Liposomes prepared dynamically by interactions between bile salt and phospholipid molecules.

Quasi-elastic light scattering (QELS) studies showed that vesicles can spontaneously form from sodium glycocholate-egg phosphatidylcholine mixed micelles upon dilution with physiological saline buffer (pH 7.5). A water-soluble drug, cytosine arabinoside, did not affect the transition pattern. Transitions were also obtained when dilutions were performed using diluted serum solutions (5% and 10% serum in buffer). However, if intermicellar bile salt monomer concentration (imc) was kept constant in diluent media, the transition was completely suppressed. Approximately 10% of the cytosine arabinoside was trapped inside vesicles which were formed in buffer, although this value decreased to approx. 2.5% when diluted serum was used. These results suggest that the mixed micelle to vesicle transition can be an alternative means to sonication in loading drugs into in vitro vesicles. A good correlation was found between the transmission electron microscopy (TEM) diameter and the mean hydrodynamic diameter obtained by QELS.