Comparison of the effects of dimyristoyl and soya phosphatidylcholine liposomes on human fibroblasts

The in vitro effects of prolonged exposure (8 days) of human skin fibroblasts to several concentrations of extruded dimyristoyl (dm-PC) and soya phosphatidylcholine (soya-PC) liposomes were compared. Prepared Liposome suspensions were added to the fibroblast culture medium at phospholipid concentrations of 10, 50, 100, 200, and 300 microM. Survival curves and values of 50% inhibitory concentration (IC50) and area under the curve (AUC) were used to compare the response of the fibroblasts to the two types of liposomes. The effect of the incorporation of vitamin E in the liposomal preparations also was determined. Fibroblasts showed greater sensitivity toward the soya-PC liposomes (IC50 = 150 microM) than the dm-PC liposomes (IC50 = 212 microM). The presence of vitamin E in the soya-PC liposomes led to a 1.9-fold increase in the IC50, while dm-PC liposomes containing vitamin E showed an IC50 that was 1.1 times higher than that shown by control vitamin-free liposomes. Soya-PC liposomes containing vitamin E at a molar ratio of 10:0.5 (phospholipid:vitamin) were best tolerated by the fibroblasts (IC50 > 300 microM). It would appear that dm-PC liposomes are better tolerated by fibroblasts than those composed of soya-PC. However, the incorporation of vitamin E into the liposomes seems to reverse this effect, and it is the vitamin-containing soya-PC liposomes that are most compatible with the growth of fibroblasts in culture.