The Use of Liposomes as Enzyme Carriers. I. Dependence of Enzyme Stability on the Method of Preparation

The stability of liposomal enzymes and the encapsulation efficiency of reverse-phase evaporation vesicles (REV) were investigated in comparison with those of the original small multilamellar liposomes (SML), by using elastase as a model enzyme. The encapsulation efficiency of REV was greatly superior to that of SML. In addition, REV retarded the inactivation of elastase in the neutral pH region, as did SML. Therefore the REV method should be useful for the preparation of carriers to encapsulate not only elastase but also other macromolecules. However, at lower pH, pH 2.63, where elastase was rapidly inactivated, REV accelerated the inactivation of the enzyme, although SML retarded it, as at neutral pH. Thus, since liposomes prepared by different methods have significantly different physicochemical properties, further and more precise studies on the methods of preparation are required.