1997 Volume 12 Issue supplement Pages 86-87
The potency of surface coating liposomes with some materials was investigated for oral delivery of peptide drugs by using insuin as a model peptide. When insulin solution was orally administered to rats, no hypoglycemic effect was observed. In contrast, mucin-coated liposome(Mucin-LIP) and PEG-coated liposome(PEG-Lip) prolonged the decrease in the glucose level after administration. Surface coating liposomes showed the slow release of insulin in the bile salt solution, whereas non-coated liposome was burst by the bile salts. Furthermore, insulin encapsulated in surface coating liposomes was stable even in the intestinal fluid. From the results of the study for the intestinal transit of liposomes, it was clarified that surface coating liposomes, especially PEG-Lip, much delayed the mean transit time of insulin. In conclusion, both the improvement of insulin stability in GI tract and the slow transit by the encapsulation of insulin in surface coating liposomes achieved the longer dulation of oral hypoglycemic activity of insulin. The surface coating should be the potential way to add desirable functions to the liposome for oral drug delivery.
