Encapsulation of the cobra cytotoxin P4 in liposomes

Cytotoxin P4 isolated from the venom of the cobra Naja nigricollis nigricollis was encapsulated in liposomes by the reverse‐phase evaporation method using phosphatidylcholine, cholesterol and phosphatidylethanolamine at molar ratios of 3:1:1. Cytotoxicity examination on murine melanoma B16F10 revealed that the activity of the entrapped cytotoxin did not change significantly and remained stable for at least 1 year at 4 degrees C without any significant leak from the liposomes (< 1%). Moreover, the activity of the cytotoxic liposomes was 20‐fold higher towards human erythrocytes. Whereas 45 micrograms of the free cytotoxin/ml were needed for total haemolysis, the cytotoxic liposomes brought about the same effect at cytotoxin concentrations of 2‐2.5 micrograms/ml, indicating the potential of the liposomes as a delivery system for the snake toxin. 1993 The Swiss Political Science Review