LIPOSOMES CONTAINING FLUORINATED STEROIDS - AN ANALYSIS BASED ON PHOTON-CORRELATION AND F-19 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

Small unilamellar liposomes containing fluorinated steroids (flumethasone and dexamethasone) were obtained. A physicochemical evaluation was conducted based on photon correlation spectroscopy (PCS) and fluorine-19 (F-19) nuclear magnetic resonance (NMR) spectroscopy compared with standard biochemical methods (HPLC). The PCS method provides a fast and adequate evaluation of some critical features of liposomes (size, physical stability). In addition, F-19 NMR spectroscopy gives substantial information, in a nondestructive manner, on steroid behavior in the membrane upon encapsulation and also when the temperature of liposomes is increased. The combined spectroscopic approach proposed here might prove useful in (1) the management of liposomal formulation, especially in the documentation of physicochemical properties, (2) pharmaceutical control in the industrial production line, and (3) control preceding injection at the clinical site. Spectroscopic techniques might offer a complementary approach to classical biochemical methods in the evaluation of the properties of a liposomal formulation and could be usefully integrated into quality control procedures.