Entrapment of soy bean trypsin inhibitor and alpha1-antitrypsin by multilamellar liposomes.

The broad-spectrum protease inhibitors, soy bean trypsin inhibitor and α₁-antitrypsin, were entrapped within anionic multilamellar liposomes; the efficiency of entrapment was 12% for α₁-antitrypsin and 14% for soy bean trypsin inhibitor. Entrapment of ³H-labeled d-glucose, a marker for the aqueous compartment, was dependent upon the nature and concentration of coentrapped antiprotease. Rechromatography of the pooled liposome fractions following solubilization with the detergent Triton X-100 demonstrated latency of the entrapped materials. In addition, entrapment of soy bean trypsin inhibitor, as well as ³H-labeled d-glucose, was shown to be proportional to the net anionie surface charge in the lipid bilayers, suggesting sequestration within the aqueous compartments of the liposomes. This localization was also indicated by the minimal adsorption of antiproteases to anionic liposomes, contrasted with the extensive electrostatic binding of the antiproteases to cationic liposomes.