Abstract
With a rapid demand to decrease the side effect of drug, a variety of drug delivery systems have been developed. This review will focus on the development of liposomes with soybean-derived sterols and their glucosides for drug carriers. Current status and further perspectives in this research field are reviewed mainly based on the results obtained in our laboratory. First we studied the different physicochemical properties of dipalmitoylphosphatidylcholine (DPPC) liposomes with soybean-derived sterols (SS) and their glucosides (SG). SS rigidifies the liposomal membrane but SG fluidizes it. SS stabilizes liposomes more than cholesterol that is conventionally used as stabilizing agents in liposomes. On the basis of this information, we developed liposomes with SS and SG for a drug carrier. Secondly we studied the stability of liposomes in the blood and biodistribution and found that liposomes with SS were stable as expected in vitro results. In particular, DPPC : SS (7 : 4, molar ratio) size 0.2 μm showed long circulation. Thirdly successful targeting of the drugs to the liver was achieved by liposomes with SG. Finally, we succeeded in developing liposomal erythropoietin and doxorubicin using liposomes with SS for sustained release of drugs. Liposomal drugs increased the pharmacological effect compared with free drugs, suggesting a decrease of side effect and long circulation. The attempt for oral administration using liposomes of peptide drugs was carried out successfully. We have established that the study of physicochemical properties of liposomes is needed rationally as the distribution of drugs in liposomes and the rigidity of liposomal membrane, prior to the development of the drug carrier of liposomes. SS is useful to stabilize liposomes and SG to targeting to the liver parenchymal cells. This information can be useful and practical for the development of liposomes for drug carriers.
