LETTERS TO THE EDITOR Influence of Size of Liposomes in Potentiating the Efficacy of Encapsulated Triethylenetetramine-hexaacetic Acid (TTHA)

Polyaminocarboxylic acids have widely been used as antidotes in heavy metal intoxication, however their hydrophilic nature renders them to be mostly distributed extracellularly. To facilitate the intracellular delivery of such chelating agent, triethlenetetraamine-hexaacetic acid (TTHA) was encapsulated in small unilamellar vesicles (SUV) or dehydration rehydration vesicles (DRV) and its effect was examined in the amelioration of cadmium toxicity. Mice were administered cadmium (0.2 mg/kg B.wt.) as CdCl2 intraperitoneally daily for five days. After a period of four weeks rest. they were given two intravenous injections of TTHA as free material or encapsulated in liposomes (0.16 m mole /kg) at a gap of 48 hours. Urinary and fecal elimination of cadmium and its distribution in the liver, kidney and spleen was monitored after TTHA treatment. The results indicate the efficacy of TTHA in removing cadmium from the body organs of preexposed animals and its excretion through urine and feces was maximum when it was encapsulated in SUV liposomes.