Targeted delivery of doxorubicin via estrone-appended liposomes.

Estrone-appended liposomal formulation of doxorubicin was designed to enhance the capability of clinically used liposomal doxorubicin formulation with the added advantage of delivery of doxorubicin to its destination site, i.e. cancerous cells over-expressing estrogen receptors (ERs). Estrone was conjugated with distearoyl phosphatidylethanolamine (DSPE) using succinic anhydride as a linker and the conjugate was characterized by IR and mass spectroscopies. Estrone-coupled liposomes were prepared with the composition of egg phosphatidylcholine/cholesterol/distearoyl phosphatidylethanolamine-estrone (PC/CHOL/DSPE-ES) at the molar and drug-lipid ratios of 7:3:0.5 and 0.1:1 (w/w), respectively. The average vesicle sizes of the conventional and estrone-appended liposomes were found to be 193 +/- 24 and 207 +/- 28 nm, respectively. The fluorescent microscopy studies were performed with estrone-appended liposomes loaded with 6-carboxyfluorescein (6-CF). Results of in vivo biodistribution studies showed that estrone-appended liposomes were effectively taken up by cells expressing ERs. The drug uptake study showed that accumulation of ligand-appended liposomes in the breast and uterus was 13.9 and 12.7 times higher when compared with plain drug, and 11.05 and 10.3 times higher when compared with conventional liposomes, respectively, after 8 h of tail vein intravenous administration. The findings are seminal for selective targeting of antineoplastic agents to the ER, which are frequently over-expressed on carcinoma of breast and uterine origin, and opens the promising possibilities for non-immunogenic, site-specific delivery of bioactive(s) to these sites.