular association were investigated. The external magnetic field increased cellular association and uptake levels independent of the structure both in vitro and in vivo. Although the level of in vitro cellular association for the tubular liposomes was higher than that for the spherical liposomes, there was no significant difference in the level of in vivo uptake of fluorescent Fe₃O₄ nanoparticles in the mouse liver. Finally, the magnetic liposomes were found to be biocompatible by haematological and serum chemical analyses. (author)