Effect Of Surface Modification In Conventional Liposome With Lipophilic Agents

Conventional liposomes normally shows frequent uptake by reticuloendothelial system(RES). To reduce the RES uptake and to prolong the biological half life researchers aimed to prepare sterically stabilized liposomes containing charged or neutral particles as surface modifier for targeting various organs for therapeutic or diagnostic purposes. Film method followed by ultracentrifugation and sonication was used for the preparation of Ethyl cysteinate dimer(ECD), Phenylalanine(Phe) and Phe-Phe-Cys(ffc) containing lipid vesicles. Phosphatidyl choline(PC) and Phosphatidyl ethanolamine(PE) were used as the phospholipids with Cholesterol(Chol) and Glutathione(GSH), both as positive charge inducer and bilayer condenser. Free and encapsulated radiopharmaceutical content was determined by conventional method and particle size was measured in electron microscopy. Biological studies were performed in rat and imaging studies performed in rabbit.The surface modified radiolabeled liposomes were highly stable and have got high entrapment efficiency. Their in vivo characteristics were found to be significantly different from conventional liposomes and free radiopharmaceuticals or ligands. The higher levels of organ uptake supported the case for lesser RES uptake. Liposomes coated with Phe has the highest uptake in brain. It has got the usefulness as diagnostics as well as a potential Central Nervous System(CNS) targeting agent.