IN-VITRO EVALUATION OF DRUG-RELEASE KINETICS FROM LIPOSOMES BY FRACTIONAL DIALYSIS

A new dialysis method was designed with the purpose of studying drug release rate from liposomes. The liposomes were diluted directly in the continuous phase and dialysed against a small volume of buffer. The dialysate was changed at 10 min intervals and the amount of carboxyfluorescein released was calculated from a standard curve. To evaluate the new method, parallel measurements were recorded with the traditional carboxyfluorescein assay, which is based on direct measurements on liposomes containing a self-quenching concentration. The new method is called fractional dialysis, and is shown to have sensitivity similar to that of the carboxyfluorescein assay. In certain cases the fractional dialysis method gives a more accurate release profile. It is suggested that fractional dialysis can be a useful alternative to other techniques for recording the in vitro release characteristics of specific drugs from liposomes or other colloidal carriers.