Abstract
Insulin encapsulated in liposomes of various lipid compositions were prepared. The amount of insulin trapped in these liposomes increased in the order, negatively charged liposomes<neutral liposomes<positively charged liposomes. In positively charged liposomes, the amount of insulin trapped increased with increase in the amount of amphiphile stearylamine. Under the conditions tested, the highest insulin content (about 50%) was obtained with liposomes composed of phosphatidyl choline/cholesterol/stearylamine in a molar ratio of 7/2/2.25. These liposomes were stable on incubation for3hr at 37°C in solutions of pepsin, trypsin, and pancreatin, and after these incubations, a considerable amount of insulin was still associated with the liposomes. However, the liposomes released almost all the insulin into the medium on treatment with bile.
When the liposomes were administered orally to rats in the3rd phase of acute alloxan diabetes, reduction of the blood glucose level was observed in7of11animals the reduction persisted for several hours and was ranging from 30 to 75%.
In alloxan diabetic rats showing hyperglycemia for 3 to 6 months, the liposomes also increased the glucose tolerance in half the animals tested.
