A COMPARISON OF CARBOXYLATE SALTS AS LIPOSOMAL CRYOPROTECTANTS

The use of liposome suspension for the delivery of water soluble drugs is limited by drug leakage on long term storage. This problem may be overcome by freezing of the liposome suspension if the damage caused b y the freeze-thaw process could be overcome. This paper describes an i nvestigation into the use of various carboxylates as cryoprotectants f or the frozen storage of liposomes. Although all the compounds investi gated reduced the leakage of an entrapped marker from the liposomes, t he choice of carboxylate salt was shown to be important in achieving m aximal cryoprotection. Acetates were shown to be more effective than f ormates, propionates and hexanoates and the tetramethylammonium salts were found to be more effective than the sodium, potassium or ammonium salts.