Binding and capture of human interferon-alpha by reverse evaporation vesicles, multilamellar vesicles, and small unilamellar vesicles.

Liposomes of various physical and chemical compositions were prepared and their ability to externally bind and internally capture human interferon alpha (HuIFN-alpha) was determined. HuIFN-alpha was bound by preformed liposomes composed of either dipalmitoyl phosphatidyl choline alone or dipalmitoyl phosphatidic acid (calcium salt), and cholesterol, with or without a phosphatidyl choline component. HuIFN-alpha could also be internally captured within liposomes both of compositions that bound or did not bind interferon. The interferon could be associated with liposomes in at least three manners: bound to the outside surface of the liposome, associated partially within the liposomal membranes, or completely internalized either within the aqueous compartments of the liposome or completely buried within the liposomal bilayer membrane. HuIFN-alpha was stably-associated with reverse-evaporation vesicles, multilamellar vesicles, and small unilamellar vesicles for 30 days at 4 degrees C. Incubation of the multilamellar vesicles at 37 degrees C caused an initial decrease in the amount of externally bound interferon, and incubation with mouse serum caused a further dissociation of the externally-bound interferon. Depending on liposome composition, incubation at 37 degrees C either had little effect on stability of internalized interferon or caused leakage of internalized interferon.