AIMTo evaluate the hypoglycemic effect of chitosan-coated and sodium alginate-coated insulin liposomes after oral administration in mice.

METHODSInsulin-liposomes were prepared by reverse-phase evaporation. Chitosan and alginate coating was carried out by mixing liposomal suspension with chitosan and sodium alginate solutions, followed by incubation. The particle size and morphology of insulin-liposomes were determined using laser light scattering instrument and transmission electron microscopy (TEM). The entrapment efficiency was analyzed using HPLC and ultracentrifuge. The protection of insulin from peptic and tryptic digestion was studied with HPLC. The hypoglycemic effects of polysaccharide-coated insulin liposomes were investigated using the glucose oxidase method after oral administration in mice.

RESULTSThe particle size of uncoated, chitosan-coated and alginate-coated insulin-liposomes was (138 +/- 31) nm, (230 +/- 20) nm and (266 +/- 19) nm, respectively. All insulin-liposomes were of spherical or ellipsoidal shape. The entrapment efficiencies were 81.6%, 73.5% and 68.7%, respectively. Insulin was protected from tryptic digestion by chitosan-coated liposomes and protected from peptic digestion by alginate-coated liposomes. The hypoglycemic effects of insulin-liposomes, coated with 0.1% chitosan and 0.1% sodium alginate, were observed.

CONCLUSIONChitosan-coated and sodium alginate-coated liposomes were shown to reduce peptic or tryptic digestion on insulin, and enhance enteral absorption of insulin.