The Effect of Cationic Polylysine on the Release of an Encapsulated Substance from pH-Sensitive Anionic Liposomes

The formation of complexes from anionic liposomes with a pH-sensitive molecular switch (flipid) and a cationic polypeptide (polylysine) embedded in the membrane with a degree of polymerization of 90, 660, and 1360 was investigated. Liposomes in the complex retain their integrity in a buffer solution with a pH of 7; The resulting complexes are resistant to dissociation in a physiological solution containing 0.15 M NaCl. Lowering the pH of the solution to 5 causes the formation of defects in the lipid bilayer by changing the conformation of the flipid, which leads to the release of the encapsulated substance from the liposomes into the surrounding solution. In this case, complexation increases both the rate of release of the encapsulated substance and the amount of the substance moving from the liposomes to the external solution. The results obtained are of interest for encapsulation and controlled drug delivery.