Studies on liposome-encapsulated heparin.

In order to prolong the anticoagulant activity of heparin in vivo, attempts were made to encapsulate heparin into liposomes. Liposome-encapsulated heparin (lipo-heparin) prepared was large multilamellar vesicles (0.5-4.0 micron in diameter). The activity of lipo-heparin was 1.6-5.2 X 10(3) U/g lipid with recovery rate ranged between 0.4 to 1.3% and stable in saline at 4 degrees C for at least two weeks. When intravenously administered into rats, the anticoagulant activity of lipo-heparin was significantly prolonged (approximately three times), as compared with that of untreated heparin. Furthermore, the activity of lipo-heparin could be neutralized by protamine sulfate. From these observations, it was concluded that liposome-encapsulation of heparin results in the prolonged anticoagulant effect in vivo and lipo-heparin may be applicable for clinical use, after further studies on side effects of liposomes are completed.